#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <memory.h>
#include <mruby.h>
#include <mruby/class.h>
#include <mruby/variable.h>
#include <mruby/array.h>
#include <mruby/string.h>
#include <mruby/data.h>
#include <mruby/variable.h>
#include "oniguruma.h"

#ifdef MRUBY_VERSION
#define mrb_args_int mrb_int
#else
#define mrb_args_int int
#endif

static void
onig_regexp_free(mrb_state *mrb, void *p) {
  onig_free((OnigRegex) p);
}

static struct mrb_data_type mrb_onig_regexp_type = {
  "PosixRegexp", onig_regexp_free
};

static void
match_data_free(mrb_state* mrb, void* p) {
  (void)mrb;
  onig_region_free((OnigRegion*)p, 1);
}

static struct mrb_data_type mrb_onig_region_type = {
  "OnigRegion", match_data_free
};

static mrb_value
onig_regexp_initialize(mrb_state *mrb, mrb_value self) {
  mrb_value str, flag = mrb_nil_value();
  mrb_get_args(mrb, "S|o", &str, &flag);

  int cflag = 0;
  OnigSyntaxType* syntax = ONIG_SYNTAX_RUBY;
  if(mrb_nil_p(flag)) {
  } else if(mrb_type(flag) == MRB_TT_TRUE) {
    cflag |= ONIG_OPTION_IGNORECASE;
  } else if(mrb_fixnum_p(flag)) {
    int int_flags = mrb_fixnum(flag);
    if(int_flags & 0x1) { cflag |= ONIG_OPTION_IGNORECASE; }
    if(int_flags & 0x2) { cflag |= ONIG_OPTION_EXTEND; }
    if(int_flags & 0x4) { cflag |= ONIG_OPTION_MULTILINE; }
  } else if(mrb_string_p(flag)) {
    char const* str_flags = mrb_string_value_ptr(mrb, flag);
    if(strchr(str_flags, 'i')) { cflag |= ONIG_OPTION_IGNORECASE; }
    if(strchr(str_flags, 'x')) { cflag |= ONIG_OPTION_EXTEND; }
    if(strchr(str_flags, 'm')) { cflag |= ONIG_OPTION_MULTILINE; }
  } else {
    mrb_raisef(mrb, E_ARGUMENT_ERROR, "unknown regexp flag: %S", flag);
  }

  OnigErrorInfo einfo;
  OnigRegex reg;
  int result = onig_new(&reg, (OnigUChar*)RSTRING_PTR(str), (OnigUChar*) RSTRING_PTR(str) + RSTRING_LEN(str),
                        cflag, ONIG_ENCODING_UTF8, syntax, &einfo);
  if (result != ONIG_NORMAL) {
    char err[ONIG_MAX_ERROR_MESSAGE_LEN] = "";
    onig_error_code_to_str((OnigUChar*)err, result);
    mrb_raisef(mrb, E_ARGUMENT_ERROR, "'%S' is an invalid regular expression because %S.",
               str, mrb_str_new_cstr(mrb, err));
  }
  mrb_iv_set(mrb, self, mrb_intern_lit(mrb, "@source"), str);

  DATA_PTR(self) = reg;
  DATA_TYPE(self) = &mrb_onig_regexp_type;

  return self;
}

static mrb_value
create_onig_region(mrb_state* mrb, mrb_value const str, mrb_value rex) {
  mrb_assert(mrb_string_p(str));
  mrb_assert(mrb_type(rex) == MRB_TT_DATA && DATA_TYPE(rex) == &mrb_onig_regexp_type);
  mrb_value const c = mrb_obj_value(mrb_data_object_alloc(
      mrb, mrb_class_get(mrb, "OnigMatchData"), onig_region_new(), &mrb_onig_region_type));
  mrb_iv_set(mrb, c, mrb_intern_lit(mrb, "string"), mrb_str_dup(mrb, str));
  mrb_iv_set(mrb, c, mrb_intern_lit(mrb, "regexp"), rex);
  return c;
}

static int
onig_match_common(mrb_state* mrb, OnigRegex reg, mrb_value match_value, mrb_value str, int pos) {
  mrb_assert(mrb_string_p(str));
  mrb_assert(DATA_TYPE(match_value) == &mrb_onig_region_type);
  OnigRegion* const match = (OnigRegion*)DATA_PTR(match_value);
  OnigUChar const* str_ptr = (OnigUChar const*)RSTRING_PTR(str);
  int const result = onig_search(reg, str_ptr, str_ptr + RSTRING_LEN(str),
                                 str_ptr + pos, str_ptr + RSTRING_LEN(str), match, 0);
  if (result != ONIG_MISMATCH && result < 0) {
    char err[ONIG_MAX_ERROR_MESSAGE_LEN] = "";
    onig_error_code_to_str((OnigUChar*)err, result);
    mrb_raise(mrb, E_REGEXP_ERROR, err);
  }

  struct RObject* const cls = (struct RObject*)mrb_class_get(mrb, "OnigRegexp");
  mrb_obj_iv_set(mrb, cls, mrb_intern_lit(mrb, "@last_match"), match_value);

  if (result != ONIG_MISMATCH &&
      mrb_class_get(mrb, "Regexp") == (struct RClass*)cls &&
      mrb_bool(mrb_obj_iv_get(mrb, (struct RObject*)cls, mrb_intern_lit(mrb, "@set_global_variables"))))
  {
    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$~"), match_value);
    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$&"),
               mrb_funcall(mrb, match_value, "[]", 1, mrb_fixnum_value(0)));
    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$`"), mrb_funcall(mrb, match_value, "pre_match", 0));
    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$'"), mrb_funcall(mrb, match_value, "post_match", 0));
    mrb_gv_set(mrb, mrb_intern_lit(mrb, "$+"),
               mrb_funcall(mrb, match_value, "[]", 1, mrb_fixnum_value(match->num_regs - 1)));

    // $1 to $9
    int idx = 1;
    int const idx_max = match->num_regs > 10? 10 : match->num_regs;
    for(; idx < idx_max; ++idx) {
      char const n[] = { '$', '0' + idx };
      mrb_gv_set(mrb, mrb_intern(mrb, n, 2),
                 mrb_funcall(mrb, match_value, "[]", 1, mrb_fixnum_value(idx)));
    }

    for(; idx < 10; ++idx) {
      char const n[] = { '$', '0' + idx };
      mrb_gv_remove(mrb, mrb_intern(mrb, n, 2));
    }
  }

  return result;
}

static mrb_value
onig_regexp_match(mrb_state *mrb, mrb_value self) {
  mrb_value str;
  OnigRegex reg;
  mrb_int pos = 0;

  mrb_get_args(mrb, "S|i", &str, &pos);
  if (pos < 0 || pos >= RSTRING_LEN(str)) {
    return mrb_nil_value();
  }

  Data_Get_Struct(mrb, self, &mrb_onig_regexp_type, reg);

  mrb_value const ret = create_onig_region(mrb, str, self);
  return (onig_match_common(mrb, reg, ret, str, pos) == ONIG_MISMATCH)
      ? mrb_nil_value() : ret;
}

static mrb_value
onig_regexp_equal(mrb_state *mrb, mrb_value self) {
  mrb_value other;
  OnigRegex self_reg, other_reg;

  mrb_get_args(mrb, "o", &other);
  if (mrb_obj_equal(mrb, self, other)){
    return mrb_true_value();
  }
  if (mrb_nil_p(other)) {
    return mrb_false_value();
  }
  Data_Get_Struct(mrb, self, &mrb_onig_regexp_type, self_reg);
  Data_Get_Struct(mrb, other, &mrb_onig_regexp_type, other_reg);

  if (!self_reg || !other_reg){
      mrb_raise(mrb, E_RUNTIME_ERROR, "Invalid OnigRegexp");
  }
  if (onig_get_options(self_reg) != onig_get_options(other_reg)){
      return mrb_false_value();
  }
  return mrb_str_equal(mrb, mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "@source")), mrb_iv_get(mrb, other, mrb_intern_lit(mrb, "@source"))) ?
      mrb_true_value() : mrb_false_value();
}

static mrb_value
onig_regexp_casefold_p(mrb_state *mrb, mrb_value self) {
  OnigRegex reg;

  Data_Get_Struct(mrb, self, &mrb_onig_regexp_type, reg);
  return (onig_get_options(reg) & ONIG_OPTION_IGNORECASE) ? mrb_true_value() : mrb_false_value();
}

static mrb_value
onig_regexp_options(mrb_state *mrb, mrb_value self) {
  OnigRegex reg;
  Data_Get_Struct(mrb, self, &mrb_onig_regexp_type, reg);
  return mrb_fixnum_value(onig_get_options(reg));
}

static mrb_value
onig_regexp_version(mrb_state* mrb, mrb_value self) {
  (void)self;
  return mrb_str_new_cstr(mrb, onig_version());
}

static mrb_value
match_data_to_a(mrb_state* mrb, mrb_value self);

static mrb_int
match_data_actual_index(mrb_state* mrb, mrb_value self, mrb_value idx_value) {
  if(mrb_fixnum_p(idx_value)) { return mrb_fixnum(idx_value); }

  char const* name = NULL;
  char const* name_end = NULL;
  if(mrb_symbol_p(idx_value)) {
    mrb_int sym_len;
    name = mrb_sym2name_len(mrb, mrb_symbol(idx_value), &sym_len);
    name_end = name + sym_len;
  } else if(mrb_string_p(idx_value)) {
    name = mrb_string_value_ptr(mrb, idx_value);
    name_end = name + strlen(name);
  } else {
    mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid MatchData index type: %S", idx_value);
  }
  mrb_assert(name && name_end);

  mrb_value const regexp = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "regexp"));
  mrb_assert(!mrb_nil_p(regexp));
  mrb_assert(DATA_TYPE(regexp) == &mrb_onig_regexp_type);
  mrb_assert(DATA_TYPE(self) == &mrb_onig_region_type);
  int const idx = onig_name_to_backref_number(
      (OnigRegex)DATA_PTR(regexp), (OnigUChar const*)name, (OnigUChar const*)name_end,
      (OnigRegion*)DATA_PTR(self));
  if (idx < 0) {
    mrb_raisef(mrb, E_INDEX_ERROR, "undefined group name reference: %S", idx_value);
  }
  return idx;
}

// ISO 15.2.16.3.1
static mrb_value
match_data_index(mrb_state* mrb, mrb_value self) {
  mrb_value idx_value;
  mrb_get_args(mrb, "o", &idx_value);
  return mrb_ary_entry(match_data_to_a(mrb, self), match_data_actual_index(mrb, self, idx_value));
}

#define match_data_check_index(idx) \
  if(idx < 0 || reg->num_regs <= idx) \
    mrb_raisef(mrb, E_INDEX_ERROR, "index %S out of matches", mrb_fixnum_value(idx)) \

// ISO 15.2.16.3.2
static mrb_value
match_data_begin(mrb_state* mrb, mrb_value self) {
  mrb_value idx_value;
  mrb_get_args(mrb, "o", &idx_value);
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  mrb_int const idx = match_data_actual_index(mrb, self, idx_value);
  match_data_check_index(idx);
  return mrb_fixnum_value(reg->beg[idx]);
}

// ISO 15.2.16.3.3
static mrb_value
match_data_captures(mrb_state* mrb, mrb_value self) {
  mrb_value ary = match_data_to_a(mrb, self);
  return mrb_ary_new_from_values(mrb, RARRAY_LEN(ary) - 1, RARRAY_PTR(ary) + 1);
}

// ISO 15.2.16.3.4
static mrb_value
match_data_end(mrb_state* mrb, mrb_value self) {
  mrb_value idx_value;
  mrb_get_args(mrb, "o", &idx_value);
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  mrb_int const idx = match_data_actual_index(mrb, self, idx_value);
  match_data_check_index(idx);
  return mrb_fixnum_value(reg->end[idx]);
}

// ISO 15.2.16.3.5
static mrb_value
match_data_copy(mrb_state* mrb, mrb_value self) {
  mrb_value src_val;
  mrb_get_args(mrb, "o", &src_val);

  OnigRegion* src;
  Data_Get_Struct(mrb, src_val, &mrb_onig_region_type, src);

  OnigRegion* dst = onig_region_new();
  onig_region_copy(dst, src);

  DATA_PTR(self) = dst;
  DATA_TYPE(self) = &mrb_onig_region_type;
  mrb_iv_set(mrb, self, mrb_intern_lit(mrb, "string"), mrb_iv_get(mrb, src_val, mrb_intern_lit(mrb, "string")));
  mrb_iv_set(mrb, self, mrb_intern_lit(mrb, "regexp"), mrb_iv_get(mrb, src_val, mrb_intern_lit(mrb, "regexp")));
  return self;
}

// ISO 15.2.16.3.6
// ISO 15.2.16.3.10
static mrb_value
match_data_length(mrb_state* mrb, mrb_value self) {
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  return mrb_fixnum_value(reg->num_regs);
}

// ISO 15.2.16.3.7
static mrb_value
match_data_offset(mrb_state* mrb, mrb_value self) {
  mrb_value idx_value;
  mrb_get_args(mrb, "o", &idx_value);
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  mrb_int const idx = match_data_actual_index(mrb, self, idx_value);
  match_data_check_index(idx);
  mrb_value ret = mrb_ary_new_capa(mrb, 2);
  mrb_ary_push(mrb, ret, mrb_fixnum_value(reg->beg[idx]));
  mrb_ary_push(mrb, ret, mrb_fixnum_value(reg->end[idx]));
  return ret;
}

// ISO 15.2.16.3.8
static mrb_value
match_data_post_match(mrb_state* mrb, mrb_value self) {
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  mrb_value str = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "string"));
  return mrb_str_substr(mrb, str, reg->end[0], RSTRING_LEN(str) - reg->end[0]);
}

// ISO 15.2.16.3.9
static mrb_value
match_data_pre_match(mrb_state* mrb, mrb_value self) {
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  mrb_value str = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "string"));
  return mrb_str_substr(mrb, str, 0, reg->beg[0]);
}

// ISO 15.2.16.3.11
static mrb_value
match_data_string(mrb_state* mrb, mrb_value self) {
  return mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "string"));
}

static mrb_value
match_data_regexp(mrb_state* mrb, mrb_value self) {
  return mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "regexp"));
}

// ISO 15.2.16.3.12
static mrb_value
match_data_to_a(mrb_state* mrb, mrb_value self) {
  mrb_value cache = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "cache"));
  if(!mrb_nil_p(cache)) {
    return cache;
  }

  mrb_value str = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "string"));
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);

  mrb_value ret = mrb_ary_new_capa(mrb, reg->num_regs);
  int i, ai = mrb_gc_arena_save(mrb);
  for(i = 0; i < reg->num_regs; ++i) {
    mrb_ary_push(mrb, ret, mrb_str_substr(mrb, str, reg->beg[i], reg->end[i] - reg->beg[i]));
    mrb_gc_arena_restore(mrb, ai);
  }
  return ret;
}

// ISO 15.2.16.3.13
static mrb_value
match_data_to_s(mrb_state* mrb, mrb_value self) {
  mrb_value str = mrb_iv_get(mrb, self, mrb_intern_lit(mrb, "string"));
  OnigRegion* reg;
  Data_Get_Struct(mrb, self, &mrb_onig_region_type, reg);
  return mrb_str_substr(mrb, str, reg->beg[0], reg->end[0] - reg->beg[0]);
}

static void
append_replace_str(mrb_state* mrb, mrb_value result, mrb_value replace,
                   mrb_value src, OnigRegex reg, OnigRegion* match)
{
  mrb_assert(mrb_string_p(replace));
  char const* ch;
  char const* const end = RSTRING_PTR(replace) + RSTRING_LEN(replace);
  for(ch = RSTRING_PTR(replace); ch < end; ++ch) {
    if (*ch != '\\' || (ch + 1) >= end) {
      mrb_str_cat(mrb, result, ch, 1);
      continue;
    }

    switch(*(++ch)) { // skip back slash and get next char
      case 'k': { // group name
        if ((ch + 2) >= end || ch[1] != '<') { goto replace_expr_error; }
        char const* name_beg = ch += 2;
        while (*ch != '>') { if(++ch == end) { goto replace_expr_error; } }
        mrb_assert(ch < end);
        mrb_assert(*ch == '>');
        int const idx = onig_name_to_backref_number(
            reg, (OnigUChar const*)name_beg, (OnigUChar const*)ch, match);
        if (idx < 0) {
          mrb_raisef(mrb, E_INDEX_ERROR, "undefined group name reference: %S",
                     mrb_str_substr(mrb, replace, name_beg - RSTRING_PTR(replace), ch - name_beg));
        }
        mrb_str_cat(mrb, result, RSTRING_PTR(src) + match->beg[idx], match->end[idx] - match->beg[idx]);
      } break;

      case '\\': // escaped back slash
        mrb_str_cat(mrb, result, ch, 1);
        break;

      default:
        if (isdigit(*ch)) { // group number 0-9
          int const idx = *ch - '0';
          if (idx >= match->num_regs) {
            mrb_raisef(mrb, E_INDEX_ERROR, "undefined group number reference: %S (max: %S)",
                       mrb_fixnum_value(idx), mrb_fixnum_value(match->num_regs));
          }
          mrb_str_cat(mrb, result, RSTRING_PTR(src) + match->beg[idx], match->end[idx] - match->beg[idx]);
        } else {
          char const str[] = { '\\', *ch };
          mrb_str_cat(mrb, result, str, 2);
        }
        break;
    }
  }

  if(ch == end) { return; }

replace_expr_error:
  mrb_raisef(mrb, E_REGEXP_ERROR, "invalid replace expression: %S", replace);
}

// ISO 15.2.10.5.18
static mrb_value
string_gsub(mrb_state* mrb, mrb_value self) {
  mrb_value blk, match_expr, replace_expr = mrb_nil_value();
  int const argc = mrb_get_args(mrb, "&o|S", &blk, &match_expr, &replace_expr);

  if(mrb_string_p(match_expr)) {
    mrb_value argv[] = { match_expr, replace_expr };
    return mrb_funcall_with_block(mrb, self, mrb_intern_lit(mrb, "string_gsub"), argc, argv, blk);
  }

  if(!mrb_nil_p(blk) && !mrb_nil_p(replace_expr)) {
    mrb_raise(mrb, E_ARGUMENT_ERROR, "both block and replace expression must not be passed");
  }

  OnigRegex reg;
  Data_Get_Struct(mrb, match_expr, &mrb_onig_regexp_type, reg);
  mrb_value const result = mrb_str_new(mrb, NULL, 0);
  mrb_value const match_value = create_onig_region(mrb, self, match_expr);
  OnigRegion* const match = (OnigRegion*)DATA_PTR(match_value);
  int last_end_pos = 0;

  while(1) {
    if(onig_match_common(mrb, reg, match_value, self, last_end_pos) == ONIG_MISMATCH) { break; }

    mrb_str_cat(mrb, result, RSTRING_PTR(self) + last_end_pos, match->beg[0] - last_end_pos);

    if(mrb_nil_p(blk)) {
      append_replace_str(mrb, result, replace_expr, self, reg, match);
    } else {
      mrb_value const tmp_str = mrb_str_to_str(mrb, mrb_yield(mrb, blk, mrb_str_substr(
          mrb, self, match->beg[0], match->end[0] - match->beg[0])));
      mrb_assert(mrb_string_p(tmp_str));
      mrb_str_concat(mrb, result, tmp_str);
    }

    last_end_pos = match->end[0];
  }

  mrb_str_cat(mrb, result, RSTRING_PTR(self) + last_end_pos, RSTRING_LEN(self) - last_end_pos);
  return result;
}

// ISO 15.2.10.5.32
static mrb_value
string_scan(mrb_state* mrb, mrb_value self) {
  mrb_value blk, match_expr;
  mrb_get_args(mrb, "&o", &blk, &match_expr);

  if(mrb_string_p(match_expr)) {
    return mrb_funcall_with_block(mrb, self, mrb_intern_lit(mrb, "string_scan"),
                                  1, &match_expr, blk);
  }

  OnigRegex reg;
  Data_Get_Struct(mrb, match_expr, &mrb_onig_regexp_type, reg);
  mrb_value const result = mrb_nil_p(blk)? mrb_ary_new(mrb) : self;
  mrb_value m_value = create_onig_region(mrb, self, match_expr);
  OnigRegion* const m = (OnigRegion*)DATA_PTR(m_value);
  int last_end_pos = 0;
  int i;

  while (1) {
    if(onig_match_common(mrb, reg, m_value, self, last_end_pos) == ONIG_MISMATCH) { break; }

    if(mrb_nil_p(blk)) {
      mrb_assert(mrb_array_p(result));
      if(m->num_regs == 1) {
        mrb_ary_push(mrb, result, mrb_str_substr(mrb, self, m->beg[0], m->end[0] - m->beg[0]));
      } else {
        mrb_value const elem = mrb_ary_new_capa(mrb, m->num_regs - 1);
        for(i = 1; i < m->num_regs; ++i) {
          mrb_ary_push(mrb, elem, mrb_str_substr(mrb, self, m->beg[i], m->end[i] - m->beg[i]));
        }
        mrb_ary_push(mrb, result, elem);
      }
    } else { // call block
      mrb_assert(mrb_string_p(result));
      if(m->num_regs == 1) {
        mrb_yield(mrb, blk, mrb_str_substr(mrb, self, m->beg[0], m->end[0] - m->beg[0]));
      } else {
        mrb_value argv[m->num_regs - 1];
        for(i = 1; i < m->num_regs; ++i) {
          argv[i - 1] = mrb_str_substr(mrb, self, m->beg[i], m->end[i] - m->beg[i]);
        }
        mrb_yield_argv(mrb, blk, m->num_regs - 1, argv);
      }
    }

    last_end_pos = m->end[0];
  }

  return result;
}

// ISO 15.2.10.5.35
static mrb_value
string_split(mrb_state* mrb, mrb_value self) {
  mrb_value pattern = mrb_nil_value(); mrb_int limit = 0;
  int argc = mrb_get_args(mrb, "|oi", &pattern, &limit);

  if(argc == 0) { // check $; global variable
    pattern = mrb_gv_get(mrb, mrb_intern_lit(mrb, "$;"));
    if(!mrb_nil_p(pattern)) { argc = 1; }
  }

  if(mrb_nil_p(pattern) || mrb_string_p(pattern)) {
    return mrb_funcall(mrb, self, "string_split", argc, pattern, mrb_fixnum_value(limit));
  }

  mrb_value const result = mrb_ary_new(mrb);
  if(RSTRING_LEN(self) == 0) { return result; }

  OnigRegex reg;
  Data_Get_Struct(mrb, pattern, &mrb_onig_regexp_type, reg);
  mrb_value const match_value = create_onig_region(mrb, self, pattern);
  OnigRegion* const match = (OnigRegion*)DATA_PTR(match_value);
  int last_end_pos = 0, next_match_pos = 0;
  mrb_int num_matches = 0;

  while (limit <= 0 || (limit - 1) > num_matches) {
    int i;
    if(next_match_pos >= RSTRING_LEN(self) ||
       onig_match_common(mrb, reg, match_value, self, next_match_pos) == ONIG_MISMATCH) { break; }

    if (last_end_pos == match->end[0]) {
      ++next_match_pos;
      // Remove this loop if not using UTF-8
      for (; next_match_pos < RSTRING_LEN(self) && (RSTRING_PTR(self)[next_match_pos] & 0xC0) == 0x80;
          ++next_match_pos) {}
    } else {
      mrb_ary_push(mrb, result, mrb_str_substr(
          mrb, self, last_end_pos, match->beg[0] - last_end_pos));
      // If there are captures, add them to the array
      for (i = 1; i < match->num_regs; ++i) {
        mrb_ary_push(mrb, result, mrb_str_substr(
            mrb, self, match->beg[i], match->end[i] - match->beg[i]));
      }
      last_end_pos = match->end[0];
      next_match_pos = last_end_pos;
      ++num_matches;
    }
  }
  if (last_end_pos <= RSTRING_LEN(self)) {
    mrb_ary_push(mrb, result, mrb_str_substr(
        mrb, self, last_end_pos, RSTRING_LEN(self) - last_end_pos));
  }

  if (limit == 0) { // remove empty trailing elements
    int count = 0, i;
    for (i = RARRAY_LEN(result); i > 0; --i) {
      mrb_assert(mrb_string_p(RARRAY_PTR(result)[i - 1]));
      if (RSTRING_LEN(RARRAY_PTR(result)[i - 1]) != 0) { break; }
      else { ++count; }
    }
    if(count > 0) {
      return mrb_ary_new_from_values(mrb, RARRAY_LEN(result) - count, RARRAY_PTR(result));
    }
  }

  return result;
}

// ISO 15.2.10.5.36
static mrb_value
string_sub(mrb_state* mrb, mrb_value self) {
  mrb_value blk, match_expr, replace_expr = mrb_nil_value();
  int const argc = mrb_get_args(mrb, "&o|S", &blk, &match_expr, &replace_expr);

  if(mrb_string_p(match_expr)) {
    mrb_value argv[] = { match_expr, replace_expr };
    return mrb_funcall_with_block(mrb, self, mrb_intern_lit(mrb, "string_sub"), argc, argv, blk);
  }

  if(!mrb_nil_p(blk) && !mrb_nil_p(replace_expr)) {
    mrb_raise(mrb, E_ARGUMENT_ERROR, "both block and replace expression must not be passed");
  }

  OnigRegex reg;
  Data_Get_Struct(mrb, match_expr, &mrb_onig_regexp_type, reg);
  mrb_value const result = mrb_str_new(mrb, NULL, 0);
  mrb_value const match_value = create_onig_region(mrb, self, match_expr);
  OnigRegion* const match = (OnigRegion*)DATA_PTR(match_value);

  int const onig_result = onig_match_common(mrb, reg, match_value, self, 0);
  if(onig_result == ONIG_MISMATCH) { return self; }

  mrb_str_cat(mrb, result, RSTRING_PTR(self), match->beg[0]);

  if(mrb_nil_p(blk)) {
    append_replace_str(mrb, result, replace_expr, self, reg, match);
  } else {
    mrb_value const tmp_str = mrb_str_to_str(mrb, mrb_yield(mrb, blk, mrb_str_substr(
        mrb, self, match->beg[0], match->end[0] - match->beg[0])));
    mrb_assert(mrb_string_p(tmp_str));
    mrb_str_concat(mrb, result, tmp_str);
  }

  int const last_end_pos = match->end[0];
  mrb_str_cat(mrb, result, RSTRING_PTR(self) + last_end_pos, RSTRING_LEN(self) - last_end_pos);

  return result;
}

static mrb_value
onig_regexp_clear_global_variables(mrb_state* mrb, mrb_value self) {
  mrb_gv_remove(mrb, mrb_intern_lit(mrb, "$~"));
  mrb_gv_remove(mrb, mrb_intern_lit(mrb, "$&"));
  mrb_gv_remove(mrb, mrb_intern_lit(mrb, "$`"));
  mrb_gv_remove(mrb, mrb_intern_lit(mrb, "$'"));
  mrb_gv_remove(mrb, mrb_intern_lit(mrb, "$+"));

  int idx;
  for(idx = 1; idx < 10; ++idx) {
    char const n[] = { '$', '0' + idx };
    mrb_gv_remove(mrb, mrb_intern(mrb, n, 2));
  }

  return self;
}

static mrb_value
onig_regexp_does_set_global_variables(mrb_state* mrb, mrb_value self) {
  (void)self;
  return mrb_obj_iv_get(mrb, (struct RObject*)mrb_class_get(mrb, "OnigRegexp"),
                        mrb_intern_lit(mrb, "@set_global_variables"));
}
static mrb_value
onig_regexp_set_set_global_variables(mrb_state* mrb, mrb_value self) {
  mrb_value arg;
  mrb_get_args(mrb, "o", &arg);
  mrb_value const ret = mrb_bool_value(mrb_bool(arg));
  mrb_obj_iv_set(mrb, (struct RObject*)mrb_class_get(mrb, "OnigRegexp"),
                 mrb_intern_lit(mrb, "@set_global_variables"), ret);
  onig_regexp_clear_global_variables(mrb, self);
  return ret;
}

// ISO 15.2.15.6.2
static mrb_value
onig_regexp_escape(mrb_state* mrb, mrb_value self) {
  char* str_begin; mrb_args_int str_len;
  mrb_get_args(mrb, "s", &str_begin, &str_len);

  mrb_value const ret = mrb_str_new(mrb, NULL, 0);
  char escaped_char = 0;
  int substr_count = 0;
  char const* str = str_begin;

  for(; str < (str_begin + str_len); ++str) {
    switch(*str) {
      case '\n': escaped_char = 'n'; break;
      case '\t': escaped_char = 't'; break;
      case '\r': escaped_char = 'r'; break;
      case '\f': escaped_char = 'f'; break;

      case ' ':
      case '#':
      case '$':
      case '(':
      case ')':
      case '*':
      case '+':
      case '-':
      case '.':
      case '?':
      case '[':
      case '\\':
      case ']':
      case '^':
      case '{':
      case '|':
      case '}':
        escaped_char = *str; break;

      default: ++substr_count; continue;
    }

    mrb_str_cat(mrb, ret, str - substr_count, substr_count);
    substr_count = 0;

    char const c[] = { '\\', escaped_char };
    mrb_str_cat(mrb, ret, c, 2);
  }
  mrb_str_cat(mrb, ret, str - substr_count, substr_count);
  return ret;
}

void
mrb_mruby_onig_regexp_gem_init(mrb_state* mrb) {
  struct RClass *clazz;

  clazz = mrb_define_class(mrb, "OnigRegexp", mrb->object_class);
  MRB_SET_INSTANCE_TT(clazz, MRB_TT_DATA);

  // enable global variables setting in onig_match_common by default
  mrb_obj_iv_set(mrb, (struct RObject*)clazz, mrb_intern_lit(mrb, "@set_global_variables"), mrb_true_value());

  mrb_define_const(mrb, clazz, "IGNORECASE", mrb_fixnum_value(ONIG_OPTION_IGNORECASE));
  mrb_define_const(mrb, clazz, "EXTENDED", mrb_fixnum_value(ONIG_OPTION_EXTEND));
  mrb_define_const(mrb, clazz, "MULTILINE", mrb_fixnum_value(ONIG_OPTION_MULTILINE));

  mrb_define_method(mrb, clazz, "initialize", onig_regexp_initialize, ARGS_REQ(1) | ARGS_OPT(2));
  mrb_define_method(mrb, clazz, "==", onig_regexp_equal, ARGS_REQ(1));
  mrb_define_method(mrb, clazz, "match", onig_regexp_match, ARGS_REQ(1) | ARGS_OPT(1));
  mrb_define_method(mrb, clazz, "casefold?", onig_regexp_casefold_p, ARGS_NONE());

  mrb_define_method(mrb, clazz, "options", onig_regexp_options, MRB_ARGS_NONE());

  mrb_define_module_function(mrb, clazz, "escape", onig_regexp_escape, MRB_ARGS_REQ(1));
  mrb_define_module_function(mrb, clazz, "quote", onig_regexp_escape, MRB_ARGS_REQ(1));
  mrb_define_module_function(mrb, clazz, "version", onig_regexp_version, MRB_ARGS_NONE());
  mrb_define_module_function(mrb, clazz, "set_global_variables?", onig_regexp_does_set_global_variables, MRB_ARGS_NONE());
  mrb_define_module_function(mrb, clazz, "set_global_variables=", onig_regexp_set_set_global_variables, MRB_ARGS_REQ(1));
  mrb_define_module_function(mrb, clazz, "clear_global_variables", onig_regexp_clear_global_variables, MRB_ARGS_NONE());

  struct RClass* match_data = mrb_define_class(mrb, "OnigMatchData", mrb->object_class);
  MRB_SET_INSTANCE_TT(clazz, MRB_TT_DATA);
  mrb_undef_class_method(mrb, match_data, "new");

  // mrb_define_method(mrb, match_data, "==", &match_data_eq);
  mrb_define_method(mrb, match_data, "[]", &match_data_index, MRB_ARGS_REQ(1));
  mrb_define_method(mrb, match_data, "begin", &match_data_begin, MRB_ARGS_REQ(1));
  mrb_define_method(mrb, match_data, "captures", &match_data_captures, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "end", &match_data_end, MRB_ARGS_REQ(1));
  // mrb_define_method(mrb, match_data, "eql?", &match_data_eq);
  // mrb_define_method(mrb, match_data, "hash", &match_data_hash);
  mrb_define_method(mrb, match_data, "initialize_copy", &match_data_copy, MRB_ARGS_REQ(1));
  // mrb_define_method(mrb, match_data, "inspect", &match_data_inspect);
  mrb_define_method(mrb, match_data, "length", &match_data_length, MRB_ARGS_NONE());
  // mrb_define_method(mrb, match_data, "names", &match_data_names);
  mrb_define_method(mrb, match_data, "offset", &match_data_offset, MRB_ARGS_REQ(1));
  mrb_define_method(mrb, match_data, "post_match", &match_data_post_match, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "pre_match", &match_data_pre_match, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "regexp", &match_data_regexp, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "size", &match_data_length, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "string", &match_data_string, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "to_a", &match_data_to_a, MRB_ARGS_NONE());
  mrb_define_method(mrb, match_data, "to_s", &match_data_to_s, MRB_ARGS_NONE());
  // mrb_define_method(mrb, match_data, "values_at", &match_data_values_at);

  mrb_define_method(mrb, mrb->string_class, "onig_regexp_gsub", &string_gsub, MRB_ARGS_REQ(1) | MRB_ARGS_OPT(1) | MRB_ARGS_BLOCK());
  mrb_define_method(mrb, mrb->string_class, "onig_regexp_sub", &string_sub, MRB_ARGS_REQ(1) | MRB_ARGS_OPT(1) | MRB_ARGS_BLOCK());
  mrb_define_method(mrb, mrb->string_class, "onig_regexp_split", &string_split, MRB_ARGS_REQ(1));
  mrb_define_method(mrb, mrb->string_class, "onig_regexp_scan", &string_scan, MRB_ARGS_REQ(1) | MRB_ARGS_BLOCK());
}

void
mrb_mruby_onig_regexp_gem_final(mrb_state* mrb) {
  (void)mrb;
}

// vim:set et:
