/*
 * Copyright (C) 2015  Patrick "P. J." McDermott
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <string.h>
#include <lua.h>
#include "../logging.h"
#include "../resources/script.h"
#include "ffi.h"

/* LUA_OK is defined in Lua 5.2 but not 5.1. */
#ifndef LUA_OK
#define LUA_OK 0
#endif

static struct script *ctx;
static struct ffi_namespace root = {
	NULL,
	NULL,
	NULL,
	NULL,
	NULL,
	NULL,
};
static int call_arg_index;

static void ffi_register_functions_in_namespace(lua_State *l,
		struct ffi_namespace *parent);
static int ffi_handle_function(lua_State *l);

struct ffi_namespace *
ffi_add_namespace(struct ffi_namespace *parent, const char *name)
{
	struct ffi_namespace *new_ns;

	if (parent == NULL) {
		parent = &root;
	}

	new_ns = malloc(sizeof(*new_ns));
	if (new_ns == NULL) {
		err(1, "Failed to allocate FFI namespace \"%s\"", name);
		return NULL;
	}
	new_ns->name = strdup(name);
	new_ns->ns_head = NULL;
	new_ns->ns_tail = NULL;
	new_ns->fn_head = NULL;
	new_ns->fn_tail = NULL;
	new_ns->next = NULL;

	if (parent->ns_head == NULL) {
		parent->ns_head = new_ns;
	} else {
		parent->ns_tail->next = new_ns;
	}
	parent->ns_tail = new_ns;

	return new_ns;
}

void
ffi_add_function(struct ffi_namespace *parent, const char *name,
		void (*func)(void))
{
	struct ffi_function *new_fn;

	new_fn = malloc(sizeof(*new_fn));
	if (new_fn == NULL) {
		err(1, "Failed to allocate FFI function \"%s\"", name);
		return;
	}
	new_fn->name = strdup(name);
	new_fn->func = func;
	new_fn->next = NULL;

	if (parent->fn_head == NULL) {
		parent->fn_head = new_fn;
	} else {
		parent->fn_tail->next = new_fn;
	}
	parent->fn_tail = new_fn;
}

void
ffi_register_functions(struct script *script)
{
	ffi_register_functions_in_namespace(script->lua_state, &root);
}

static void
ffi_register_functions_in_namespace(lua_State *l, struct ffi_namespace *parent)
{
	struct ffi_namespace *ns;
	struct ffi_function *fn;

	lua_checkstack(l, 2);
	for (ns = parent->ns_head; ns != NULL; ns = ns->next) {
		lua_newtable(l);
		ffi_register_functions_in_namespace(l, ns);
		if (parent == &root) {
			lua_setglobal(l, ns->name);
		} else {
			lua_setfield(l, -2, ns->name);
		}
	}
	for (fn = parent->fn_head; fn != NULL; fn = fn->next) {
		lua_pushlightuserdata(l, fn);
		lua_pushcclosure(l, &ffi_handle_function, 1);
		lua_setfield(l, -2, fn->name);
	}
}

static int
ffi_handle_function(lua_State *l)
{
	struct ffi_function *fn;

	fn = (struct ffi_function *) lua_touserdata(l, lua_upvalueindex(1));
	fn->func();

	return 0;
}

void ffi_context_switch(struct script *script)
{
	ctx = script;
}

int
ffi_stack_get_bool(void)
{
	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	if (!lua_isboolean(ctx->lua_state, call_arg_index)) {
		warn("Bad argument #%d to %s (boolean expected)");
		return 0;
	}
	return lua_toboolean(ctx->lua_state, call_arg_index);
}

int
ffi_stack_get_int(void)
{
#if LUA_VERSION_NUM <= 501
	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	return lua_tointeger(ctx->lua_state, call_arg_index);
#elif LUA_VERSION_NUM == 502
	int v;
	int is_int;

	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	v = lua_tointegerx(ctx->lua_state, call_arg_index, &is_int);
	if (!is_int) {
		warn("Bad argument #%d to %s (integer expected)");
		return 0;
	}
	return v;
#elif LUA_VERSION_NUM >= 503
	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	if (!lua_isinteger(ctx->lua_state, call_arg_index)) {
		warn("Bad argument #%d to %s (integer expected)");
		return 0;
	}
	return lua_tointeger(ctx->lua_state, call_arg_index);
#endif
}

double
ffi_stack_get_float(void)
{
	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	if (!lua_isnumber(ctx->lua_state, call_arg_index)) {
		warn("Bad argument #%d to %s (number expected)");
		return 0;
	}
	return lua_tonumber(ctx->lua_state, call_arg_index);
}

const char *
ffi_stack_get_string(void)
{
	if (lua_gettop(ctx->lua_state) < ++call_arg_index) {
		warn("Bad argument #%d to %s (no value)");
		return 0;
	}
	if (!lua_isstring(ctx->lua_state, call_arg_index)) {
		warn("Bad argument #%d to %s (string expected)");
		return 0;
	}
	return lua_tostring(ctx->lua_state, call_arg_index);
}

void
ffi_prepare_call(const char *func)
{
	lua_getglobal(ctx->lua_state, func);
	call_arg_index = 0;
}

void
ffi_stack_set_bool(int v)
{
	lua_pushboolean(ctx->lua_state, v);
}

void
ffi_stack_set_int(int v)
{
	lua_pushinteger(ctx->lua_state, v);
}

void
ffi_stack_set_float(double v)
{
	lua_pushnumber(ctx->lua_state, v);
}

void
ffi_stack_set_string(const char *v)
{
	lua_pushstring(ctx->lua_state, v);
}

void
ffi_call(void)
{
	if (lua_pcall(ctx->lua_state, call_arg_index, 0, 0) != LUA_OK) {
		err(1, "Error calling function: %s\n",
				lua_tostring(ctx->lua_state, -1));
	}
}