/*
 * melisma - extensible and scriptable audio engine
 * Copyright (C) 2026  Ludvig Gunne Lindström
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <lauxlib.h>
#include "melisma.h"
#include "melisma/ring.h"

static int fn = LUA_NOREF;
static struct termios tty = {0};
static struct termios oldtty = {0};
static lua_State *state;
static ml_ring *ring = NULL;

static void make_arg(lua_State *s, size_t len, const void *data)
{
	lua_pushlstring(s,data,len);
}

static void io_handler(int fd, int flags, void *args)
{
	char c;

	if (read(fd,&c,sizeof c) <= 0)
	{
		return;
	}

	ml_ring_put_blocking(ring,*(uint8_t*) &c);
}

static void cleanup(void)
{
	tcsetattr(STDIN_FILENO,TCSANOW,&oldtty);
}

static void proc(const ml_proc_args *args)
{
	if (fn == LUA_NOREF)
	{
		return;
	}

	char buf[1];
	while (ml_ring_read(ring,buf,sizeof buf) == sizeof buf)
	{
		lua_pushlstring(state,buf,sizeof buf);
		int arg = luaL_ref(state,LUA_REGISTRYINDEX);
		ml_schedule_event(0,fn,arg);
	}
}

static void setup(lua_State *s)
{
	static bool init = false;

	if (init)
	{
		return;
	}

	init = true;

	tcgetattr(STDIN_FILENO,&oldtty);
	tty = oldtty;
	tty.c_lflag &= ~ECHO;
	tty.c_lflag &= ~ICANON;
	tcsetattr(STDIN_FILENO,TCSANOW,&tty);
	tcflush(STDIN_FILENO,TCIFLUSH);

	ml_add_io_handler(STDIN_FILENO,POLLIN,io_handler,NULL);
	ring = ml_ring_init(4096);
	state = s;

	ml_node *node = ml_create_node(proc,NULL);
	ml_channel *src = ml_add_output(node);
	ml_channel *dst = ml_add_input(ml_get_root_node());
	ml_connect(src,dst);
	ml_label_node(node,"keycallback");

	atexit(cleanup);
}

static int l_set(lua_State *s)
{
	if (fn != LUA_NOREF)
	{
		luaL_unref(s,LUA_REGISTRYINDEX,fn);
		fn = LUA_NOREF;
	}

	if (lua_isnil(s,1))
	{
		return 0;
	}

	luaL_checktype(s,1,LUA_TFUNCTION);
	lua_pushvalue(s,1);
	fn = luaL_ref(s,LUA_REGISTRYINDEX);

	setup(s);

	return 0;
}

int luaopen_melisma_keycallback(lua_State *s)
{
/*** Set callback for keyboard input.
	local mkeycallback = require 'melisma.keycallback'

	mkeycallback.set(function(c)
		print('you pressed', c)
	end)
@module keycallback
*/
	lua_newtable(s);
	int tbl = lua_absindex(s,lua_gettop(s));

/*** Set the callback.
@function set
@tparam function fn Callback function.
*/
	lua_pushcfunction(s,l_set);
	lua_setfield(s,tbl,"set");

	lua_settop(s,tbl);
	return 1;
}