/*
 * Copyright (C) Xiaozhe Wang (chaoslawful)
 * Copyright (C) Yichun Zhang (agentzh)
 */


#ifndef DDEBUG
#define DDEBUG 0
#endif
#include "ddebug.h"


#include "ngx_http_lua_setby.h"
#include "ngx_http_lua_exception.h"
#include "ngx_http_lua_util.h"
#include "ngx_http_lua_pcrefix.h"
#include "ngx_http_lua_time.h"
#include "ngx_http_lua_log.h"
#include "ngx_http_lua_regex.h"
#include "ngx_http_lua_variable.h"
#include "ngx_http_lua_string.h"
#include "ngx_http_lua_misc.h"
#include "ngx_http_lua_consts.h"
#include "ngx_http_lua_shdict.h"
#include "ngx_http_lua_util.h"


static void ngx_http_lua_set_by_lua_env(lua_State *L, ngx_http_request_t *r,
    size_t nargs, ngx_http_variable_value_t *args);


/* keys in Lua thread for fetching args and nargs in set_by_lua* */

#define ngx_http_lua_nargs_key  "__ngx_nargs"

#define ngx_http_lua_args_key  "__ngx_args"


ngx_int_t
ngx_http_lua_set_by_chunk(lua_State *L, ngx_http_request_t *r, ngx_str_t *val,
    ngx_http_variable_value_t *args, size_t nargs, ngx_str_t *script)
{
    size_t           i;
    ngx_int_t        rc;
    u_char          *err_msg;
    size_t           len;
    u_char          *data;
#if (NGX_PCRE)
    ngx_pool_t      *old_pool;
#endif

    dd("nargs: %d", (int) nargs);

    dd("set Lua VM panic handler");

    lua_atpanic(L, ngx_http_lua_atpanic);

    NGX_LUA_EXCEPTION_TRY {
        dd("initialize nginx context in Lua VM, code chunk at "
           "stack top    sp = 1");
        ngx_http_lua_set_by_lua_env(L, r, nargs, args);

        /*  passing directive arguments to the user code */
        for (i = 0; i < nargs; i++) {
            lua_pushlstring(L, (const char *) args[i].data, args[i].len);
        }

#if (NGX_PCRE)
        /* XXX: work-around to nginx regex subsystem */
        old_pool = ngx_http_lua_pcre_malloc_init(r->pool);
#endif

        lua_pushcfunction(L, ngx_http_lua_traceback);
        lua_insert(L, 1);  /* put it under chunk and args */

        dd("protected call user code");

        rc = lua_pcall(L, nargs, 1, 1);

        dd("after protected call user code");

        lua_remove(L, 1);  /* remove traceback function */

#if (NGX_PCRE)
        /* XXX: work-around to nginx regex subsystem */
        ngx_http_lua_pcre_malloc_done(old_pool);
#endif

        if (rc != 0) {
            /*  error occurred when running loaded code */
            err_msg = (u_char *) lua_tolstring(L, -1, &len);

            if (err_msg == NULL) {
                err_msg = (u_char *) "unknown reason";
                len = sizeof("unknown reason") - 1;
            }

            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                          "failed to run set_by_lua*: %*s", len, err_msg);

            lua_settop(L, 0);    /*  clear remaining elems on stack */

            return NGX_ERROR;
        }

        data = (u_char *) lua_tolstring(L, -1, &len);

        if (data) {
            val->data = ngx_palloc(r->pool, len);
            if (val->data == NULL) {
                return NGX_ERROR;
            }

            ngx_memcpy(val->data, data, len);
            val->len = len;

        } else {
            val->data = NULL;
            val->len = 0;
        }

    } NGX_LUA_EXCEPTION_CATCH {

        dd("nginx execution restored");
        return NGX_ERROR;
    }

    /*  clear Lua stack */
    lua_settop(L, 0);

    return NGX_OK;
}


int
ngx_http_lua_setby_param_get(lua_State *L)
{
    int         idx;
    int         n;

    ngx_http_variable_value_t       *v;

    idx = luaL_checkint(L, 2);
    idx--;

    /*  get number of args from globals */
    lua_getglobal(L, ngx_http_lua_nargs_key);
    n = (int) lua_tointeger(L, -1);

    /*  get args from globals */
    lua_getglobal(L, ngx_http_lua_args_key);
    v = lua_touserdata(L, -1);

    if (idx < 0 || idx > n - 1) {
        lua_pushnil(L);

    } else {
        lua_pushlstring(L, (const char *) (v[idx].data), v[idx].len);
    }

    return 1;
}


/**
 * Set environment table for the given code closure.
 *
 * Before:
 *         | code closure | <- top
 *         |      ...     |
 *
 * After:
 *         | code closure | <- top
 *         |      ...     |
 * */
static void
ngx_http_lua_set_by_lua_env(lua_State *L, ngx_http_request_t *r, size_t nargs,
    ngx_http_variable_value_t *args)
{
    /*  set nginx request pointer to current lua thread's globals table */
    ngx_http_lua_set_req(L, r);

    lua_pushinteger(L, nargs);
    lua_setglobal(L, ngx_http_lua_nargs_key);

    lua_pushlightuserdata(L, args);
    lua_setglobal(L, ngx_http_lua_args_key);

    /**
     * we want to create empty environment for current script
     *
     * newt = {}
     * newt["_G"] = newt
     * setmetatable(newt, {__index = _G})
     *
     * if a function or symbol is not defined in our env, __index will lookup
     * in the global env.
     *
     * all variables created in the script-env will be thrown away at the end
     * of the script run.
     * */
    ngx_http_lua_create_new_globals_table(L, 0 /* narr */, 1 /* nrec */);

    /*  {{{ make new env inheriting main thread's globals table */
    /* the metatable for the new env */
    lua_createtable(L, 0 /* narr */, 1 /* nrec */);
    ngx_http_lua_get_globals_table(L);
    lua_setfield(L, -2, "__index");
    lua_setmetatable(L, -2);    /*  setmetatable(newt, {__index = _G}) */
    /*  }}} */

    lua_setfenv(L, -2);    /*  set new running env for the code closure */
}

/* vi:set ft=c ts=4 sw=4 et fdm=marker: */