text: // This is an open source non-commercial project. Dear PVS-Studio, please check
  // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
  
  /// change.c: functions related to changing text
  
  #include "nvim/assert.h"
  #include "nvim/buffer.h"
  #include "nvim/buffer_updates.h"
  #include "nvim/change.h"
  #include "nvim/charset.h"
  #include "nvim/cursor.h"
  #include "nvim/diff.h"
  #include "nvim/edit.h"
  #include "nvim/eval.h"
  #include "nvim/extmark.h"
  #include "nvim/fileio.h"
  #include "nvim/fold.h"
  #include "nvim/indent.h"
  #include "nvim/indent_c.h"
  #include "nvim/mark.h"
  #include "nvim/memline.h"
  #include "nvim/move.h"
  #include "nvim/option.h"
  #include "nvim/plines.h"
  #include "nvim/screen.h"
  #include "nvim/search.h"
  #include "nvim/state.h"
  #include "nvim/ui.h"
  #include "nvim/undo.h"
  
  #ifdef INCLUDE_GENERATED_DECLARATIONS
  # include "change.c.generated.h"
  #endif
  
  /// If the file is readonly, give a warning message with the first change.
  /// Don't do this for autocommands.
  /// Doesn't use emsg(), because it flushes the macro buffer.
  /// If we have undone all changes b_changed will be false, but "b_did_warn"
  /// will be true.
  /// "col" is the column for the message; non-zero when in insert mode and
  /// 'showmode' is on.
  /// Careful: may trigger autocommands that reload the buffer.
  void change_warning(buf_T *buf, int col)
  {
    static const char *w_readonly = N_("W10: Warning: Changing a readonly file");
  
    if (buf->b_did_warn == false
        && curbufIsChanged() == 0
        && !autocmd_busy
        && buf->b_p_ro) {
      buf->b_ro_locked++;
      apply_autocmds(EVENT_FILECHANGEDRO, NULL, NULL, false, buf);
      buf->b_ro_locked--;
      if (!buf->b_p_ro) {
        return;
      }
      // Do what msg() does, but with a column offset if the warning should
      // be after the mode message.
      msg_start();
      if (msg_row == Rows - 1) {
        msg_col = col;
      }
      msg_source(HL_ATTR(HLF_W));
      msg_ext_set_kind("wmsg");
      msg_puts_attr(_(w_readonly), HL_ATTR(HLF_W) | MSG_HIST);
      set_vim_var_string(VV_WARNINGMSG, _(w_readonly), -1);
      msg_clr_eos();
      (void)msg_end();
      if (msg_silent == 0 && !silent_mode && ui_active()) {
        ui_flush();
        os_delay(1002L, true);  // give the user time to think about it
      }
      buf->b_did_warn = true;
      redraw_cmdline = false;  // don't redraw and erase the message
      if (msg_row < Rows - 1) {
        showmode();
      }
    }
  }
  
  /// Call this function when something in the current buffer is changed.
  ///
  /// Most often called through changed_bytes() and changed_lines(), which also
  /// mark the area of the display to be redrawn.
  ///
  /// Careful: may trigger autocommands that reload the buffer.
  void changed(void)
  {
    if (!curbuf->b_changed) {
      int save_msg_scroll = msg_scroll;
  
      // Give a warning about changing a read-only file.  This may also
      // check-out the file, thus change "curbuf"!
      change_warning(curbuf, 0);
  
      // Create a swap file if that is wanted.
      // Don't do this for "nofile" and "nowrite" buffer types.
      if (curbuf->b_may_swap
          && !bt_dontwrite(curbuf)) {
        bool save_need_wait_return = need_wait_return;
  
        need_wait_return = false;
        ml_open_file(curbuf);
  
        // The ml_open_file() can cause an ATTENTION message.
        // Wait two seconds, to make sure the user reads this unexpected
        // message.  Since we could be anywhere, call wait_return() now,
        // and don't let the emsg() set msg_scroll.
        if (need_wait_return && emsg_silent == 0) {
          ui_flush();
          os_delay(2002L, true);
          wait_return(true);
          msg_scroll = save_msg_scroll;
        } else {
          need_wait_return = save_need_wait_return;
        }
      }
      changed_internal();
    }
    buf_inc_changedtick(curbuf);
  
    // If a pattern is highlighted, the position may now be invalid.
    highlight_match = false;
  }
  
  /// Internal part of changed(), no user interaction.
  /// Also used for recovery.
  void changed_internal(void)
  {
    curbuf->b_changed = true;
    curbuf->b_changed_invalid = true;
    ml_setflags(curbuf);
    redraw_buf_status_later(curbuf);
    redraw_tabline = true;
    need_maketitle = true;  // set window title later
  }
  
  /// Common code for when a change was made.
  /// See changed_lines() for the arguments.
  /// Careful: may trigger autocommands that reload the buffer.
  static void changed_common(linenr_T lnum, colnr_T col, linenr_T lnume, long xtra)
  {
    // mark the buffer as modified
    changed();
  
    if (curwin->w_p_diff && diff_internal()) {
      curtab->tp_diff_update = true;
    }
  
    // set the '. mark
    if (!cmdmod.keepjumps) {
      RESET_FMARK(&curbuf->b_last_change, ((pos_T) { lnum, col, 0 }), 0);
  
      // Create a new entry if a new undo-able change was started or we
      // don't have an entry yet.
      if (curbuf->b_new_change || curbuf->b_changelistlen == 0) {
        int add;
        if (curbuf->b_changelistlen == 0) {
          add = true;
        } else {
          // Don't create a new entry when the line number is the same
          // as the last one and the column is not too far away.  Avoids
          // creating many entries for typing "xxxxx".
          pos_T *p = &curbuf->b_changelist[curbuf->b_changelistlen - 1].mark;
          if (p->lnum != lnum) {
            add = true;
          } else {
            int cols = comp_textwidth(false);
            if (cols == 0) {
              cols = 79;
            }
            add = (p->col + cols < col || col + cols < p->col);
          }
        }
        if (add) {
          // This is the first of a new sequence of undo-able changes
          // and it's at some distance of the last change.  Use a new
          // position in the changelist.
          curbuf->b_new_change = false;
  
          if (curbuf->b_changelistlen == JUMPLISTSIZE) {
            // changelist is full: remove oldest entry
            curbuf->b_changelistlen = JUMPLISTSIZE - 1;
            memmove(curbuf->b_changelist, curbuf->b_changelist + 1,
                    sizeof(curbuf->b_changelist[0]) * (JUMPLISTSIZE - 1));
            FOR_ALL_TAB_WINDOWS(tp, wp) {
              // Correct position in changelist for other windows on
              // this buffer.
              if (wp->w_buffer == curbuf && wp->w_changelistidx > 0) {
                wp->w_changelistidx--;
              }
            }
          }
          FOR_ALL_TAB_WINDOWS(tp, wp) {
            // For other windows, if the position in the changelist is
            // at the end it stays at the end.
            if (wp->w_buffer == curbuf
                && wp->w_changelistidx == curbuf->b_changelistlen) {
              wp->w_changelistidx++;
            }
          }
          curbuf->b_changelistlen++;
        }
      }
      curbuf->b_changelist[curbuf->b_changelistlen - 1] =
        curbuf->b_last_change;
      // The current window is always after the last change, so that "g,"
      // takes you back to it.
      curwin->w_changelistidx = curbuf->b_changelistlen;
    }
  
    FOR_ALL_TAB_WINDOWS(tp, wp) {
      if (wp->w_buffer == curbuf) {
        // Mark this window to be redrawn later.
        if (wp->w_redr_type < VALID) {
          wp->w_redr_type = VALID;
        }
  
        // Check if a change in the buffer has invalidated the cached
        // values for the cursor.
        // Update the folds for this window.  Can't postpone this, because
        // a following operator might work on the whole fold: ">>dd".
        linenr_T last = lnume + xtra - 1;  // last line after the change
        foldUpdate(wp, lnum, last);
  
        // The change may cause lines above or below the change to become
        // included in a fold.  Set lnum/lnume to the first/last line that
        // might be displayed differently.
        // Set w_cline_folded here as an efficient way to update it when
        // inserting lines just above a closed fold.
        bool folded = hasFoldingWin(wp, lnum, &lnum, NULL, false, NULL);
        if (wp->w_cursor.lnum == lnum) {
          wp->w_cline_folded = folded;
        }
        folded = hasFoldingWin(wp, last, NULL, &last, false, NULL);
        if (wp->w_cursor.lnum == last) {
          wp->w_cline_folded = folded;
        }
  
        // If the changed line is in a range of previously folded lines,
        // compare with the first line in that range.
        if (wp->w_cursor.lnum <= lnum) {
          int i = find_wl_entry(wp, lnum);
          if (i >= 0 && wp->w_cursor.lnum > wp->w_lines[i].wl_lnum) {
            changed_line_abv_curs_win(wp);
          }
        }
  
        if (wp->w_cursor.lnum > lnum) {
          changed_line_abv_curs_win(wp);
        } else if (wp->w_cursor.lnum == lnum && wp->w_cursor.col >= col) {
          changed_cline_bef_curs_win(wp);
        }
        if (wp->w_botline >= lnum) {
          // Assume that botline doesn't change (inserted lines make
          // other lines scroll down below botline).
          approximate_botline_win(wp);
        }
  
        // Check if any w_lines[] entries have become invalid.
        // For entries below the change: Correct the lnums for
        // inserted/deleted lines.  Makes it possible to stop displaying
        // after the change.
        for (int i = 0; i < wp->w_lines_valid; i++) {
          if (wp->w_lines[i].wl_valid) {
            if (wp->w_lines[i].wl_lnum >= lnum) {
              if (wp->w_lines[i].wl_lnum < lnume) {
                // line included in change
                wp->w_lines[i].wl_valid = false;
              } else if (xtra != 0) {
                // line below change
                wp->w_lines[i].wl_lnum += xtra;
                wp->w_lines[i].wl_lastlnum += xtra;
              }
            } else if (wp->w_lines[i].wl_lastlnum >= lnum) {
              // change somewhere inside this range of folded lines,
              // may need to be redrawn
              wp->w_lines[i].wl_valid = false;
            }
          }
        }
  
        // Take care of side effects for setting w_topline when folds have
        // changed.  Esp. when the buffer was changed in another window.
        if (hasAnyFolding(wp)) {
          set_topline(wp, wp->w_topline);
        }
  
        // If lines have been added or removed, relative numbering always
        // requires a redraw.
        if (wp->w_p_rnu && xtra != 0) {
          wp->w_last_cursor_lnum_rnu = 0;
          redraw_later(wp, VALID);
        }
  
        // Cursor line highlighting probably need to be updated with
        // "VALID" if it's below the change.
        // If the cursor line is inside the change we need to redraw more.
        if (wp->w_p_cul) {
          if (xtra == 0) {
            redraw_later(wp, VALID);
          } else if (lnum <= wp->w_last_cursorline) {
            redraw_later(wp, SOME_VALID);
          }
        }
      }
    }
  
    // Call update_screen() later, which checks out what needs to be redrawn,
    // since it notices b_mod_set and then uses b_mod_*.
    if (must_redraw < VALID) {
      must_redraw = VALID;
    }
  
    // when the cursor line is changed always trigger CursorMoved
    if (lnum <= curwin->w_cursor.lnum
        && lnume + (xtra < 0 ? -xtra : xtra) > curwin->w_cursor.lnum) {
      curwin->w_last_cursormoved.lnum = 0;
    }
  }
  
  static void changedOneline(buf_T *buf, linenr_T lnum)
  {
    if (buf->b_mod_set) {
      // find the maximum area that must be redisplayed
      if (lnum < buf->b_mod_top) {
        buf->b_mod_top = lnum;
      } else if (lnum >= buf->b_mod_bot) {
        buf->b_mod_bot = lnum + 1;
      }
    } else {
      // set the area that must be redisplayed to one line
      buf->b_mod_set = true;
      buf->b_mod_top = lnum;
      buf->b_mod_bot = lnum + 1;
      buf->b_mod_xlines = 0;
    }
  }
  
  /// Changed bytes within a single line for the current buffer.
  /// - marks the windows on this buffer to be redisplayed
  /// - marks the buffer changed by calling changed()
  /// - invalidates cached values
  /// Careful: may trigger autocommands that reload the buffer.
  void changed_bytes(linenr_T lnum, colnr_T col)
  {
    changedOneline(curbuf, lnum);
    changed_common(lnum, col, lnum + 1, 0L);
    // notify any channels that are watching
    buf_updates_send_changes(curbuf, lnum, 1, 1, true);
  
    // Diff highlighting in other diff windows may need to be updated too.
    if (curwin->w_p_diff) {
      FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
        if (wp->w_p_diff && wp != curwin) {
          redraw_later(wp, VALID);
          linenr_T wlnum = diff_lnum_win(lnum, wp);
          if (wlnum > 0) {
            changedOneline(wp->w_buffer, wlnum);
          }
        }
      }
    }
  }
  
  /// insert/delete bytes at column
  ///
  /// Like changed_bytes() but also adjust extmark for "new" bytes.
  void inserted_bytes(linenr_T lnum, colnr_T col, int old, int new)
  {
    if (curbuf_splice_pending == 0) {
      extmark_splice_cols(curbuf, (int)lnum-1, col, old, new, kExtmarkUndo);
    }
  
    changed_bytes(lnum, col);
  }
  
  /// Appended "count" lines below line "lnum" in the current buffer.
  /// Must be called AFTER the change and after mark_adjust().
  /// Takes care of marking the buffer to be redrawn and sets the changed flag.
  void appended_lines(linenr_T lnum, long count)
  {
    changed_lines(lnum + 1, 0, lnum + 1, count, true);
  }
  
  /// Like appended_lines(), but adjust marks first.
  void appended_lines_mark(linenr_T lnum, long count)
  {
    // Skip mark_adjust when adding a line after the last one, there can't
    // be marks there. But it's still needed in diff mode.
    if (lnum + count < curbuf->b_ml.ml_line_count || curwin->w_p_diff) {
      mark_adjust(lnum + 1, (linenr_T)MAXLNUM, count, 0L, kExtmarkUndo);
    } else {
      extmark_adjust(curbuf, lnum + 1, (linenr_T)MAXLNUM, count, 0L,
                     kExtmarkUndo);
    }
    changed_lines(lnum + 1, 0, lnum + 1, count, true);
  }
  
  /// Deleted "count" lines at line "lnum" in the current buffer.
  /// Must be called AFTER the change and after mark_adjust().
  /// Takes care of marking the buffer to be redrawn and sets the changed flag.
  void deleted_lines(linenr_T lnum, long count)
  {
    changed_lines(lnum, 0, lnum + count, -count, true);
  }
  
  /// Like deleted_lines(), but adjust marks first.
  /// Make sure the cursor is on a valid line before calling, a GUI callback may
  /// be triggered to display the cursor.
  void deleted_lines_mark(linenr_T lnum, long count)
  {
    // if we deleted the entire buffer, we need to implicitly add a new empty line
    bool made_empty = (count > 0) && curbuf->b_ml.ml_flags & ML_EMPTY;
  
    mark_adjust(lnum, (linenr_T)(lnum + count - 1), (long)MAXLNUM,
                -count + (made_empty?1:0),
                kExtmarkUndo);
    changed_lines(lnum, 0, lnum + count, -count, true);
  }
  
  /// Marks the area to be redrawn after a change.
  ///
  /// @param buf the buffer where lines were changed
  /// @param lnum first line with change
  /// @param lnume line below last changed line
  /// @param xtra number of extra lines (negative when deleting)
  void changed_lines_buf(buf_T *buf, linenr_T lnum, linenr_T lnume, long xtra)
  {
    if (buf->b_mod_set) {
      // find the maximum area that must be redisplayed
      if (lnum < buf->b_mod_top) {
        buf->b_mod_top = lnum;
      }
      if (lnum < buf->b_mod_bot) {
        // adjust old bot position for xtra lines
        buf->b_mod_bot += xtra;
        if (buf->b_mod_bot < lnum) {
          buf->b_mod_bot = lnum;
        }
      }
      if (lnume + xtra > buf->b_mod_bot) {
        buf->b_mod_bot = lnume + xtra;
      }
      buf->b_mod_xlines += xtra;
    } else {
      // set the area that must be redisplayed
      buf->b_mod_set = true;
      buf->b_mod_top = lnum;
      buf->b_mod_bot = lnume + xtra;
      buf->b_mod_xlines = xtra;
    }
  }
  
  /// Changed lines for the current buffer.
  /// Must be called AFTER the change and after mark_adjust().
  /// - mark the buffer changed by calling changed()
  /// - mark the windows on this buffer to be redisplayed
  /// - invalidate cached values
  /// "lnum" is the first line that needs displaying, "lnume" the first line
  /// below the changed lines (BEFORE the change).
  /// When only inserting lines, "lnum" and "lnume" are equal.
  /// Takes care of calling changed() and updating b_mod_*.
  /// Careful: may trigger autocommands that reload the buffer.
  ///
  /// @param lnum  first line with change
  /// @param col  column in first line with change
  /// @param lnume  line below last changed line
  /// @param xtra  number of extra lines (negative when deleting)
  /// @param do_buf_event  some callers like undo/redo call changed_lines() and
  /// then increment changedtick *again*. This flag allows these callers to send
  /// the nvim_buf_lines_event events after they're done modifying changedtick.
  void changed_lines(linenr_T lnum, colnr_T col, linenr_T lnume, long xtra, bool do_buf_event)
  {
    changed_lines_buf(curbuf, lnum, lnume, xtra);
  
    if (xtra == 0 && curwin->w_p_diff && !diff_internal()) {
      // When the number of lines doesn't change then mark_adjust() isn't
      // called and other diff buffers still need to be marked for
      // displaying.
      linenr_T wlnum;
  
      FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
        if (wp->w_p_diff && wp != curwin) {
          redraw_later(wp, VALID);
          wlnum = diff_lnum_win(lnum, wp);
          if (wlnum > 0) {
            changed_lines_buf(wp->w_buffer, wlnum,
                              lnume - lnum + wlnum, 0L);
          }
        }
      }
    }
  
    changed_common(lnum, col, lnume, xtra);
  
    if (do_buf_event) {
      int64_t num_added = (int64_t)(lnume + xtra - lnum);
      int64_t num_removed = lnume - lnum;
      buf_updates_send_changes(curbuf, lnum, num_added, num_removed, true);
    }
  }
  
  /// Called when the changed flag must be reset for buffer `buf`.
  /// When `ff` is true also reset 'fileformat'.
  /// When `always_inc_changedtick` is true b:changedtick is incremented even
  /// when the changed flag was off.
  void unchanged(buf_T *buf, int ff, bool always_inc_changedtick)
  {
    if (buf->b_changed || (ff && file_ff_differs(buf, false))) {
      buf->b_changed = false;
      buf->b_changed_invalid = true;
      ml_setflags(buf);
      if (ff) {
        save_file_ff(buf);
      }
      redraw_buf_status_later(buf);
      redraw_tabline = true;
      need_maketitle = true;  // set window title later
      buf_inc_changedtick(buf);
    } else if (always_inc_changedtick) {
      buf_inc_changedtick(buf);
    }
  }
  
  /// Insert string "p" at the cursor position.  Stops at a NUL byte.
  /// Handles Replace mode and multi-byte characters.
  void ins_bytes(char_u *p)
  {
    ins_bytes_len(p, STRLEN(p));
  }
  
  /// Insert string "p" with length "len" at the cursor position.
  /// Handles Replace mode and multi-byte characters.
  void ins_bytes_len(char_u *p, size_t len)
  {
    size_t n;
    for (size_t i = 0; i < len; i += n) {
      // avoid reading past p[len]
      n = (size_t)utfc_ptr2len_len(p + i, (int)(len - i));
      ins_char_bytes(p + i, n);
    }
  }
  
  /// Insert or replace a single character at the cursor position.
  /// When in REPLACE or VREPLACE mode, replace any existing character.
  /// Caller must have prepared for undo.
  /// For multi-byte characters we get the whole character, the caller must
  /// convert bytes to a character.
  void ins_char(int c)
  {
    char_u buf[MB_MAXBYTES + 1];
    size_t n = (size_t)utf_char2bytes(c, buf);
  
    // When "c" is 0x100, 0x200, etc. we don't want to insert a NUL byte.
    // Happens for CTRL-Vu9900.
    if (buf[0] == 0) {
      buf[0] = '\n';
    }
    ins_char_bytes(buf, n);
  }
  
  void ins_char_bytes(char_u *buf, size_t charlen)
  {
    // Break tabs if needed.
    if (virtual_active() && curwin->w_cursor.coladd > 0) {
      coladvance_force(getviscol());
    }
  
    size_t col = (size_t)curwin->w_cursor.col;
    linenr_T lnum = curwin->w_cursor.lnum;
    char_u *oldp = ml_get(lnum);
    size_t linelen = STRLEN(oldp) + 1;  // length of old line including NUL
  
    // The lengths default to the values for when not replacing.
    size_t oldlen = 0;        // nr of bytes inserted
    size_t newlen = charlen;  // nr of bytes deleted (0 when not replacing)
  
    if (State & REPLACE_FLAG) {
      if (State & VREPLACE_FLAG) {
        // Disable 'list' temporarily, unless 'cpo' contains the 'L' flag.
        // Returns the old value of list, so when finished,
        // curwin->w_p_list should be set back to this.
        int old_list = curwin->w_p_list;
        if (old_list && vim_strchr(p_cpo, CPO_LISTWM) == NULL) {
          curwin->w_p_list = false;
        }
        // In virtual replace mode each character may replace one or more
        // characters (zero if it's a TAB).  Count the number of bytes to
        // be deleted to make room for the new character, counting screen
        // cells.  May result in adding spaces to fill a gap.
        colnr_T vcol;
        getvcol(curwin, &curwin->w_cursor, NULL, &vcol, NULL);
        colnr_T new_vcol = vcol + win_chartabsize(curwin, buf, vcol);
        while (oldp[col + oldlen] != NUL && vcol < new_vcol) {
          vcol += win_chartabsize(curwin, oldp + col + oldlen, vcol);
          // Don't need to remove a TAB that takes us to the right
          // position.
          if (vcol > new_vcol && oldp[col + oldlen] == TAB) {
            break;
          }
          oldlen += (size_t)utfc_ptr2len(oldp + col + oldlen);
          // Deleted a bit too much, insert spaces.
          if (vcol > new_vcol) {
            newlen += (size_t)(vcol - new_vcol);
          }
        }
        curwin->w_p_list = old_list;
      } else if (oldp[col] != NUL) {
        // normal replace
        oldlen = (size_t)utfc_ptr2len(oldp + col);
      }
  
  
      // Push the replaced bytes onto the replace stack, so that they can be
      // put back when BS is used.  The bytes of a multi-byte character are
      // done the other way around, so that the first byte is popped off
      // first (it tells the byte length of the character).
      replace_push(NUL);
      for (size_t i = 0; i < oldlen; i++) {
        i += (size_t)replace_push_mb(oldp + col + i) - 1;
      }
    }
  
    char_u *newp = xmalloc(linelen + newlen - oldlen);
  
    // Copy bytes before the cursor.
    if (col > 0) {
      memmove(newp, oldp, col);
    }
  
    // Copy bytes after the changed character(s).
    char_u *p = newp + col;
    if (linelen > col + oldlen) {
      memmove(p + newlen, oldp + col + oldlen,
              (size_t)(linelen - col - oldlen));
    }
  
    // Insert or overwrite the new character.
    memmove(p, buf, charlen);
  
    // Fill with spaces when necessary.
    for (size_t i = charlen; i < newlen; i++) {
      p[i] = ' ';
    }
  
    // Replace the line in the buffer.
    ml_replace(lnum, newp, false);
  
    // mark the buffer as changed and prepare for displaying
    inserted_bytes(lnum, (colnr_T)col, (int)oldlen, (int)newlen);
  
    // If we're in Insert or Replace mode and 'showmatch' is set, then briefly
    // show the match for right parens and braces.
    if (p_sm && (State & INSERT)
        && msg_silent == 0
        && !ins_compl_active()) {
      showmatch(utf_ptr2char(buf));
    }
  
    if (!p_ri || (State & REPLACE_FLAG)) {
      // Normal insert: move cursor right
      curwin->w_cursor.col += (int)charlen;
    }
    // TODO(Bram): should try to update w_row here, to avoid recomputing it later.
  }
  
  /// Insert a string at the cursor position.
  /// Note: Does NOT handle Replace mode.
  /// Caller must have prepared for undo.
  void ins_str(char_u *s)
  {
    int newlen = (int)STRLEN(s);
    linenr_T lnum = curwin->w_cursor.lnum;
  
    if (virtual_active() && curwin->w_cursor.coladd > 0) {
      coladvance_force(getviscol());
    }
  
    colnr_T col = curwin->w_cursor.col;
    char_u *oldp = ml_get(lnum);
    int oldlen = (int)STRLEN(oldp);
  
    char_u *newp = (char_u *)xmalloc((size_t)oldlen + (size_t)newlen + 1);
    if (col > 0) {
      memmove(newp, oldp, (size_t)col);
    }
    memmove(newp + col, s, (size_t)newlen);
    int bytes = oldlen - col + 1;
    assert(bytes >= 0);
    memmove(newp + col + newlen, oldp + col, (size_t)bytes);
    ml_replace(lnum, newp, false);
    inserted_bytes(lnum, col, 0, newlen);
    curwin->w_cursor.col += newlen;
  }
  
  // Delete one character under the cursor.
  // If "fixpos" is true, don't leave the cursor on the NUL after the line.
  // Caller must have prepared for undo.
  //
  // return FAIL for failure, OK otherwise
  int del_char(bool fixpos)
  {
    // Make sure the cursor is at the start of a character.
    mb_adjust_cursor();
    if (*get_cursor_pos_ptr() == NUL) {
      return FAIL;
    }
    return del_chars(1L, fixpos);
  }
  
  /// Like del_bytes(), but delete characters instead of bytes.
  int del_chars(long count, int fixpos)
  {
    int bytes = 0;
    char_u *p = get_cursor_pos_ptr();
    for (long i = 0; i < count && *p != NUL; i++) {
      int l = utfc_ptr2len(p);
      bytes += l;
      p += l;
    }
    return del_bytes(bytes, fixpos, true);
  }
  
  /// Delete "count" bytes under the cursor.
  /// If "fixpos" is true, don't leave the cursor on the NUL after the line.
  /// Caller must have prepared for undo.
  ///
  /// @param  count           number of bytes to be deleted
  /// @param  fixpos_arg      leave the cursor on the NUL after the line
  /// @param  use_delcombine  'delcombine' option applies
  ///
  /// @return FAIL for failure, OK otherwise
  int del_bytes(colnr_T count, bool fixpos_arg, bool use_delcombine)
  {
    linenr_T lnum = curwin->w_cursor.lnum;
    colnr_T col = curwin->w_cursor.col;
    bool fixpos = fixpos_arg;
    char_u *oldp = ml_get(lnum);
    colnr_T oldlen = (colnr_T)STRLEN(oldp);
  
    // Can't do anything when the cursor is on the NUL after the line.
    if (col >= oldlen) {
      return FAIL;
    }
    // If "count" is zero there is nothing to do.
    if (count == 0) {
      return OK;
    }
    // If "count" is negative the caller must be doing something wrong.
    if (count < 1) {
      siemsg("E292: Invalid count for del_bytes(): %ld", (int64_t)count);
      return FAIL;
    }
  
    // If 'delcombine' is set and deleting (less than) one character, only
    // delete the last combining character.
    if (p_deco && use_delcombine
        && utfc_ptr2len(oldp + col) >= count) {
      int cc[MAX_MCO];
  
      (void)utfc_ptr2char(oldp + col, cc);
      if (cc[0] != NUL) {
        // Find the last composing char, there can be several.
        int n = col;
        do {
          col = n;
          count = utf_ptr2len(oldp + n);
          n += count;
        } while (utf_composinglike(oldp + col, oldp + n));
        fixpos = false;
      }
    }
  
    // When count is too big, reduce it.
    int movelen = oldlen - col - count + 1;  // includes trailing NUL
    if (movelen <= 1) {
      // If we just took off the last character of a non-blank line, and
      // fixpos is true, we don't want to end up positioned at the NUL,
      // unless "restart_edit" is set or 'virtualedit' contains "onemore".
      if (col > 0 && fixpos && restart_edit == 0
          && (get_ve_flags() & VE_ONEMORE) == 0) {
        curwin->w_cursor.col--;
        curwin->w_cursor.coladd = 0;
        curwin->w_cursor.col -= utf_head_off(oldp, oldp + curwin->w_cursor.col);
      }
      count = oldlen - col;
      movelen = 1;
    }
  
    // If the old line has been allocated the deletion can be done in the
    // existing line. Otherwise a new line has to be allocated.
    bool was_alloced = ml_line_alloced();     // check if oldp was allocated
    char_u *newp;
    if (was_alloced) {
      ml_add_deleted_len(curbuf->b_ml.ml_line_ptr, oldlen);
      newp = oldp;                            // use same allocated memory
    } else {                                  // need to allocate a new line
      newp = xmalloc((size_t)(oldlen + 1 - count));
      memmove(newp, oldp, (size_t)col);
    }
    memmove(newp + col, oldp + col + count, (size_t)movelen);
    if (!was_alloced) {
      ml_replace(lnum, newp, false);
    }
  
    // mark the buffer as changed and prepare for displaying
    inserted_bytes(lnum, col, count, 0);
  
    return OK;
  }
  
  /// Copy the indent from ptr to the current line (and fill to size).
  /// Leaves the cursor on the first non-blank in the line.
  /// @return true if the line was changed.
  int copy_indent(int size, char_u *src)
  {
    char_u *p = NULL;
    char_u *line = NULL;
    int ind_len;
    int line_len = 0;
    int tab_pad;
  
    // Round 1: compute the number of characters needed for the indent
    // Round 2: copy the characters.
    for (int round = 1; round <= 2; round++) {
      int todo = size;
      ind_len = 0;
      int ind_done = 0;
      int ind_col = 0;
      char_u *s = src;
  
      // Count/copy the usable portion of the source line.
      while (todo > 0 && ascii_iswhite(*s)) {
        if (*s == TAB) {
          tab_pad = tabstop_padding(ind_done,
                                    curbuf->b_p_ts,
                                    curbuf->b_p_vts_array);
  
          // Stop if this tab will overshoot the target.
          if (todo < tab_pad) {
            break;
          }
          todo -= tab_pad;
          ind_done += tab_pad;
          ind_col += tab_pad;
        } else {
          todo--;
          ind_done++;
          ind_col++;
        }
        ind_len++;
  
        if (p != NULL) {
          *p++ = *s;
        }
        s++;
      }
  
      // Fill to next tabstop with a tab, if possible.
      tab_pad = tabstop_padding(ind_done, curbuf->b_p_ts, curbuf->b_p_vts_array);
  
      if ((todo >= tab_pad) && !curbuf->b_p_et) {
        todo -= tab_pad;
        ind_len++;
        ind_col += tab_pad;
  
        if (p != NULL) {
          *p++ = TAB;
        }
      }
  
      // Add tabs required for indent.
      if (!curbuf->b_p_et) {
        for (;;) {
          tab_pad = tabstop_padding(ind_col,
                                    curbuf->b_p_ts,
                                    curbuf->b_p_vts_array);
          if (todo < tab_pad) {
            break;
          }
          todo -= tab_pad;
          ind_len++;
          ind_col += tab_pad;
          if (p != NULL) {
            *p++ = TAB;
          }
        }
      }
  
      // Count/add spaces required for indent.
      while (todo > 0) {
        todo--;
        ind_len++;
  
        if (p != NULL) {
          *p++ = ' ';
        }
      }
  
      if (p == NULL) {
        // Allocate memory for the result: the copied indent, new indent
        // and the rest of the line.
        line_len = (int)STRLEN(get_cursor_line_ptr()) + 1;
        assert(ind_len + line_len >= 0);
        size_t line_size;
        STRICT_ADD(ind_len, line_len, &line_size, size_t);
        line = xmalloc(line_size);
        p = line;
      }
    }
  
    // Append the original line
    memmove(p, get_cursor_line_ptr(), (size_t)line_len);
  
    // Replace the line
    ml_replace(curwin->w_cursor.lnum, line, false);
  
    // Put the cursor after the indent.
    curwin->w_cursor.col = ind_len;
    return true;
  }
  
  /// open_line: Add a new line below or above the current line.
  ///
  /// For VREPLACE mode, we only add a new line when we get to the end of the
  /// file, otherwise we just start replacing the next line.
  ///
  /// Caller must take care of undo.  Since VREPLACE may affect any number of
  /// lines however, it may call u_save_cursor() again when starting to change a
  /// new line.
  /// "flags": OPENLINE_DELSPACES delete spaces after cursor
  ///          OPENLINE_DO_COM    format comments
  ///          OPENLINE_KEEPTRAIL keep trailing spaces
  ///          OPENLINE_MARKFIX   adjust mark positions after the line break
  ///          OPENLINE_COM_LIST  format comments with list or 2nd line indent
  ///
  /// "second_line_indent": indent for after ^^D in Insert mode or if flag
  ///                       OPENLINE_COM_LIST
  /// "did_do_comment" is set to true when intentionally putting the comment
  /// leader in fromt of the new line.
  ///
  /// @param dir  FORWARD or BACKWARD
  ///
  /// @return true on success, false on failure
  int open_line(int dir, int flags, int second_line_indent, bool *did_do_comment)
  {
    char_u *next_line = NULL;       // copy of the next line
    char_u *p_extra = NULL;         // what goes to next line
    colnr_T less_cols = 0;          // less columns for mark in new line
    colnr_T less_cols_off = 0;      // columns to skip for mark adjust
    pos_T old_cursor;               // old cursor position
    colnr_T newcol = 0;             // new cursor column
    int newindent = 0;              // auto-indent of the new line
    bool trunc_line = false;        // truncate current line afterwards
    bool retval = false;            // return value
    int extra_len = 0;              // length of p_extra string
    int lead_len;                   // length of comment leader
    int comment_start = 0;          // start index of the comment leader
    char_u *lead_flags;             // position in 'comments' for comment leader
    char_u *leader = NULL;          // copy of comment leader
    char_u *allocated = NULL;       // allocated memory
    char_u *p;
    char_u saved_char = NUL;        // init for GCC
    pos_T *pos;
    bool do_si = (!p_paste && curbuf->b_p_si && !curbuf->b_p_cin
                  && *curbuf->b_p_inde == NUL);
    bool do_cindent;
    bool no_si = false;             // reset did_si afterwards
    int first_char = NUL;           // init for GCC
    int vreplace_mode;
    bool did_append;                // appended a new line
    int saved_pi = curbuf->b_p_pi;  // copy of preserveindent setting
  
    linenr_T lnum = curwin->w_cursor.lnum;
    colnr_T mincol = curwin->w_cursor.col + 1;
  
    // make a copy of the current line so we can mess with it
    char_u *saved_line = vim_strsave(get_cursor_line_ptr());
  
    if (State & VREPLACE_FLAG) {
      // With VREPLACE we make a copy of the next line, which we will be
      // starting to replace.  First make the new line empty and let vim play
      // with the indenting and comment leader to its heart's content.  Then
      // we grab what it ended up putting on the new line, put back the
      // original line, and call ins_char() to put each new character onto
      // the line, replacing what was there before and pushing the right
      // stuff onto the replace stack.  -- webb.
      if (curwin->w_cursor.lnum < orig_line_count) {
        next_line = vim_strsave(ml_get(curwin->w_cursor.lnum + 1));
      } else {
        next_line = vim_strsave((char_u *)"");
      }
  
      // In VREPLACE mode, a NL replaces the rest of the line, and starts
      // replacing the next line, so push all of the characters left on the
      // line onto the replace stack.  We'll push any other characters that
      // might be replaced at the start of the next line (due to autoindent
      // etc) a bit later.
      replace_push(NUL);      // Call twice because BS over NL expects it
      replace_push(NUL);
      p = saved_line + curwin->w_cursor.col;
      while (*p != NUL) {
        p += replace_push_mb(p);
      }
      saved_line[curwin->w_cursor.col] = NUL;
    }
  
    if ((State & INSERT)
        && !(State & VREPLACE_FLAG)) {
      p_extra = saved_line + curwin->w_cursor.col;
      if (do_si) {  // need first char after new line break
        p = skipwhite(p_extra);
        first_char = *p;
      }
      extra_len = (int)STRLEN(p_extra);
      saved_char = *p_extra;
      *p_extra = NUL;
    }
  
    u_clearline();                // cannot do "U" command when adding lines
    did_si = false;
    ai_col = 0;
  
    // If we just did an auto-indent, then we didn't type anything on
    // the prior line, and it should be truncated.  Do this even if 'ai' is not
    // set because automatically inserting a comment leader also sets did_ai.
    if (dir == FORWARD && did_ai) {
      trunc_line = true;
    }
  
    // If 'autoindent' and/or 'smartindent' is set, try to figure out what
    // indent to use for the new line.
    if (curbuf->b_p_ai
        || do_si) {
      // count white space on current line
      newindent = get_indent_str_vtab(saved_line,
                                      curbuf->b_p_ts,
                                      curbuf->b_p_vts_array, false);
      if (newindent == 0 && !(flags & OPENLINE_COM_LIST)) {
        newindent = second_line_indent;  // for ^^D command in insert mode
      }
  
      // Do smart indenting.
      // In insert/replace mode (only when dir == FORWARD)
      // we may move some text to the next line. If it starts with '{'
      // don't add an indent. Fixes inserting a NL before '{' in line
      //   "if (condition) {"
      if (!trunc_line && do_si && *saved_line != NUL
          && (p_extra == NULL || first_char != '{')) {
        char_u *ptr;
  
        old_cursor = curwin->w_cursor;
        ptr = saved_line;
        if (flags & OPENLINE_DO_COM) {
          lead_len = get_leader_len(ptr, NULL, false, true);
        } else {
          lead_len = 0;
        }
        if (dir == FORWARD) {
          // Skip preprocessor directives, unless they are recognised as comments.
          if (lead_len == 0 && ptr[0] == '#') {
            while (ptr[0] == '#' && curwin->w_cursor.lnum > 1) {
              ptr = ml_get(--curwin->w_cursor.lnum);
            }
            newindent = get_indent();
          }
          if (flags & OPENLINE_DO_COM) {
            lead_len = get_leader_len(ptr, NULL, false, true);
          } else {
            lead_len = 0;
          }
          if (lead_len > 0) {
            // This case gets the following right:
            //     \*
            //      * A comment (read '\' as '/').
            //      */
            //     #define IN_THE_WAY
            //     This should line up here;
            p = skipwhite(ptr);
            if (p[0] == '/' && p[1] == '*') {
              p++;
            }
            if (p[0] == '*') {
              for (p++; *p; p++) {
                if (p[0] == '/' && p[-1] == '*') {
                  // End of C comment, indent should line up
                  // with the line containing the start of
                  // the comment
                  curwin->w_cursor.col = (colnr_T)(p - ptr);
                  if ((pos = findmatch(NULL, NUL)) != NULL) {
                    curwin->w_cursor.lnum = pos->lnum;
                    newindent = get_indent();
                  }
                }
              }
            }
          } else {      // Not a comment line
            // Find last non-blank in line
            p = ptr + STRLEN(ptr) - 1;
            while (p > ptr && ascii_iswhite(*p)) {
              p--;
            }
            char_u last_char = *p;
  
            // find the character just before the '{' or ';'
            if (last_char == '{' || last_char == ';') {
              if (p > ptr) {
                p--;
              }
              while (p > ptr && ascii_iswhite(*p)) {
                p--;
              }
            }
            // Try to catch lines that are split over multiple
            // lines.  eg:
            //     if (condition &&
            //             condition) {
            //         Should line up here!
            //     }
            if (*p == ')') {
              curwin->w_cursor.col = (colnr_T)(p - ptr);
              if ((pos = findmatch(NULL, '(')) != NULL) {
                curwin->w_cursor.lnum = pos->lnum;
                newindent = get_indent();
                ptr = get_cursor_line_ptr();
              }
            }
            // If last character is '{' do indent, without
            // checking for "if" and the like.
            if (last_char == '{') {
              did_si = true;              // do indent
              no_si = true;               // don't delete it when '{' typed
              // Look for "if" and the like, use 'cinwords'.
              // Don't do this if the previous line ended in ';' or
              // '}'.
            } else if (last_char != ';' && last_char != '}'
                       && cin_is_cinword(ptr)) {
              did_si = true;
            }
          }
        } else {  // dir == BACKWARD
          // Skip preprocessor directives, unless they are
          // recognised as comments.
          if (lead_len == 0 && ptr[0] == '#') {
            bool was_backslashed = false;
  
            while ((ptr[0] == '#' || was_backslashed)
                   && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
              if (*ptr && ptr[STRLEN(ptr) - 1] == '\\') {
                was_backslashed = true;
              } else {
                was_backslashed = false;
              }
              ptr = ml_get(++curwin->w_cursor.lnum);
            }
            if (was_backslashed) {
              newindent = 0;  // Got to end of file
            } else {
              newindent = get_indent();
            }
          }
          p = skipwhite(ptr);
          if (*p == '}') {            // if line starts with '}': do indent
            did_si = true;
          } else {                    // can delete indent when '{' typed
            can_si_back = true;
          }
        }
        curwin->w_cursor = old_cursor;
      }
      if (do_si) {
        can_si = true;
      }
  
      did_ai = true;
    }
  
    // May do indenting after opening a new line.
    do_cindent = !p_paste && (curbuf->b_p_cin || *curbuf->b_p_inde != NUL)
                 && in_cinkeys(dir == FORWARD ? KEY_OPEN_FORW : KEY_OPEN_BACK,
                               ' ', linewhite(curwin->w_cursor.lnum));
  
    // Find out if the current line starts with a comment leader.
    // This may then be inserted in front of the new line.
    end_comment_pending = NUL;
    if (flags & OPENLINE_DO_COM) {
      lead_len = get_leader_len(saved_line, &lead_flags, dir == BACKWARD, true);
      if (lead_len == 0 && do_cindent && dir == FORWARD) {
        // Check for a line comment after code.
        comment_start = check_linecomment(saved_line);
        if (comment_start != MAXCOL) {
          lead_len = get_leader_len(saved_line + comment_start,
                                    &lead_flags, false, true);
          if (lead_len != 0) {
            lead_len += comment_start;
            if (did_do_comment != NULL) {
              *did_do_comment = true;
            }
          }
        }
      }
    } else {
      lead_len = 0;
    }
    if (lead_len > 0) {
      char_u *lead_repl = NULL;              // replaces comment leader
      int lead_repl_len = 0;                  // length of *lead_repl
      char_u lead_middle[COM_MAX_LEN];        // middle-comment string
      char_u lead_end[COM_MAX_LEN];           // end-comment string
      char_u *comment_end = NULL;            // where lead_end has been found
      int extra_space = false;                // append extra space
      int current_flag;
      int require_blank = false;              // requires blank after middle
      char_u *p2;
  
      // If the comment leader has the start, middle or end flag, it may not
      // be used or may be replaced with the middle leader.
      for (p = lead_flags; *p && *p != ':'; p++) {
        if (*p == COM_BLANK) {
          require_blank = true;
          continue;
        }
        if (*p == COM_START || *p == COM_MIDDLE) {
          current_flag = *p;
          if (*p == COM_START) {
            // Doing "O" on a start of comment does not insert leader.
            if (dir == BACKWARD) {
              lead_len = 0;
              break;
            }
  
            // find start of middle part
            (void)copy_option_part(&p, lead_middle, COM_MAX_LEN, ",");
            require_blank = false;
          }
  
          // Isolate the strings of the middle and end leader.
          while (*p && p[-1] != ':') {  // find end of middle flags
            if (*p == COM_BLANK) {
              require_blank = true;
            }
            p++;
          }
          (void)copy_option_part(&p, lead_middle, COM_MAX_LEN, ",");
  
          while (*p && p[-1] != ':') {  // find end of end flags
            // Check whether we allow automatic ending of comments
            if (*p == COM_AUTO_END) {
              end_comment_pending = -1;  // means we want to set it
            }
            p++;
          }
          size_t n = copy_option_part(&p, lead_end, COM_MAX_LEN, ",");
  
          if (end_comment_pending == -1) {  // we can set it now
            end_comment_pending = lead_end[n - 1];
          }
  
          // If the end of the comment is in the same line, don't use
          // the comment leader.
          if (dir == FORWARD) {
            for (p = saved_line + lead_len; *p; p++) {
              if (STRNCMP(p, lead_end, n) == 0) {
                comment_end = p;
                lead_len = 0;
                break;
              }
            }
          }
  
          // Doing "o" on a start of comment inserts the middle leader.
          if (lead_len > 0) {
            if (current_flag == COM_START) {
              lead_repl = lead_middle;
              lead_repl_len = (int)STRLEN(lead_middle);
            }
  
            // If we have hit RETURN immediately after the start
            // comment leader, then put a space after the middle
            // comment leader on the next line.
            if (!ascii_iswhite(saved_line[lead_len - 1])
                && ((p_extra != NULL
                     && (int)curwin->w_cursor.col == lead_len)
                    || (p_extra == NULL
                        && saved_line[lead_len] == NUL)
                    || require_blank)) {
              extra_space = true;
            }
          }
          break;
        }
        if (*p == COM_END) {
          // Doing "o" on the end of a comment does not insert leader.
          // Remember where the end is, might want to use it to find the
          // start (for C-comments).
          if (dir == FORWARD) {
            comment_end = skipwhite(saved_line);
            lead_len = 0;
            break;
          }
  
          // Doing "O" on the end of a comment inserts the middle leader.
          // Find the string for the middle leader, searching backwards.
          while (p > curbuf->b_p_com && *p != ',') {
            p--;
          }
          for (lead_repl = p; lead_repl > curbuf->b_p_com
               && lead_repl[-1] != ':'; lead_repl--) {
          }
          lead_repl_len = (int)(p - lead_repl);
  
          // We can probably always add an extra space when doing "O" on
          // the comment-end
          extra_space = true;
  
          // Check whether we allow automatic ending of comments
          for (p2 = p; *p2 && *p2 != ':'; p2++) {
            if (*p2 == COM_AUTO_END) {
              end_comment_pending = -1;  // means we want to set it
            }
          }
          if (end_comment_pending == -1) {
            // Find last character in end-comment string
            while (*p2 && *p2 != ',') {
              p2++;
            }
            end_comment_pending = p2[-1];
          }
          break;
        }
        if (*p == COM_FIRST) {
          // Comment leader for first line only: Don't repeat leader
          // when using "O", blank out leader when using "o".
          if (dir == BACKWARD) {
            lead_len = 0;
          } else {
            lead_repl = (char_u *)"";
            lead_repl_len = 0;
          }
          break;
        }
      }
      if (lead_len > 0) {
        // allocate buffer (may concatenate p_extra later)
        int bytes = lead_len
                    + lead_repl_len
                    + extra_space
                    + extra_len
                    + (second_line_indent > 0 ? second_line_indent : 0)
                    + 1;
        assert(bytes >= 0);
        leader = xmalloc((size_t)bytes);
        allocated = leader;  // remember to free it later
  
        STRLCPY(leader, saved_line, lead_len + 1);
  
        // TODO(vim): handle multi-byte and double width chars
        for (int li = 0; li < comment_start; li++) {
          if (!ascii_iswhite(leader[li])) {
            leader[li] = ' ';
          }
        }
  
        // Replace leader with lead_repl, right or left adjusted
        if (lead_repl != NULL) {
          int c = 0;
          int off = 0;
  
          for (p = lead_flags; *p != NUL && *p != ':';) {
            if (*p == COM_RIGHT || *p == COM_LEFT) {
              c = *p++;
            } else if (ascii_isdigit(*p) || *p == '-') {
              off = getdigits_int(&p, true, 0);
            } else {
              p++;
            }
          }
          if (c == COM_RIGHT) {  // right adjusted leader
            // find last non-white in the leader to line up with
            for (p = leader + lead_len - 1; p > leader
                 && ascii_iswhite(*p); p--) {
            }
            p++;
  
            // Compute the length of the replaced characters in
            // screen characters, not bytes.
            {
              int repl_size = vim_strnsize(lead_repl,
                                           lead_repl_len);
              int old_size = 0;
              char_u *endp = p;
              int l;
  
              while (old_size < repl_size && p > leader) {
                MB_PTR_BACK(leader, p);
                old_size += ptr2cells(p);
              }
              l = lead_repl_len - (int)(endp - p);
              if (l != 0) {
                memmove(endp + l, endp,
                        (size_t)((leader + lead_len) - endp));
              }
              lead_len += l;
            }
            memmove(p, lead_repl, (size_t)lead_repl_len);
            if (p + lead_repl_len > leader + lead_len) {
              p[lead_repl_len] = NUL;
            }
  
            // blank-out any other chars from the old leader.
            while (--p >= leader) {
              int l = utf_head_off(leader, p);
  
              if (l > 1) {
                p -= l;
                if (ptr2cells(p) > 1) {
                  p[1] = ' ';
                  l--;
                }
                memmove(p + 1, p + l + 1,
                        (size_t)((leader + lead_len) - (p + l + 1)));
                lead_len -= l;
                *p = ' ';
              } else if (!ascii_iswhite(*p)) {
                *p = ' ';
              }
            }
          } else {  // left adjusted leader
            p = skipwhite(leader);
            // Compute the length of the replaced characters in
            // screen characters, not bytes. Move the part that is
            // not to be overwritten.
            {
              int repl_size = vim_strnsize(lead_repl,
                                           lead_repl_len);
              int i;
              int l;
  
              for (i = 0; i < lead_len && p[i] != NUL; i += l) {
                l = utfc_ptr2len(p + i);
                if (vim_strnsize(p, i + l) > repl_size) {
                  break;
                }
              }
              if (i != lead_repl_len) {
                memmove(p + lead_repl_len, p + i,
                        (size_t)(lead_len - i - (p - leader)));
                lead_len += lead_repl_len - i;
              }
            }
            memmove(p, lead_repl, (size_t)lead_repl_len);
  
            // Replace any remaining non-white chars in the old
            // leader by spaces.  Keep Tabs, the indent must
            // remain the same.
            for (p += lead_repl_len; p < leader + lead_len; p++) {
              if (!ascii_iswhite(*p)) {
                // Don't put a space before a TAB.
                if (p + 1 < leader + lead_len && p[1] == TAB) {
                  lead_len--;
                  memmove(p, p + 1, (size_t)(leader + lead_len - p));
                } else {
                  int l = utfc_ptr2len(p);
  
                  if (l > 1) {
                    if (ptr2cells(p) > 1) {
                      // Replace a double-wide char with
                      // two spaces
                      l--;
                      *p++ = ' ';
                    }
                    memmove(p + 1, p + l, (size_t)(leader + lead_len - p));
                    lead_len -= l - 1;
                  }
                  *p = ' ';
                }
              }
            }
            *p = NUL;
          }
  
          // Recompute the indent, it may have changed.
          if (curbuf->b_p_ai
              || do_si) {
            newindent = get_indent_str_vtab(leader,
                                            curbuf->b_p_ts,
                                            curbuf->b_p_vts_array, false);
          }
  
          // Add the indent offset
          if (newindent + off < 0) {
            off = -newindent;
            newindent = 0;
          } else {
            newindent += off;
          }
  
          // Correct trailing spaces for the shift, so that
          // alignment remains equal.
          while (off > 0 && lead_len > 0
                 && leader[lead_len - 1] == ' ') {
            // Don't do it when there is a tab before the space
            if (vim_strchr(skipwhite(leader), '\t') != NULL) {
              break;
            }
            lead_len--;
            off--;
          }
  
          // If the leader ends in white space, don't add an
          // extra space
          if (lead_len > 0 && ascii_iswhite(leader[lead_len - 1])) {
            extra_space = false;
          }
          leader[lead_len] = NUL;
        }
  
        if (extra_space) {
          leader[lead_len++] = ' ';
          leader[lead_len] = NUL;
        }
  
        newcol = lead_len;
  
        // if a new indent will be set below, remove the indent that
        // is in the comment leader
        if (newindent
            || did_si) {
          while (lead_len && ascii_iswhite(*leader)) {
            lead_len--;
            newcol--;
            leader++;
          }
        }
  
        did_si = can_si = false;
      } else if (comment_end != NULL) {
        // We have finished a comment, so we don't use the leader.
        // If this was a C-comment and 'ai' or 'si' is set do a normal
        // indent to align with the line containing the start of the
        // comment.
        if (comment_end[0] == '*' && comment_end[1] == '/'
            && (curbuf->b_p_ai || do_si)) {
          old_cursor = curwin->w_cursor;
          curwin->w_cursor.col = (colnr_T)(comment_end - saved_line);
          if ((pos = findmatch(NULL, NUL)) != NULL) {
            curwin->w_cursor.lnum = pos->lnum;
            newindent = get_indent();
          }
          curwin->w_cursor = old_cursor;
        }
      }
    }
  
    // (State == INSERT || State == REPLACE), only when dir == FORWARD
    if (p_extra != NULL) {
      *p_extra = saved_char;              // restore char that NUL replaced
  
      // When 'ai' set or "flags" has OPENLINE_DELSPACES, skip to the first
      // non-blank.
      //
      // When in REPLACE mode, put the deleted blanks on the replace stack,
      // preceded by a NUL, so they can be put back when a BS is entered.
      if (REPLACE_NORMAL(State)) {
        replace_push(NUL);            // end of extra blanks
      }
      if (curbuf->b_p_ai || (flags & OPENLINE_DELSPACES)) {
        while ((*p_extra == ' ' || *p_extra == '\t')
               && !utf_iscomposing(utf_ptr2char(p_extra + 1))) {
          if (REPLACE_NORMAL(State)) {
            replace_push(*p_extra);
          }
          p_extra++;
          less_cols_off++;
        }
      }
  
      // columns for marks adjusted for removed columns
      less_cols = (int)(p_extra - saved_line);
    }
  
    if (p_extra == NULL) {
      p_extra = (char_u *)"";                 // append empty line
    }
  
    // concatenate leader and p_extra, if there is a leader
    if (lead_len > 0) {
      if (flags & OPENLINE_COM_LIST && second_line_indent > 0) {
        int i;
        int padding = second_line_indent
                      - (newindent + (int)STRLEN(leader));
  
        // Here whitespace is inserted after the comment char.
        // Below, set_indent(newindent, SIN_INSERT) will insert the
        // whitespace needed before the comment char.
        for (i = 0; i < padding; i++) {
          STRCAT(leader, " ");
          less_cols--;
          newcol++;
        }
      }
      STRCAT(leader, p_extra);
      p_extra = leader;
      did_ai = true;          // So truncating blanks works with comments
      less_cols -= lead_len;
    } else {
      end_comment_pending = NUL;  // turns out there was no leader
    }
  
    curbuf_splice_pending++;
    old_cursor = curwin->w_cursor;
    if (dir == BACKWARD) {
      curwin->w_cursor.lnum--;
    }
    if (!(State & VREPLACE_FLAG) || old_cursor.lnum >= orig_line_count) {
      if (ml_append(curwin->w_cursor.lnum, p_extra, (colnr_T)0, false) == FAIL) {
        goto theend;
      }
      // Postpone calling changed_lines(), because it would mess up folding
      // with markers.
      // Skip mark_adjust when adding a line after the last one, there can't
      // be marks there. But still needed in diff mode.
      if (curwin->w_cursor.lnum + 1 < curbuf->b_ml.ml_line_count
          || curwin->w_p_diff) {
        mark_adjust(curwin->w_cursor.lnum + 1, (linenr_T)MAXLNUM, 1L, 0L,
                    kExtmarkNOOP);
      }
      did_append = true;
    } else {
      // In VREPLACE mode we are starting to replace the next line.
      curwin->w_cursor.lnum++;
      if (curwin->w_cursor.lnum >= Insstart.lnum + vr_lines_changed) {
        // In case we NL to a new line, BS to the previous one, and NL
        // again, we don't want to save the new line for undo twice.
        (void)u_save_cursor();  // errors are ignored!
        vr_lines_changed++;
      }
      ml_replace(curwin->w_cursor.lnum, p_extra, true);
      changed_bytes(curwin->w_cursor.lnum, 0);
      // TODO(vigoux): extmark_splice_cols here??
      curwin->w_cursor.lnum--;
      did_append = false;
    }
  
    inhibit_delete_count++;
    if (newindent
        || did_si) {
      curwin->w_cursor.lnum++;
      if (did_si) {
        int sw = get_sw_value(curbuf);
  
        if (p_sr) {
          newindent -= newindent % sw;
        }
        newindent += sw;
      }
      // Copy the indent
      if (curbuf->b_p_ci) {
        (void)copy_indent(newindent, saved_line);
  
        // Set the 'preserveindent' option so that any further screwing
        // with the line doesn't entirely destroy our efforts to preserve
        // it.  It gets restored at the function end.
        curbuf->b_p_pi = true;
      } else {
        (void)set_indent(newindent, SIN_INSERT|SIN_NOMARK);
      }
      less_cols -= curwin->w_cursor.col;
  
      ai_col = curwin->w_cursor.col;
  
      // In REPLACE mode, for each character in the new indent, there must
      // be a NUL on the replace stack, for when it is deleted with BS
      if (REPLACE_NORMAL(State)) {
        for (colnr_T n = 0; n < curwin->w_cursor.col; n++) {
          replace_push(NUL);
        }
      }
      newcol += curwin->w_cursor.col;
      if (no_si) {
        did_si = false;
      }
    }
    inhibit_delete_count--;
  
    // In REPLACE mode, for each character in the extra leader, there must be
    // a NUL on the replace stack, for when it is deleted with BS.
    if (REPLACE_NORMAL(State)) {
      while (lead_len-- > 0) {
        replace_push(NUL);
      }
    }
  
    curwin->w_cursor = old_cursor;
  
    if (dir == FORWARD) {
      if (trunc_line || (State & INSERT)) {
        // truncate current line at cursor
        saved_line[curwin->w_cursor.col] = NUL;
        // Remove trailing white space, unless OPENLINE_KEEPTRAIL used.
        if (trunc_line && !(flags & OPENLINE_KEEPTRAIL)) {
          truncate_spaces(saved_line);
        }
        ml_replace(curwin->w_cursor.lnum, saved_line, false);
  
        int new_len = (int)STRLEN(saved_line);
  
        // TODO(vigoux): maybe there is issues there with expandtabs ?
        int cols_spliced = 0;
        if (new_len < curwin->w_cursor.col) {
          extmark_splice_cols(curbuf, (int)curwin->w_cursor.lnum - 1,
                              new_len, curwin->w_cursor.col - new_len, 0, kExtmarkUndo);
          cols_spliced = curwin->w_cursor.col - new_len;
        }
  
        saved_line = NULL;
        if (did_append) {
          changed_lines(curwin->w_cursor.lnum, curwin->w_cursor.col,
                        curwin->w_cursor.lnum + 1, 1L, true);
          did_append = false;
  
          // Move marks after the line break to the new line.
          if (flags & OPENLINE_MARKFIX) {
            mark_col_adjust(curwin->w_cursor.lnum,
                            curwin->w_cursor.col + less_cols_off,
                            1L, (long)-less_cols, 0);
          }
          // Always move extmarks - Here we move only the line where the
          // cursor is, the previous mark_adjust takes care of the lines after
          int cols_added = mincol-1+less_cols_off-less_cols;
          extmark_splice(curbuf, (int)lnum-1, mincol-1 - cols_spliced,
                         0, less_cols_off, less_cols_off,
                         1, cols_added, 1 + cols_added, kExtmarkUndo);
        } else {
          changed_bytes(curwin->w_cursor.lnum, curwin->w_cursor.col);
        }
      }
  
      // Put the cursor on the new line.  Careful: the scrollup() above may
      // have moved w_cursor, we must use old_cursor.
      curwin->w_cursor.lnum = old_cursor.lnum + 1;
    }
    if (did_append) {
      changed_lines(curwin->w_cursor.lnum, 0, curwin->w_cursor.lnum, 1L, true);
      // bail out and just get the final length of the line we just manipulated
      bcount_t extra = (bcount_t)STRLEN(ml_get(curwin->w_cursor.lnum));
      extmark_splice(curbuf, (int)curwin->w_cursor.lnum-1, 0,
                     0, 0, 0, 1, 0, 1+extra, kExtmarkUndo);
    }
    curbuf_splice_pending--;
  
    curwin->w_cursor.col = newcol;
    curwin->w_cursor.coladd = 0;
  
    // In VREPLACE mode, we are handling the replace stack ourselves, so stop
    // fixthisline() from doing it (via change_indent()) by telling it we're in
    // normal INSERT mode.
    if (State & VREPLACE_FLAG) {
      vreplace_mode = State;  // So we know to put things right later
      State = INSERT;
    } else {
      vreplace_mode = 0;
    }
    // May do lisp indenting.
    if (!p_paste
        && leader == NULL
        && curbuf->b_p_lisp
        && curbuf->b_p_ai) {
      fixthisline(get_lisp_indent);
      ai_col = (colnr_T)getwhitecols_curline();
    }
    // May do indenting after opening a new line.
    if (do_cindent) {
      do_c_expr_indent();
      ai_col = (colnr_T)getwhitecols_curline();
    }
    if (vreplace_mode != 0) {
      State = vreplace_mode;
    }
  
    // Finally, VREPLACE gets the stuff on the new line, then puts back the
    // original line, and inserts the new stuff char by char, pushing old stuff
    // onto the replace stack (via ins_char()).
    if (State & VREPLACE_FLAG) {
      // Put new line in p_extra
      p_extra = vim_strsave(get_cursor_line_ptr());
  
      // Put back original line
      ml_replace(curwin->w_cursor.lnum, next_line, false);
  
      // Insert new stuff into line again
      curwin->w_cursor.col = 0;
      curwin->w_cursor.coladd = 0;
      ins_bytes(p_extra);         // will call changed_bytes()
      xfree(p_extra);
      next_line = NULL;
    }
  
    retval = true;                // success!
  theend:
    curbuf->b_p_pi = saved_pi;
    xfree(saved_line);
    xfree(next_line);
    xfree(allocated);
    return retval;
  }  // NOLINT(readability/fn_size)
  
  /// Delete from cursor to end of line.
  /// Caller must have prepared for undo.
  /// If "fixpos" is true fix the cursor position when done.
  void truncate_line(int fixpos)
  {
    char_u *newp;
    linenr_T lnum = curwin->w_cursor.lnum;
    colnr_T col = curwin->w_cursor.col;
  
    if (col == 0) {
      newp = vim_strsave((char_u *)"");
    } else {
      newp = vim_strnsave(ml_get(lnum), (size_t)col);
    }
    ml_replace(lnum, newp, false);
  
    // mark the buffer as changed and prepare for displaying
    changed_bytes(lnum, curwin->w_cursor.col);
  
    // If "fixpos" is true we don't want to end up positioned at the NUL.
    if (fixpos && curwin->w_cursor.col > 0) {
      curwin->w_cursor.col--;
    }
  }
  
  /// Delete "nlines" lines at the cursor.
  /// Saves the lines for undo first if "undo" is true.
  void del_lines(long nlines, bool undo)
  {
    long n;
    linenr_T first = curwin->w_cursor.lnum;
  
    if (nlines <= 0) {
      return;
    }
  
    // save the deleted lines for undo
    if (undo && u_savedel(first, nlines) == FAIL) {
      return;
    }
  
    for (n = 0; n < nlines;) {
      if (curbuf->b_ml.ml_flags & ML_EMPTY) {  // nothing to delete
        break;
      }
  
      ml_delete(first, true);
      n++;
  
      // If we delete the last line in the file, stop
      if (first > curbuf->b_ml.ml_line_count) {
        break;
      }
    }
  
    // Correct the cursor position before calling deleted_lines_mark(), it may
    // trigger a callback to display the cursor.
    curwin->w_cursor.col = 0;
    check_cursor_lnum();
  
    // adjust marks, mark the buffer as changed and prepare for displaying
    deleted_lines_mark(first, n);
  }
  
  /// Returns the length in bytes of the prefix of the given string which introduces a comment.
  ///
  /// If this string is not a comment then 0 is returned.
  /// When "flags" is not NULL, it is set to point to the flags of the recognized comment leader.
  /// "backward" must be true for the "O" command.
  /// If "include_space" is set, include trailing whitespace while calculating the length.
  int get_leader_len(char_u *line, char_u **flags, bool backward, bool include_space)
  {
    int j;
    int got_com = false;
    char_u part_buf[COM_MAX_LEN];         // buffer for one option part
    char_u *string;                  // pointer to comment string
    char_u *list;
    int middle_match_len = 0;
    char_u *prev_list;
    char_u *saved_flags = NULL;
  
    int result = 0;
    int i = 0;
    while (ascii_iswhite(line[i])) {  // leading white space is ignored
      i++;
    }
  
    // Repeat to match several nested comment strings.
    while (line[i] != NUL) {
      // scan through the 'comments' option for a match
      int found_one = false;
      for (list = curbuf->b_p_com; *list;) {
        // Get one option part into part_buf[].  Advance "list" to next
        // one.  Put "string" at start of string.
        if (!got_com && flags != NULL) {
          *flags = list;              // remember where flags started
        }
        prev_list = list;
        (void)copy_option_part(&list, part_buf, COM_MAX_LEN, ",");
        string = vim_strchr(part_buf, ':');
        if (string == NULL) {         // missing ':', ignore this part
          continue;
        }
        *string++ = NUL;              // isolate flags from string
  
        // If we found a middle match previously, use that match when this
        // is not a middle or end.
        if (middle_match_len != 0
            && vim_strchr(part_buf, COM_MIDDLE) == NULL
            && vim_strchr(part_buf, COM_END) == NULL) {
          break;
        }
  
        // When we already found a nested comment, only accept further
        // nested comments.
        if (got_com && vim_strchr(part_buf, COM_NEST) == NULL) {
          continue;
        }
  
        // When 'O' flag present and using "O" command skip this one.
        if (backward && vim_strchr(part_buf, COM_NOBACK) != NULL) {
          continue;
        }
  
        // Line contents and string must match.
        // When string starts with white space, must have some white space
        // (but the amount does not need to match, there might be a mix of
        // TABs and spaces).
        if (ascii_iswhite(string[0])) {
          if (i == 0 || !ascii_iswhite(line[i - 1])) {
            continue;            // missing white space
          }
          while (ascii_iswhite(string[0])) {
            string++;
          }
        }
        for (j = 0; string[j] != NUL && string[j] == line[i + j]; j++) {
        }
        if (string[j] != NUL) {
          continue;          // string doesn't match
        }
        // When 'b' flag used, there must be white space or an
        // end-of-line after the string in the line.
        if (vim_strchr(part_buf, COM_BLANK) != NULL
            && !ascii_iswhite(line[i + j]) && line[i + j] != NUL) {
          continue;
        }
  
        // We have found a match, stop searching unless this is a middle
        // comment. The middle comment can be a substring of the end
        // comment in which case it's better to return the length of the
        // end comment and its flags.  Thus we keep searching with middle
        // and end matches and use an end match if it matches better.
        if (vim_strchr(part_buf, COM_MIDDLE) != NULL) {
          if (middle_match_len == 0) {
            middle_match_len = j;
            saved_flags = prev_list;
          }
          continue;
        }
        if (middle_match_len != 0 && j > middle_match_len) {
          // Use this match instead of the middle match, since it's a
          // longer thus better match.
          middle_match_len = 0;
        }
  
        if (middle_match_len == 0) {
          i += j;
        }
        found_one = true;
        break;
      }
  
      if (middle_match_len != 0) {
        // Use the previously found middle match after failing to find a
        // match with an end.
        if (!got_com && flags != NULL) {
          *flags = saved_flags;
        }
        i += middle_match_len;
        found_one = true;
      }
  
      // No match found, stop scanning.
      if (!found_one) {
        break;
      }
  
      result = i;
  
      // Include any trailing white space.
      while (ascii_iswhite(line[i])) {
        i++;
      }
  
      if (include_space) {
        result = i;
      }
  
      // If this comment doesn't nest, stop here.
      got_com = true;
      if (vim_strchr(part_buf, COM_NEST) == NULL) {
        break;
      }
    }
    return result;
  }
  
  /// Return the offset at which the last comment in line starts. If there is no
  /// comment in the whole line, -1 is returned.
  ///
  /// When "flags" is not null, it is set to point to the flags describing the
  /// recognized comment leader.
  int get_last_leader_offset(char_u *line, char_u **flags)
  {
    int result = -1;
    int j;
    int lower_check_bound = 0;
    char_u *string;
    char_u *com_leader;
    char_u *com_flags;
    char_u *list;
    char_u part_buf[COM_MAX_LEN];         // buffer for one option part
  
    // Repeat to match several nested comment strings.
    int i = (int)STRLEN(line);
    while (--i >= lower_check_bound) {
      // scan through the 'comments' option for a match
      int found_one = false;
      for (list = curbuf->b_p_com; *list;) {
        char_u *flags_save = list;
  
        // Get one option part into part_buf[].  Advance list to next one.
        // put string at start of string.
        (void)copy_option_part(&list, part_buf, COM_MAX_LEN, ",");
        string = vim_strchr(part_buf, ':');
        if (string == NULL) {  // If everything is fine, this cannot actually
                               // happen.
          continue;
        }
        *string++ = NUL;          // Isolate flags from string.
        com_leader = string;
  
        // Line contents and string must match.
        // When string starts with white space, must have some white space
        // (but the amount does not need to match, there might be a mix of
        // TABs and spaces).
        if (ascii_iswhite(string[0])) {
          if (i == 0 || !ascii_iswhite(line[i - 1])) {
            continue;
          }
          while (ascii_iswhite(*string)) {
            string++;
          }
        }
        for (j = 0; string[j] != NUL && string[j] == line[i + j]; j++) {
          // do nothing
        }
        if (string[j] != NUL) {
          continue;
        }
  
        // When 'b' flag used, there must be white space or an
        // end-of-line after the string in the line.
        if (vim_strchr(part_buf, COM_BLANK) != NULL
            && !ascii_iswhite(line[i + j]) && line[i + j] != NUL) {
          continue;
        }
  
        if (vim_strchr(part_buf, COM_MIDDLE) != NULL) {
          // For a middlepart comment, only consider it to match if
          // everything before the current position in the line is
          // whitespace.  Otherwise we would think we are inside a
          // comment if the middle part appears somewhere in the middle
          // of the line.  E.g. for C the "*" appears often.
          for (j = 0; j <= i && ascii_iswhite(line[j]); j++) {
          }
          if (j < i) {
            continue;
          }
        }
  
        // We have found a match, stop searching.
        found_one = true;
  
        if (flags) {
          *flags = flags_save;
        }
        com_flags = flags_save;
  
        break;
      }
  
      if (found_one) {
        char_u part_buf2[COM_MAX_LEN];            // buffer for one option part
        int len1, len2, off;
  
        result = i;
        // If this comment nests, continue searching.
        if (vim_strchr(part_buf, COM_NEST) != NULL) {
          continue;
        }
  
        lower_check_bound = i;
  
        // Let's verify whether the comment leader found is a substring
        // of other comment leaders. If it is, let's adjust the
        // lower_check_bound so that we make sure that we have determined
        // the comment leader correctly.
  
        while (ascii_iswhite(*com_leader)) {
          com_leader++;
        }
        len1 = (int)STRLEN(com_leader);
  
        for (list = curbuf->b_p_com; *list;) {
          char_u *flags_save = list;
  
          (void)copy_option_part(&list, part_buf2, COM_MAX_LEN, ",");
          if (flags_save == com_flags) {
            continue;
          }
          string = vim_strchr(part_buf2, ':');
          string++;
          while (ascii_iswhite(*string)) {
            string++;
          }
          len2 = (int)STRLEN(string);
          if (len2 == 0) {
            continue;
          }
  
          // Now we have to verify whether string ends with a substring
          // beginning the com_leader.
          for (off = (len2 > i ? i : len2); off > 0 && off + len1 > len2;) {
            off--;
            if (!STRNCMP(string + off, com_leader, len2 - off)) {
              if (i - off < lower_check_bound) {
                lower_check_bound = i - off;
              }
            }
          }
        }
      }
    }
    return result;
  }
  