#include "redis.h"
#include "sha1.h"

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

int luaRedisCommand(lua_State *lua) {
    int j, argc = lua_gettop(lua);
    struct redisCommand *cmd;
    robj **argv;
    redisClient *c = server.lua_client;
    sds reply;

    argv = zmalloc(sizeof(robj*)*argc);
    for (j = 0; j < argc; j++)
        argv[j] = createStringObject(lua_tostring(lua,j+1),lua_strlen(lua,j+1));

    /* Command lookup */
    cmd = lookupCommand(argv[0]->ptr);
    if (!cmd) {
        zfree(argv);
        lua_pushnil(lua);
        lua_pushstring(lua,"Unknown Redis command called from Lua script");
        return 2;
    }
    /* Run the command in the context of a fake client */
    c->argv = argv;
    c->argc = argc;
    cmd->proc(c);

    /* Convert the result of the Redis command into a suitable Lua type.
     * The first thing we need is to create a single string from the client
     * output buffers. */
    reply = sdsempty();
    if (c->bufpos) {
        reply = sdscatlen(reply,c->bufpos,c->buf);
        c->bufpos = 0;
    }
    while(listLength(c->reply)) {
        robj *o = listNodeValue(listFirst(c->reply));

        sdscatlen(reply,o->ptr,sdslen(o->ptr));
        listDelNode(c->reply,listFirst(c->reply));
    }
    lua_pushnumber(lua,1);

    /* Clean up. Command code may have changed argv/argc so we use the
     * argv/argc of the client instead of the local variables. */
    for (j = 0; j < c->argc; j++)
        decrRefCount(c->argv[j]);
    zfree(c->argv);

    return 1;
}

void scriptingInit(void) {
    lua_State *lua = lua_open();
    luaL_openlibs(lua);

    /* Register the 'r' command */
    lua_pushcfunction(lua,luaRedisCommand);
    lua_setglobal(lua,"r");

    /* Create the (non connected) client that we use to execute Redis commands
     * inside the Lua interpreter */
    server.lua_client = createClient(-1);

    server.lua = lua;
}

/* Hash the scripit into a SHA1 digest. We use this as Lua function name.
 * Digest should point to a 41 bytes buffer: 40 for SHA1 converted into an
 * hexadecimal number, plus 1 byte for null term. */
void hashScript(char *digest, char *script, size_t len) {
    SHA1_CTX ctx;
    unsigned char hash[20];
    char *cset = "0123456789abcdef";
    int j;

    SHA1Init(&ctx);
    SHA1Update(&ctx,(unsigned char*)script,len);
    SHA1Final(hash,&ctx);

    for (j = 0; j < 20; j++) {
        digest[j*2] = cset[((hash[j]&0xF0)>>4)];
        digest[j*2+1] = cset[(hash[j]&0xF)];
    }
    digest[40] = '\0';
}

void luaReplyToRedisReply(redisClient *c, lua_State *lua) {
    int t = lua_type(lua,1);

    switch(t) {
    case LUA_TSTRING:
        addReplyBulkCBuffer(c,(char*)lua_tostring(lua,1),lua_strlen(lua,1));
        break;
    case LUA_TBOOLEAN:
        addReply(c,lua_toboolean(lua,1) ? shared.cone : shared.czero);
        break;
    case LUA_TNUMBER:
        addReplyLongLong(c,(long long)lua_tonumber(lua,1));
        break;
    default:
        addReply(c,shared.nullbulk);
    }
    lua_pop(lua,1);
}

void evalCommand(redisClient *c) {
    lua_State *lua = server.lua;
    char funcname[43];

    /* We obtain the script SHA1, then check if this function is already
     * defined into the Lua state */
    funcname[0] = 'f';
    funcname[1] = '_';
    hashScript(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
    lua_getglobal(lua, funcname);
    if (lua_isnil(lua,1)) {
        /* Function not defined... let's define it. */
        sds funcdef = sdsempty();

        lua_pop(lua,1); /* remove the nil from the stack */
        funcdef = sdscat(funcdef,"function ");
        funcdef = sdscatlen(funcdef,funcname,42);
        funcdef = sdscatlen(funcdef," ()\n",4);
        funcdef = sdscatlen(funcdef,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
        funcdef = sdscatlen(funcdef,"\nend\n",5);
        printf("Defining:\n%s\n",funcdef);

        if (luaL_loadbuffer(lua,funcdef,sdslen(funcdef),"func definition")) {
            addReplyErrorFormat(c,"Error compiling script (new function): %s\n",
                lua_tostring(lua,-1));
            lua_pop(lua,1);
            return;
        }
        if (lua_pcall(lua,0,0,0)) {
            addReplyErrorFormat(c,"Error running script (new function): %s\n",
                lua_tostring(lua,-1));
            lua_pop(lua,1);
            return;
        }
        lua_getglobal(lua, funcname);
    }
    
    /* At this point whatever this script was never seen before or if it was
     * already defined, we can call it. We have zero arguments and expect
     * a single return value. */
    if (lua_pcall(lua,0,1,0)) {
        addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
            funcname, lua_tostring(lua,-1));
        lua_pop(lua,1);
        return;
    }
    luaReplyToRedisReply(c,lua);
}