/*
 * 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 <string.h>
#include <lauxlib.h>
#include "melisma.h"
#include "mutil.h"

#define MIXER_TYPENAME "mixer"

static void proc(const ml_proc_args *args)
{
	float *out = args->out[0];

	memset(out,0,args->nframes * sizeof(out[0]));

	for (size_t i = 0; i < args->icnt; i++)
	{
		const float *in = args->in[i];

		for (size_t j = 0; j < args->nframes; j++)
		{
			out[j] += in[j];
		}
	}
}

static int l_init(lua_State *s)
{
	int n = lua_gettop(s);

	if (n == 0)
	{
		luaL_error(s,"need at least one input channel");
	}

	ml_node *node = ml_create_node(proc,NULL);
	ml_label_node(node,"mix");

	for (int i = 0; i < n; i++)
	{
		ml_channel *src = mutil_get_channel(s,i+1);
		ml_channel *dst = ml_add_input(node);
		ml_connect(src,dst);
	}

	ml_channel *out = ml_add_output(node);

	*(void**) lua_newuserdata(s,sizeof(void*)) = out;
	luaL_setmetatable(s,MIXER_TYPENAME);

	return 1;
}

static int l_out(lua_State *s)
{
	ml_channel *c = *(void**) luaL_checkudata(s,1,MIXER_TYPENAME);
	*(void**) lua_newuserdata(s,sizeof(void*)) = c;
	luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
	return 1;
}

int luaopen_melisma_mixer(lua_State *s)
{
	ml_check_version();

/*** Mix signals.

	local mmixer = require 'melisma.mixer'

	local signals = ...
	local mixer = mmixer.init(table.unpack(signals))

@classmod mixer
*/
	lua_newtable(s);
	int tbl = lua_gettop(s);

/*** Mix input signals in to a single output signal.
@static
@function init
@tparam channel ... Input signals.
@treturn mixer The newly created mixer unit.
*/
	lua_pushcfunction(s,l_init);
	lua_setfield(s,tbl,"init");

	lua_pushcfunction(s,l_out);
	lua_setfield(s,tbl,MUTIL_OUTPUT_CHANNEL_FUNCTION);

	luaL_newmetatable(s,MIXER_TYPENAME);
	int mt = lua_gettop(s);

	lua_pushvalue(s,tbl);
	lua_setfield(s,mt,"__index");

	lua_settop(s,tbl);
	return 1;
}