midi-sequencer/c-backend/src/main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>

#include "pattern_store.h"
#include "sequencer.h"
#include "socket_server.h"
#include "../generated/protocol.h"

/* ── Application context ──────────────────────────────────────────── */

typedef struct {
	Pattern_Store  ps;
	Sequencer      seq;
	Socket_Server  srv;
} App;

static App g_app;

/* ── Send callback for sequencer ─────────────────────────────────── */

static void seq_send(void *ctx, const uint8_t *buf, int len) {
	App *app = (App *)ctx;
	socket_server_send(&app->srv, buf, len);
}

/* ── Frame handler ────────────────────────────────────────────────── */

static void send_ack(App *app, uint8_t acked_type) {
	uint8_t buf[16];
	Msg_Ack ack = { .acked_type = acked_type };
	int len = proto_encode_ack(buf, &ack);
	socket_server_send(&app->srv, buf, len);
}

static void send_error(App *app, uint8_t code, uint8_t context_type) {
	uint8_t buf[16];
	Msg_Error err = { .code = code, .context_type = context_type };
	int len = proto_encode_error(buf, &err);
	socket_server_send(&app->srv, buf, len);
}

static void on_frame(uint8_t rt, const uint8_t *payload, uint16_t payload_len, void *ctx) {
	App *app = (App *)ctx;

	switch (rt) {
	case RT_HELLO: {
		Msg_Hello msg;
		if (proto_decode_hello(payload, payload_len, &msg) < 0) goto bad_payload;
		fprintf(stderr, "main: HELLO from client, version=%u\n", msg.version);
		/* Reply with our HELLO */
		uint8_t buf[16];
		Msg_Hello reply = { .version = PROTOCOL_VERSION };
		int len = proto_encode_hello(buf, &reply);
		socket_server_send(&app->srv, buf, len);
		return;
	}
	case RT_DEFINE_PATTERN: {
		Msg_Define_Pattern msg;
		if (proto_decode_define_pattern(payload, payload_len, &msg) < 0) goto bad_payload;
		pattern_store_define(&app->ps, msg.pattern_id, msg.steps, msg.channel);
		break;
	}
	case RT_CLEAR_PATTERN: {
		Msg_Clear_Pattern msg;
		if (proto_decode_clear_pattern(payload, payload_len, &msg) < 0) goto bad_payload;
		pattern_store_clear(&app->ps, msg.pattern_id);
		break;
	}
	case RT_ADD_NOTE: {
		Msg_Add_Note msg;
		if (proto_decode_add_note(payload, payload_len, &msg) < 0) goto bad_payload;
		if (pattern_store_add_note(&app->ps, msg.pattern_id, msg.step,
		                           msg.note, msg.velocity, msg.duration_steps) < 0) {
			send_error(app, 0x01, rt);
			return;
		}
		break;
	}
	case RT_ADD_SUB_PATTERN: {
		Msg_Add_Sub_Pattern msg;
		if (proto_decode_add_sub_pattern(payload, payload_len, &msg) < 0) goto bad_payload;
		if (pattern_store_add_sub_ref(&app->ps, msg.pattern_id, msg.step,
		                              msg.sub_pattern_id) < 0) {
			send_error(app, 0x02, rt);
			return;
		}
		break;
	}
	case RT_PLAY: {
		Msg_Play msg;
		if (proto_decode_play(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_stop(&app->seq);
		sequencer_add_track(&app->seq, msg.pattern_id);
		sequencer_play(&app->seq);
		break;
	}
	case RT_STOP: {
		sequencer_stop(&app->seq);
		break;
	}
	case RT_SET_TEMPO: {
		Msg_Set_Tempo msg;
		if (proto_decode_set_tempo(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_set_tempo(&app->seq, msg.bpm_x10);
		break;
	}
	case RT_PREVIEW_NOTE: {
		Msg_Preview_Note msg;
		if (proto_decode_preview_note(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_preview_note(&app->seq, msg.channel, msg.note, msg.velocity, msg.duration_ms);
		break;
	}
	case RT_ADD_TRACK: {
		Msg_Add_Track msg;
		if (proto_decode_add_track(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_add_track(&app->seq, msg.pattern_id);
		break;
	}
	case RT_REMOVE_TRACK: {
		Msg_Remove_Track msg;
		if (proto_decode_remove_track(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_remove_track(&app->seq, msg.pattern_id);
		break;
	}
	case RT_PLAY_TRACKS: {
		sequencer_play(&app->seq);
		break;
	}
	case RT_SET_TRACK_MUTE: {
		Msg_Set_Track_Mute msg;
		if (proto_decode_set_track_mute(payload, payload_len, &msg) < 0) goto bad_payload;
		sequencer_set_track_mute(&app->seq, msg.pattern_id, msg.muted);
		break;
	}
	default:
		fprintf(stderr, "main: unknown record type 0x%02x\n", rt);
		return;
	}

	send_ack(app, rt);
	return;

bad_payload:
	fprintf(stderr, "main: bad payload for record type 0x%02x\n", rt);
	send_error(app, 0xFF, rt);
}

/* ── Connect / disconnect callbacks ──────────────────────────────── */

static void on_connect(int fd, void *ctx) {
	(void)fd;
	(void)ctx;
	fprintf(stderr, "main: node client connected\n");
}

static void on_disconnect(void *ctx) {
	App *app = (App *)ctx;
	sequencer_stop(&app->seq);
	fprintf(stderr, "main: node client disconnected, playback stopped\n");
}

/* ── Signal handler ───────────────────────────────────────────────── */

static volatile int g_running = 1;
static void on_signal(int sig) { (void)sig; g_running = 0; }

/* ── Entry point ──────────────────────────────────────────────────── */

int main(int argc, char *argv[]) {
	const char *socket_path = argc > 1 ? argv[1] : "/tmp/midi-sequencer.sock";
	const char *alsa_name   = argc > 2 ? argv[2] : "midi-sequencer";

	fprintf(stderr, "midi-sequencer starting\n");
	fprintf(stderr, "  socket : %s\n", socket_path);
	fprintf(stderr, "  ALSA   : %s\n", alsa_name);

	pattern_store_init(&g_app.ps);

	if (sequencer_init(&g_app.seq, &g_app.ps, alsa_name, seq_send, &g_app) < 0) {
		fprintf(stderr, "main: sequencer init failed\n");
		return 1;
	}

	if (socket_server_start(&g_app.srv, socket_path,
	                        on_frame, on_connect, on_disconnect, &g_app) < 0) {
		fprintf(stderr, "main: socket server failed to start\n");
		return 1;
	}

	signal(SIGINT,  on_signal);
	signal(SIGTERM, on_signal);

	fprintf(stderr, "midi-sequencer ready, waiting for node client\n");
	while (g_running) {
		sleep(1);
	}

	fprintf(stderr, "midi-sequencer shutting down\n");
	socket_server_stop(&g_app.srv);
	sequencer_destroy(&g_app.seq);
	pattern_store_destroy(&g_app.ps);
	return 0;
}