/*

** $Id: lutf8lib.c $

** Standard library for UTF-8 manipulation

** See Copyright Notice in lua.h

*/

#define lutf8lib_c

#define LUA_LIB

#include "lprefix.h"

#include <limits.h>

#include <stdlib.h>

#include <string.h>

#include "lua.h"

#include "lauxlib.h"

#include "lualib.h"

#include "llimits.h"

#define MAXUNICODE  0x10FFFFu

#define MAXUTF    0x7FFFFFFFu

#define MSGInvalid  "invalid UTF-8 code"

#define iscont(c) (((c) & 0xC0) == 0x80)

#define iscontp(p)  iscont(*(p))

/* from strlib */

/* translate a relative string position: negative means back from end */

static lua_Integer u_posrelat (lua_Integer pos, size_t len) {

  if (pos >= 0) return pos;

  else if (0u - (size_t)pos > len) return 0;

  else return (lua_Integer)len + pos + 1;

}

/*

** Decode one UTF-8 sequence, returning NULL if byte sequence is

** invalid.  The array 'limits' stores the minimum value for each

** sequence length, to check for overlong representations. Its first

** entry forces an error for non-ASCII bytes with no continuation

** bytes (count == 0).

*/

static const char *utf8_decode (const char *s, l_uint32 *val, int strict) {

  static const l_uint32 limits[] =

        {~(l_uint32)0, 0x80, 0x800, 0x10000u, 0x200000u, 0x4000000u};

  unsigned int c = (unsigned char)s[0];

  l_uint32 res = 0;  /* final result */

  if (c < 0x80)  /* ASCII? */

    res = c;

  else if (c >= 0xfe)  /* c >= 1111 1110b ? */

    return NULL;  /* would need six or more continuation bytes */

  else {

    int count = 0;  /* to count number of continuation bytes */

    for (; c & 0x40; c <<= 1) {  /* while it needs continuation bytes... */

      unsigned int cc = (unsigned char)s[++count];  /* read next byte */

      if (!iscont(cc))  /* not a continuation byte? */

        return NULL;  /* invalid byte sequence */

      res = (res << 6) | (cc & 0x3F);  /* add lower 6 bits from cont. byte */

    }

    lua_assert(count <= 5);

    res |= ((l_uint32)(c & 0x7F) << (count * 5));  /* add first byte */

    if (res > MAXUTF || res < limits[count])

      return NULL;  /* invalid byte sequence */

    s += count;  /* skip continuation bytes read */

  }

  if (strict) {

    /* check for invalid code points; too large or surrogates */

    if (res > MAXUNICODE || (0xD800u <= res && res <= 0xDFFFu))

      return NULL;

  }

  if (val) *val = res;

  return s + 1;  /* +1 to include first byte */

}

/*

** utf8len(s [, i [, j [, lax]]]) --> number of characters that

** start in the range [i,j], or nil + current position if 's' is not

** well formed in that interval

*/

static int utflen (lua_State *L) {

  lua_Integer n = 0;  /* counter for the number of characters */

  size_t len;  /* string length in bytes */

  const char *s = luaL_checklstring(L, 1, &len);

  lua_Integer posi = u_posrelat(luaL_optinteger(L, 2, 1), len);

  lua_Integer posj = u_posrelat(luaL_optinteger(L, 3, -1), len);

  int lax = lua_toboolean(L, 4);

  luaL_argcheck(L, 1 <= posi && --posi <= (lua_Integer)len, 2,

                   "initial position out of bounds");

  luaL_argcheck(L, --posj < (lua_Integer)len, 3,

                   "final position out of bounds");

  while (posi <= posj) {

    const char *s1 = utf8_decode(s + posi, NULL, !lax);

    if (s1 == NULL) {  /* conversion error? */

      luaL_pushfail(L);  /* return fail ... */

      lua_pushinteger(L, posi + 1);  /* ... and current position */

      return 2;

    }

    posi = ct_diff2S(s1 - s);

    n++;

  }

  lua_pushinteger(L, n);

  return 1;

}

/*

** codepoint(s, [i, [j [, lax]]]) -> returns codepoints for all

** characters that start in the range [i,j]

*/

static int codepoint (lua_State *L) {

  size_t len;

  const char *s = luaL_checklstring(L, 1, &len);

  lua_Integer posi = u_posrelat(luaL_optinteger(L, 2, 1), len);

  lua_Integer pose = u_posrelat(luaL_optinteger(L, 3, posi), len);

  int lax = lua_toboolean(L, 4);

  int n;

  const char *se;

  luaL_argcheck(L, posi >= 1, 2, "out of bounds");

  luaL_argcheck(L, pose <= (lua_Integer)len, 3, "out of bounds");

  if (posi > pose) return 0;  /* empty interval; return no values */

  if (pose - posi >= INT_MAX)  /* (lua_Integer -> int) overflow? */

    return luaL_error(L, "string slice too long");

  n = (int)(pose -  posi) + 1;  /* upper bound for number of returns */

  luaL_checkstack(L, n, "string slice too long");

  n = 0;  /* count the number of returns */

  se = s + pose;  /* string end */

  for (s += posi - 1; s < se;) {

    l_uint32 code;

    s = utf8_decode(s, &code, !lax);

    if (s == NULL)

      return luaL_error(L, MSGInvalid);

    lua_pushinteger(L, l_castU2S(code));

    n++;

  }

  return n;

}

static void pushutfchar (lua_State *L, int arg) {

  lua_Unsigned code = (lua_Unsigned)luaL_checkinteger(L, arg);

  luaL_argcheck(L, code <= MAXUTF, arg, "value out of range");

  lua_pushfstring(L, "%U", cast(unsigned long, code));

}

/*

** utfchar(n1, n2, ...)  -> char(n1)..char(n2)...

*/

static int utfchar (lua_State *L) {

  int n = lua_gettop(L);  /* number of arguments */

  if (n == 1)  /* optimize common case of single char */

    pushutfchar(L, 1);

  else {

    int i;

    luaL_Buffer b;

    luaL_buffinit(L, &b);

    for (i = 1; i <= n; i++) {

      pushutfchar(L, i);

      luaL_addvalue(&b);

    }

    luaL_pushresult(&b);

  }

  return 1;

}

/*

** offset(s, n, [i])  -> indices where n-th character counting from

**   position 'i' starts and ends; 0 means character at 'i'.

*/

static int byteoffset (lua_State *L) {

  size_t len;

  const char *s = luaL_checklstring(L, 1, &len);

  lua_Integer n  = luaL_checkinteger(L, 2);

  lua_Integer posi = (n >= 0) ? 1 : cast_st2S(len) + 1;

  posi = u_posrelat(luaL_optinteger(L, 3, posi), len);

  luaL_argcheck(L, 1 <= posi && --posi <= (lua_Integer)len, 3,

                   "position out of bounds");

  if (n == 0) {

    /* find beginning of current byte sequence */

    while (posi > 0 && iscontp(s + posi)) posi--;

  }

  else {

    if (iscontp(s + posi))

      return luaL_error(L, "initial position is a continuation byte");

    if (n < 0) {

      while (n < 0 && posi > 0) {  /* move back */

        do {  /* find beginning of previous character */

          posi--;

        } while (posi > 0 && iscontp(s + posi));

        n++;

      }

    }

    else {

      n--;  /* do not move for 1st character */

      while (n > 0 && posi < (lua_Integer)len) {

        do {  /* find beginning of next character */

          posi++;

        } while (iscontp(s + posi));  /* (cannot pass final '\0') */

        n--;

      }

    }

  }

  if (n != 0) {  /* did not find given character? */

    luaL_pushfail(L);

    return 1;

  }

  lua_pushinteger(L, posi + 1);  /* initial position */

  if ((s[posi] & 0x80) != 0) {  /* multi-byte character? */

    if (iscont(s[posi]))

      return luaL_error(L, "initial position is a continuation byte");

    while (iscontp(s + posi + 1))

      posi++;  /* skip to last continuation byte */

  }

  /* else one-byte character: final position is the initial one */

  lua_pushinteger(L, posi + 1);  /* 'posi' now is the final position */

  return 2;

}

static int iter_aux (lua_State *L, int strict) {

  size_t len;

  const char *s = luaL_checklstring(L, 1, &len);

  lua_Unsigned n = (lua_Unsigned)lua_tointeger(L, 2);

  if (n < len) {

    while (iscontp(s + n)) n++;  /* go to next character */

  }

  if (n >= len)  /* (also handles original 'n' being negative) */

    return 0;  /* no more codepoints */

  else {

    l_uint32 code;

    const char *next = utf8_decode(s + n, &code, strict);

    if (next == NULL || iscontp(next))

      return luaL_error(L, MSGInvalid);

    lua_pushinteger(L, l_castU2S(n + 1));

    lua_pushinteger(L, l_castU2S(code));

    return 2;

  }

}

static int iter_auxstrict (lua_State *L) {

  return iter_aux(L, 1);

}

static int iter_auxlax (lua_State *L) {

  return iter_aux(L, 0);

}

static int iter_codes (lua_State *L) {

  int lax = lua_toboolean(L, 2);

  const char *s = luaL_checkstring(L, 1);

  luaL_argcheck(L, !iscontp(s), 1, MSGInvalid);

  lua_pushcfunction(L, lax ? iter_auxlax : iter_auxstrict);

  lua_pushvalue(L, 1);

  lua_pushinteger(L, 0);

  return 3;

}

/* pattern to match a single UTF-8 character */

#define UTF8PATT  "[\0-\x7F\xC2-\xFD][\x80-\xBF]*"

static const luaL_Reg funcs[] = {

  {"offset", byteoffset},

  {"codepoint", codepoint},

  {"char", utfchar},

  {"len", utflen},

  {"codes", iter_codes},

  /* placeholders */

  {"charpattern", NULL},

  {NULL, NULL}

};

LUAMOD_API int luaopen_utf8 (lua_State *L) {

  luaL_newlib(L, funcs);

  lua_pushlstring(L, UTF8PATT, sizeof(UTF8PATT)/sizeof(char) - 1);

  lua_setfield(L, -2, "charpattern");

  return 1;

}