/*
** $Id: lutf8lib.c,v 1.16.1.1 2017/04/19 17:29:57 roberto Exp $
** Standard library for UTF-8 manipulation
** See Copyright Notice in lua.h
*/

#define lutf8lib_c
#define LUA_LIB

//#include "lprefix.h"


#include <assert.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"
#include "util.h"

#define MAXUNICODE      0x10FFFF

#define iscont(p)       ((*(p) & 0xC0) == 0x80)


/* 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.
*/
static const char *utf8_decode (const char *o, int *val) {
	static const unsigned int limits[] = {0xFF, 0x7F, 0x7FF, 0xFFFF};
	const unsigned char *s = (const unsigned char *)o;
	unsigned int c = s[0];
	unsigned int res = 0; /* final result */
	if (c < 0x80) /* ascii? */
		res = c;
	else {
		int count = 0; /* to count number of continuation bytes */
		while (c & 0x40) { /* still have continuation bytes? */
			int cc = s[++count]; /* read next byte */
			if ((cc & 0xC0) != 0x80) /* not a continuation byte? */
				return NULL; /* invalid byte sequence */
			res = (res << 6) | (cc & 0x3F); /* add lower 6 bits from cont. byte */
			c <<= 1; /* to test next bit */
		}
		res |= ((c & 0x7F) << (count * 5)); /* add first byte */
		if (count > 3 || res > MAXUNICODE || res <= limits[count]) {
			return NULL; /* invalid byte sequence */
		}
		s += count; /* skip continuation bytes read */
	}
	if (val) *val = res;
	return (const char *)s + 1; /* +1 to include first byte */
}


/*
** utf8len(s [, i [, j]]) --> 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) {
	int n = 0;
	size_t len;
	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);
	luaL_argcheck(L, 1 <= posi && --posi <= (lua_Integer) len, 2,
	              "initial position out of string");
	luaL_argcheck(L, --posj < (lua_Integer) len, 3,
	              "final position out of string");
	lua_gasuse(L, 50);
	while (posi <= posj) {
		const char *s1;
		lua_gasuse(L, GAS_MID);
		s1 = utf8_decode(s + posi, NULL);
		if (s1 == NULL) { /* conversion error? */
			lua_pushnil(L); /* return nil ... */
			lua_pushinteger(L, posi + 1); /* ... and current position */
			return 2;
		}
		posi = s1 - s;
		n++;
	}
	lua_pushinteger(L, n);
	return 1;
}


/*
** codepoint(s, [i, [j]])  -> 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 n;
	const char *se;

	lua_gasuse(L, 50);

	luaL_argcheck(L, posi >= 1, 2, "out of range");
	luaL_argcheck(L, pose <= (lua_Integer)len, 3, "out of range");
	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;
	luaL_checkstack(L, n, "string slice too long");

	n = 0;
	se = s + pose;
	for (s += posi - 1; s < se;) {
		int code;
		lua_gasuse(L, GAS_MID);
		s = utf8_decode(s, &code);
		if (s == NULL) {
			return luaL_error(L, "invalid UTF-8 code");
		}
		lua_pushinteger(L, code);
		n++;
	}

	return n;
}


static void pushutfchar (lua_State *L, int arg) {
	char buf[UTF8_MAX];
	int size;

	lua_Integer code = luaL_checkinteger(L, arg);
	lua_gasuse(L, GAS_MID);
	luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, "value out of range");
	size = lua_util_utf8_encode(buf, code);
	lua_pushlstring(L, buf, size);
}


/*
** 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])  -> index where n-th character counting from
**   position 'i' starts; 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 : len + 1;
	size_t move = 0;

	lua_gasuse(L, 50);

	posi = u_posrelat(luaL_optinteger(L, 3, posi), len);
	luaL_argcheck(L, 1 <= posi && --posi <= (lua_Integer) len, 3,
	              "position out of range");
	if (n == 0) {
		/* find beginning of current byte sequence */
		while (posi > 0 && iscont(s + posi)) {
			posi--;
			move++;
		}
	} else {
		if (iscont(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--;
					move++;
				} while (posi > 0 && iscont(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++;
					move++;
				} while (iscont(s + posi)); /* (cannot pass final '\0') */
				n--;
			}
		}
	}

	lua_gasuse_mul(L, GAS_FASTEST, move);

	if (n == 0) /* did it find given character? */
		lua_pushinteger(L, posi + 1);
	else /* no such character */
		lua_pushnil(L);
	return 1;
}


static int iter_aux (lua_State *L) {
	size_t len;
	const char *s = luaL_checklstring(L, 1, &len);
	lua_Integer n = lua_tointeger(L, 2) - 1;

	lua_gasuse(L, GAS_MID);

	if (n < 0) { /* first iteration? */
		n = 0; /* start from here */
	} else if (n < (lua_Integer) len) {
		n++; /* skip current byte */
		while (iscont(s + n)) n++; /* and its continuations */
	}

	if (n >= (lua_Integer) len) {
		return 0; /* no more codepoints */
	} else {
		int code;
		const char *next = utf8_decode(s + n, &code);
		if (next == NULL || iscont(next)) {
			return luaL_error(L, "invalid UTF-8 code");
		}
		lua_pushinteger(L, n + 1);
		lua_pushinteger(L, code);
		return 2;
	}
}


static int iter_codes (lua_State *L) {
	lua_gasuse(L, 50);
	luaL_checkstring(L, 1);
	lua_pushcfunction(L, iter_aux);
	lua_pushvalue(L, 1);
	lua_pushinteger(L, 0);
	return 3;
}


/* pattern to match a single UTF-8 character */
//#define UTF8PATT	"[\0-\x7F\xC2-\xF4][\x80-\xBF]*"


static const luaL_Reg funcs[] = {
	{"offset", byteoffset},
	{"codepoint", codepoint},
	{"char", utfchar},
	{"len", utflen},
	{"codes", iter_codes},
	{NULL, NULL}
};


int luaopen_utf8 (lua_State *L) {
	luaL_register(L, "utf8", funcs);
	//luaL_newlib(L, funcs);
	lua_pop(L, 1);
	return 1;
}
