text: /* NetHack 3.7	spell.c	$NHDT-Date: 1611522041 2021/01/24 21:00:41 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.113 $ */
  /*      Copyright (c) M. Stephenson 1988                          */
  /* NetHack may be freely redistributed.  See license for details. */
  
  #include "hack.h"
  
  /* spellmenu arguments; 0 thru n-1 used as g.spl_book[] index when swapping */
  #define SPELLMENU_CAST (-2)
  #define SPELLMENU_VIEW (-1)
  #define SPELLMENU_SORT (MAXSPELL) /* special menu entry */
  
  /* spell retention period, in turns; at 10% of this value, player becomes
     eligible to reread the spellbook and regain 100% retention (the threshold
     used to be 1000 turns, which was 10% of the original 10000 turn retention
     period but didn't get adjusted when that period got doubled to 20000) */
  #define KEEN 20000
  /* x: need to add 1 when used for reading a spellbook rather than for hero
     initialization; spell memory is decremented at the end of each turn,
     including the turn on which the spellbook is read; without the extra
     increment, the hero used to get cheated out of 1 turn of retention */
  #define incrnknow(spell, x) (g.spl_book[spell].sp_know = KEEN + (x))
  
  #define spellev(spell) g.spl_book[spell].sp_lev
  #define spellname(spell) OBJ_NAME(objects[spellid(spell)])
  #define spellet(spell) \
      ((char) ((spell < 26) ? ('a' + spell) : ('A' + spell - 26)))
  
  static int spell_let_to_idx(char);
  static boolean cursed_book(struct obj * bp);
  static boolean confused_book(struct obj *);
  static void deadbook(struct obj *);
  static int learn(void);
  static boolean rejectcasting(void);
  static boolean getspell(int *);
  static int QSORTCALLBACK spell_cmp(const genericptr, const genericptr);
  static void sortspells(void);
  static boolean spellsortmenu(void);
  static boolean dospellmenu(const char *, int, int *);
  static int percent_success(int);
  static char *spellretention(int, char *);
  static int throwspell(void);
  static void cast_protection(void);
  static void spell_backfire(int);
  static const char *spelltypemnemonic(int);
  static boolean spell_aim_step(genericptr_t, int, int);
  
  /* The roles[] table lists the role-specific values for tuning
   * percent_success().
   *
   * Reasoning:
   *   spelbase, spelheal:
   *      Arc are aware of magic through historical research
   *      Bar abhor magic (Conan finds it "interferes with his animal instincts")
   *      Cav are ignorant to magic
   *      Hea are very aware of healing magic through medical research
   *      Kni are moderately aware of healing from Paladin training
   *      Mon use magic to attack and defend in lieu of weapons and armor
   *      Pri are very aware of healing magic through theological research
   *      Ran avoid magic, preferring to fight unseen and unheard
   *      Rog are moderately aware of magic through trickery
   *      Sam have limited magical awareness, preferring meditation to conjuring
   *      Tou are aware of magic from all the great films they have seen
   *      Val have limited magical awareness, preferring fighting
   *      Wiz are trained mages
   *
   *      The arms penalty is lessened for trained fighters Bar, Kni, Ran,
   *      Sam, Val -- the penalty is its metal interference, not encumbrance.
   *      The `spelspec' is a single spell which is fundamentally easier
   *      for that role to cast.
   *
   *  spelspec, spelsbon:
   *      Arc map masters (SPE_MAGIC_MAPPING)
   *      Bar fugue/berserker (SPE_HASTE_SELF)
   *      Cav born to dig (SPE_DIG)
   *      Hea to heal (SPE_CURE_SICKNESS)
   *      Kni to turn back evil (SPE_TURN_UNDEAD)
   *      Mon to preserve their abilities (SPE_RESTORE_ABILITY)
   *      Pri to bless (SPE_REMOVE_CURSE)
   *      Ran to hide (SPE_INVISIBILITY)
   *      Rog to find loot (SPE_DETECT_TREASURE)
   *      Sam to be At One (SPE_CLAIRVOYANCE)
   *      Tou to smile (SPE_CHARM_MONSTER)
   *      Val control the cold (SPE_CONE_OF_COLD)
   *      Wiz all really, but SPE_MAGIC_MISSILE is their party trick
   *
   *      See percent_success() below for more comments.
   *
   *  uarmbon, uarmsbon, uarmhbon, uarmgbon, uarmfbon:
   *      Fighters find body armour & shield a little less limiting.
   *      Headgear, Gauntlets and Footwear are not role-specific (but
   *      still have an effect, except helm of brilliance, which is designed
   *      to permit magic-use).
   */
  
  #define uarmhbon 4 /* Metal helmets interfere with the mind */
  #define uarmgbon 6 /* Casting channels through the hands */
  #define uarmfbon 2 /* All metal interferes to some degree */
  
  /* since the spellbook itself doesn't blow up, don't say just "explodes" */
  static const char explodes[] = "radiates explosive energy";
  
  /* convert a letter into a number in the range 0..51, or -1 if not a letter */
  static int
  spell_let_to_idx(char ilet)
  {
      int indx;
  
      indx = ilet - 'a';
      if (indx >= 0 && indx < 26)
          return indx;
      indx = ilet - 'A';
      if (indx >= 0 && indx < 26)
          return indx + 26;
      return -1;
  }
  
  /* TRUE: book should be destroyed by caller */
  static boolean
  cursed_book(struct obj* bp)
  {
      boolean was_in_use;
      int lev = objects[bp->otyp].oc_level;
      int dmg = 0;
  
      switch (rn2(lev)) {
      case 0:
          You_feel("a wrenching sensation.");
          tele(); /* teleport him */
          break;
      case 1:
          You_feel("threatened.");
          aggravate();
          break;
      case 2:
          make_blinded(Blinded + rn1(100, 250), TRUE);
          break;
      case 3:
          take_gold();
          break;
      case 4:
          pline("These runes were just too much to comprehend.");
          make_confused(HConfusion + rn1(7, 16), FALSE);
          break;
      case 5:
          pline_The("book was coated with contact poison!");
          if (uarmg) {
              erode_obj(uarmg, "gloves", ERODE_CORRODE, EF_GREASE | EF_VERBOSE);
              break;
          }
          /* temp disable in_use; death should not destroy the book */
          was_in_use = bp->in_use;
          bp->in_use = FALSE;
          losestr(Poison_resistance ? rn1(2, 1) : rn1(4, 3));
          losehp(rnd(Poison_resistance ? 6 : 10), "contact-poisoned spellbook",
                 KILLED_BY_AN);
          bp->in_use = was_in_use;
          break;
      case 6:
          if (Antimagic) {
              shieldeff(u.ux, u.uy);
              pline_The("book %s, but you are unharmed!", explodes);
          } else {
              pline("As you read the book, it %s in your %s!", explodes,
                    body_part(FACE));
              dmg = 2 * rnd(10) + 5;
              losehp(Maybe_Half_Phys(dmg), "exploding rune", KILLED_BY_AN);
          }
          return TRUE;
      default:
          rndcurse();
          break;
      }
      return FALSE;
  }
  
  /* study while confused: returns TRUE if the book is destroyed */
  static boolean
  confused_book(struct obj* spellbook)
  {
      boolean gone = FALSE;
  
      if (!rn2(3) && spellbook->otyp != SPE_BOOK_OF_THE_DEAD) {
          spellbook->in_use = TRUE; /* in case called from learn */
          pline(
           "Being confused you have difficulties in controlling your actions.");
          display_nhwindow(WIN_MESSAGE, FALSE);
          You("accidentally tear the spellbook to pieces.");
          if (!objects[spellbook->otyp].oc_name_known
              && !objects[spellbook->otyp].oc_uname)
              docall(spellbook);
          useup(spellbook);
          gone = TRUE;
      } else {
          You("find yourself reading the %s line over and over again.",
              spellbook == g.context.spbook.book ? "next" : "first");
      }
      return gone;
  }
  
  /* special effects for The Book of the Dead; reading it while blind is
     allowed so that needs to be taken into account too */
  static void
  deadbook(struct obj* book2)
  {
      struct monst *mtmp, *mtmp2;
      coord mm;
  
      You("turn the pages of the Book of the Dead...");
      makeknown(SPE_BOOK_OF_THE_DEAD);
      book2->dknown = 1; /* in case blind now and hasn't been seen yet */
      /* KMH -- Need ->known to avoid "_a_ Book of the Dead" */
      book2->known = 1;
      if (invocation_pos(u.ux, u.uy) && !On_stairs(u.ux, u.uy)) {
          register struct obj *otmp;
          register boolean arti1_primed = FALSE, arti2_primed = FALSE,
                           arti_cursed = FALSE;
  
          if (book2->cursed) {
              pline_The("%s!",
                        Blind ? "Book seems to be ignoring you"
                              : "runes appear scrambled.  You can't read them");
              return;
          }
  
          if (!u.uhave.bell || !u.uhave.menorah) {
              pline("A chill runs down your %s.", body_part(SPINE));
              if (!u.uhave.bell)
                  You_hear("a faint chime...");
              if (!u.uhave.menorah)
                  pline("Vlad's doppelganger is amused.");
              return;
          }
  
          for (otmp = g.invent; otmp; otmp = otmp->nobj) {
              if (otmp->otyp == CANDELABRUM_OF_INVOCATION && otmp->spe == 7
                  && otmp->lamplit) {
                  if (!otmp->cursed)
                      arti1_primed = TRUE;
                  else
                      arti_cursed = TRUE;
              }
              if (otmp->otyp == BELL_OF_OPENING
                  && (g.moves - otmp->age) < 5L) { /* you rang it recently */
                  if (!otmp->cursed)
                      arti2_primed = TRUE;
                  else
                      arti_cursed = TRUE;
              }
          }
  
          if (arti_cursed) {
              pline_The("invocation fails!");
              /* this used to say "your artifacts" but the invocation tools
                 are not artifacts */
              pline("At least one of your relics is cursed...");
          } else if (arti1_primed && arti2_primed) {
              unsigned soon =
                  (unsigned) d(2, 6); /* time til next intervene() */
  
              /* successful invocation */
              mkinvokearea();
              u.uevent.invoked = 1;
              record_achievement(ACH_INVK);
              /* in case you haven't killed the Wizard yet, behave as if
                 you just did */
              u.uevent.udemigod = 1; /* wizdead() */
              if (!u.udg_cnt || u.udg_cnt > soon)
                  u.udg_cnt = soon;
          } else { /* at least one relic not prepared properly */
              You("have a feeling that %s is amiss...", something);
              goto raise_dead;
          }
          return;
      }
  
      /* when not an invocation situation */
      if (book2->cursed) {
   raise_dead:
  
          You("raised the dead!");
          /* first maybe place a dangerous adversary */
          if (!rn2(3) && ((mtmp = makemon(&mons[PM_MASTER_LICH], u.ux, u.uy,
                                          NO_MINVENT)) != 0
                          || (mtmp = makemon(&mons[PM_NALFESHNEE], u.ux, u.uy,
                                             NO_MINVENT)) != 0)) {
              mtmp->mpeaceful = 0;
              set_malign(mtmp);
          }
          /* next handle the affect on things you're carrying */
          (void) unturn_dead(&g.youmonst);
          /* last place some monsters around you */
          mm.x = u.ux;
          mm.y = u.uy;
          mkundead(&mm, TRUE, NO_MINVENT);
      } else if (book2->blessed) {
          for (mtmp = fmon; mtmp; mtmp = mtmp2) {
              mtmp2 = mtmp->nmon; /* tamedog() changes chain */
              if (DEADMONSTER(mtmp))
                  continue;
  
              if ((is_undead(mtmp->data) || is_vampshifter(mtmp))
                  && cansee(mtmp->mx, mtmp->my)) {
                  mtmp->mpeaceful = TRUE;
                  if (sgn(mtmp->data->maligntyp) == sgn(u.ualign.type)
                      && distu(mtmp->mx, mtmp->my) < 4)
                      if (mtmp->mtame) {
                          if (mtmp->mtame < 20)
                              mtmp->mtame++;
                      } else
                          (void) tamedog(mtmp, (struct obj *) 0);
                  else
                      monflee(mtmp, 0, FALSE, TRUE);
              }
          }
      } else {
          switch (rn2(3)) {
          case 0:
              Your("ancestors are annoyed with you!");
              break;
          case 1:
              pline_The("headstones in the cemetery begin to move!");
              break;
          default:
              pline("Oh my!  Your name appears in the book!");
          }
      }
      return;
  }
  
  /* 'book' has just become cursed; if we're reading it, interrupt */
  void
  book_cursed(struct obj *book)
  {
      if (book->cursed && g.multi >= 0
          && g.occupation == learn && g.context.spbook.book == book) {
          pline("%s shut!", Tobjnam(book, "slam"));
          set_bknown(book, 1);
          stop_occupation();
      }
  }
  
  DISABLE_WARNING_FORMAT_NONLITERAL
  
  static int
  learn(void)
  {
      int i;
      short booktype;
      char splname[BUFSZ];
      boolean costly = TRUE;
      struct obj *book = g.context.spbook.book;
  
      /* JDS: lenses give 50% faster reading; 33% smaller read time */
      if (g.context.spbook.delay && ublindf && ublindf->otyp == LENSES && rn2(2))
          g.context.spbook.delay++;
      if (Confusion) { /* became confused while learning */
          (void) confused_book(book);
          g.context.spbook.book = 0; /* no longer studying */
          g.context.spbook.o_id = 0;
          nomul(g.context.spbook.delay); /* remaining delay is uninterrupted */
          g.multi_reason = "reading a book";
          g.nomovemsg = 0;
          g.context.spbook.delay = 0;
          return 0;
      }
      if (g.context.spbook.delay) {
          /* not if (g.context.spbook.delay++), so at end delay == 0 */
          g.context.spbook.delay++;
          return 1; /* still busy */
      }
      exercise(A_WIS, TRUE); /* you're studying. */
      booktype = book->otyp;
      if (booktype == SPE_BOOK_OF_THE_DEAD) {
          deadbook(book);
          return 0;
      }
  
      Sprintf(splname,
              objects[booktype].oc_name_known ? "\"%s\"" : "the \"%s\" spell",
              OBJ_NAME(objects[booktype]));
      for (i = 0; i < MAXSPELL; i++)
          if (spellid(i) == booktype || spellid(i) == NO_SPELL)
              break;
  
      if (i == MAXSPELL) {
          impossible("Too many spells memorized!");
      } else if (spellid(i) == booktype) {
          /* normal book can be read and re-read a total of 4 times */
          if (book->spestudied > MAX_SPELL_STUDY) {
              pline("This spellbook is too faint to be read any more.");
              book->otyp = booktype = SPE_BLANK_PAPER;
              /* reset spestudied as if polymorph had taken place */
              book->spestudied = rn2(book->spestudied);
          } else {
              Your("knowledge of %s is %s.", splname,
                   spellknow(i) ? "keener" : "restored");
              incrnknow(i, 1);
              book->spestudied++;
              exercise(A_WIS, TRUE); /* extra study */
          }
          makeknown((int) booktype);
      } else { /* (spellid(i) == NO_SPELL) */
          /* for a normal book, spestudied will be zero, but for
             a polymorphed one, spestudied will be non-zero and
             one less reading is available than when re-learning */
          if (book->spestudied >= MAX_SPELL_STUDY) {
              /* pre-used due to being the product of polymorph */
              pline("This spellbook is too faint to read even once.");
              book->otyp = booktype = SPE_BLANK_PAPER;
              /* reset spestudied as if polymorph had taken place */
              book->spestudied = rn2(book->spestudied);
          } else {
              g.spl_book[i].sp_id = booktype;
              g.spl_book[i].sp_lev = objects[booktype].oc_level;
              incrnknow(i, 1);
              book->spestudied++;
              if (!i)
                  /* first is always 'a', so no need to mention the letter */
                  You("learn %s.", splname);
              else
                  You("add %s to your repertoire, as '%c'.",
                      splname, spellet(i));
          }
          makeknown((int) booktype);
      }
  
      if (book->cursed) { /* maybe a demon cursed it */
          if (cursed_book(book)) {
              useup(book);
              g.context.spbook.book = 0;
              g.context.spbook.o_id = 0;
              return 0;
          }
      }
      if (costly)
          check_unpaid(book);
      g.context.spbook.book = 0;
      g.context.spbook.o_id = 0;
      return 0;
  }
  
  RESTORE_WARNING_FORMAT_NONLITERAL
  
  int
  study_book(register struct obj* spellbook)
  {
      int booktype = spellbook->otyp, i;
      boolean confused = (Confusion != 0);
      boolean too_hard = FALSE;
  
      /* attempting to read dull book may make hero fall asleep */
      if (!confused && !Sleep_resistance
          && objdescr_is(spellbook, "dull")) {
          const char *eyes;
          int dullbook = rnd(25) - ACURR(A_WIS);
  
          /* adjust chance if hero stayed awake, got interrupted, retries */
          if (g.context.spbook.delay && spellbook == g.context.spbook.book)
              dullbook -= rnd(objects[booktype].oc_level);
  
          if (dullbook > 0) {
              eyes = body_part(EYE);
              if (eyecount(g.youmonst.data) > 1)
                  eyes = makeplural(eyes);
              pline("This book is so dull that you can't keep your %s open.",
                    eyes);
              dullbook += rnd(2 * objects[booktype].oc_level);
              fall_asleep(-dullbook, TRUE);
              return 1;
          }
      }
  
      if (g.context.spbook.delay && !confused
          && spellbook == g.context.spbook.book
          /* handle the sequence: start reading, get interrupted, have
             g.context.spbook.book become erased somehow, resume reading it */
          && booktype != SPE_BLANK_PAPER) {
          You("continue your efforts to %s.",
              (booktype == SPE_NOVEL) ? "read the novel" : "memorize the spell");
      } else {
          /* KMH -- Simplified this code */
          if (booktype == SPE_BLANK_PAPER) {
              pline("This spellbook is all blank.");
              makeknown(booktype);
              return 1;
          }
  
          /* 3.6 tribute */
          if (booktype == SPE_NOVEL) {
              /* Obtain current Terry Pratchett book title */
              const char *tribtitle = noveltitle(&spellbook->novelidx);
  
              if (read_tribute("books", tribtitle, 0, (char *) 0, 0,
                               spellbook->o_id)) {
                  if (!u.uconduct.literate++)
                      livelog_printf(LL_CONDUCT,
                                     "became literate by reading %s", tribtitle);
                  check_unpaid(spellbook);
                  makeknown(booktype);
                  if (!u.uevent.read_tribute) {
                      record_achievement(ACH_NOVL);
                      /* give bonus of 20 xp and 4*20+0 pts */
                      more_experienced(20, 0);
                      newexplevel();
                      u.uevent.read_tribute = 1; /* only once */
                  }
              }
              return 1;
          }
  
          switch (objects[booktype].oc_level) {
          case 1:
          case 2:
              g.context.spbook.delay = -objects[booktype].oc_delay;
              break;
          case 3:
          case 4:
              g.context.spbook.delay = -(objects[booktype].oc_level - 1)
                                     * objects[booktype].oc_delay;
              break;
          case 5:
          case 6:
              g.context.spbook.delay =
                  -objects[booktype].oc_level * objects[booktype].oc_delay;
              break;
          case 7:
              g.context.spbook.delay = -8 * objects[booktype].oc_delay;
              break;
          default:
              impossible("Unknown spellbook level %d, book %d;",
                         objects[booktype].oc_level, booktype);
              return 0;
          }
  
          /* check to see if we already know it and want to refresh our memory */
          for (i = 0; i < MAXSPELL; i++)
              if (spellid(i) == booktype || spellid(i) == NO_SPELL)
                  break;
          if (spellid(i) == booktype && spellknow(i) > KEEN / 10) {
              You("know \"%s\" quite well already.", OBJ_NAME(objects[booktype]));
              if (yn("Refresh your memory anyway?") == 'n')
                  return 0;
          }
  
          /* Books are often wiser than their readers (Rus.) */
          spellbook->in_use = TRUE;
          if (!spellbook->blessed && spellbook->otyp != SPE_BOOK_OF_THE_DEAD) {
              if (spellbook->cursed) {
                  too_hard = TRUE;
              } else {
                  /* uncursed - chance to fail */
                  int read_ability = ACURR(A_INT) + 4 + u.ulevel / 2
                                     - 2 * objects[booktype].oc_level
                               + ((ublindf && ublindf->otyp == LENSES) ? 2 : 0);
  
                  /* only wizards know if a spell is too difficult */
                  if (Role_if(PM_WIZARD) && read_ability < 20 && !confused) {
                      char qbuf[QBUFSZ];
  
                      Sprintf(qbuf,
                      "This spellbook is %sdifficult to comprehend.  Continue?",
                              (read_ability < 12 ? "very " : ""));
                      if (yn(qbuf) != 'y') {
                          spellbook->in_use = FALSE;
                          return 1;
                      }
                  }
                  /* its up to random luck now */
                  if (rnd(20) > read_ability) {
                      too_hard = TRUE;
                  }
              }
          }
  
          if (too_hard) {
              boolean gone = cursed_book(spellbook);
  
              nomul(g.context.spbook.delay); /* study time */
              g.multi_reason = "reading a book";
              g.nomovemsg = 0;
              g.context.spbook.delay = 0;
              if (gone || !rn2(3)) {
                  if (!gone)
                      pline_The("spellbook crumbles to dust!");
                  if (!objects[spellbook->otyp].oc_name_known
                      && !objects[spellbook->otyp].oc_uname)
                      docall(spellbook);
                  useup(spellbook);
              } else
                  spellbook->in_use = FALSE;
              return 1;
          } else if (confused) {
              if (!confused_book(spellbook)) {
                  spellbook->in_use = FALSE;
              }
              nomul(g.context.spbook.delay);
              g.multi_reason = "reading a book";
              g.nomovemsg = 0;
              g.context.spbook.delay = 0;
              return 1;
          }
          spellbook->in_use = FALSE;
  
          You("begin to %s the runes.",
              spellbook->otyp == SPE_BOOK_OF_THE_DEAD ? "recite" : "memorize");
      }
  
      g.context.spbook.book = spellbook;
      if (g.context.spbook.book)
          g.context.spbook.o_id = g.context.spbook.book->o_id;
      set_occupation(learn, "studying", 0);
      return 1;
  }
  
  /* a spellbook has been destroyed or the character has changed levels;
     the stored address for the current book is no longer valid */
  void
  book_disappears(struct obj* obj)
  {
      if (obj == g.context.spbook.book) {
          g.context.spbook.book = (struct obj *) 0;
          g.context.spbook.o_id = 0;
      }
  }
  
  /* renaming an object usually results in it having a different address;
     so the sequence start reading, get interrupted, name the book, resume
     reading would read the "new" book from scratch */
  void
  book_substitution(struct obj* old_obj, struct obj* new_obj)
  {
      if (old_obj == g.context.spbook.book) {
          g.context.spbook.book = new_obj;
          if (g.context.spbook.book)
              g.context.spbook.o_id = g.context.spbook.book->o_id;
      }
  }
  
  /* called from moveloop() */
  void
  age_spells(void)
  {
      int i;
      /*
       * The time relative to the hero (a pass through move
       * loop) causes all spell knowledge to be decremented.
       * The hero's speed, rest status, conscious status etc.
       * does not alter the loss of memory.
       */
      for (i = 0; i < MAXSPELL && spellid(i) != NO_SPELL; i++)
          if (spellknow(i))
              decrnknow(i);
      return;
  }
  
  /* return True if spellcasting is inhibited;
     only covers a small subset of reasons why casting won't work */
  static boolean
  rejectcasting(void)
  {
      /* rejections which take place before selecting a particular spell */
      if (Stunned) {
          You("are too impaired to cast a spell.");
          return TRUE;
      } else if (!can_chant(&g.youmonst)) {
          You("are unable to chant the incantation.");
          return TRUE;
      } else if (!freehand()) {
          /* Note: !freehand() occurs when weapon and shield (or two-handed
           * weapon) are welded to hands, so "arms" probably doesn't need
           * to be makeplural(bodypart(ARM)).
           *
           * But why isn't lack of free arms (for gesturing) an issue when
           * poly'd hero has no limbs?
           */
          Your("arms are not free to cast!");
          return TRUE;
      }
      return FALSE;
  }
  
  /*
   * Return TRUE if a spell was picked, with the spell index in the return
   * parameter.  Otherwise return FALSE.
   */
  static boolean
  getspell(int* spell_no)
  {
      int nspells, idx;
      char ilet, lets[BUFSZ], qbuf[QBUFSZ];
  
      if (spellid(0) == NO_SPELL) {
          You("don't know any spells right now.");
          return FALSE;
      }
      if (rejectcasting())
          return FALSE; /* no spell chosen */
  
      if (flags.menu_style == MENU_TRADITIONAL) {
          /* we know there is at least 1 known spell */
          for (nspells = 1; nspells < MAXSPELL && spellid(nspells) != NO_SPELL;
               nspells++)
              continue;
  
          if (nspells == 1)
              Strcpy(lets, "a");
          else if (nspells < 27)
              Sprintf(lets, "a-%c", 'a' + nspells - 1);
          else if (nspells == 27)
              Sprintf(lets, "a-zA");
          /* this assumes that there are at most 52 spells... */
          else
              Sprintf(lets, "a-zA-%c", 'A' + nspells - 27);
  
          for (;;) {
              Snprintf(qbuf, sizeof(qbuf), "Cast which spell? [%s *?]",
                       lets);
              ilet = yn_function(qbuf, (char *) 0, '\0');
              if (ilet == '*' || ilet == '?')
                  break; /* use menu mode */
              if (index(quitchars, ilet))
                  return FALSE;
  
              idx = spell_let_to_idx(ilet);
              if (idx < 0 || idx >= nspells) {
                  You("don't know that spell.");
                  continue; /* ask again */
              }
              *spell_no = idx;
              return TRUE;
          }
      }
      return dospellmenu("Choose which spell to cast", SPELLMENU_CAST,
                         spell_no);
  }
  
  /* the 'Z' command -- cast a spell */
  int
  docast(void)
  {
      int spell_no;
  
      if (getspell(&spell_no))
          return spelleffects(spell_no, FALSE);
      return 0;
  }
  
  static const char *
  spelltypemnemonic(int skill)
  {
      switch (skill) {
      case P_ATTACK_SPELL:
          return "attack";
      case P_HEALING_SPELL:
          return "healing";
      case P_DIVINATION_SPELL:
          return "divination";
      case P_ENCHANTMENT_SPELL:
          return "enchantment";
      case P_CLERIC_SPELL:
          return "clerical";
      case P_ESCAPE_SPELL:
          return "escape";
      case P_MATTER_SPELL:
          return "matter";
      default:
          impossible("Unknown spell skill, %d;", skill);
          return "";
      }
  }
  
  int
  spell_skilltype(int booktype)
  {
      return objects[booktype].oc_skill;
  }
  
  static void
  cast_protection(void)
  {
      int l = u.ulevel, loglev = 0,
          gain, natac = u.uac + u.uspellprot;
      /* note: u.uspellprot is subtracted when find_ac() factors it into u.uac,
         so adding here factors it back out
         (versions prior to 3.6 had this backwards) */
  
      /* loglev=log2(u.ulevel)+1 (1..5) */
      while (l) {
          loglev++;
          l /= 2;
      }
  
      /* The more u.uspellprot you already have, the less you get,
       * and the better your natural ac, the less you get.
       *
       *  LEVEL AC    SPELLPROT from successive SPE_PROTECTION casts
       *      1     10    0,  1,  2,  3,  4
       *      1      0    0,  1,  2,  3
       *      1    -10    0,  1,  2
       *      2-3   10    0,  2,  4,  5,  6,  7,  8
       *      2-3    0    0,  2,  4,  5,  6
       *      2-3  -10    0,  2,  3,  4
       *      4-7   10    0,  3,  6,  8,  9, 10, 11, 12
       *      4-7    0    0,  3,  5,  7,  8,  9
       *      4-7  -10    0,  3,  5,  6
       *      7-15 -10    0,  3,  5,  6
       *      8-15  10    0,  4,  7, 10, 12, 13, 14, 15, 16
       *      8-15   0    0,  4,  7,  9, 10, 11, 12
       *      8-15 -10    0,  4,  6,  7,  8
       *     16-30  10    0,  5,  9, 12, 14, 16, 17, 18, 19, 20
       *     16-30   0    0,  5,  9, 11, 13, 14, 15
       *     16-30 -10    0,  5,  8,  9, 10
       */
      natac = (10 - natac) / 10; /* convert to positive and scale down */
      gain = loglev - (int) u.uspellprot / (4 - min(3, natac));
  
      if (gain > 0) {
          if (!Blind) {
              int rmtyp;
              const char *hgolden = hcolor(NH_GOLDEN), *atmosphere;
  
              if (u.uspellprot) {
                  pline_The("%s haze around you becomes more dense.", hgolden);
              } else {
                  rmtyp = levl[u.ux][u.uy].typ;
                  atmosphere = u.uswallow
                                  ? ((u.ustuck->data == &mons[PM_FOG_CLOUD])
                                     ? "mist"
                                     : is_whirly(u.ustuck->data)
                                        ? "maelstrom"
                                        : is_animal(u.ustuck->data)
                                           ? "maw"
                                           : "ooze")
                                  : (u.uinwater
                                     ? hliquid("water")
                                     : (rmtyp == CLOUD)
                                        ? "cloud"
                                        : IS_TREE(rmtyp)
                                           ? "vegetation"
                                           : IS_STWALL(rmtyp)
                                              ? "stone"
                                              : "air");
                  pline_The("%s around you begins to shimmer with %s haze.",
                            atmosphere, an(hgolden));
              }
          }
          u.uspellprot += gain;
          u.uspmtime = (P_SKILL(spell_skilltype(SPE_PROTECTION)) == P_EXPERT)
                          ? 20 : 10;
          if (!u.usptime)
              u.usptime = u.uspmtime;
          find_ac();
      } else {
          Your("skin feels warm for a moment.");
      }
  }
  
  /* attempting to cast a forgotten spell will cause disorientation */
  static void
  spell_backfire(int spell)
  {
      long duration = (long) ((spellev(spell) + 1) * 3), /* 6..24 */
           old_stun = (HStun & TIMEOUT), old_conf = (HConfusion & TIMEOUT);
  
      /* Prior to 3.4.1, only effect was confusion; it still predominates.
       *
       * 3.6.0: this used to override pre-existing confusion duration
       * (cases 0..8) and pre-existing stun duration (cases 4..9);
       * increase them instead.   (Hero can no longer cast spells while
       * Stunned, so the potential increment to stun duration here is
       * just hypothetical.)
       */
      switch (rn2(10)) {
      case 0:
      case 1:
      case 2:
      case 3:
          make_confused(old_conf + duration, FALSE); /* 40% */
          break;
      case 4:
      case 5:
      case 6:
          make_confused(old_conf + 2L * duration / 3L, FALSE); /* 30% */
          make_stunned(old_stun + duration / 3L, FALSE);
          break;
      case 7:
      case 8:
          make_stunned(old_stun + 2L * duration / 3L, FALSE); /* 20% */
          make_confused(old_conf + duration / 3L, FALSE);
          break;
      case 9:
          make_stunned(old_stun + duration, FALSE); /* 10% */
          break;
      }
      return;
  }
  
  int
  spelleffects(int spell, boolean atme)
  {
      int energy, damage, chance, n, intell;
      int otyp, skill, role_skill, res = 0;
      boolean confused = (Confusion != 0);
      boolean physical_damage = FALSE;
      struct obj *pseudo;
      coord cc;
  
      /*
       * Reject attempting to cast while stunned or with no free hands.
       * Already done in getspell() to stop casting before choosing
       * which spell, but duplicated here for cases where spelleffects()
       * gets called directly for ^T without intrinsic teleport capability
       * or #turn for non-priest/non-knight.
       * (There's no duplication of messages; when the rejection takes
       * place in getspell(), we don't get called.)
       */
      if (rejectcasting()) {
          return 0; /* no time elapses */
      }
  
      /*
       * Spell casting no longer affects knowledge of the spell. A
       * decrement of spell knowledge is done every turn.
       */
      if (spellknow(spell) <= 0) {
          Your("knowledge of this spell is twisted.");
          pline("It invokes nightmarish images in your mind...");
          spell_backfire(spell);
          return 1;
      } else if (spellknow(spell) <= KEEN / 200) { /* 100 turns left */
          You("strain to recall the spell.");
      } else if (spellknow(spell) <= KEEN / 40) { /* 500 turns left */
          You("have difficulty remembering the spell.");
      } else if (spellknow(spell) <= KEEN / 20) { /* 1000 turns left */
          Your("knowledge of this spell is growing faint.");
      } else if (spellknow(spell) <= KEEN / 10) { /* 2000 turns left */
          Your("recall of this spell is gradually fading.");
      }
      /*
       *  Note: dotele() also calculates energy use and checks nutrition
       *  and strength requirements; it any of these change, update it too.
       */
      energy = (spellev(spell) * 5); /* 5 <= energy <= 35 */
  
      if (u.uhunger <= 10 && spellid(spell) != SPE_DETECT_FOOD) {
          You("are too hungry to cast that spell.");
          return 0;
      } else if (ACURR(A_STR) < 4 && spellid(spell) != SPE_RESTORE_ABILITY) {
          You("lack the strength to cast spells.");
          return 0;
      } else if (check_capacity(
                  "Your concentration falters while carrying so much stuff.")) {
          return 1;
      }
  
      /* if the cast attempt is already going to fail due to insufficient
         energy (ie, u.uen < energy), the Amulet's drain effect won't kick
         in and no turn will be consumed; however, when it does kick in,
         the attempt may fail due to lack of energy after the draining, in
         which case a turn will be used up in addition to the energy loss */
      if (u.uhave.amulet && u.uen >= energy) {
          You_feel("the amulet draining your energy away.");
          /* this used to be 'energy += rnd(2 * energy)' (without 'res'),
             so if amulet-induced cost was more than u.uen, nothing
             (except the "don't have enough energy" message) happened
             and player could just try again (and again and again...);
             now we drain some energy immediately, which has a
             side-effect of not increasing the hunger aspect of casting */
          u.uen -= rnd(2 * energy);
          if (u.uen < 0)
              u.uen = 0;
          g.context.botl = 1;
          res = 1; /* time is going to elapse even if spell doesn't get cast */
      }
  
      if (energy > u.uen) {
          You("don't have enough energy to cast that spell.");
          return res;
      } else {
          if (spellid(spell) != SPE_DETECT_FOOD) {
              int hungr = energy * 2;
  
              /* If hero is a wizard, their current intelligence
               * (bonuses + temporary + current)
               * affects hunger reduction in casting a spell.
               * 1. int = 17-18 no reduction
               * 2. int = 16    1/4 hungr
               * 3. int = 15    1/2 hungr
               * 4. int = 1-14  normal reduction
               * The reason for this is:
               * a) Intelligence affects the amount of exertion
               * in thinking.
               * b) Wizards have spent their life at magic and
               * understand quite well how to cast spells.
               */
              intell = acurr(A_INT);
              if (!Role_if(PM_WIZARD))
                  intell = 10;
              switch (intell) {
              case 25:
              case 24:
              case 23:
              case 22:
              case 21:
              case 20:
              case 19:
              case 18:
              case 17:
                  hungr = 0;
                  break;
              case 16:
                  hungr /= 4;
                  break;
              case 15:
                  hungr /= 2;
                  break;
              }
              /* don't put player (quite) into fainting from
               * casting a spell, particularly since they might
               * not even be hungry at the beginning; however,
               * this is low enough that they must eat before
               * casting anything else except detect food
               */
              if (hungr > u.uhunger - 3)
                  hungr = u.uhunger - 3;
              morehungry(hungr);
          }
      }
  
      chance = percent_success(spell);
      if (confused || (rnd(100) > chance)) {
          You("fail to cast the spell correctly.");
          u.uen -= energy / 2;
          g.context.botl = 1;
          return 1;
      }
  
      u.uen -= energy;
      g.context.botl = 1;
      exercise(A_WIS, TRUE);
      /* pseudo is a temporary "false" object containing the spell stats */
      pseudo = mksobj(spellid(spell), FALSE, FALSE);
      pseudo->blessed = pseudo->cursed = 0;
      pseudo->quan = 20L; /* do not let useup get it */
      /*
       * Find the skill the hero has in a spell type category.
       * See spell_skilltype for categories.
       */
      otyp = pseudo->otyp;
      skill = spell_skilltype(otyp);
      role_skill = P_SKILL(skill);
  
      switch (otyp) {
      /*
       * At first spells act as expected.  As the hero increases in skill
       * with the appropriate spell type, some spells increase in their
       * effects, e.g. more damage, further distance, and so on, without
       * additional cost to the spellcaster.
       */
      case SPE_FIREBALL:
      case SPE_CONE_OF_COLD:
          if (role_skill >= P_SKILLED) {
              if (throwspell()) {
                  cc.x = u.dx;
                  cc.y = u.dy;
                  n = rnd(8) + 1;
                  while (n--) {
                      if (!u.dx && !u.dy && !u.dz) {
                          if ((damage = zapyourself(pseudo, TRUE)) != 0) {
                              char buf[BUFSZ];
                              Sprintf(buf, "zapped %sself with a spell",
                                      uhim());
                              losehp(damage, buf, NO_KILLER_PREFIX);
                          }
                      } else {
                          explode(u.dx, u.dy,
                                  otyp - SPE_MAGIC_MISSILE + 10,
                                  spell_damage_bonus(u.ulevel / 2 + 1), 0,
                                  (otyp == SPE_CONE_OF_COLD)
                                     ? EXPL_FROSTY
                                     : EXPL_FIERY);
                      }
                      u.dx = cc.x + rnd(3) - 2;
                      u.dy = cc.y + rnd(3) - 2;
                      if (!isok(u.dx, u.dy) || !cansee(u.dx, u.dy)
                          || IS_STWALL(levl[u.dx][u.dy].typ) || u.uswallow) {
                          /* Spell is reflected back to center */
                          u.dx = cc.x;
                          u.dy = cc.y;
                      }
                  }
              }
              break;
          } /* else */
          /*FALLTHRU*/
  
      /* these spells are all duplicates of wand effects */
      case SPE_FORCE_BOLT:
          physical_damage = TRUE;
      /*FALLTHRU*/
      case SPE_SLEEP:
      case SPE_MAGIC_MISSILE:
      case SPE_KNOCK:
      case SPE_SLOW_MONSTER:
      case SPE_WIZARD_LOCK:
      case SPE_DIG:
      case SPE_TURN_UNDEAD:
      case SPE_POLYMORPH:
      case SPE_TELEPORT_AWAY:
      case SPE_CANCELLATION:
      case SPE_FINGER_OF_DEATH:
      case SPE_LIGHT:
      case SPE_DETECT_UNSEEN:
      case SPE_HEALING:
      case SPE_EXTRA_HEALING:
      case SPE_DRAIN_LIFE:
      case SPE_STONE_TO_FLESH:
          if (objects[otyp].oc_dir != NODIR) {
              if (otyp == SPE_HEALING || otyp == SPE_EXTRA_HEALING) {
                  /* healing and extra healing are actually potion effects,
                     but they've been extended to take a direction like wands */
                  if (role_skill >= P_SKILLED)
                      pseudo->blessed = 1;
              }
              if (atme) {
                  u.dx = u.dy = u.dz = 0;
              } else if (!getdir((char *) 0)) {
                  /* getdir cancelled, re-use previous direction */
                  /*
                   * FIXME:  reusing previous direction only makes sense
                   * if there is an actual previous direction.  When there
                   * isn't one, the spell gets cast at self which is rarely
                   * what the player intended.  Unfortunately, the way
                   * spelleffects() is organized means that aborting with
                   * "nevermind" is not an option.
                   */
                  pline_The("magical energy is released!");
              }
              if (!u.dx && !u.dy && !u.dz) {
                  if ((damage = zapyourself(pseudo, TRUE)) != 0) {
                      char buf[BUFSZ];
  
                      Sprintf(buf, "zapped %sself with a spell", uhim());
                      if (physical_damage)
                          damage = Maybe_Half_Phys(damage);
                      losehp(damage, buf, NO_KILLER_PREFIX);
                  }
              } else
                  weffects(pseudo);
          } else
              weffects(pseudo);
          update_inventory(); /* spell may modify inventory */
          break;
  
      /* these are all duplicates of scroll effects */
      case SPE_REMOVE_CURSE:
      case SPE_CONFUSE_MONSTER:
      case SPE_DETECT_FOOD:
      case SPE_CAUSE_FEAR:
      case SPE_IDENTIFY:
          /* high skill yields effect equivalent to blessed scroll */
          if (role_skill >= P_SKILLED)
              pseudo->blessed = 1;
      /*FALLTHRU*/
      case SPE_CHARM_MONSTER:
      case SPE_MAGIC_MAPPING:
      case SPE_CREATE_MONSTER:
          (void) seffects(pseudo);
          break;
  
      /* these are all duplicates of potion effects */
      case SPE_HASTE_SELF:
      case SPE_DETECT_TREASURE:
      case SPE_DETECT_MONSTERS:
      case SPE_LEVITATION:
      case SPE_RESTORE_ABILITY:
          /* high skill yields effect equivalent to blessed potion */
          if (role_skill >= P_SKILLED)
              pseudo->blessed = 1;
      /*FALLTHRU*/
      case SPE_INVISIBILITY:
          (void) peffects(pseudo);
          break;
      /* end of potion-like spells */
  
      case SPE_CURE_BLINDNESS:
          healup(0, 0, FALSE, TRUE);
          break;
      case SPE_CURE_SICKNESS:
          if (Sick)
              You("are no longer ill.");
          if (Slimed)
              make_slimed(0L, "The slime disappears!");
          healup(0, 0, TRUE, FALSE);
          break;
      case SPE_CREATE_FAMILIAR:
          (void) make_familiar((struct obj *) 0, u.ux, u.uy, FALSE);
          break;
      case SPE_CLAIRVOYANCE:
          if (!BClairvoyant) {
              if (role_skill >= P_SKILLED)
                  pseudo->blessed = 1; /* detect monsters as well as map */
              do_vicinity_map(pseudo);
          /* at present, only one thing blocks clairvoyance */
          } else if (uarmh && uarmh->otyp == CORNUTHAUM)
              You("sense a pointy hat on top of your %s.", body_part(HEAD));
          break;
      case SPE_PROTECTION:
          cast_protection();
          break;
      case SPE_JUMPING:
          if (!jump(max(role_skill, 1)))
              pline1(nothing_happens);
          break;
      default:
          impossible("Unknown spell %d attempted.", spell);
          obfree(pseudo, (struct obj *) 0);
          return 0;
      }
  
      /* gain skill for successful cast */
      use_skill(skill, spellev(spell));
  
      obfree(pseudo, (struct obj *) 0); /* now, get rid of it */
      return 1;
  }
  
  /*ARGSUSED*/
  static boolean
  spell_aim_step(genericptr_t arg UNUSED, int x, int y)
  {
      if (!isok(x,y))
          return FALSE;
      if (!ZAP_POS(levl[x][y].typ)
          && !(IS_DOOR(levl[x][y].typ) && (levl[x][y].doormask & D_ISOPEN)))
          return FALSE;
      return TRUE;
  }
  
  /* Choose location where spell takes effect. */
  static int
  throwspell(void)
  {
      coord cc, uc;
      struct monst *mtmp;
  
      if (u.uinwater) {
          pline("You're joking!  In this weather?");
          return 0;
      } else if (Is_waterlevel(&u.uz)) {
          You("had better wait for the sun to come out.");
          return 0;
      }
  
      pline("Where do you want to cast the spell?");
      cc.x = u.ux;
      cc.y = u.uy;
      if (getpos(&cc, TRUE, "the desired position") < 0)
          return 0; /* user pressed ESC */
      clear_nhwindow(WIN_MESSAGE); /* discard any autodescribe feedback */
  
      /* The number of moves from hero to where the spell drops.*/
      if (distmin(u.ux, u.uy, cc.x, cc.y) > 10) {
          pline_The("spell dissipates over the distance!");
          return 0;
      } else if (u.uswallow) {
          pline_The("spell is cut short!");
          exercise(A_WIS, FALSE); /* What were you THINKING! */
          u.dx = 0;
          u.dy = 0;
          return 1;
      } else if (((cc.x != u.ux || cc.y != u.uy) && !cansee(cc.x, cc.y)
                  && (!(mtmp = m_at(cc.x, cc.y)) || !canspotmon(mtmp)))
                 || IS_STWALL(levl[cc.x][cc.y].typ)) {
          Your("mind fails to lock onto that location!");
          return 0;
      }
  
      uc.x = u.ux;
      uc.y = u.uy;
  
      walk_path(&uc, &cc, spell_aim_step, (genericptr_t) 0);
  
      u.dx = cc.x;
      u.dy = cc.y;
      return 1;
  }
  
  /* add/hide/remove/unhide teleport-away on behalf of dotelecmd() to give
     more control to behavior of ^T when used in wizard mode */
  int
  tport_spell(int what)
  {
      static struct tport_hideaway {
          struct spell savespell;
          int tport_indx;
      } save_tport;
      int i;
  /* also defined in teleport.c */
  #define NOOP_SPELL  0
  #define HIDE_SPELL  1
  #define ADD_SPELL   2
  #define UNHIDESPELL 3
  #define REMOVESPELL 4
  
      for (i = 0; i < MAXSPELL; i++)
          if (spellid(i) == SPE_TELEPORT_AWAY || spellid(i) == NO_SPELL)
              break;
      if (i == MAXSPELL) {
          impossible("tport_spell: spellbook full");
          /* wizard mode ^T is not able to honor player's menu choice */
      } else if (spellid(i) == NO_SPELL) {
          if (what == HIDE_SPELL || what == REMOVESPELL) {
              save_tport.tport_indx = MAXSPELL;
          } else if (what == UNHIDESPELL) {
              /*assert( save_tport.savespell.sp_id == SPE_TELEPORT_AWAY );*/
              g.spl_book[save_tport.tport_indx] = save_tport.savespell;
              save_tport.tport_indx = MAXSPELL; /* burn bridge... */
          } else if (what == ADD_SPELL) {
              save_tport.savespell = g.spl_book[i];
              save_tport.tport_indx = i;
              g.spl_book[i].sp_id = SPE_TELEPORT_AWAY;
              g.spl_book[i].sp_lev = objects[SPE_TELEPORT_AWAY].oc_level;
              g.spl_book[i].sp_know = KEEN;
              return REMOVESPELL; /* operation needed to reverse */
          }
      } else { /* spellid(i) == SPE_TELEPORT_AWAY */
          if (what == ADD_SPELL || what == UNHIDESPELL) {
              save_tport.tport_indx = MAXSPELL;
          } else if (what == REMOVESPELL) {
              /*assert( i == save_tport.tport_indx );*/
              g.spl_book[i] = save_tport.savespell;
              save_tport.tport_indx = MAXSPELL;
          } else if (what == HIDE_SPELL) {
              save_tport.savespell = g.spl_book[i];
              save_tport.tport_indx = i;
              g.spl_book[i].sp_id = NO_SPELL;
              return UNHIDESPELL; /* operation needed to reverse */
          }
      }
      return NOOP_SPELL;
  }
  
  /* forget a random selection of known spells due to amnesia;
     they used to be lost entirely, as if never learned, but now we
     just set the memory retention to zero so that they can't be cast */
  void
  losespells(void)
  {
      int n, nzap, i;
  
      /* in case reading has been interrupted earlier, discard context */
      g.context.spbook.book = 0;
      g.context.spbook.o_id = 0;
      /* count the number of known spells */
      for (n = 0; n < MAXSPELL; ++n)
          if (spellid(n) == NO_SPELL)
              break;
  
      /* lose anywhere from zero to all known spells;
         if confused, use the worse of two die rolls */
      nzap = rn2(n + 1);
      if (Confusion) {
          i = rn2(n + 1);
          if (i > nzap)
              nzap = i;
      }
      /* good Luck might ameliorate spell loss */
      if (nzap > 1 && !rnl(7))
          nzap = rnd(nzap);
  
      /*
       * Forget 'nzap' out of 'n' known spells by setting their memory
       * retention to zero.  Every spell has the same probability to be
       * forgotten, even if its retention is already zero.
       *
       * Perhaps we should forget the corresponding book too?
       *
       * (3.4.3 removed spells entirely from the list, but always did
       * so from its end, so the 'nzap' most recently learned spells
       * were the ones lost by default.  Player had sort control over
       * the list, so could move the most useful spells to front and
       * only lose them if 'nzap' turned out to be a large value.
       *
       * Discarding from the end of the list had the virtue of making
       * casting letters for lost spells become invalid and retaining
       * the original letter for the ones which weren't lost, so there
       * was no risk to the player of accidentally casting the wrong
       * spell when using a letter that was in use prior to amnesia.
       * That wouldn't be the case if we implemented spell loss spread
       * throughout the list of known spells; every spell located past
       * the first lost spell would end up with new letter assigned.)
       */
      for (i = 0; nzap > 0; ++i) {
          /* when nzap is small relative to the number of spells left,
             the chance to lose spell [i] is small; as the number of
             remaining candidates shrinks, the chance per candidate
             gets bigger; overall, exactly nzap entries are affected */
          if (rn2(n - i) < nzap) {
              /* lose access to spell [i] */
              spellknow(i) = 0;
  #if 0
              /* also forget its book */
              forget_single_object(spellid(i));
  #endif
              /* and abuse wisdom */
              exercise(A_WIS, FALSE);
              /* there's now one less spell slated to be forgotten */
              --nzap;
          }
      }
  }
  
  /*
   * Allow player to sort the list of known spells.  Manually swapping
   * pairs of them becomes very tedious once the list reaches two pages.
   *
   * Possible extensions:
   *      provide means for player to control ordering of skill classes;
   *      provide means to supply value N such that first N entries stick
   *      while rest of list is being sorted;
   *      make chosen sort order be persistent such that when new spells
   *      are learned, they get inserted into sorted order rather than be
   *      appended to the end of the list?
   */
  enum spl_sort_types {
      SORTBY_LETTER = 0,
      SORTBY_ALPHA,
      SORTBY_LVL_LO,
      SORTBY_LVL_HI,
      SORTBY_SKL_AL,
      SORTBY_SKL_LO,
      SORTBY_SKL_HI,
      SORTBY_CURRENT,
      SORTRETAINORDER,
  
      NUM_SPELL_SORTBY
  };
  
  static const char *spl_sortchoices[NUM_SPELL_SORTBY] = {
      "by casting letter",
      "alphabetically",
      "by level, low to high",
      "by level, high to low",
      "by skill group, alphabetized within each group",
      "by skill group, low to high level within group",
      "by skill group, high to low level within group",
      "maintain current ordering",
      /* a menu choice rather than a sort choice */
      "reassign casting letters to retain current order",
  };
  
  /* qsort callback routine */
  static int QSORTCALLBACK
  spell_cmp(const genericptr vptr1, const genericptr vptr2)
  {
      /*
       * gather up all of the possible parameters except spell name
       * in advance, even though some might not be needed:
       *  indx. = spl_orderindx[] index into g.spl_book[];
       *  otyp. = g.spl_book[] index into objects[];
       *  levl. = spell level;
       *  skil. = skill group aka spell class.
       */
      int indx1 = *(int *) vptr1, indx2 = *(int *) vptr2,
          otyp1 = g.spl_book[indx1].sp_id, otyp2 = g.spl_book[indx2].sp_id,
          levl1 = objects[otyp1].oc_level, levl2 = objects[otyp2].oc_level,
          skil1 = objects[otyp1].oc_skill, skil2 = objects[otyp2].oc_skill;
  
      switch (g.spl_sortmode) {
      case SORTBY_LETTER:
          return indx1 - indx2;
      case SORTBY_ALPHA:
          break;
      case SORTBY_LVL_LO:
          if (levl1 != levl2)
              return levl1 - levl2;
          break;
      case SORTBY_LVL_HI:
          if (levl1 != levl2)
              return levl2 - levl1;
          break;
      case SORTBY_SKL_AL:
          if (skil1 != skil2)
              return skil1 - skil2;
          break;
      case SORTBY_SKL_LO:
          if (skil1 != skil2)
              return skil1 - skil2;
          if (levl1 != levl2)
              return levl1 - levl2;
          break;
      case SORTBY_SKL_HI:
          if (skil1 != skil2)
              return skil1 - skil2;
          if (levl1 != levl2)
              return levl2 - levl1;
          break;
      case SORTBY_CURRENT:
      default:
          return (vptr1 < vptr2) ? -1
                                 : (vptr1 > vptr2); /* keep current order */
      }
      /* tie-breaker for most sorts--alphabetical by spell name */
      return strcmpi(OBJ_NAME(objects[otyp1]), OBJ_NAME(objects[otyp2]));
  }
  
  /* sort the index used for display order of the "view known spells"
     list (sortmode == SORTBY_xxx), or sort the spellbook itself to make
     the current display order stick (sortmode == SORTRETAINORDER) */
  static void
  sortspells(void)
  {
      int i;
  #if defined(SYSV) || defined(DGUX)
      unsigned n;
  #else
      int n;
  #endif
  
      if (g.spl_sortmode == SORTBY_CURRENT)
          return;
      for (n = 0; n < MAXSPELL && spellid(n) != NO_SPELL; ++n)
          continue;
      if (n < 2)
          return; /* not enough entries to need sorting */
  
      if (!g.spl_orderindx) {
          /* we haven't done any sorting yet; list is in casting order */
          if (g.spl_sortmode == SORTBY_LETTER /* default */
              || g.spl_sortmode == SORTRETAINORDER)
              return;
          /* allocate enough for full spellbook rather than just N spells */
          g.spl_orderindx = (int *) alloc(MAXSPELL * sizeof(int));
          for (i = 0; i < MAXSPELL; i++)
              g.spl_orderindx[i] = i;
      }
  
      if (g.spl_sortmode == SORTRETAINORDER) {
          struct spell tmp_book[MAXSPELL];
  
          /* sort g.spl_book[] rather than spl_orderindx[];
             this also updates the index to reflect the new ordering (we
             could just free it since that ordering becomes the default) */
          for (i = 0; i < MAXSPELL; i++)
              tmp_book[i] = g.spl_book[g.spl_orderindx[i]];
          for (i = 0; i < MAXSPELL; i++)
              g.spl_book[i] = tmp_book[i], g.spl_orderindx[i] = i;
          g.spl_sortmode = SORTBY_LETTER; /* reset */
          return;
      }
  
      /* usual case, sort the index rather than the spells themselves */
      qsort((genericptr_t) g.spl_orderindx, n, sizeof *g.spl_orderindx, spell_cmp);
      return;
  }
  
  /* called if the [sort spells] entry in the view spells menu gets chosen */
  static boolean
  spellsortmenu(void)
  {
      winid tmpwin;
      menu_item *selected;
      anything any;
      char let;
      int i, n, choice;
  
      tmpwin = create_nhwindow(NHW_MENU);
      start_menu(tmpwin, MENU_BEHAVE_STANDARD);
      any = cg.zeroany; /* zero out all bits */
  
      for (i = 0; i < SIZE(spl_sortchoices); i++) {
          if (i == SORTRETAINORDER) {
              let = 'z'; /* assumes fewer than 26 sort choices... */
              /* separate final choice from others with a blank line */
              any.a_int = 0;
              add_menu(tmpwin, &nul_glyphinfo, &any, 0, 0,
                       ATR_NONE, "", MENU_ITEMFLAGS_NONE);
          } else {
              let = 'a' + i;
          }
          any.a_int = i + 1;
          add_menu(tmpwin, &nul_glyphinfo, &any, let, 0,
                   ATR_NONE, spl_sortchoices[i],
                   (i == g.spl_sortmode) ? MENU_ITEMFLAGS_SELECTED : MENU_ITEMFLAGS_NONE);
      }
      end_menu(tmpwin, "View known spells list sorted");
  
      n = select_menu(tmpwin, PICK_ONE, &selected);
      destroy_nhwindow(tmpwin);
      if (n > 0) {
          choice = selected[0].item.a_int - 1;
          /* skip preselected entry if we have more than one item chosen */
          if (n > 1 && choice == g.spl_sortmode)
              choice = selected[1].item.a_int - 1;
          free((genericptr_t) selected);
          g.spl_sortmode = choice;
          return TRUE;
      }
      return FALSE;
  }
  
  /* the '+' command -- view known spells */
  int
  dovspell(void)
  {
      char qbuf[QBUFSZ];
      int splnum, othnum;
      struct spell spl_tmp;
  
      if (spellid(0) == NO_SPELL) {
          You("don't know any spells right now.");
      } else {
          while (dospellmenu("Currently known spells",
                             SPELLMENU_VIEW, &splnum)) {
              if (splnum == SPELLMENU_SORT) {
                  if (spellsortmenu())
                      sortspells();
              } else {
                  Sprintf(qbuf, "Reordering spells; swap '%c' with",
                          spellet(splnum));
                  if (!dospellmenu(qbuf, splnum, &othnum))
                      break;
  
                  spl_tmp = g.spl_book[splnum];
                  g.spl_book[splnum] = g.spl_book[othnum];
                  g.spl_book[othnum] = spl_tmp;
              }
          }
      }
      if (g.spl_orderindx) {
          free((genericptr_t) g.spl_orderindx);
          g.spl_orderindx = 0;
      }
      g.spl_sortmode = SORTBY_LETTER; /* 0 */
      return 0;
  }
  
  DISABLE_WARNING_FORMAT_NONLITERAL
  
  static boolean
  dospellmenu(
      const char *prompt,
      int splaction, /* SPELLMENU_CAST, SPELLMENU_VIEW, or g.spl_book[] index */
      int *spell_no)
  {
      winid tmpwin;
      int i, n, how, splnum;
      char buf[BUFSZ], retentionbuf[24];
      const char *fmt;
      menu_item *selected;
      anything any;
  
      tmpwin = create_nhwindow(NHW_MENU);
      start_menu(tmpwin, MENU_BEHAVE_STANDARD);
      any = cg.zeroany; /* zero out all bits */
  
      /*
       * The correct spacing of the columns when not using
       * tab separation depends on the following:
       * (1) that the font is monospaced, and
       * (2) that selection letters are pre-pended to the
       * given string and are of the form "a - ".
       */
      if (!iflags.menu_tab_sep) {
          Sprintf(buf, "%-20s     Level %-12s Fail Retention", "    Name",
                  "Category");
          fmt = "%-20s  %2d   %-12s %3d%% %9s";
      } else {
          Sprintf(buf, "Name\tLevel\tCategory\tFail\tRetention");
          fmt = "%s\t%-d\t%s\t%-d%%\t%s";
      }
      add_menu(tmpwin, &nul_glyphinfo, &any, 0, 0,
               iflags.menu_headings, buf, MENU_ITEMFLAGS_NONE);
      for (i = 0; i < MAXSPELL && spellid(i) != NO_SPELL; i++) {
          splnum = !g.spl_orderindx ? i : g.spl_orderindx[i];
          Sprintf(buf, fmt, spellname(splnum), spellev(splnum),
                  spelltypemnemonic(spell_skilltype(spellid(splnum))),
                  100 - percent_success(splnum),
                  spellretention(splnum, retentionbuf));
  
          any.a_int = splnum + 1; /* must be non-zero */
          add_menu(tmpwin, &nul_glyphinfo, &any, spellet(splnum), 0,
                   ATR_NONE, buf,
                   (splnum == splaction)
                      ? MENU_ITEMFLAGS_SELECTED : MENU_ITEMFLAGS_NONE);
      }
      how = PICK_ONE;
      if (splaction == SPELLMENU_VIEW) {
          if (spellid(1) == NO_SPELL) {
              /* only one spell => nothing to swap with */
              how = PICK_NONE;
          } else {
              /* more than 1 spell, add an extra menu entry */
              any.a_int = SPELLMENU_SORT + 1;
              add_menu(tmpwin, &nul_glyphinfo, &any, '+', 0,
                       ATR_NONE, "[sort spells]", MENU_ITEMFLAGS_NONE);
          }
      }
      end_menu(tmpwin, prompt);
  
      n = select_menu(tmpwin, how, &selected);
      destroy_nhwindow(tmpwin);
      if (n > 0) {
          *spell_no = selected[0].item.a_int - 1;
          /* menu selection for `PICK_ONE' does not
             de-select any preselected entry */
          if (n > 1 && *spell_no == splaction)
              *spell_no = selected[1].item.a_int - 1;
          free((genericptr_t) selected);
          /* default selection of preselected spell means that
             user chose not to swap it with anything */
          if (*spell_no == splaction)
              return FALSE;
          return TRUE;
      } else if (splaction >= 0) {
          /* explicit de-selection of preselected spell means that
             user is still swapping but not for the current spell */
          *spell_no = splaction;
          return TRUE;
      }
      return FALSE;
  }
  
  RESTORE_WARNING_FORMAT_NONLITERAL
  
  static int
  percent_success(int spell)
  {
      /* Intrinsic and learned ability are combined to calculate
       * the probability of player's success at cast a given spell.
       */
      int chance, splcaster, special, statused;
      int difficulty;
      int skill;
      /* Knights don't get metal armor penalty for clerical spells */
      boolean paladin_bonus = Role_if(PM_KNIGHT)
          && spell_skilltype(spellid(spell)) == P_CLERIC_SPELL;
  
      /* Calculate intrinsic ability (splcaster) */
  
      splcaster = g.urole.spelbase;
      special = g.urole.spelheal;
      statused = ACURR(g.urole.spelstat);
  
      if (uarm && is_metallic(uarm) && !paladin_bonus)
          splcaster += (uarmc && uarmc->otyp == ROBE) ? g.urole.spelarmr / 2
                                                      : g.urole.spelarmr;
      else if (uarmc && uarmc->otyp == ROBE)
          splcaster -= g.urole.spelarmr;
      if (uarms)
          splcaster += g.urole.spelshld;
  
      if (!paladin_bonus) {
          if (uarmh && is_metallic(uarmh) && uarmh->otyp != HELM_OF_BRILLIANCE)
              splcaster += uarmhbon;
          if (uarmg && is_metallic(uarmg))
              splcaster += uarmgbon;
          if (uarmf && is_metallic(uarmf))
              splcaster += uarmfbon;
      }
  
      if (spellid(spell) == g.urole.spelspec)
          splcaster += g.urole.spelsbon;
  
      /* `healing spell' bonus */
      if (spellid(spell) == SPE_HEALING || spellid(spell) == SPE_EXTRA_HEALING
          || spellid(spell) == SPE_CURE_BLINDNESS
          || spellid(spell) == SPE_CURE_SICKNESS
          || spellid(spell) == SPE_RESTORE_ABILITY
          || spellid(spell) == SPE_REMOVE_CURSE)
          splcaster += special;
  
      if (splcaster > 20)
          splcaster = 20;
  
      /* Calculate learned ability */
  
      /* Players basic likelihood of being able to cast any spell
       * is based of their `magic' statistic. (Int or Wis)
       */
      chance = 11 * statused / 2;
  
      /*
       * High level spells are harder.  Easier for higher level casters.
       * The difficulty is based on the hero's level and their skill level
       * in that spell type.
       */
      skill = P_SKILL(spell_skilltype(spellid(spell)));
      skill = max(skill, P_UNSKILLED) - 1; /* unskilled => 0 */
      difficulty =
          (spellev(spell) - 1) * 4 - ((skill * 6) + (u.ulevel / 3) + 1);
  
      if (difficulty > 0) {
          /* Player is too low level or unskilled. */
          chance -= isqrt(900 * difficulty + 2000);
      } else {
          /* Player is above level.  Learning continues, but the
           * law of diminishing returns sets in quickly for
           * low-level spells.  That is, a player quickly gains
           * no advantage for raising level.
           */
          int learning = 15 * -difficulty / spellev(spell);
          chance += learning > 20 ? 20 : learning;
      }
  
      /* Clamp the chance: >18 stat and advanced learning only help
       * to a limit, while chances below "hopeless" only raise the
       * specter of overflowing 16-bit ints (and permit wearing a
       * shield to raise the chances :-).
       */
      if (chance < 0)
          chance = 0;
      if (chance > 120)
          chance = 120;
  
      /* Wearing anything but a light shield makes it very awkward
       * to cast a spell.  The penalty is not quite so bad for the
       * player's role-specific spell.
       */
      if (uarms && weight(uarms) > (int) objects[SMALL_SHIELD].oc_weight) {
          if (spellid(spell) == g.urole.spelspec) {
              chance /= 2;
          } else {
              chance /= 4;
          }
      }
  
      /* Finally, chance (based on player intell/wisdom and level) is
       * combined with ability (based on player intrinsics and
       * encumbrances).  No matter how intelligent/wise and advanced
       * a player is, intrinsics and encumbrance can prevent casting;
       * and no matter how able, learning is always required.
       */
      chance = chance * (20 - splcaster) / 15 - splcaster;
  
      /* Clamp to percentile */
      if (chance > 100)
          chance = 100;
      if (chance < 0)
          chance = 0;
  
      return chance;
  }
  
  static char *
  spellretention(int idx, char * outbuf)
  {
      long turnsleft, percent, accuracy;
      int skill;
  
      skill = P_SKILL(spell_skilltype(spellid(idx)));
      skill = max(skill, P_UNSKILLED); /* restricted same as unskilled */
      turnsleft = spellknow(idx);
      *outbuf = '\0'; /* lint suppression */
  
      if (turnsleft < 1L) {
          /* spell has expired; hero can't successfully cast it anymore */
          Strcpy(outbuf, "(gone)");
      } else if (turnsleft >= (long) KEEN) {
          /* full retention, first turn or immediately after reading book */
          Strcpy(outbuf, "100%");
      } else {
          /*
           * Retention is displayed as a range of percentages of
           * amount of time left until memory of the spell expires;
           * the precision of the range depends upon hero's skill
           * in this spell.
           *    expert:  2% intervals; 1-2,   3-4,  ...,   99-100;
           *   skilled:  5% intervals; 1-5,   6-10, ...,   95-100;
           *     basic: 10% intervals; 1-10, 11-20, ...,   91-100;
           * unskilled: 25% intervals; 1-25, 26-50, 51-75, 76-100.
           *
           * At the low end of each range, a value of N% really means
           * (N-1)%+1 through N%; so 1% is "greater than 0, at most 200".
           * KEEN is a multiple of 100; KEEN/100 loses no precision.
           */
          percent = (turnsleft - 1L) / ((long) KEEN / 100L) + 1L;
          accuracy =
              (skill == P_EXPERT) ? 2L : (skill == P_SKILLED)
                                             ? 5L
                                             : (skill == P_BASIC) ? 10L : 25L;
          /* round up to the high end of this range */
          percent = accuracy * ((percent - 1L) / accuracy + 1L);
          Sprintf(outbuf, "%ld%%-%ld%%", percent - accuracy + 1L, percent);
      }
      return outbuf;
  }
  
  /* Learn a spell during creation of the initial inventory */
  void
  initialspell(struct obj* obj)
  {
      int i, otyp = obj->otyp;
  
      for (i = 0; i < MAXSPELL; i++)
          if (spellid(i) == NO_SPELL || spellid(i) == otyp)
              break;
  
      if (i == MAXSPELL) {
          impossible("Too many spells memorized!");
      } else if (spellid(i) != NO_SPELL) {
          /* initial inventory shouldn't contain duplicate spellbooks */
          impossible("Spell %s already known.", OBJ_NAME(objects[otyp]));
      } else {
          g.spl_book[i].sp_id = otyp;
          g.spl_book[i].sp_lev = objects[otyp].oc_level;
          incrnknow(i, 0);
      }
      return;
  }
  
  /*spell.c*/
  