text: /*
   * This file is part of the Micro Python project, http://micropython.org/
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2013, 2014 Damien P. George
   * Copyright (c) 2014 Paul Sokolovsky
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  #include <stdint.h>
  #include <stdio.h>
  #include <string.h>
  #include <assert.h>
  
  #include "mpconfig.h"
  #include "nlr.h"
  #include "misc.h"
  #include "qstr.h"
  #include "lexer.h"
  #include "lexerunix.h"
  #include "parse.h"
  #include "obj.h"
  #include "objmodule.h"
  #include "parsehelper.h"
  #include "compile.h"
  #include "runtime0.h"
  #include "runtime.h"
  #include "builtin.h"
  
  #if 0 // print debugging info
  #define DEBUG_PRINT (1)
  #define DEBUG_printf DEBUG_printf
  #else // don't print debugging info
  #define DEBUG_printf(...) (void)0
  #endif
  
  #define PATH_SEP_CHAR '/'
  
  mp_import_stat_t stat_dir_or_file(vstr_t *path) {
      //printf("stat %s\n", vstr_str(path));
      mp_import_stat_t stat = mp_import_stat(vstr_str(path));
      if (stat == MP_IMPORT_STAT_DIR) {
          return stat;
      }
      vstr_add_str(path, ".py");
      stat = mp_import_stat(vstr_str(path));
      if (stat == MP_IMPORT_STAT_FILE) {
          return stat;
      }
      return MP_IMPORT_STAT_NO_EXIST;
  }
  
  mp_import_stat_t find_file(const char *file_str, uint file_len, vstr_t *dest) {
      // extract the list of paths
      uint path_num = 0;
      mp_obj_t *path_items;
  #if MICROPY_PY_SYS
      mp_obj_list_get(mp_sys_path, &path_num, &path_items);
  #endif
  
      if (path_num == 0) {
          // mp_sys_path is empty, so just use the given file name
          vstr_add_strn(dest, file_str, file_len);
          return stat_dir_or_file(dest);
      } else {
          // go through each path looking for a directory or file
          for (int i = 0; i < path_num; i++) {
              vstr_reset(dest);
              uint p_len;
              const char *p = mp_obj_str_get_data(path_items[i], &p_len);
              if (p_len > 0) {
                  vstr_add_strn(dest, p, p_len);
                  vstr_add_char(dest, PATH_SEP_CHAR);
              }
              vstr_add_strn(dest, file_str, file_len);
              mp_import_stat_t stat = stat_dir_or_file(dest);
              if (stat != MP_IMPORT_STAT_NO_EXIST) {
                  return stat;
              }
          }
  
          // could not find a directory or file
          return MP_IMPORT_STAT_NO_EXIST;
      }
  }
  
  void do_load(mp_obj_t module_obj, vstr_t *file) {
      // create the lexer
      mp_lexer_t *lex = mp_lexer_new_from_file(vstr_str(file));
  
      if (lex == NULL) {
          // we verified the file exists using stat, but lexer could still fail
          nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ImportError, "No module named '%s'", vstr_str(file)));
      }
  
      qstr source_name = mp_lexer_source_name(lex);
  
      // save the old context
      mp_obj_dict_t *old_locals = mp_locals_get();
      mp_obj_dict_t *old_globals = mp_globals_get();
  
      // set the new context
      mp_locals_set(mp_obj_module_get_globals(module_obj));
      mp_globals_set(mp_obj_module_get_globals(module_obj));
  
      // parse the imported script
      mp_parse_error_kind_t parse_error_kind;
      mp_parse_node_t pn = mp_parse(lex, MP_PARSE_FILE_INPUT, &parse_error_kind);
  
      if (pn == MP_PARSE_NODE_NULL) {
          // parse error; clean up and raise exception
          mp_obj_t exc = mp_parse_make_exception(lex, parse_error_kind);
          mp_lexer_free(lex);
          mp_locals_set(old_locals);
          mp_globals_set(old_globals);
          nlr_raise(exc);
      }
  
      mp_lexer_free(lex);
  
      // compile the imported script
      mp_obj_t module_fun = mp_compile(pn, source_name, MP_EMIT_OPT_NONE, false);
      mp_parse_node_free(pn);
  
      if (module_fun == mp_const_none) {
          // TODO handle compile error correctly
          mp_locals_set(old_locals);
          mp_globals_set(old_globals);
          nlr_raise(mp_obj_new_exception_msg(&mp_type_SyntaxError, "Syntax error in imported module"));
      }
  
      // complied successfully, execute it
      nlr_buf_t nlr;
      if (nlr_push(&nlr) == 0) {
          mp_call_function_0(module_fun);
          nlr_pop();
      } else {
          // exception; restore context and re-raise same exception
          mp_locals_set(old_locals);
          mp_globals_set(old_globals);
          nlr_raise(nlr.ret_val);
      }
      mp_locals_set(old_locals);
      mp_globals_set(old_globals);
  }
  
  mp_obj_t mp_builtin___import__(uint n_args, mp_obj_t *args) {
  #if DEBUG_PRINT
      printf("__import__:\n");
      for (int i = 0; i < n_args; i++) {
          printf("  ");
          mp_obj_print(args[i], PRINT_REPR);
          printf("\n");
      }
  #endif
  
      mp_obj_t module_name = args[0];
      mp_obj_t fromtuple = mp_const_none;
      int level = 0;
      if (n_args >= 4) {
          fromtuple = args[3];
          if (n_args >= 5) {
              level = MP_OBJ_SMALL_INT_VALUE(args[4]);
          }
      }
  
      uint mod_len;
      const char *mod_str = (const char*)mp_obj_str_get_data(module_name, &mod_len);
  
      if (level != 0) {
          // What we want to do here is to take name of current module,
          // chop <level> trailing components, and concatenate with passed-in
          // module name, thus resolving relative import name into absolue.
          // This even appears to be correct per
          // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
          // "Relative imports use a module's __name__ attribute to determine that
          // module's position in the package hierarchy."
          mp_obj_t this_name_q = mp_obj_dict_get(mp_globals_get(), MP_OBJ_NEW_QSTR(MP_QSTR___name__));
          assert(this_name_q != MP_OBJ_NULL);
  #if DEBUG_PRINT
          printf("Current module: ");
          mp_obj_print(this_name_q, PRINT_REPR);
          printf("\n");
  #endif
  
          uint this_name_l;
          const char *this_name = (const char*)mp_obj_str_get_data(this_name_q, &this_name_l);
  
          uint dots_seen = 0;
          const char *p = this_name + this_name_l - 1;
          while (p > this_name) {
              if (*p == '.') {
                  dots_seen++;
                  if (--level == 0) {
                      break;
                  }
              }
              p--;
          }
  
          if (dots_seen == 0 && level == 1) {
              // http://legacy.python.org/dev/peps/pep-0328/#relative-imports-and-name
              // "If the module's name does not contain any package information
              // (e.g. it is set to '__main__') then relative imports are
              // resolved as if the module were a top level module, regardless
              // of where the module is actually located on the file system."
              // Supposedly this if catches this condition and resolve it properly
              // TODO: But nobody knows for sure. This condition happens when
              // package's __init__.py does something like "import .submod". So,
              // maybe we should check for package here? But quote above doesn't
              // talk about packages, it talks about dot-less module names.
              p = this_name + this_name_l;
          } else if (level != 0) {
              nlr_raise(mp_obj_new_exception_msg(&mp_type_ImportError, "Invalid relative import"));
          }
  
          uint new_mod_l = (mod_len == 0 ? p - this_name : p - this_name + 1 + mod_len);
          char *new_mod = alloca(new_mod_l);
          memcpy(new_mod, this_name, p - this_name);
          if (mod_len != 0) {
              new_mod[p - this_name] = '.';
              memcpy(new_mod + (p - this_name) + 1, mod_str, mod_len);
          }
  
          qstr new_mod_q = qstr_from_strn(new_mod, new_mod_l);
          DEBUG_printf("Resolved relative name: %s\n", qstr_str(new_mod_q));
          module_name = MP_OBJ_NEW_QSTR(new_mod_q);
          mod_str = new_mod;
          mod_len = new_mod_l;
      }
  
      // check if module already exists
      mp_obj_t module_obj = mp_module_get(mp_obj_str_get_qstr(module_name));
      if (module_obj != MP_OBJ_NULL) {
          DEBUG_printf("Module already loaded\n");
          // If it's not a package, return module right away
          char *p = strchr(mod_str, '.');
          if (p == NULL) {
              return module_obj;
          }
          // If fromlist is not empty, return leaf module
          if (fromtuple != mp_const_none) {
              return module_obj;
          }
          // Otherwise, we need to return top-level package
          qstr pkg_name = qstr_from_strn(mod_str, p - mod_str);
          return mp_module_get(pkg_name);
      }
      DEBUG_printf("Module not yet loaded\n");
  
      uint last = 0;
      VSTR_FIXED(path, MICROPY_ALLOC_PATH_MAX)
      module_obj = MP_OBJ_NULL;
      mp_obj_t top_module_obj = MP_OBJ_NULL;
      mp_obj_t outer_module_obj = MP_OBJ_NULL;
      uint i;
      for (i = 1; i <= mod_len; i++) {
          if (i == mod_len || mod_str[i] == '.') {
              // create a qstr for the module name up to this depth
              qstr mod_name = qstr_from_strn(mod_str, i);
              DEBUG_printf("Processing module: %s\n", qstr_str(mod_name));
              DEBUG_printf("Previous path: %s\n", vstr_str(&path));
  
              // find the file corresponding to the module name
              mp_import_stat_t stat;
              if (vstr_len(&path) == 0) {
                  // first module in the dotted-name; search for a directory or file
                  stat = find_file(mod_str, i, &path);
              } else {
                  // latter module in the dotted-name; append to path
                  vstr_add_char(&path, PATH_SEP_CHAR);
                  vstr_add_strn(&path, mod_str + last, i - last);
                  stat = stat_dir_or_file(&path);
              }
              DEBUG_printf("Current path: %s\n", vstr_str(&path));
  
              // fail if we couldn't find the file
              if (stat == MP_IMPORT_STAT_NO_EXIST) {
                  nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ImportError, "No module named '%s'", qstr_str(mod_name)));
              }
  
              module_obj = mp_module_get(mod_name);
              if (module_obj == MP_OBJ_NULL) {
                  // module not already loaded, so load it!
  
                  module_obj = mp_obj_new_module(mod_name);
  
                  if (stat == MP_IMPORT_STAT_DIR) {
                      DEBUG_printf("%s is dir\n", vstr_str(&path));
                      // https://docs.python.org/3/reference/import.html
                      // "Specifically, any module that contains a __path__ attribute is considered a package."
                      mp_store_attr(module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path), false));
                      vstr_add_char(&path, PATH_SEP_CHAR);
                      vstr_add_str(&path, "__init__.py");
                      if (mp_import_stat(vstr_str(&path)) != MP_IMPORT_STAT_FILE) {
                          vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                          printf("Notice: %s is imported as namespace package\n", vstr_str(&path));
                      } else {
                          do_load(module_obj, &path);
                          vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                      }
                  } else { // MP_IMPORT_STAT_FILE
                      do_load(module_obj, &path);
                      // TODO: We cannot just break here, at the very least, we must execute
                      // trailer code below. But otherwise if there're remaining components,
                      // that would be (??) object path within module, not modules path within FS.
                      // break;
                  }
              }
              if (outer_module_obj != MP_OBJ_NULL) {
                  qstr s = qstr_from_strn(mod_str + last, i - last);
                  mp_store_attr(outer_module_obj, s, module_obj);
              }
              outer_module_obj = module_obj;
              if (top_module_obj == MP_OBJ_NULL) {
                  top_module_obj = module_obj;
              }
              last = i + 1;
          }
      }
  
      if (i < mod_len) {
          // we loaded a package, now need to load objects from within that package
          // TODO
          assert(0);
      }
  
      // If fromlist is not empty, return leaf module
      if (fromtuple != mp_const_none) {
          return module_obj;
      }
      // Otherwise, we need to return top-level package
      return top_module_obj;
  }
  
  MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_builtin___import___obj, 1, 5, mp_builtin___import__);
  