// title: midified arpeggiator/auto-accompaniment using patterns
// author: 56228375
// description:
// Proof of concept code for a midified arpeggiator/auto-accompaniment system, quickly reacting to chord changes
// Midi is received as input, and supercollider's default instrument (I know, I know) is generating the output.
// This code is accompaniment to a blog article at https://technogems.blogspot.com/2020/01/making-arpeggiator-in-supercollider.html
// Let me know if you have ideas for improvement! (code-wise or feature-wise)
// code:
(
s.waitForBoot({
	var right, left;
	var n0, n1, n2;
	var note_getter;

	MIDIdef.freeAll;
	if (~midi_initilized.isNil) {
		MIDIClient.init;
		MIDIIn.connectAll;
		~midi_initialized = 1;
	};

	~note_table = 0!127;
	~n = nil;

	MIDIdef.noteOn(
		\mynoteonhandler, // just a name for this handler
		{
			|val, num, chan, src|
			~note_table[num] = 1; // update note table and update ~n
			~n = ~note_table.selectIndices({|item, i| item != 0});
		}
	);

	MIDIdef.noteOff(
		\mynoteoffhandler, // just a name for this handler
		{
			|val, num, chan, src|
			~note_table[num] = 0; // update note table and update ~n
			/*
			// only enable the following lines if you want the arpeggio to stop as soon as you release the keys
			~n = ~note_table.selectIndices({|item, i| item != 0});
			if (~n == []) { ~n = nil; };
			*/
		}
	);

	note_getter = {
		| index |
		Plazy {
			if (~n.isNil) {
				Pseq([Rest(1)]);
			} {
				~n[index] ?? (~n[0] ?? Pseq([Rest(1)]));
			};
		};
	};

	n0 = note_getter.(0);
	n1 = note_getter.(1);
	n2 = note_getter.(2);

	right = Pbind(
		\instrument, \default,
		\midinote, Pseq([ n0, n2, n1, n2] ++ (([ n0, n2, n1, n2] + 12)!2).flatten),
		\dur, Pseq([1, 1, 1, 1, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ].normalizeSum*2)
	);
	left = Pbind(
		\instrument, \default,
		\midinote, Pseq([ n0, n2, n0, n2, n0, n2, n0, n2] - 12),
		\dur, Pseq([1, 1, 1, 1, 1, 1, 1, 1].normalizeSum*2)
	);
	if (~player.notNil) { ~player.stop; };
	~player = Pn(Ppar([right,left])).play;
});
)