local args = {...};
local menu = {};
local box = nil;
local song = nil;
local action = 'mainList';
local maxtoshow = 12;
local selected = tonumber(args[1]);
local startat = 1;

for _,side in ipairs({"left"; "right"; "back"; "bottom"; "top"; "front"}) do
	if peripheral.getType(side) == "note" then
		box = peripheral.wrap(side);
		break;
	end
end

if turtle ~= nil then
	maxtoshow = 7;
end

function newSong(x)
	return {
		fh = x;
		length = 0;
		height = 0;
		name = "";
		author = "";
		originalAuthor = "";
		description = "";
		tempo = 10.00; --tks per second
		autoSaving = 0;
		autoSaveDur = 0;
		timeSig = 4;
		minSpent = 0;
		leftClicks = 0;
		rightClicks = 0;
		blocksAdded = 0;
		blocksRemoved = 0;
		midi = "";
		music = { wait={}; inst={}; note={}; };
	};
end

for _, file in ipairs(fs.list("songs")) do
  if fs.isDir(file) == false and string.find(file, ".nbs", -4, true) ~= nil then -- if file and ends in ".nbs"
  	menu[#menu+1] = file;
  end
end

function showInfo()
	term.clear();
	print("Now Playing: \n\n\n\n\n\n          " .. song.name);
	print("\n\n\n\n\n\nAuthor: " .. song.author);
	print("Original Author: " .. song.originalAuthor);
	print("Description: ");
	print(song.description);
end

function readInt(fh) --little endian, fh is open in rb mode
	local ret = 0;
	local x = fh.read();
	if x == nil then return nil; end
	ret = x;
	x = fh.read();
	if x == nil then return nil; end
	ret = (x * 0x100) + ret;
	x = fh.read();
	if x == nil then return nil; end
	ret = (x * 0x10000) + ret;
	x = fh.read();
	if x == nil then return nil; end
	ret = (x * 0x1000000) + ret;
	return ret;
end

function readShort(fh) --little endian, fh is open in rb mode
	local ret = 0;
	local x = fh.read();
	if x == nil then return nil; end
	ret = x;
	x = fh.read();
	if x == nil then return nil; end
	ret = (x * 0x100) + ret;
	return ret;
end

function readString(fh, len) --fh is open in rb mode
	local ret = "";
	local x = 0;
	for i = 1, len do
		x = fh.read();
		if x == nil then return nil; end
		ret = ret .. string.char(x);
	end
	return ret;
end

function readHeader()
	song.length 		= readShort(song.fh);
	song.height 		= readShort(song.fh);
	song.name 			= readString(song.fh, readInt(song.fh));
	song.author 		= readString(song.fh, readInt(song.fh));
	song.originalAuthor = readString(song.fh, readInt(song.fh));
	song.description 	= readString(song.fh, readInt(song.fh));
	song.tempo 			= 1.000 / ( readShort(song.fh) / 100.00 );
	song.autoSaving 	= song.fh.read();
	song.autoSaveDur 	= song.fh.read();
	song.timeSig 		= song.fh.read();
	song.minSpent 		= readInt(song.fh);
	song.leftClicks 	= readInt(song.fh);
	song.rightClicks 	= readInt(song.fh);
	song.blocksAdded 	= readInt(song.fh);
	song.blocksRemoved 	= readInt(song.fh);
	song.midi 			= readString(song.fh, readInt(song.fh));
end

function readNotes()
	local curtk = 1;
	local tk = -1;
	local layer = -1;
	local inst = 0;
	local note = 33; -- MC is 33 to 57

	while true do
		tk = readShort(song.fh);
		if tk == nil then return false; end
		if tk == 0 then break; end
		while true do
			song.music.wait[curtk] = (tk * song.tempo) * 0.975; -- * 0.975 to speed it up a bit because lua slow
			layer = readShort(song.fh); --can't do anything with this info (yet?)
			if layer == nil then return false; end
			if layer == 0 then break; end
			song.music.inst[curtk]=song.fh.read();
			if song.music.inst[curtk] == 0 then
				song.music.inst[curtk] = 0;
			elseif song.music.inst[curtk] == 2 then
				song.music.inst[curtk] = 1;
			elseif song.music.inst[curtk] == 3 then
				song.music.inst[curtk] = 2;
			elseif song.music.inst[curtk] == 4 then
				song.music.inst[curtk] = 3;
			elseif song.music.inst[curtk] == 1 then
				song.music.inst[curtk] = 4;
			end
			song.music.note[curtk]=song.fh.read()-33;
			tk = 0;
			curtk = curtk + 1;
		end
	end
	return true;
end

function playNotes()
	for i = 1, #song.music.wait - 1 do
		if song.music.wait[i] ~= 0 then
			os.sleep(song.music.wait[i]);
		end
		--box.playNote(song.music.inst[i], song.music.note[i]);
		pcall(box.playNote, song.music.inst[i], song.music.note[i]);
	end
end

function printSongs(x)
	action = 'mainList';
	term.clear();
    action = 'playSong';
	return selected, x;
end

if box == nil then
	print("No Iron Noteblock Detected");
else
	selected, startat = printSongs(1);
	while true do
		if action == 'playSong' then
			song = newSong(fs.open("songs/" .. menu[tonumber(tostring(selected))], "rb"));
			readHeader();
			showInfo();
			readNotes();
			song.fh.close();
			playNotes();
			--loops if don't change action
			action = 'mainList';
		else
			if action == 'backNextMenu' then
				if selected == 1 then
					startat = startat - maxtoshow;
					if startat < 1 then startat = 1; end
					selected, startat = printSongs(startat);
				elseif selected == 2 then
					startat = startat + maxtoshow
					if startat > #menu then startat = 1; end
					selected, startat = printSongs(startat);
				else --if selected == 0 then
					selected, startat = printSongs(startat);
				end
			elseif action =='mainList' then
				selected, startat = printSongs(startat);
			end
		end
	end
end