// SysEx protocol between the Weights card and its web editor
// (web/index.html), used when a computer is plugged into the Computer's USB
// socket and the card is acting as a USB MIDI device.
//
// Every message is  F0 7D 47 <cmd> <payload...> F7
// (7D is the MIDI 'non-commercial' manufacturer ID, 47 is 'G').
// All values are 7-bit; wider values are sent as two bytes, high 7 bits first.
//
// Fader values are in 8mu fader units, 0-127, sent page by page (16 pages
// of 8 faders), the pages numbered
//   0 NOTES     1 OCTAVES     2 GATES     3 RATCHETS      (buttons A-D)
//   4 NOTES 2   5 OCTAVES 2   6 GATES 2   7 RATCHETS 2    (A-D pressed again)
//   8 ATTACK    9 DECAY      10 PLUCK    11 DEPTH         (and again)
//  12 ATTACK 2 13 DECAY 2    14 PLUCK 2  15 DEPTH 2       (and again)
// (Version 1 had only pages 0-7; version 2 had a different list of scales.)
//
// Web -> card
//   HELLO     01                        card replies with STATE
//   SET       03 page fader value       one fader value
//   SET_ALL   04 version tempo(2) values[128]
//   PAGE      05 page                   page shown on the Computer's LEDs
//   RESET     06                        default faders; card replies with STATE
//   PING      09                        sent every second; STATUS flows while
//                                       pings keep arriving
//   TEMPO     0A tempo(2)               internal clock, 40-300 BPM
//
// Card -> web
//   STATE     02 version page tempo(2) values[128]
//   STATUS    07 flags flags2 scale ratio slew attack decay pluck
//                steplen(2) steppos stepcount  voice1[14] voice2[14] tempo(2) busy parts[6]
//             flags      bit 0 following a clock at Pulse In 1, bit 1 8mu on
//                        the card, bit 2 switch up (knobs are scale, clock
//                        and slew, not decay, attack and pluck), bit 3 a
//                        knob is waiting to pick up its setting, bit 4
//                        switch held down (Main is the tempo), bits 5 and
//                        6 a jack in Audio In 1 and 2 (Audio Out 1 and 2
//                        are then that input through the envelope)
//             flags2     bits 0-2 the X, Y and Main knob is waiting, bits 3-6
//                        voice 2 shares the NOTES, OCTAVES, GATES, RATCHETS
//                        first page (its second page is all zero)
//             scale      0-36, as kScales in weights.h
//             ratio      0-10: /8 /6 /4 /3 /2 x1 x2 x3 x4 x6 x8
//             slew attack decay pluck   the knob settings, 0-127
//             steplen    milliseconds a step lasts, as estimated
//             steppos    position through the step, 0-127
//             stepcount  counts steps, 0-127 and round again
//             voice      note fader, note of the scale, octave fader, gate
//                        fader, ratchet fader (0-7 each), hit count (0-127
//                        and round), bit 0 gate up, envelope (0-127),
//                        pitch(2) in millivolts offset by 8192, then the
//                        ATTACK, DECAY, PLUCK and DEPTH faders drawn (0-7,
//                        or 8 for none: that page is off)
//             tempo      the internal clock, BPM (from Main with the switch
//                        held down, or from TEMPO)
//             busy       the longest the card's audio interrupt took over the
//                        last second, in microseconds (it has about 20)
//             parts      the same for each part of the work: the engine
//                        alone, the engine drawing new choices, the knobs,
//                        the 8mu, the LEDs and this status

#ifndef WEIGHTS_SYSEX_H
#define WEIGHTS_SYSEX_H

#include <stdint.h>

namespace sysex
{

static constexpr uint8_t kMfr = 0x7D;
static constexpr uint8_t kProduct = 0x47;
static constexpr uint8_t kVersion = 3;
static constexpr int kNumValues = 16 * 8;

enum Cmd : uint8_t
{
	Hello = 0x01,
	State = 0x02,
	Set = 0x03,
	SetAll = 0x04,
	Page = 0x05,
	Reset = 0x06,
	Status = 0x07,
	Ping = 0x09,
	Tempo = 0x0A,
};

// Collects one SysEx message from a byte stream.  Feed() returns true when
// a complete message for this card has arrived; its command and payload are
// then in cmd, payload and length.
struct Parser
{
	static constexpr int kMax = 160;
	uint8_t buf[kMax];
	int n = 0;
	bool in = false;

	uint8_t cmd = 0;
	const uint8_t *payload = nullptr;
	int length = 0;

	bool Feed(uint8_t b)
	{
		if (b == 0xF0)
		{
			in = true;
			n = 0;
			return false;
		}
		if (!in) return false;
		if (b == 0xF7)
		{
			in = false;
			if (n < 3 || buf[0] != kMfr || buf[1] != kProduct) return false;
			cmd = buf[2];
			payload = buf + 3;
			length = n - 3;
			return true;
		}
		if (b & 0x80)
		{
			// Any other status byte aborts the message, except real-time
			// bytes, which may legally appear inside SysEx
			if (b < 0xF8) in = false;
			return false;
		}
		if (n < kMax) buf[n++] = b;
		else in = false;
		return false;
	}
};

inline int Header(uint8_t *out, uint8_t cmd)
{
	out[0] = 0xF0;
	out[1] = kMfr;
	out[2] = kProduct;
	out[3] = cmd;
	return 4;
}

inline int Put14(uint8_t *out, int32_t v)
{
	if (v < 0) v = 0;
	if (v > 16383) v = 16383;
	out[0] = uint8_t(v >> 7);
	out[1] = uint8_t(v & 0x7F);
	return 2;
}

inline int32_t Get14(const uint8_t *in)
{
	return (int32_t(in[0] & 0x7F) << 7) | (in[1] & 0x7F);
}

static constexpr int kVoiceLen = 14;
static constexpr int kStateLen = 4 + 4 + kNumValues + 1;
static constexpr int kStatusLen = 4 + 8 + 4 + 2 * kVoiceLen + 2 + 1 + 6 + 1;

} // namespace sysex

#endif