Merge branch '8-add-tui' - tests not passing

engine/src/channel.c

@@ -0,0 +1,41 @@
+// cppcheck-suppress missingIncludeSystem
+#include "channel.h"
+#include <jack/jack.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <string.h>
+
+void channel_add(jack_client_t *client, int idx) {
+  char in_name[64], out_name[64];
+  snprintf(in_name, sizeof(in_name), "channel%d_input", next_channel_id);
+  snprintf(out_name, sizeof(out_name), "channel%d_output", next_channel_id);
+
+  channels[idx].audio_in = jack_port_register(
+      client, in_name, JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
+  channels[idx].audio_out = jack_port_register(
+      client, out_name, JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0);
+  if (!channels[idx].audio_in || !channels[idx].audio_out) {
+    fprintf(stderr, "Failed to register ports for channel %d\n",
+            next_channel_id);
+    /* Do NOT mark channel active – process loop will skip it */
+    atomic_store(&channels[idx].active, 0);
+    return;
+  }
+
+  atomic_store(&channels[idx].active, 1);
+  atomic_store(&channels[idx].state, STATE_IDLE);
+  channels[idx].prev_state = -1;
+  channels[idx].loop_count = 0;
+  channels[idx].record_pos = 0;
+  channels[idx].playback_pos = 0;
+  channels[idx].save_ring = NULL;
+
+  next_channel_id++;
+  channel_count++;
+}
+
+void channel_remove(jack_client_t *client, int idx) {
+  (void)client;
+  atomic_store(&channels[idx].active, 0);
+  channel_count--;
+}

engine/src/channel.h

@@ -0,0 +1,47 @@
+#ifndef CHANNEL_H
+#define CHANNEL_H
+
+// cppcheck-suppress missingIncludeSystem
+#include <jack/jack.h>
+#include <stdatomic.h>
+
+#define LOOP_BUF_SIZE  (5 * 48000)
+#define MAX_CHANNELS   16
+
+#include "ringbuffer.h"
+
+typedef enum {
+    STATE_IDLE,
+    STATE_RECORD,
+    STATE_LOOPING,
+    STATE_PAUSED
+} looper_state;
+
+struct channel_t {
+    atomic_int    state;
+    atomic_int    prev_state;
+    float         loop_buffer[LOOP_BUF_SIZE];
+    atomic_int    loop_count;
+    atomic_int    record_pos;
+    atomic_int    playback_pos;
+    atomic_int    active;
+    jack_port_t  *audio_in;
+    jack_port_t  *audio_out;
+
+    _Atomic RingBuf *save_ring;
+};
+
+/* Globals declared in looper.c */
+extern struct channel_t channels[MAX_CHANNELS];
+extern atomic_int  channel_count;
+extern atomic_int  channel_capacity;
+extern int         next_channel_id;
+extern atomic_int  cmd_add;
+extern atomic_int  cmd_remove;
+extern atomic_int  cmd_load;
+extern atomic_int  cmd_save;
+
+void channel_add(jack_client_t *client, int idx);
+void channel_remove(jack_client_t *client, int idx);
+
+#endif

engine/src/command.h

@@ -0,0 +1,26 @@
+#ifndef COMMAND_H
+#define COMMAND_H
+
+typedef enum {
+    CMD_CYCLE,          // toggle record/stop for the current scene of a channel
+    CMD_STOP,           // force to idle for all scenes
+    CMD_BIND_CHANNEL,   // bind a channel index (data = channel)
+    CMD_UNBIND,         // reset bind to channel 0
+    CMD_ADD_CHANNEL,    // add a new dynamic channel
+    CMD_REMOVE_CHANNEL, // remove last dynamic channel
+    CMD_ADD_MIDI_CHANNEL, // add a new dynamic MIDI channel
+    CMD_LOAD,           // load WAV file into channel 0
+    CMD_SAVE,           // save loop as WAV file
+    CMD_NEXT_SCENE,
+    CMD_PREV_SCENE,
+    CMD_ADD_SCENE,
+    CMD_REMOVE_SCENE,
+} cmd_type_t;
+
+typedef struct {
+    cmd_type_t type;
+    int        channel;   // which channel; -1 means "current/bound"
+    int        data;      // extra parameter (e.g. bind channel number)
+} command_t;
+
+#endif

engine/src/looper.c

@@ -0,0 +1,508 @@
+// cppcheck-suppress missingIncludeSystem
+#include "looper.h"
+#include "channel.h"
+#include "midi.h"
+#include "wav.h"
+#include "ringbuffer.h"
+#include "pipe.h"
+#include <jack/jack.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <jack/midiport.h>
+#include <math.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "queue.h"
+#include "command.h"
+
+/* Global command queues */
+spsc_queue_t cmd_queue;
+spsc_queue_t cmd_queue_main_midi;
+spsc_queue_t cmd_queue_main_fifo;
+
+#define STATUS_FIFO "/tmp/looper_status"
+
+/* writer status fd */
+static int status_fd = -1;
+
+static void looper_write_status(void) {
+    if (status_fd < 0)
+        return;
+    char buf[256];
+    for (int ch = 0; ch < MAX_CHANNELS; ch++) {
+        if (!atomic_load(&channels[ch].active))
+            continue;
+        int state_val = atomic_load(&channels[ch].state);
+        const char *state_str;
+        switch (state_val) {
+            case STATE_IDLE:    state_str = "IDLE";    break;
+            case STATE_RECORD:  state_str = "RECORD";  break;
+            case STATE_LOOPING: state_str = "LOOPING"; break;
+            case STATE_PAUSED:  state_str = "PAUSED";  break;
+            default:            state_str = "UNKNOWN";
+        }
+        int n = snprintf(buf, sizeof(buf),
+                         "CH=%d SC=%d STATE=%s\n",
+                         ch, 0, state_str);
+        if (n > 0) {
+            int ret = write(status_fd, buf, n);
+            (void)ret;
+        }
+    }
+}
+
+/* Global state (shared across files) */
+struct channel_t channels[MAX_CHANNELS];
+atomic_int channel_count = 0;
+atomic_int channel_capacity = MAX_CHANNELS;
+int next_channel_id = 1;
+atomic_int cmd_add = 0;
+atomic_int cmd_remove = 0;
+atomic_int cmd_load = 0;
+atomic_int cmd_save = 0;
+jack_port_t *midi_control_port = NULL;
+jack_port_t *midi_clock_port = NULL;
+atomic_int control_key_active = 0;
+atomic_int bind_channel = 0;
+
+/* Deferred removal index (1 second grace) */
+static int pending_unregister_idx = -1;
+
+/* writer thread function and sample rate holder */
+static void *writer_thread(void *arg);
+static int global_sample_rate = 0;
+
+/* execute a single command (called from looper_process_commands) */
+static void exec_command(command_t cmd, jack_client_t *client) {
+    int ch = cmd.channel;
+    if (ch < 0) ch = 0;
+
+    switch (cmd.type) {
+    case CMD_CYCLE: {
+      int state = atomic_load(&channels[ch].state);
+      switch (state) {
+      case STATE_IDLE:
+        atomic_store(&channels[ch].state, STATE_RECORD);
+        break;
+      case STATE_RECORD:
+        atomic_store(&channels[ch].state, STATE_LOOPING);
+        break;
+      case STATE_LOOPING:
+        atomic_store(&channels[ch].state, STATE_PAUSED);
+        break;
+      case STATE_PAUSED:
+        atomic_store(&channels[ch].state, STATE_LOOPING);
+        break;
+      }
+      atomic_store(&channels[ch].prev_state, -1);
+      break;
+    }
+    case CMD_STOP:
+      atomic_store(&channels[ch].state, STATE_IDLE);
+      atomic_store(&channels[ch].prev_state, -1);
+      break;
+
+    case CMD_ADD_CHANNEL:
+    case CMD_ADD_MIDI_CHANNEL: {
+      int idx;
+      for (idx = 0; idx < MAX_CHANNELS; idx++)
+        if (!channels[idx].active)
+          break;
+      if (idx < MAX_CHANNELS)
+        channel_add(client, idx);
+      break;
+    }
+
+    case CMD_REMOVE_CHANNEL: {
+      int remove_idx = -1;
+      for (int idx = 1; idx < MAX_CHANNELS; idx++)
+        if (channels[idx].active)
+          remove_idx = idx;
+      if (remove_idx != -1) {
+        channel_remove(client, remove_idx);
+        pending_unregister_idx = remove_idx;
+      }
+      break;
+    }
+
+    case CMD_BIND_CHANNEL:
+      atomic_store(&bind_channel, cmd.data);
+      break;
+
+    case CMD_UNBIND:
+      atomic_store(&bind_channel, 0);
+      break;
+
+    case CMD_LOAD:
+      atomic_store(&cmd_load, 1);
+      break;
+
+    case CMD_SAVE:
+      atomic_store(&cmd_save, 1);
+      break;
+
+    case CMD_ADD_SCENE:
+    case CMD_REMOVE_SCENE:
+    case CMD_NEXT_SCENE:
+    case CMD_PREV_SCENE:
+      break;
+
+    default:
+      break;
+    }
+}
+
+/* ----------------------------------------------------------------
+ * process callback
+ * ---------------------------------------------------------------- */
+int process_callback(jack_nframes_t nframes, void *arg) {
+  (void)arg;
+
+  if (midi_control_port) {
+    void *midi_ctrl_buf = jack_port_get_buffer(midi_control_port, nframes);
+    if (midi_ctrl_buf) {
+      midi_handle_events(midi_ctrl_buf, nframes);
+    }
+  }
+
+  /* process each active channel */
+  for (int c = 0; c < MAX_CHANNELS; c++) {
+    if (!atomic_load(&channels[c].active))
+      continue;
+
+    /* Guard against NULL ports (e.g. if port registration failed) */
+    if (!channels[c].audio_in || !channels[c].audio_out) {
+      fprintf(stderr, "WARN: channel %d has NULL audio port(s), skipping\n", c);
+      continue;
+    }
+
+    const jack_default_audio_sample_t *in =
+        (const jack_default_audio_sample_t *)jack_port_get_buffer(
+            channels[c].audio_in, nframes);
+    jack_default_audio_sample_t *out =
+        (jack_default_audio_sample_t *)jack_port_get_buffer(
+            channels[c].audio_out, nframes);
+    if (!out)
+      continue;
+
+    int state = atomic_load(&channels[c].state);
+
+    if (state != atomic_load(&channels[c].prev_state)) {
+      switch (state) {
+      case STATE_RECORD:
+        atomic_store(&channels[c].record_pos, 0);
+        atomic_store(&channels[c].loop_count, 0);
+        break;
+      case STATE_LOOPING:
+        if (atomic_load(&channels[c].prev_state) == STATE_RECORD &&
+            atomic_load(&channels[c].record_pos) > 0)
+          atomic_store(&channels[c].loop_count,
+                       atomic_load(&channels[c].record_pos));
+        atomic_store(&channels[c].playback_pos, 0);
+        break;
+      default:
+        break;
+      }
+    }
+
+    jack_nframes_t i;
+    switch (state) {
+    case STATE_RECORD:
+      if (in) {
+        float *f_out = (float *)out;
+        const float *f_in = (const float *)in;
+        for (i = 0; i < nframes; i++) {
+          int rp = atomic_fetch_add(&channels[c].record_pos, 1);
+          if (rp < LOOP_BUF_SIZE)
+            channels[c].loop_buffer[rp] = f_in[i];
+          f_out[i] = f_in[i];
+        }
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
+
+    case STATE_LOOPING:
+      int lc = atomic_load(&channels[c].loop_count);
+      if (lc > 0) {
+        float *outf = (float *)out;
+        for (i = 0; i < nframes; i++) {
+          int pp = atomic_load(&channels[c].playback_pos);
+          outf[i] = channels[c].loop_buffer[pp];
+          atomic_store(&channels[c].playback_pos, (pp + 1) % lc);
+        }
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
+
+    case STATE_PAUSED:
+      memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      break;
+
+    default: /* IDLE */
+      if (in) {
+        memcpy(out, in, sizeof(jack_default_audio_sample_t) * nframes);
+      } else {
+        memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
+      }
+      break;
+    }
+
+    // push loop output into save ring if saving (atomic load)
+    RingBuf *r = (RingBuf *)atomic_load_explicit(&channels[c].save_ring,
+                                                 memory_order_acquire);
+    if (r != NULL) {
+      if (state == STATE_LOOPING && atomic_load(&channels[c].loop_count) > 0) {
+        const float *outf = (const float *)out;
+        ring_write(r, outf, nframes);
+      }
+    }
+
+    atomic_store(&channels[c].prev_state, state);
+  }
+
+  /* MIDI clock events – affect channel 0 only */
+  if (midi_clock_port) {
+    void *midi_clock_buf = jack_port_get_buffer(midi_clock_port, nframes);
+    if (midi_clock_buf) {
+      jack_nframes_t n_clock_events = jack_midi_get_event_count(midi_clock_buf);
+      jack_midi_event_t cev;
+      for (jack_nframes_t j = 0; j < n_clock_events; j++) {
+        if (jack_midi_event_get(&cev, midi_clock_buf, j) != 0)
+          continue;
+        if (cev.size >= 1) {
+          unsigned char msg = cev.buffer[0];
+          switch (msg) {
+          case 0xFA: {
+            int s = atomic_load(&channels[0].state);
+            if (s == STATE_IDLE)
+              atomic_store(&channels[0].state, STATE_RECORD);
+            break;
+          }
+          case 0xFC:
+            atomic_store(&channels[0].state, STATE_IDLE);
+            break;
+          case 0xFB: {
+            int s = atomic_load(&channels[0].state);
+            if (s == STATE_PAUSED)
+              atomic_store(&channels[0].state, STATE_LOOPING);
+            break;
+          }
+          default:
+            break;
+          }
+        }
+      }
+    }
+  }
+
+  return 0;
+}
+
+/* ----------------------------------------------------------------
+ * shutdown callback
+ * ---------------------------------------------------------------- */
+void jack_shutdown_cb(void *arg) {
+  (void)arg;
+  fprintf(stderr, "JACK shutdown\n");
+  exit(0);
+}
+
+
+/* ----------------------------------------------------------------
+ * looper initialisation
+ * ---------------------------------------------------------------- */
+int looper_init(jack_client_t *client) {
+  /* store sample rate for writer thread */
+  global_sample_rate = jack_get_sample_rate(client);
+
+  /* create status FIFO (ignore if already exists) */
+  mkfifo(STATUS_FIFO, 0666);
+
+  /* open the status FIFO for reading+writing so writes work even without reader */
+  status_fd = open(STATUS_FIFO, O_RDWR);
+  if (status_fd < 0) {
+      perror("open status FIFO");
+  }
+
+  queue_init(&cmd_queue);
+  queue_init(&cmd_queue_main_midi);
+  queue_init(&cmd_queue_main_fifo);
+
+  /* start the FIFO reader thread */
+  pipe_start_reader();
+
+
+  /* channel 0 */
+  channels[0].active = 1;
+  atomic_store(&channels[0].state, STATE_IDLE);
+  atomic_store(&channels[0].prev_state, -1);
+  channels[0].loop_count = 0;
+  atomic_store(&channels[0].record_pos, 0);
+  atomic_store(&channels[0].playback_pos, 0);
+  atomic_store_explicit(&channels[0].save_ring, NULL, memory_order_release);
+
+  channels[0].audio_in = jack_port_register(
+      client, "input", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
+  channels[0].audio_out = jack_port_register(
+      client, "output", JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0);
+  if (!channels[0].audio_in || !channels[0].audio_out) {
+    fprintf(stderr, "Could not create audio ports for channel 0\n");
+    return -1;
+  }
+  channel_count = 1;
+
+  midi_control_port = jack_port_register(
+      client, "control", JACK_DEFAULT_MIDI_TYPE, JackPortIsInput, 0);
+  midi_clock_port = jack_port_register(client, "clock", JACK_DEFAULT_MIDI_TYPE,
+                                       JackPortIsInput, 0);
+  if (!midi_control_port || !midi_clock_port) {
+    fprintf(stderr, "Could not create MIDI ports\n");
+    return -1;
+  }
+
+  return 0;
+}
+
+/* ----------------------------------------------------------------
+ * writer thread – consumes the save ring and writes WAV file
+ * ---------------------------------------------------------------- */
+static void *writer_thread(void *arg) {
+  struct channel_t *ch = (struct channel_t *)arg;
+  RingBuf *ring = (RingBuf *)ch->save_ring;
+  if (!ring)
+    return NULL;
+
+  static const char *path = "save.wav";
+  unsigned sr = (unsigned)global_sample_rate;
+  if (sr == 0)
+    sr = 48000;
+
+  int lc = atomic_load(&ch->loop_count);
+  float *outbuf = malloc((size_t)lc * sizeof(float));
+  if (!outbuf) {
+    ring_destroy(ring);
+    free(ring);
+    ch->save_ring = NULL;
+    return NULL;
+  }
+  size_t collected = 0;
+  size_t want = (size_t)lc;
+  while (collected < want) {
+    size_t got = ring_read(ring, outbuf + collected, want - collected);
+    collected += got;
+    if (got == 0) {
+      struct timespec req = {.tv_sec = 0, .tv_nsec = 10000000};
+      nanosleep(&req, NULL);
+    }
+  }
+  wav_write(path, outbuf, (unsigned)lc, sr);
+  free(outbuf);
+
+  ring_destroy(ring);
+  free(ring);
+  atomic_store_explicit(&ch->save_ring, NULL, memory_order_release);
+  return NULL;
+}
+
+/* ----------------------------------------------------------------
+ * main‑loop command processing
+ * ---------------------------------------------------------------- */
+void looper_process_commands(jack_client_t *client) {
+  /* process commands from the three queues FIRST */
+  command_t cmd;
+  while (queue_pop(&cmd_queue, &cmd))
+    exec_command(cmd, client);
+  while (queue_pop(&cmd_queue_main_midi, &cmd))
+    exec_command(cmd, client);
+  while (queue_pop(&cmd_queue_main_fifo, &cmd))
+    exec_command(cmd, client);
+
+  /* Unregister any ports that were marked for deferred removal.
+     By now the real‑time thread has had at least one full cycle
+     to see the `active = 0` store. */
+  if (pending_unregister_idx != -1) {
+    int idx = pending_unregister_idx;
+    if (channels[idx].audio_in)
+      jack_port_unregister(client, channels[idx].audio_in);
+    if (channels[idx].audio_out)
+      jack_port_unregister(client, channels[idx].audio_out);
+    pending_unregister_idx = -1;
+  }
+
+  /* ---------- add channel ---------- */
+  if (atomic_exchange(&cmd_add, 0)) {
+    int idx;
+    for (idx = 0; idx < MAX_CHANNELS; idx++)
+      if (!channels[idx].active)
+        break;
+    if (idx < MAX_CHANNELS) {
+      channel_add(client, idx);
+    }
+  }
+
+  /* ---------- remove channel ---------- */
+  if (atomic_exchange(&cmd_remove, 0)) {
+    int remove_idx = -1;
+    for (int idx = 1; idx < MAX_CHANNELS; idx++)
+      if (channels[idx].active)
+        remove_idx = idx;
+    if (remove_idx != -1) {
+      /* Mark inactive now; ports will be unregistered next round */
+      channel_remove(client, remove_idx);
+      pending_unregister_idx = remove_idx;
+    }
+  }
+
+  /* ---------- load command ---------- */
+  if (atomic_exchange(&cmd_load, 0)) {
+    float *buf = NULL;
+    unsigned frames = 0;
+    printf("LOAD: wav_read called\n");
+    if (wav_read("loop.wav", &buf, &frames) == 0 && frames > 0) {
+      printf("LOAD: success, frames=%u\n", frames);
+      if (frames > LOOP_BUF_SIZE)
+        frames = LOOP_BUF_SIZE;
+      memcpy(channels[0].loop_buffer, buf, frames * sizeof(float));
+      atomic_store(&channels[0].loop_count, (int)frames);
+      atomic_store(&channels[0].record_pos, 0);
+      atomic_store(&channels[0].playback_pos, 0);
+      atomic_store(&channels[0].state, STATE_LOOPING);
+      atomic_store(&channels[0].prev_state, -1);
+      free(buf);
+    } else {
+      fprintf(stderr, "Failed to load loop.wav\n");
+      printf("LOAD: FAILED\n");
+    }
+  }
+
+  /* ---------- save command (writer thread) ---------- */
+  if (atomic_exchange(&cmd_save, 0)) {
+    int lc = atomic_load(&channels[0].loop_count);
+    if (atomic_load(&channels[0].state) == STATE_LOOPING && lc > 0 &&
+        channels[0].save_ring == NULL) {
+      RingBuf *ring = (RingBuf *)malloc(sizeof(RingBuf));
+      if (ring) {
+        size_t sz = (size_t)lc * 2;
+        if (ring_init(ring, sz) == 0) {
+          atomic_store_explicit(&channels[0].save_ring, (_Atomic RingBuf *)ring,
+                                memory_order_release);
+          pthread_t th;
+          pthread_create(&th, NULL, writer_thread, &channels[0]);
+          pthread_detach(th);
+        } else {
+          free(ring);
+        }
+      }
+    }
+  }
+
+  /* write current state to status FIFO */
+  looper_write_status();
+}

engine/src/looper.h

@@ -0,0 +1,19 @@
+#ifndef LOOPER_H
+#define LOOPER_H
+
+// cppcheck-suppress missingIncludeSystem
+#include <jack/jack.h>
+
+/* Initialisation – must be called after setting process callback */
+int looper_init(jack_client_t *client);
+
+/* Process callback – to be called by JACK */
+int process_callback(jack_nframes_t nframes, void *arg);
+
+/* Shutdown callback */
+void jack_shutdown_cb(void *arg);
+
+/* Main‑loop command processing (add/remove channels) */
+void looper_process_commands(jack_client_t *client);
+
+#endif

engine/src/main.c

@@ -0,0 +1,51 @@
+// cppcheck-suppress missingIncludeSystem
+#include "looper.h"
+#include <jack/jack.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+
+int main(int argc, char *argv[]) {
+  (void)argc;
+  (void)argv;
+  const char *client_name = "looper";
+  jack_options_t options = JackNullOption;
+  jack_status_t status;
+
+  jack_client_t *client = jack_client_open(client_name, options, &status);
+  if (client == NULL) {
+    fprintf(stderr, "jack_client_open() failed, status = 0x%2.0x\n", status);
+    if (status & JackServerFailed)
+      fprintf(stderr, "Unable to connect to JACK server\n");
+    return 1;
+  }
+
+  if (status & JackNameNotUnique)
+    client_name = jack_get_client_name(client);
+
+  jack_set_process_callback(client, process_callback, NULL);
+  jack_on_shutdown(client, jack_shutdown_cb, NULL);
+
+  if (looper_init(client) != 0) {
+    fprintf(stderr, "looper initialisation failed\n");
+    jack_client_close(client);
+    return 1;
+  }
+
+  if (jack_activate(client)) {
+    fprintf(stderr, "Cannot activate client\n");
+    jack_client_close(client);
+    return 1;
+  }
+
+  fprintf(stderr, "looper running (client name '%s')\n", client_name);
+
+  while (1) {
+    looper_process_commands(client);
+    { struct timespec ts = { .tv_sec = 0, .tv_nsec = 50000000 }; nanosleep(&ts, NULL); } /* check commands every 50 ms */
+  }
+
+  jack_client_close(client);
+  return 0;
+}

engine/src/midi.c

@@ -0,0 +1,119 @@
+// cppcheck-suppress missingIncludeSystem
+#include "midi.h"
+#include "channel.h"
+#include <jack/jack.h>
+#include <jack/midiport.h>
+#include <stdatomic.h>
+
+extern atomic_int control_key_active;
+extern atomic_int cmd_add;
+extern atomic_int cmd_remove;
+extern atomic_int cmd_load;
+extern atomic_int cmd_save;
+extern atomic_int bind_channel;
+
+void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
+  (void)nframes;
+  jack_nframes_t nevents = jack_midi_get_event_count(port_buffer);
+  jack_midi_event_t ev;
+
+  for (jack_nframes_t i = 0; i < nevents; i++) {
+    if (jack_midi_event_get(&ev, port_buffer, i) != 0)
+      continue;
+    if (ev.size < 3)
+      continue;
+
+    unsigned char status = ev.buffer[0];
+    unsigned char note = ev.buffer[1];
+    unsigned char vel = ev.buffer[2];
+
+    /* note‑on */
+    if ((status & 0xf0) == 0x90 && vel > 0) {
+      if (note == 64) {
+        atomic_store(&control_key_active, 1);
+      } else {
+        int ck = atomic_load(&control_key_active);
+        if (ck) {
+          atomic_store(&control_key_active, 0);
+          if (note < 16) {
+            atomic_store(&bind_channel, note);
+          } else {
+            switch (note) {
+            case 60:
+              atomic_store(&cmd_add, 1);
+              break;
+            case 61:
+              atomic_store(&cmd_remove, 1);
+              break;
+            case 62: /* trigger looper – channel via bind_channel */
+            {
+              int bch = atomic_load(&bind_channel);
+              if (bch >= 0 && bch < MAX_CHANNELS) {
+                int cur = atomic_load(&channels[bch].state);
+                switch (cur) {
+                case STATE_IDLE:
+                  atomic_store(&channels[bch].state, STATE_RECORD);
+                  break;
+                case STATE_RECORD:
+                  atomic_store(&channels[bch].state, STATE_LOOPING);
+                  break;
+                case STATE_LOOPING:
+                  atomic_store(&channels[bch].state, STATE_PAUSED);
+                  break;
+                case STATE_PAUSED:
+                  atomic_store(&channels[bch].state, STATE_LOOPING);
+                  break;
+                }
+              }
+            } break;
+            case 63: /* unbind – reset bind to channel 0 */
+              atomic_store(&bind_channel, 0);
+              break;
+            case 70: /* load WAV into channel 0 */
+              atomic_store(&cmd_load, 1);
+              break;
+            case 71: /* save WAV of channel 0 */
+              atomic_store(&cmd_save, 1);
+              break;
+            default:
+              break;
+            }
+          }
+        } else {
+          /* direct mapping */
+          switch (note) {
+          case 1: /* toggle channel 0 */
+          {
+            int cur0 = atomic_load(&channels[0].state);
+            switch (cur0) {
+            case STATE_IDLE:
+              atomic_store(&channels[0].state, STATE_RECORD);
+              break;
+            case STATE_RECORD:
+              atomic_store(&channels[0].state, STATE_LOOPING);
+              break;
+            case STATE_LOOPING:
+              atomic_store(&channels[0].state, STATE_PAUSED);
+              break;
+            case STATE_PAUSED:
+              atomic_store(&channels[0].state, STATE_LOOPING);
+              break;
+            }
+          } break;
+          case 60:
+            atomic_store(&cmd_add, 1);
+            break;
+          case 61:
+            atomic_store(&cmd_remove, 1);
+            break;
+          default:
+            break;
+          }
+        }
+      }
+    } else if ((status & 0xf0) == 0x80 ||
+               ((status & 0xf0) == 0x90 && vel == 0)) {
+      atomic_store(&control_key_active, 0);
+    }
+  }
+}

engine/src/midi.h

@@ -0,0 +1,9 @@
+#ifndef MIDI_H
+#define MIDI_H
+
+// cppcheck-suppress missingIncludeSystem
+#include <jack/types.h>
+
+void midi_handle_events(void *port_buffer, jack_nframes_t nframes);
+
+#endif

engine/src/pipe.c

@@ -0,0 +1,105 @@
+#include "pipe.h"
+#include "command.h"
+#include "queue.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#define FIFO_PATH "/tmp/looper_cmd"
+#define LINE_MAX 256
+
+/* forward‑declare the global queues (defined in looper.c) */
+extern spsc_queue_t cmd_queue;
+extern spsc_queue_t cmd_queue_main_fifo;
+
+static void *pipe_thread_func(void *arg) {
+  (void)arg;
+  char line[LINE_MAX];
+
+  while (1) {
+    FILE *fifo = fopen(FIFO_PATH, "r");
+    if (!fifo) {
+      perror("fopen fifo");
+      return NULL;
+    }
+
+    while (fgets(line, sizeof(line), fifo)) {
+      /* strip newline */
+      size_t len = strlen(line);
+      if (len > 0 && line[len - 1] == '\n')
+        line[len - 1] = '\0';
+
+      if (strcmp(line, "add") == 0) {
+        command_t cmd = {.type = CMD_ADD_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "add_midi") == 0) {
+        command_t cmd = {.type = CMD_ADD_MIDI_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "remove") == 0) {
+        command_t cmd = {.type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strncmp(line, "record ", 7) == 0) {
+        int ch = atoi(line + 7);
+        command_t cmd = {.type = CMD_CYCLE, .channel = ch, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "stop") == 0) {
+        command_t cmd = {.type = CMD_STOP, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strncmp(line, "bind ", 5) == 0) {
+        int ch = atoi(line + 5);
+        command_t cmd = {.type = CMD_BIND_CHANNEL, .channel = -1, .data = ch};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "unbind") == 0) {
+        command_t cmd = {.type = CMD_UNBIND, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "scene_add") == 0) {
+        command_t cmd = {.type = CMD_ADD_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "scene_remove") == 0) {
+        command_t cmd = {.type = CMD_REMOVE_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "scene_next") == 0) {
+        command_t cmd = {.type = CMD_NEXT_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "scene_prev") == 0) {
+        command_t cmd = {.type = CMD_PREV_SCENE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "load") == 0) {
+        command_t cmd = {.type = CMD_LOAD, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      } else if (strcmp(line, "save") == 0) {
+        command_t cmd = {.type = CMD_SAVE, .channel = -1, .data = 0};
+        queue_push(&cmd_queue, cmd);
+      }
+      /* ignore unknown lines */
+    }
+    /* EOF – all writers closed, reopen for next connection */
+    fclose(fifo);
+    {
+      struct timespec ts = {.tv_sec = 0, .tv_nsec = 50000000};
+      nanosleep(&ts, NULL);
+    } /* small pause before retrying */
+  }
+  return NULL; /* unreachable */
+}
+
+int pipe_start_reader(void) {
+  /* create FIFO if it doesn't exist */
+  if (mkfifo(FIFO_PATH, 0666) != 0 && errno != EEXIST) {
+    perror("mkfifo");
+    return -1;
+  }
+  pthread_t tid;
+  if (pthread_create(&tid, NULL, pipe_thread_func, NULL) != 0) {
+    perror("pthread_create");
+    return -1;
+  }
+  pthread_detach(tid); /* we don't need to join */
+  return 0;
+}

engine/src/pipe.h

@@ -0,0 +1,9 @@
+#ifndef PIPE_H
+#define PIPE_H
+
+/* Start the FIFO reader thread.
+ * Creates /tmp/looper_cmd (or aborts on error).
+ * Returns 0 on success, -1 on failure. */
+int pipe_start_reader(void);
+
+#endif

engine/src/queue.c

@@ -0,0 +1,31 @@
+#include "queue.h"
+#include <stdatomic.h>
+#include <stdbool.h>
+
+void queue_init(spsc_queue_t *q) {
+  /* nothing to allocate, just ensure head/tail start at 0 */
+  q->head = 0;
+  q->tail = 0;
+}
+
+bool queue_push(spsc_queue_t *q, command_t cmd) {
+  int h = atomic_load_explicit(&q->head, memory_order_relaxed);
+  int t = atomic_load_explicit(&q->tail, memory_order_acquire);
+  int next = (h + 1) % QUEUE_CAPACITY;
+  if (next == t)
+    return false; /* queue full */
+  q->buffer[h] = cmd;
+  atomic_store_explicit(&q->head, next, memory_order_release);
+  return true;
+}
+
+bool queue_pop(spsc_queue_t *q, command_t *cmd) {
+  int t = atomic_load_explicit(&q->tail, memory_order_relaxed);
+  int h = atomic_load_explicit(&q->head, memory_order_acquire);
+  if (t == h)
+    return false; /* queue empty */
+  *cmd = q->buffer[t];
+  atomic_store_explicit(&q->tail, (t + 1) % QUEUE_CAPACITY,
+                        memory_order_release);
+  return true;
+}

engine/src/queue.h

@@ -0,0 +1,31 @@
+#ifndef QUEUE_H
+#define QUEUE_H
+
+#include "command.h"
+#include <stdbool.h>
+
+/* Fixed‑size lock‑free SPSC queue (single producer, single consumer).
+ * The queue is safe for one thread writing (producer) and one thread
+ * reading (consumer).  No locks, no dynamic memory allocation.
+ * Must be initialised before first use.  All operations are RT‑safe. */
+
+#define QUEUE_CAPACITY 256
+
+typedef struct {
+    command_t  buffer[QUEUE_CAPACITY];
+    /* head: index where next element will be written (producer only)
+     * tail: index of next element to read (consumer only) */
+    int head;
+    int tail;
+} spsc_queue_t;
+
+/* Initialise queue (must be called once before any push/pop). */
+void queue_init(spsc_queue_t *q);
+
+/* Push a command.  Returns true on success, false if queue full. */
+bool queue_push(spsc_queue_t *q, command_t cmd);
+
+/* Pop a command.  Returns true if a command was retrieved, false if empty. */
+bool queue_pop(spsc_queue_t *q, command_t *cmd);
+
+#endif

engine/src/ringbuffer.c

@@ -0,0 +1,76 @@
+#include "ringbuffer.h"
+#include <stdlib.h>
+
+static inline size_t load_head(const RingBuf *r) {
+  return atomic_load_explicit(&r->head, memory_order_relaxed);
+}
+static inline size_t load_tail(const RingBuf *r) {
+  return atomic_load_explicit(&r->tail, memory_order_relaxed);
+}
+static inline void store_head(RingBuf *r, size_t v) {
+  atomic_store_explicit(&r->head, v, memory_order_relaxed);
+}
+static inline void store_tail(RingBuf *r, size_t v) {
+  atomic_store_explicit(&r->tail, v, memory_order_relaxed);
+}
+
+int ring_init(RingBuf *r, size_t capacity) {
+  r->buf = (float *)malloc(capacity * sizeof(float));
+  if (!r->buf)
+    return -1;
+  r->capacity = capacity;
+  store_head(r, 0);
+  store_tail(r, 0);
+  return 0;
+}
+
+void ring_destroy(RingBuf *r) {
+  free(r->buf);
+  r->buf = NULL;
+  r->capacity = 0;
+}
+
+static size_t ring_readable(const RingBuf *r) {
+  size_t h = load_head(r);
+  size_t t = load_tail(r);
+  if (h >= t)
+    return h - t;
+  else
+    return r->capacity - (t - h);
+}
+
+static size_t ring_writeable(const RingBuf *r) {
+  return r->capacity - 1 - ring_readable(r);
+}
+
+size_t ring_write(RingBuf *r, const float *data, size_t count) {
+  size_t avail = ring_writeable(r);
+  if (count > avail)
+    count = avail;
+  if (count == 0)
+    return 0;
+  size_t head = load_head(r);
+  size_t cap = r->capacity;
+  for (size_t i = 0; i < count; ++i) {
+    r->buf[head] = data[i];
+    head = (head + 1) % cap;
+  }
+  store_head(r, head);
+  return count;
+}
+
+size_t ring_read(RingBuf *r, float *data, size_t count) {
+  size_t avail = ring_readable(r);
+  if (count > avail)
+    count = avail;
+  if (count == 0)
+    return 0;
+  size_t tail = load_tail(r);
+  size_t cap = r->capacity;
+  for (size_t i = 0; i < count; ++i) {
+    data[i] = r->buf[tail];
+    tail = (tail + 1) % cap;
+  }
+  store_tail(r, tail);
+  return count;
+}

engine/src/ringbuffer.h

@@ -0,0 +1,19 @@
+#ifndef RINGBUFFER_H
+#define RINGBUFFER_H
+
+#include <stddef.h>
+#include <stdatomic.h>
+
+typedef struct {
+    atomic_size_t head;
+    atomic_size_t tail;
+    size_t        capacity;
+    float        *buf;
+} RingBuf;
+
+int  ring_init(RingBuf *r, size_t capacity);
+void ring_destroy(RingBuf *r);
+size_t ring_write(RingBuf *r, const float *data, size_t count);
+size_t ring_read(RingBuf *r, float *data, size_t count);
+
+#endif

engine/src/wav.c

@@ -0,0 +1,41 @@
+#include "wav.h"
+#include "channel.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <sndfile.h>
+
+int wav_read(const char *path, float **buffer, unsigned *frames) {
+    SF_INFO info;
+    info.format = 0;
+    SNDFILE *sf = sf_open(path, SFM_READ, &info);
+    if (!sf) return -1;
+
+    /* We need mono 16-bit PCM; refuse anything else */
+    if (info.channels != 1 || info.samplerate <= 0) {
+        sf_close(sf);
+        return -1;
+    }
+
+    unsigned total = (info.frames > (sf_count_t)LOOP_BUF_SIZE) ? LOOP_BUF_SIZE : (unsigned)info.frames;
+    float *buf = (float*)malloc(total * sizeof(float));
+    if (!buf) { sf_close(sf); return -1; }
+
+    sf_count_t nread = sf_readf_float(sf, buf, total);
+    sf_close(sf);
+    *buffer = buf;
+    *frames = (unsigned)nread;
+    return 0;
+}
+
+int wav_write(const char *path, const float *data, unsigned frames, unsigned sample_rate) {
+    SF_INFO info;
+    info.samplerate = sample_rate;
+    info.channels = 1;
+    info.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16;
+    SNDFILE *sf = sf_open(path, SFM_WRITE, &info);
+    if (!sf) return -1;
+
+    sf_writef_float(sf, data, frames);
+    sf_close(sf);
+    return 0;
+}

engine/src/wav.h

@@ -0,0 +1,9 @@
+#ifndef WAV_H
+#define WAV_H
+
+#include <stddef.h>
+
+int wav_read(const char *path, float **buffer, unsigned *frames);
+int wav_write(const char *path, const float *data, unsigned frames, unsigned sample_rate);
+
+#endif