#define LUA_LIB

#include <lua.h>
#include <lauxlib.h>

#include <time.h>
#include <unistd.h>

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include "atomic.h"

#define DEFAULT_CAP 64
#define MAX_NUMBER 1024
// avoid circular reference while encodeing
#define MAX_DEPTH 128

#define BSON_REAL 1
#define BSON_STRING 2
#define BSON_DOCUMENT 3
#define BSON_ARRAY 4
#define BSON_BINARY 5
#define BSON_UNDEFINED 6
#define BSON_OBJECTID 7
#define BSON_BOOLEAN 8
#define BSON_DATE 9
#define BSON_NULL 10
#define BSON_REGEX 11
#define BSON_DBPOINTER 12
#define BSON_JSCODE 13
#define BSON_SYMBOL 14
#define BSON_CODEWS 15
#define BSON_INT32 16
#define BSON_TIMESTAMP 17
#define BSON_INT64 18
#define BSON_MINKEY 255
#define BSON_MAXKEY 127

#define BSON_TYPE_SHIFT 5

static char bson_numstrs[MAX_NUMBER][4];
static int bson_numstr_len[MAX_NUMBER];

struct bson {
	int size;
	int cap;
	uint8_t *ptr;
	uint8_t buffer[DEFAULT_CAP];
};

struct bson_reader {
	const uint8_t * ptr;
	int size;
};

static inline int32_t
get_length(const uint8_t * data) {
	const uint8_t * b = (const uint8_t *)data;
	int32_t len = b[0] | b[1]<<8 | b[2]<<16 | b[3]<<24;
	return len;
}

static inline void
bson_destroy(struct bson *b) {
	if (b->ptr != b->buffer) {
		free(b->ptr);
	}
}

static inline void
bson_create(struct bson *b) {
	b->size = 0;
	b->cap = DEFAULT_CAP;
	b->ptr = b->buffer;
}

static inline void
bson_reserve(struct bson *b, int sz) {
	if (b->size + sz <= b->cap)
		return;
	do {
		b->cap *= 2;
	} while (b->cap <= b->size + sz);

	if (b->ptr == b->buffer) {
		b->ptr = (uint8_t*)malloc(b->cap);
		memcpy(b->ptr, b->buffer, b->size);
	} else {
		b->ptr = (uint8_t*)realloc(b->ptr, b->cap);
	}
}

static inline void
check_reader(lua_State *L, struct bson_reader *br, int sz) {
	if (br->size < sz) {
		luaL_error(L, "Invalid bson block (%d:%d)", br->size, sz);
	}
}

static inline int
read_byte(lua_State *L, struct bson_reader *br) {
	check_reader(L, br, 1);
	const uint8_t * b = br->ptr;
	int r =  b[0];
	++br->ptr;
	--br->size;

	return r;
}

static inline int32_t
read_int32(lua_State *L, struct bson_reader *br) {
	check_reader(L, br, 4);
	const uint8_t * b = br->ptr;
	uint32_t v = b[0] | b[1]<<8 | b[2]<<16 | b[3]<<24;
	br->ptr+=4;
	br->size-=4;
	return (int32_t)v;
}

static inline int64_t
read_int64(lua_State *L, struct bson_reader *br) {
	check_reader(L, br, 8);
	const uint8_t * b = br->ptr;
	uint32_t lo = b[0] | b[1]<<8 | b[2]<<16 | b[3]<<24;
	uint32_t hi = b[4] | b[5]<<8 | b[6]<<16 | b[7]<<24;
	uint64_t v = (uint64_t)lo | (uint64_t)hi<<32;
	br->ptr+=8;
	br->size-=8;
	return (int64_t)v;
}

static inline lua_Number
read_double(lua_State *L, struct bson_reader *br) {
	check_reader(L, br, 8);
	union {
		uint64_t i;
		double d;
	} v;
	const uint8_t * b = br->ptr;
	uint32_t lo = b[0] | b[1]<<8 | b[2]<<16 | b[3]<<24;
	uint32_t hi = b[4] | b[5]<<8 | b[6]<<16 | b[7]<<24;
	v.i = (uint64_t)lo | (uint64_t)hi<<32;
	br->ptr+=8;
	br->size-=8;
	return v.d;
}

static inline const void *
read_bytes(lua_State *L, struct bson_reader *br, int sz) {
	const void * r = br->ptr;
	check_reader(L, br, sz);
	br->ptr+=sz;
	br->size-=sz;
	return r;
}

static inline const char *
read_cstring(lua_State *L, struct bson_reader *br, size_t *sz) {
	int i;
	for (i=0;;i++) {
		if (i==br->size) {
			luaL_error(L, "Invalid bson block : cstring");
		}
		if (br->ptr[i] == '\0') {
			break;
		}
	}
	*sz = i;
	const char * r = (const char *)br->ptr;
	br->ptr += i+1;
	br->size -= i+1;
	return r;
}

static inline void
write_byte(struct bson *b, uint8_t v) {
	bson_reserve(b,1);
	b->ptr[b->size++] = v;
}

static inline void
write_int32(struct bson *b, int32_t v) {
	uint32_t uv = (uint32_t)v;
	bson_reserve(b,4);
	b->ptr[b->size++] = uv & 0xff;
	b->ptr[b->size++] = (uv >> 8)&0xff;
	b->ptr[b->size++] = (uv >> 16)&0xff;
	b->ptr[b->size++] = (uv >> 24)&0xff;
}

static inline void
write_length(struct bson *b, int32_t v, int off) {
	uint32_t uv = (uint32_t)v;
	b->ptr[off++] = uv & 0xff;
	b->ptr[off++] = (uv >> 8)&0xff;
	b->ptr[off++] = (uv >> 16)&0xff;
	b->ptr[off++] = (uv >> 24)&0xff;
}

#define MAXUNICODE	0x10FFFF

static int
utf8_copy(const char *s, char *d, size_t limit) {
	static const unsigned int limits[] = {0xFF, 0x7F, 0x7FF, 0xFFFF};
	unsigned int c = s[0];
	unsigned int res = 0;
	if (limit < 1)
		return 0;
	d[0] = s[0];
	if (c < 0x80) {
		return 1;
	} else {
		int count = 0;
		while (c & 0x40) {
			int cc = s[++count];
			if (limit <= count || (cc & 0xC0) != 0x80)
				return 0;
			d[count] = s[count];
			res = (res << 6) | (cc & 0x3F);
			c <<= 1;
		}
		res |= ((c & 0x7F) << (count * 5));
		if (count > 3 || res > MAXUNICODE || res <= limits[count])
			return 0;
		return count+1;
	}
}

static void
write_string(struct bson *b, lua_State *L, const char *key, size_t sz) {
	bson_reserve(b,sz+1);
	char *dst = (char *)(b->ptr + b->size);
	const char *src = key;
	size_t n = sz;
	while(n > 0) {
		int c = utf8_copy(src, dst, n);
		if (c == 0) {
			luaL_error(L, "Invalid utf8 string");
		}
		src += c;
		dst += c;
		n -= c;
	}
	b->ptr[b->size+sz] = '\0';
	b->size+=sz+1;
}

static inline int
reserve_length(struct bson *b) {
	int sz = b->size;
	bson_reserve(b,4);
	b->size +=4;
	return sz;
}

static inline void
write_int64(struct bson *b, int64_t v) {
	uint64_t uv = (uint64_t)v;
	int i;
	bson_reserve(b,8);
	for (i=0;i<64;i+=8) {
		b->ptr[b->size++] = (uv>>i) & 0xff;
	}
}

static inline void
write_double(struct bson *b, lua_Number d) {
	union {
		double d;
		uint64_t i;
	} v;
	v.d = d;
	int i;
	bson_reserve(b,8);
	for (i=0;i<64;i+=8) {
		b->ptr[b->size++] = (v.i>>i) & 0xff;
	}
}

static inline void
append_key(struct bson *bs, lua_State *L, int type, const char *key, size_t sz) {
	write_byte(bs, type);
	write_string(bs, L, key, sz);
}

static inline int
is_32bit(int64_t v) {
	return v >= INT32_MIN && v <= INT32_MAX;
}

static void
append_number(struct bson *bs, lua_State *L, const char *key, size_t sz) {
	if (lua_isinteger(L, -1)) {
		int64_t i = lua_tointeger(L, -1);
		if (is_32bit(i)) {
			append_key(bs, L, BSON_INT32, key, sz);
			write_int32(bs, i);
		} else {
			append_key(bs, L, BSON_INT64, key, sz);
			write_int64(bs, i);
		}
	} else {
		lua_Number d = lua_tonumber(L,-1);
		append_key(bs, L, BSON_REAL, key, sz);
		write_double(bs, d);
	}
}

static void append_table(struct bson *bs, lua_State *L, const char *key, size_t sz, int depth);

static void
write_binary(struct bson *b, const void * buffer, size_t sz) {
	int length = reserve_length(b);
	bson_reserve(b,sz);
	memcpy(b->ptr + b->size, buffer, sz);	// include sub type
	b->size+=sz;
	write_length(b, sz-1, length);	// not include sub type
}

static void
append_one(struct bson *bs, lua_State *L, const char *key, size_t sz, int depth) {
	int vt = lua_type(L,-1);
	switch(vt) {
	case LUA_TNUMBER:
		append_number(bs, L, key, sz);
		break;
	case LUA_TUSERDATA: {
		append_key(bs, L, BSON_DOCUMENT, key, sz);
		int32_t * doc = (int32_t*)lua_touserdata(L,-1);
		int32_t sz = *doc;
		bson_reserve(bs,sz);
		memcpy(bs->ptr + bs->size, doc, sz);
		bs->size += sz;
		break;
	}
	case LUA_TSTRING: {
		size_t len;
		const char * str = lua_tolstring(L,-1,&len);
		if (len > 1 && str[0]==0) {
			int subt = (uint8_t)str[1];
			append_key(bs, L, subt, key, sz);
			switch(subt) {
			case BSON_BINARY:
				write_binary(bs, str+2, len-2);
				break;
			case BSON_OBJECTID:
				if (len != 2+12) {
					luaL_error(L, "Invalid object id %s", str+2);
				}
				// go though
			case BSON_JSCODE:
			case BSON_DBPOINTER:
			case BSON_SYMBOL:
			case BSON_CODEWS:
				bson_reserve(bs,len-2);
				memcpy(bs->ptr + bs->size, str+2, len-2);
				bs->size += len-2;
				break;
			case BSON_DATE: {
				if (len != 2+4) {
					luaL_error(L, "Invalid date");
				}
				const uint32_t * ts = (const uint32_t *)(str + 2);
				int64_t v = (int64_t)*ts * 1000;
				write_int64(bs, v);
				break;
			}
			case BSON_TIMESTAMP: {
				if (len != 2+8) {
					luaL_error(L, "Invalid timestamp");
				}
				const uint32_t * inc = (const uint32_t *)(str + 2);
				const uint32_t * ts = (const uint32_t *)(str + 6);
				write_int32(bs, *inc);
				write_int32(bs, *ts);
				break;
			}
			case BSON_REGEX: {
				str+=2;
				len-=3;
				size_t i;
				for (i=0;i<len;i++) {
					if (str[len-i-1]==0) {
						break;
					}
				}
				write_string(bs, L, str, len-i-1);
				write_string(bs, L, str + len-i, i);
				break;
			}
			case BSON_MINKEY:
			case BSON_MAXKEY:
			case BSON_NULL:
				break;
			case BSON_INT64: {
				if (len != 2 + 8) {
					luaL_error(L, "Invalid int64");
				}
				const int64_t * v = (const int64_t *)(str + 2);
				write_int64(bs, *v);
				break;
			}
			default:
				luaL_error(L,"Invalid subtype %d", subt);
			}
		} else {
			size_t len;
			const char * str = lua_tolstring(L,-1,&len);
			append_key(bs, L, BSON_STRING, key, sz);
			int off = reserve_length(bs);
			write_string(bs, L, str, len);
			write_length(bs, len+1, off);		
		}
		break;
	}
	case LUA_TTABLE:
		append_table(bs, L, key, sz, depth+1);
		break;
	case LUA_TBOOLEAN:
		append_key(bs, L, BSON_BOOLEAN, key, sz);
		write_byte(bs, lua_toboolean(L,-1));
		break;
	case LUA_TNIL:
		luaL_error(L, "Bson array has a hole (nil), Use bson.null instead");
	default:
		luaL_error(L, "Invalid value type : %s", lua_typename(L,vt));
	}
}

static inline int 
bson_numstr( char *str, unsigned int i ) {
	if ( i < MAX_NUMBER) {
		memcpy( str, bson_numstrs[i], 4 );
		return bson_numstr_len[i];
	} else {
		return sprintf( str,"%u", i );
	}
}

static void
pack_array(lua_State *L, struct bson *b, int depth, size_t len) {
	int length = reserve_length(b);
	size_t i;
	for (i=1;i<=len;i++) {
		char numberkey[32];
		size_t sz = bson_numstr(numberkey, i - 1);
		const char * key = numberkey;
		lua_geti(L, -1, i);
		append_one(b, L, key, sz, depth);
		lua_pop(L, 1);
	}
	write_byte(b,0);
	write_length(b, b->size - length, length);
}

static void
pack_dict_data(lua_State *L, struct bson *b, int depth, int kt) {
	const char * key = NULL;
	size_t sz;
	switch(kt) {
	case LUA_TNUMBER:
		luaL_error(L, "Bson dictionary's key can't be number");
		break;
	case LUA_TSTRING:
		key = lua_tolstring(L,-2,&sz);
		append_one(b, L, key, sz, depth);
		lua_pop(L,1);
		break;
	default:
		luaL_error(L, "Invalid key type : %s", lua_typename(L, kt));
		return;
	}
}

static void
pack_simple_dict(lua_State *L, struct bson *b, int depth) {
	int length = reserve_length(b);
	lua_pushnil(L);
	while(lua_next(L,-2) != 0) {
		int kt = lua_type(L, -2);
		pack_dict_data(L, b, depth, kt);
	}
	write_byte(b,0);
	write_length(b, b->size - length, length);
}

static void
pack_meta_dict(lua_State *L, struct bson *b, int depth) {
	int length = reserve_length(b);

	lua_pushvalue(L, -2); // push meta_obj
	lua_call(L, 1, 3); // call __pairs_func => next_func, t_data, first_k
	for(;;) {
		lua_pushvalue(L, -2); // copy data
		lua_pushvalue(L, -2); // copy k
		lua_copy(L, -5, -3); // copy next_func replace old_k
		lua_call(L, 2, 2); // call next_func

		int kt = lua_type(L, -2);
		if (kt == LUA_TNIL) {
			lua_pop(L, 4); // pop all k, v, next_func, obj
			break;
		}
		pack_dict_data(L, b, depth, kt);
	}
	write_byte(b,0);
	write_length(b, b->size - length, length);
}

static bool
is_rawarray(lua_State *L) {
	lua_pushnil(L);
	if (lua_next(L, -2) == 0) {
		// empty table
		return false;
	}
	lua_Integer firstkey = lua_isinteger(L, -2) ? lua_tointeger(L, -2) : 0;
	lua_pop(L, 2);
	if (firstkey <= 1) {
		return firstkey > 0;
	}
	return firstkey <= lua_rawlen(L, -1);
}

static void
append_table(struct bson *bs, lua_State *L, const char *key, size_t sz, int depth) {
	if (depth > MAX_DEPTH) {
		luaL_error(L, "Too depth while encoding bson");
	}
	luaL_checkstack(L, 16, NULL);	// reserve enough stack space to pack table
	if (luaL_getmetafield(L, -1, "__len") != LUA_TNIL) {
		lua_pushvalue(L, -2);
		lua_call(L, 1, 1);
		if (!lua_isinteger(L, -1)) {
			luaL_error(L, "__len should return integer");
		}
		size_t len = lua_tointeger(L, -1);
		lua_pop(L, 1);
		append_key(bs, L, BSON_ARRAY, key, sz);
		pack_array(L, bs, depth, len);
	} else if (luaL_getmetafield(L, -1, "__pairs") != LUA_TNIL) {
		append_key(bs, L, BSON_DOCUMENT, key, sz);
		pack_meta_dict(L, bs, depth);
	} else if (is_rawarray(L)) {
		append_key(bs, L, BSON_ARRAY, key, sz);
		pack_array(L, bs, depth, lua_rawlen(L, -1));
	} else {
		append_key(bs, L, BSON_DOCUMENT, key, sz);
		pack_simple_dict(L, bs, depth);
	}
}

static void
pack_ordered_dict(lua_State *L, struct bson *b, int n, int depth) {
	int length = reserve_length(b);
	int i;
	size_t sz;
	// the first key is at index n
	const char * key = lua_tolstring(L, n, &sz);
	for (i=0;i<n;i+=2) {
		if (key == NULL) {
			luaL_error(L, "Argument %d need a string", i+1);
		}
		lua_pushvalue(L, i+1);
		append_one(b, L, key, sz, depth);
		lua_pop(L,1);
		key = lua_tolstring(L, i+2, &sz);	// next key
	}
	write_byte(b,0);
	write_length(b, b->size - length, length);
}
 
static int
ltostring(lua_State *L) {
	size_t sz = lua_rawlen(L, 1);
	void * ud = lua_touserdata(L,1);
	lua_pushlstring(L, (const char*)ud, sz);
	return 1;
}

static int
llen(lua_State *L) {
	size_t sz = lua_rawlen(L, 1);
	lua_pushinteger(L, sz);
	return 1;
}

static void
make_object(lua_State *L, int type, const void * ptr, size_t len) {
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, type);
	luaL_addlstring(&b, (const char*)ptr, len);
	luaL_pushresult(&b);
}

static void
unpack_dict(lua_State *L, struct bson_reader *br, bool array) {
	luaL_checkstack(L, 16, NULL);	// reserve enough stack space to unpack table
	int sz = read_int32(L, br);
	const void * bytes = read_bytes(L, br, sz-5);
	struct bson_reader t = { (const uint8_t*)bytes, sz-5 };
	int end = read_byte(L, br);
	if (end != '\0') {
		luaL_error(L, "Invalid document end");
	}

	lua_newtable(L);

	for (;;) {
		if (t.size == 0)
			break;
		int bt = read_byte(L, &t);
		size_t klen = 0;
		const char * key = read_cstring(L, &t, &klen);
		if (array) {
			int id = strtol(key, NULL, 10) + 1;
			lua_pushinteger(L,id);
		} else {
			lua_pushlstring(L, key, klen);
		}
		switch (bt) {
		case BSON_REAL:
			lua_pushnumber(L, read_double(L, &t));
			break;
		case BSON_BOOLEAN:
			lua_pushboolean(L, read_byte(L, &t));
			break;
		case BSON_STRING: {
			int sz = read_int32(L, &t);
			if (sz <= 0) {
				luaL_error(L, "Invalid bson string , length = %d", sz);
			}
			lua_pushlstring(L, (const char*)read_bytes(L, &t, sz), sz-1);
			break;
		}
		case BSON_DOCUMENT:
			unpack_dict(L, &t, false);
			break;
		case BSON_ARRAY:
			unpack_dict(L, &t, true);
			break;
		case BSON_BINARY: {
			int sz = read_int32(L, &t);
			int subtype = read_byte(L, &t);

			luaL_Buffer b;
			luaL_buffinit(L, &b);
			luaL_addchar(&b, 0);
			luaL_addchar(&b, BSON_BINARY);
			luaL_addchar(&b, subtype);
			luaL_addlstring(&b, (const char*)read_bytes(L, &t, sz), sz);
			luaL_pushresult(&b);
			break;
		}
		case BSON_OBJECTID:
			make_object(L, BSON_OBJECTID, read_bytes(L, &t, 12), 12);
			break;
		case BSON_DATE: {
			int64_t date = read_int64(L, &t);
			uint32_t v = date / 1000;
			make_object(L, BSON_DATE, &v, 4);
			break;
		}
		case BSON_MINKEY:
		case BSON_MAXKEY:
		case BSON_NULL: {
			char key[] = { 0, (char)bt };
			lua_pushlstring(L, key, sizeof(key));
			break;
		}
		case BSON_REGEX: {
			size_t rlen1=0;
			size_t rlen2=0;
			const char * r1 = read_cstring(L, &t, &rlen1);
			const char * r2 = read_cstring(L, &t, &rlen2);
			luaL_Buffer b;
			luaL_buffinit(L, &b);
			luaL_addchar(&b, 0);
			luaL_addchar(&b, BSON_REGEX);
			luaL_addlstring(&b, r1, rlen1);
			luaL_addchar(&b,0);
			luaL_addlstring(&b, r2, rlen2);
			luaL_addchar(&b,0);
			luaL_pushresult(&b);
			break;
		}
		case BSON_INT32:
			lua_pushinteger(L, read_int32(L, &t));
			break;
		case BSON_TIMESTAMP: {
			int32_t inc = read_int32(L, &t);
			int32_t ts = read_int32(L, &t);

			luaL_Buffer b;
			luaL_buffinit(L, &b);
			luaL_addchar(&b, 0);
			luaL_addchar(&b, BSON_TIMESTAMP);
			luaL_addlstring(&b, (const char *)&inc, 4);
			luaL_addlstring(&b, (const char *)&ts, 4);
			luaL_pushresult(&b);
			break;
		}
		case BSON_INT64:
			lua_pushinteger(L, read_int64(L, &t));
			break;
		case BSON_DBPOINTER: {
			const void * ptr = t.ptr;
			int sz = read_int32(L, &t);
			read_bytes(L, &t, sz+12);
			make_object(L, BSON_DBPOINTER, ptr, sz + 16);
			break;
		}
		case BSON_JSCODE:
		case BSON_SYMBOL: {
			const void * ptr = t.ptr;
			int sz = read_int32(L, &t);
			read_bytes(L, &t, sz);
			make_object(L, bt, ptr, sz + 4);
			break;
		}
		case BSON_CODEWS: {
			const void * ptr = t.ptr;
			int sz = read_int32(L, &t);
			read_bytes(L, &t, sz-4);
			make_object(L, bt, ptr, sz);
			break;
		}
		default:
			// unsupported
			luaL_error(L, "Invalid bson type : %d", bt);
			lua_pop(L,1);
			continue;
		}
		lua_rawset(L,-3);
	}
}

static int
lmakeindex(lua_State *L) {
	int32_t *bson = (int32_t*)luaL_checkudata(L,1,"bson");
	const uint8_t * start = (const uint8_t *)bson;
	struct bson_reader br = { start+4, get_length(start) - 5 };
	lua_newtable(L);

	for (;;) {
		if (br.size == 0)
			break;
		int bt = read_byte(L, &br);
		size_t klen = 0;
		const char * key = read_cstring(L, &br, &klen);
		int field_size = 0;
		switch (bt) {
		case BSON_INT64:
		case BSON_TIMESTAMP: 
		case BSON_DATE:
		case BSON_REAL:
			field_size = 8;
			break;
		case BSON_BOOLEAN:
			field_size = 1;
			break;
		case BSON_JSCODE:
		case BSON_SYMBOL: 
		case BSON_STRING: {
			int sz = read_int32(L, &br);
			read_bytes(L, &br, sz);
			break;
		}
		case BSON_CODEWS:
		case BSON_ARRAY:
		case BSON_DOCUMENT: {
			int sz = read_int32(L, &br);
			read_bytes(L, &br, sz-4);
			break;
		}
		case BSON_BINARY: {
			int sz = read_int32(L, &br);
			read_bytes(L, &br, sz+1);
			break;
		}
		case BSON_OBJECTID:
			field_size = 12;
			break;
		case BSON_MINKEY:
		case BSON_MAXKEY:
		case BSON_NULL:
			break;
		case BSON_REGEX: {
			size_t rlen1=0;
			size_t rlen2=0;
			read_cstring(L, &br, &rlen1);
			read_cstring(L, &br, &rlen2);
			break;
		}
		case BSON_INT32:
			field_size = 4;
			break;
		case BSON_DBPOINTER: {
			int sz = read_int32(L, &br);
			read_bytes(L, &br, sz+12);
			break;
		}
		default:
			// unsupported
			luaL_error(L, "Invalid bson type : %d", bt);
			lua_pop(L,1);
			continue;
		}
		if (field_size > 0) {
			int id = bt | (int)(br.ptr - start) << BSON_TYPE_SHIFT;
			read_bytes(L, &br, field_size);
			lua_pushlstring(L, key, klen);
			lua_pushinteger(L,id);
			lua_rawset(L,-3);
		}
	}
	lua_setiuservalue(L,1,1);
	lua_settop(L,1);

	return 1;
}

static void
replace_object(lua_State *L, int type, struct bson * bs) {
	size_t len = 0;
	const char * data = luaL_checklstring(L,3, &len);
	if (len < 6 || data[0] != 0 || data[1] != type) {
		luaL_error(L, "Type mismatch, need bson type %d", type);
	}
	switch (type) {
	case BSON_OBJECTID:
		if (len != 2+12) {
			luaL_error(L, "Invalid object id");
		}
		memcpy(bs->ptr, data+2, 12);
		break;
	case BSON_DATE: {
		if (len != 2+4) {
			luaL_error(L, "Invalid date");
		}
		const uint32_t * ts = (const uint32_t *)(data + 2);
		int64_t v = (int64_t)*ts * 1000;
		write_int64(bs, v);
		break;
	}
	case BSON_TIMESTAMP: {
		if (len != 2+8) {
			luaL_error(L, "Invalid timestamp");
		}
		const uint32_t * inc = (const uint32_t *)(data + 2);
		const uint32_t * ts = (const uint32_t *)(data + 6);
		write_int32(bs, *inc);
		write_int32(bs, *ts);
		break;
	}
	}
}

static int
lreplace(lua_State *L) {
	lua_getiuservalue(L,1,1);
	if (!lua_istable(L,-1)) {
		return luaL_error(L, "call makeindex first");
	}
	lua_pushvalue(L,2);
	if (lua_rawget(L, -2) != LUA_TNUMBER) {
		return luaL_error(L, "Can't replace key : %s", lua_tostring(L,2));
	}
	int id = lua_tointeger(L, -1);
	int type = id & ((1<<(BSON_TYPE_SHIFT)) - 1);
	int offset = id >> BSON_TYPE_SHIFT;
	uint8_t * start = (uint8_t*)lua_touserdata(L,1);
	struct bson b = { 0,16, start + offset };
	switch (type) {
	case BSON_REAL:
		write_double(&b, luaL_checknumber(L, 3));
		break;
	case BSON_BOOLEAN:
		write_byte(&b, lua_toboolean(L,3));
		break;
	case BSON_OBJECTID:
	case BSON_DATE:
	case BSON_TIMESTAMP:
		replace_object(L, type, &b);
		break;
	case BSON_INT32: {
		if (!lua_isinteger(L, 3)) {
			luaL_error(L, "%f must be a 32bit integer ", lua_tonumber(L, 3));
		}
		int32_t i = lua_tointeger(L,3);
		write_int32(&b, i);
		break;
	}
	case BSON_INT64: {
		if (!lua_isinteger(L, 3)) {
			luaL_error(L, "%f must be a 64bit integer ", lua_tonumber(L, 3));
		}
		int64_t i = lua_tointeger(L,3);
		write_int64(&b, i);
		break;
	}
	default:
		luaL_error(L, "Can't replace type %d", type);
		break;
	}
	return 0;
}

static int
ldecode(lua_State *L) {
	const int32_t * data = (const int32_t*)lua_touserdata(L,1);
	if (data == NULL) {
		return 0;
	}
	const uint8_t * b = (const uint8_t *)data;
	int32_t len = get_length(b);
	struct bson_reader br = { b , len };

	unpack_dict(L, &br, false);

	return 1;
}

static void
bson_meta(lua_State *L) {
	if (luaL_newmetatable(L, "bson")) {
		luaL_Reg l[] = {
			{ "decode", ldecode },
			{ "makeindex", lmakeindex },
			{ NULL, NULL },
		};
		luaL_newlib(L,l);
		lua_setfield(L, -2, "__index");
		lua_pushcfunction(L, ltostring);
		lua_setfield(L, -2, "__tostring");
		lua_pushcfunction(L, llen);
		lua_setfield(L, -2, "__len");
		lua_pushcfunction(L, lreplace);
		lua_setfield(L, -2, "__newindex");
	}
	lua_setmetatable(L, -2);
}

static int
encode_bson(lua_State *L) {
	struct bson *b = (struct bson*)lua_touserdata(L, 2);
	lua_settop(L, 1);
	if (luaL_getmetafield(L, -1, "__pairs") != LUA_TNIL) {
		pack_meta_dict(L, b, 0);
	} else {
		pack_simple_dict(L, b, 0);
	}
	void * ud = lua_newuserdatauv(L, b->size, 1);
	memcpy(ud, b->ptr, b->size);
	return 1;
}

static int
lencode(lua_State *L) {
	struct bson b;
	lua_settop(L,1);
	luaL_checktype(L, 1, LUA_TTABLE);
	bson_create(&b);
	lua_pushcfunction(L, encode_bson);
	lua_pushvalue(L, 1);
	lua_pushlightuserdata(L, &b);
	if (lua_pcall(L, 2, 1, 0) != LUA_OK) {
		bson_destroy(&b);
		return lua_error(L);
	}
	bson_destroy(&b);
	bson_meta(L);
	return 1;
}

static int
encode_bson_byorder(lua_State *L) {
	int n = lua_gettop(L);
	struct bson *b = (struct bson*)lua_touserdata(L, n);
	lua_settop(L, --n);
	pack_ordered_dict(L, b, n, 0);
	lua_settop(L,0);
	void * ud = lua_newuserdatauv(L, b->size, 1);
	memcpy(ud, b->ptr, b->size);
	return 1;
}

static int
lencode_order(lua_State *L) {
	struct bson b;
	int n = lua_gettop(L);
	if (n%2 != 0) {
		return luaL_error(L, "Invalid ordered dict");
	}
	bson_create(&b);
	lua_pushvalue(L, 1);	// copy the first arg to n
	lua_pushcfunction(L, encode_bson_byorder);
	lua_replace(L, 1);
	lua_pushlightuserdata(L, &b);
	if (lua_pcall(L, n+1, 1, 0) != LUA_OK) {
		bson_destroy(&b);
		return lua_error(L);
	}
	bson_destroy(&b);
	bson_meta(L);
	return 1;
}

static int
ldate(lua_State *L) {
	int d = luaL_checkinteger(L,1);
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, BSON_DATE);
	luaL_addlstring(&b, (const char *)&d, sizeof(d));
	luaL_pushresult(&b);

	return 1;
}

static int
lint64(lua_State *L) {
	int64_t d = luaL_checkinteger(L, 1);
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, BSON_INT64);
	luaL_addlstring(&b, (const char *)&d, sizeof(d));
	luaL_pushresult(&b);

	return 1;
}

static int
ltimestamp(lua_State *L) {
	int d = luaL_checkinteger(L,1);
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, BSON_TIMESTAMP);
	if (lua_isnoneornil(L,2)) {
		static uint32_t inc = 0;
		luaL_addlstring(&b, (const char *)&inc, sizeof(inc));
		++inc;
	} else {
		uint32_t i = (uint32_t)lua_tointeger(L,2);
		luaL_addlstring(&b, (const char *)&i, sizeof(i));
	}
	luaL_addlstring(&b, (const char *)&d, sizeof(d));
	luaL_pushresult(&b);

	return 1;
}

static int
lregex(lua_State *L) {
	luaL_checkstring(L,1);
	if (lua_gettop(L) < 2) {
		lua_pushliteral(L,"");
	}
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, BSON_REGEX);
	lua_pushvalue(L,1);
	luaL_addvalue(&b);
	luaL_addchar(&b,0);
	lua_pushvalue(L,2);
	luaL_addvalue(&b);
	luaL_addchar(&b,0);
	luaL_pushresult(&b);

	return 1;
}

static int
lbinary(lua_State *L) {
	lua_settop(L,1);
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	luaL_addchar(&b, 0);
	luaL_addchar(&b, BSON_BINARY);
	luaL_addchar(&b, 0);	// sub type
	lua_pushvalue(L,1);
	luaL_addvalue(&b);
	luaL_pushresult(&b);

	return 1;
}

static int
lsubtype(lua_State *L, int subtype, const uint8_t * buf, size_t sz) {
	switch(subtype) {
	case BSON_BINARY:
		lua_pushvalue(L, lua_upvalueindex(6));
		lua_pushlstring(L, (const char *)buf+1, sz-1);
		lua_pushinteger(L, buf[0]);
		return 3;
	case BSON_OBJECTID: {
		if (sz != 12) {
			return luaL_error(L, "Invalid object id");
		}
		char oid[24];
		int i;
		const uint8_t * id = buf;
		static const char *hex = "0123456789abcdef";
		for (i=0;i<12;i++) {
			oid[i*2] = hex[id[i] >> 4];
			oid[i*2+1] = hex[id[i] & 0xf];
		}
		lua_pushvalue(L, lua_upvalueindex(7));
		lua_pushlstring(L, oid, 24);

		return 2;
	}
	case BSON_DATE: {
		if (sz != 4) {
			return luaL_error(L, "Invalid date");
		}
		int d = *(const int *)buf;
		lua_pushvalue(L, lua_upvalueindex(9));
		lua_pushinteger(L, d);
		return 2;
	}
	case BSON_TIMESTAMP: {
		if (sz != 8) {
			return luaL_error(L, "Invalid timestamp");
		}
		const uint32_t * ts = (const uint32_t *)buf;
		lua_pushvalue(L, lua_upvalueindex(8));
		lua_pushinteger(L, (lua_Integer)ts[1]);
		lua_pushinteger(L, (lua_Integer)ts[0]);
		return 3;
	}
	case BSON_REGEX: {
		--sz;
		size_t i;
		const uint8_t *str = buf;
		for (i=0;i<sz;i++) {
			if (str[sz-i-1]==0) {
				break;
			}
		}
		lua_pushvalue(L, lua_upvalueindex(10));
		if (i==sz) {
			return luaL_error(L, "Invalid regex");
		}
		lua_pushlstring(L, (const char *)str, sz - i - 1);
		lua_pushlstring(L, (const char *)str+sz-i, i);
		return 3;
	}
	case BSON_MINKEY:
		lua_pushvalue(L, lua_upvalueindex(11));
		return 1;
	case BSON_MAXKEY:
		lua_pushvalue(L, lua_upvalueindex(12));
		return 1;
	case BSON_NULL:
		lua_pushvalue(L, lua_upvalueindex(4));
		return 1;
	case BSON_JSCODE:
	case BSON_DBPOINTER:
	case BSON_SYMBOL:
	case BSON_CODEWS:
		lua_pushvalue(L, lua_upvalueindex(14));
		lua_pushlstring(L, (const char *)buf, sz);
		return 2;
	case BSON_INT64: {
		if (sz != 8) {
			return luaL_error(L, "Invalid int64");
		}
		int64_t d = *(const int64_t *)buf;
		lua_pushvalue(L, lua_upvalueindex(13));
		lua_pushinteger(L, d);
		return 2;
	}
	default:
		return luaL_error(L, "Invalid subtype %d", subtype);
	}
}

static int
ltype(lua_State *L) {
	int t = lua_type(L,1);
	int type = 0;
	switch (t) {
	case LUA_TNUMBER:
		type = 1;
		break;
	case LUA_TBOOLEAN:
		type = 2;
		break;
	case LUA_TTABLE:
		type = 3;
		break;
	case LUA_TNIL:
		lua_pushvalue(L, lua_upvalueindex(4));
		return 1;
	case LUA_TSTRING: {
		size_t len = 0;
		const char * str = lua_tolstring(L,1,&len);
		if (str[0] == 0 && len >= 2) {
			return lsubtype(L, (uint8_t)str[1], (const uint8_t *)str+2, len-2);
		} else {
			type = 5;
			break;
		}
	}
	default:
		return luaL_error(L, "Invalid type %s",lua_typename(L,t));
	}
	lua_pushvalue(L, lua_upvalueindex(type));
	lua_pushvalue(L,1);
	return 2;
}

static void
typeclosure(lua_State *L) {
	static const char * typename_[] = {
		"number",	// 1
		"boolean",	// 2
		"table",	// 3
		"nil",		// 4
		"string",	// 5
		"binary",	// 6
		"objectid",	// 7
		"timestamp",    // 8
		"date",		// 9
		"regex",	// 10
		"minkey",	// 11
		"maxkey",	// 12
		"int64",	// 13
		"unsupported", // 14
	};
	int i;
	int n = sizeof(typename_)/sizeof(typename_[0]);
	for (i=0;i<n;i++) {
		lua_pushstring(L, typename_[i]);
	}
	lua_pushcclosure(L, ltype, n);
}

static uint8_t oid_header[5];
static ATOM_ULONG oid_counter;

static void
init_oid_header() {
	if (ATOM_LOAD(&oid_counter)) {
		// already init
		return;
	}
	pid_t pid = getpid();
	uint32_t h = 0;
	char hostname[256];
	if (gethostname(hostname, sizeof(hostname))==0) {
		int i;
		for (i=0;i<sizeof(hostname) && hostname[i];i++) {
			h = h ^ ((h<<5)+(h>>2)+hostname[i]);
 		}
		h ^= i;
	}
	oid_header[0] = h & 0xff;
	oid_header[1] = (h>>8) & 0xff;
	oid_header[2] = (h>>16) & 0xff;
	oid_header[3] = pid & 0xff;
	oid_header[4] = (pid >> 8) & 0xff;
	
	unsigned long c = h ^ time(NULL) ^ (uintptr_t)&h;
	if (c == 0) {
		c = 1;
	}
	ATOM_STORE(&oid_counter, c);
}

static inline int
hextoint(char c) {
	if (c>='0' && c<='9')
		return c-'0';
	if (c>='a' && c<='z')
		return c-'a'+10;
	if (c>='A' && c<='Z')
		return c-'A'+10;
	return 0;
}

static int
lobjectid(lua_State *L) {
	uint8_t oid[14] = { 0, BSON_OBJECTID };
	if (lua_isstring(L,1)) {
		size_t len;
		const char * str = lua_tolstring(L,1,&len);
		if (len != 24) {
			return luaL_error(L, "Invalid objectid %s", str);
		}
		int i;
		for (i=0;i<12;i++) {
			oid[i+2] = hextoint(str[i*2]) << 4 | hextoint(str[i*2+1]);
		}
	} else {
		time_t ti = time(NULL);
		// old_counter is a static var, use atom inc.
		uint32_t id = ATOM_FINC(&oid_counter);

		oid[2] = (ti>>24) & 0xff;
		oid[3] = (ti>>16) & 0xff;
		oid[4] = (ti>>8) & 0xff;
		oid[5] = ti & 0xff;
		memcpy(oid+6 , oid_header, 5);
		oid[11] = (id>>16) & 0xff; 
		oid[12] = (id>>8) & 0xff; 
		oid[13] = id & 0xff;
	}
	lua_pushlstring( L, (const char *)oid, 14);

	return 1;
}

LUAMOD_API int
luaopen_bson(lua_State *L) {
	luaL_checkversion(L);
	int i;
	for (i=0;i<MAX_NUMBER;i++) {
		char tmp[8];
		bson_numstr_len[i] = sprintf(tmp,"%d",i);
		memcpy(bson_numstrs[i], tmp, bson_numstr_len[i]);
	}
	luaL_Reg l[] = {
		{ "encode", lencode },
		{ "encode_order", lencode_order },
		{ "date", ldate },
		{ "timestamp", ltimestamp  },
		{ "regex", lregex },
		{ "binary", lbinary },
		{ "objectid", lobjectid },
		{ "int64", lint64 },
		{ "decode", ldecode },
		{ NULL,  NULL },
	};

	luaL_newlib(L,l);

	typeclosure(L);
	lua_setfield(L,-2,"type");
	char null[] = { 0, BSON_NULL };
	lua_pushlstring(L, null, sizeof(null));
	lua_setfield(L,-2,"null");
	char minkey[] = { 0, (char)BSON_MINKEY };
	lua_pushlstring(L, minkey, sizeof(minkey));
	lua_setfield(L,-2,"minkey");
	char maxkey[] = { 0, BSON_MAXKEY };
	lua_pushlstring(L, maxkey, sizeof(maxkey));
	lua_setfield(L,-2,"maxkey");
	init_oid_header();

	return 1;
}