#include <iconv.h>
#include <errno.h>
#include <wchar.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>
#include "locale_impl.h"

#define UTF_32BE 0300
#define UTF_16LE 0301
#define UTF_16BE 0302
#define UTF_32LE 0303
#define UCS2BE 0304
#define UCS2LE 0305
#define WCHAR_T 0306
#define US_ASCII 0307
#define UTF_8 0310
#define EUC_JP 0320
#define SHIFT_JIS 0321
#define GB18030 0330
#define GBK 0331
#define GB2312 0332
#define BIG5 0340
#define EUC_KR 0350

/* Definitions of charmaps. Each charmap consists of:
 * 1. Empty-string-terminated list of null-terminated aliases.
 * 2. Special type code or number of elided entries.
 * 3. Character table (size determined by field 2). */

static const unsigned char charmaps[] =
    "utf8\0char\0\0\310"
    "wchart\0\0\306"
    "ucs2\0ucs2be\0\0\304"
    "ucs2le\0\0\305"
    "utf16\0utf16be\0\0\302"
    "utf16le\0\0\301"
    "ucs4\0ucs4be\0utf32\0utf32be\0\0\300"
    "ucs4le\0utf32le\0\0\303"
    "ascii\0usascii\0iso646\0iso646us\0\0\307"
    "eucjp\0\0\320"
    "shiftjis\0sjis\0\0\321"
    "gb18030\0\0\330"
    "gbk\0\0\331"
    "gb2312\0\0\332"
    "big5\0bigfive\0cp950\0big5hkscs\0\0\340"
    "euckr\0ksc5601\0ksx1001\0cp949\0\0\350"
#include "codepages.h"
    ;

static const unsigned short legacy_chars[] = {
#include "legacychars.h"
};

static const unsigned short jis0208[84][94] = {
#include "jis0208.h"
};

static const unsigned short gb18030[126][190] = {
#include "gb18030.h"
};

static const unsigned short big5[89][157] = {
#include "big5.h"
};

static const unsigned short hkscs[] = {
#include "hkscs.h"
};

static const unsigned short ksc[93][94] = {
#include "ksc.h"
};

static int fuzzycmp(const unsigned char* a, const unsigned char* b) {
  for (; *a && *b; a++, b++) {
    while (*a && (*a | 32U) - 'a' > 26 && *a - '0' > 10U)
      a++;
    if ((*a | 32U) != *b)
      return 1;
  }
  return *a != *b;
}

static size_t find_charmap(const void* name) {
  const unsigned char* s;
  if (!*(char*)name)
    name = charmaps; /* "utf8" */
  for (s = charmaps; *s;) {
    if (!fuzzycmp(name, s)) {
      for (; *s; s += strlen((void*)s) + 1)
        ;
      return s + 1 - charmaps;
    }
    s += strlen((void*)s) + 1;
    if (!*s) {
      if (s[1] > 0200)
        s += 2;
      else
        s += 2 + (128U - s[1]) / 4 * 5;
    }
  }
  return -1;
}

iconv_t iconv_open(const char* to, const char* from) {
  size_t f, t;

  if ((t = find_charmap(to)) == -1 || (f = find_charmap(from)) == -1 ||
      (charmaps[t] >= 0320)) {
    errno = EINVAL;
    return (iconv_t)-1;
  }

  return (void*)(f << 16 | t);
}

int iconv_close(iconv_t cd) {
  return 0;
}

static unsigned get_16(const unsigned char* s, int e) {
  e &= 1;
  return s[e] << 8 | s[1 - e];
}

static void put_16(unsigned char* s, unsigned c, int e) {
  e &= 1;
  s[e] = c >> 8;
  s[1 - e] = c;
}

static unsigned get_32(const unsigned char* s, int e) {
  e &= 3;
  return ((unsigned)s[e]) << 24 | s[e ^ 1] << 16 | s[e ^ 2] << 8 | s[e ^ 3];
}

static void put_32(unsigned char* s, unsigned c, int e) {
  e &= 3;
  s[e ^ 0] = c >> 24;
  s[e ^ 1] = c >> 16;
  s[e ^ 2] = c >> 8;
  s[e ^ 3] = c;
}

/* Adapt as needed */
#define mbrtowc_utf8 mbrtowc
#define wctomb_utf8 wctomb

size_t iconv(iconv_t cd0,
             char** restrict in,
             size_t* restrict inb,
             char** restrict out,
             size_t* restrict outb) {
  size_t x = 0;
  unsigned long cd = (unsigned long)cd0;
  unsigned to = cd & 0xffff;
  unsigned from = cd >> 16;
  const unsigned char* map = charmaps + from + 1;
  const unsigned char* tomap = charmaps + to + 1;
  mbstate_t st = {0};
  wchar_t wc;
  unsigned c, d;
  size_t k, l;
  int err;
  unsigned char type = map[-1];
  unsigned char totype = tomap[-1];
  locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;

  if (!in || !*in || !*inb)
    return 0;

  *ploc = UTF8_LOCALE;

  for (; *inb; *in += l, *inb -= l) {
    c = *(unsigned char*)*in;
    l = 1;

    if (c >= 128 || type - UTF_32BE < 7U)
      switch (type) {
        case UTF_8:
          l = mbrtowc_utf8(&wc, *in, *inb, &st);
          if (!l)
            l++;
          else if (l == (size_t)-1)
            goto ilseq;
          else if (l == (size_t)-2)
            goto starved;
          c = wc;
          break;
        case US_ASCII:
          goto ilseq;
        case WCHAR_T:
          l = sizeof(wchar_t);
          if (*inb < l)
            goto starved;
          c = *(wchar_t*)*in;
          if (0) {
            case UTF_32BE:
            case UTF_32LE:
              l = 4;
              if (*inb < 4)
                goto starved;
              c = get_32((void*)*in, type);
          }
          if (c - 0xd800u < 0x800u || c >= 0x110000u)
            goto ilseq;
          break;
        case UCS2BE:
        case UCS2LE:
        case UTF_16BE:
        case UTF_16LE:
          l = 2;
          if (*inb < 2)
            goto starved;
          c = get_16((void*)*in, type);
          if ((unsigned)(c - 0xdc00) < 0x400)
            goto ilseq;
          if ((unsigned)(c - 0xd800) < 0x400) {
            if (type - UCS2BE < 2U)
              goto ilseq;
            l = 4;
            if (*inb < 4)
              goto starved;
            d = get_16((void*)(*in + 2), type);
            if ((unsigned)(d - 0xdc00) >= 0x400)
              goto ilseq;
            c = ((c - 0xd7c0) << 10) + (d - 0xdc00);
          }
          break;
        case SHIFT_JIS:
          if (c - 0xa1 <= 0xdf - 0xa1) {
            c += 0xff61 - 0xa1;
            break;
          }
          l = 2;
          if (*inb < 2)
            goto starved;
          d = *((unsigned char*)*in + 1);
          if (c - 129 <= 159 - 129)
            c -= 129;
          else if (c - 224 <= 239 - 224)
            c -= 193;
          else
            goto ilseq;
          c *= 2;
          if (d - 64 <= 158 - 64) {
            if (d == 127)
              goto ilseq;
            if (d > 127)
              d--;
            d -= 64;
          } else if (d - 159 <= 252 - 159) {
            c++;
            d -= 159;
          }
          c = jis0208[c][d];
          if (!c)
            goto ilseq;
          break;
        case EUC_JP:
          l = 2;
          if (*inb < 2)
            goto starved;
          d = *((unsigned char*)*in + 1);
          if (c == 0x8e) {
            c = d;
            if (c - 0xa1 > 0xdf - 0xa1)
              goto ilseq;
            c += 0xff61 - 0xa1;
            break;
          }
          c -= 0xa1;
          d -= 0xa1;
          if (c >= 84 || d >= 94)
            goto ilseq;
          c = jis0208[c][d];
          if (!c)
            goto ilseq;
          break;
        case GB2312:
          if (c < 0xa1)
            goto ilseq;
        case GBK:
        case GB18030:
          c -= 0x81;
          if (c >= 126)
            goto ilseq;
          l = 2;
          if (*inb < 2)
            goto starved;
          d = *((unsigned char*)*in + 1);
          if (d < 0xa1 && type == GB2312)
            goto ilseq;
          if (d - 0x40 >= 191 || d == 127) {
            if (d - '0' > 9 || type != GB18030)
              goto ilseq;
            l = 4;
            if (*inb < 4)
              goto starved;
            c = (10 * c + d - '0') * 1260;
            d = *((unsigned char*)*in + 2);
            if (d - 0x81 > 126)
              goto ilseq;
            c += 10 * (d - 0x81);
            d = *((unsigned char*)*in + 3);
            if (d - '0' > 9)
              goto ilseq;
            c += d - '0';
            c += 128;
            for (d = 0; d <= c;) {
              k = 0;
              for (int i = 0; i < 126; i++)
                for (int j = 0; j < 190; j++)
                  if (gb18030[i][j] - d <= c - d)
                    k++;
              d = c + 1;
              c += k;
            }
            break;
          }
          d -= 0x40;
          if (d > 63)
            d--;
          c = gb18030[c][d];
          break;
        case BIG5:
          l = 2;
          if (*inb < 2)
            goto starved;
          d = *((unsigned char*)*in + 1);
          if (d - 0x40 >= 0xff - 0x40 || d - 0x7f < 0xa1 - 0x7f)
            goto ilseq;
          d -= 0x40;
          if (d > 0x3e)
            d -= 0x22;
          if (c - 0xa1 >= 0xfa - 0xa1) {
            if (c - 0x87 >= 0xff - 0x87)
              goto ilseq;
            if (c < 0xa1)
              c -= 0x87;
            else
              c -= 0x87 + (0xfa - 0xa1);
            c = (hkscs[4867 + (c * 157 + d) / 16] >> (c * 157 + d) % 16) % 2
                    << 17 |
                hkscs[c * 157 + d];
            /* A few HKSCS characters map to pairs of UCS
             * characters. These are mapped to surrogate
             * range in the hkscs table then hard-coded
             * here. Ugly, yes. */
            if (c / 256 == 0xdc) {
              if (totype - 0300U > 8)
                k = 2;
              else
                k = "\10\4\4\10\4\4\10\2\4"[totype - 0300];
              if (k > *outb)
                goto toobig;
              x += iconv((iconv_t)(uintptr_t)to,
                         &(char*){&"\303\212\314\204"
                                   "\303\212\314\214"
                                   "\303\252\314\204"
                                   "\303\252\314\214"[c % 256]},
                         &(size_t){4}, out, outb);
              continue;
            }
            if (!c)
              goto ilseq;
            break;
          }
          c -= 0xa1;
          c = big5[c][d] |
              (c == 0x27 && (d == 0x3a || d == 0x3c || d == 0x42)) << 17;
          if (!c)
            goto ilseq;
          break;
        case EUC_KR:
          l = 2;
          if (*inb < 2)
            goto starved;
          d = *((unsigned char*)*in + 1);
          c -= 0xa1;
          d -= 0xa1;
          if (c >= 93 || d >= 94) {
            c += (0xa1 - 0x81);
            d += 0xa1;
            if (c >= 93 || (c >= 0xc6 - 0x81 && d > 0x52))
              goto ilseq;
            if (d - 'A' < 26)
              d = d - 'A';
            else if (d - 'a' < 26)
              d = d - 'a' + 26;
            else if (d - 0x81 < 0xff - 0x81)
              d = d - 0x81 + 52;
            else
              goto ilseq;
            if (c < 0x20)
              c = 178 * c + d;
            else
              c = 178 * 0x20 + 84 * (c - 0x20) + d;
            c += 0xac00;
            for (d = 0xac00; d <= c;) {
              k = 0;
              for (int i = 0; i < 93; i++)
                for (int j = 0; j < 94; j++)
                  if (ksc[i][j] - d <= c - d)
                    k++;
              d = c + 1;
              c += k;
            }
            break;
          }
          c = ksc[c][d];
          if (!c)
            goto ilseq;
          break;
        default:
          if (c < 128 + type)
            break;
          c -= 128 + type;
          c = legacy_chars[(map[c * 5 / 4] >> (2 * c % 8)) |
                           ((map[c * 5 / 4 + 1] << (8 - 2 * c % 8)) & 1023)];
          if (!c)
            c = *(unsigned char*)*in;
          if (c == 1)
            goto ilseq;
      }

    switch (totype) {
      case WCHAR_T:
        if (*outb < sizeof(wchar_t))
          goto toobig;
        *(wchar_t*)*out = c;
        *out += sizeof(wchar_t);
        *outb -= sizeof(wchar_t);
        break;
      case UTF_8:
        if (*outb < 4) {
          char tmp[4];
          k = wctomb_utf8(tmp, c);
          if (*outb < k)
            goto toobig;
          memcpy(*out, tmp, k);
        } else
          k = wctomb_utf8(*out, c);
        *out += k;
        *outb -= k;
        break;
      case US_ASCII:
        if (c > 0x7f)
        subst:
        x++, c = '*';
      default:
        if (*outb < 1)
          goto toobig;
        if (c < 128 + totype) {
        revout:
          *(*out)++ = c;
          *outb -= 1;
          break;
        }
        d = c;
        for (c = 0; c < 128 - totype; c++) {
          if (d == legacy_chars[(tomap[c * 5 / 4] >> (2 * c % 8)) |
                                ((tomap[c * 5 / 4 + 1] << (8 - 2 * c % 8)) &
                                 1023)]) {
            c += 128;
            goto revout;
          }
        }
        goto subst;
      case UCS2BE:
      case UCS2LE:
      case UTF_16BE:
      case UTF_16LE:
        if (c < 0x10000 || type - UCS2BE < 2U) {
          if (c >= 0x10000)
            c = 0xFFFD;
          if (*outb < 2)
            goto toobig;
          put_16((void*)*out, c, totype);
          *out += 2;
          *outb -= 2;
          break;
        }
        if (*outb < 4)
          goto toobig;
        c -= 0x10000;
        put_16((void*)*out, (c >> 10) | 0xd800, totype);
        put_16((void*)(*out + 2), (c & 0x3ff) | 0xdc00, totype);
        *out += 4;
        *outb -= 4;
        break;
      case UTF_32BE:
      case UTF_32LE:
        if (*outb < 4)
          goto toobig;
        put_32((void*)*out, c, totype);
        *out += 4;
        *outb -= 4;
        break;
    }
  }
  *ploc = loc;
  return x;
ilseq:
  err = EILSEQ;
  x = -1;
  goto end;
toobig:
  err = E2BIG;
  x = -1;
  goto end;
starved:
  err = EINVAL;
  x = -1;
end:
  errno = err;
  *ploc = loc;
  return x;
}