/**
 * fc_pipe.c — Framecache slot → stdout pipe adapter.
 *
 * Opens a framecache slot as a consumer and writes raw video frames to
 * stdout in a continuous stream. capture-manager.js spawns this process
 * and feeds its stdout to ffmpeg as a rawvideo pipe input — identical to
 * the way DeckLink bridges currently pipe raw frames.
 *
 * Each consumer instance has its own independent read cursor, so multiple
 * fc_pipe processes reading from the same slot never interfere with each
 * other. This is how growing + proxy + HLS all read the same SDI signal
 * simultaneously.
 *
 * Usage:
 *   fc_pipe <slot_id> [wait_ms]
 *
 * Writes raw UYVY422 frame data to stdout. Terminates on:
 *   - SIGTERM / SIGINT (clean stop from capture-manager)
 *   - stdout EPIPE (ffmpeg exited)
 *   - Slot disappears (bridge stopped)
 *
 * Exit codes:
 *   0  clean stop (SIGTERM)
 *   1  slot not found within wait_ms
 *   2  stdout write error (EPIPE)
 */

#include "../src/slot.h"
#include "fc_client.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <fcntl.h>

static volatile int g_stop = 0;
static void on_signal(int s) { (void)s; g_stop = 1; }

/* Write all bytes to fd. Returns 0 on success, -1 on EPIPE/error. */
static int write_all_fd(int fd, const void *buf, size_t len) {
    const uint8_t *p = (const uint8_t *)buf;
    size_t off = 0;
    while (off < len) {
        ssize_t n = write(fd, p + off, len - off);
        if (n > 0) { off += (size_t)n; continue; }
        if (n < 0 && errno == EINTR) continue;
        return -1; /* EPIPE or other fatal error */
    }
    return 0;
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <slot_id> [wait_ms]\n", argv[0]);
        return 1;
    }
    const char *slot_id = argv[1];
    uint64_t wait_ms = argc >= 3 ? (uint64_t)atoll(argv[2]) : 30000;

    signal(SIGTERM, on_signal);
    signal(SIGINT,  on_signal);
    signal(SIGPIPE, SIG_IGN);   /* detect EPIPE via write() return value */

    /* Set stdout to binary mode — no newline translation */
    fcntl(STDOUT_FILENO, F_SETFL,
          fcntl(STDOUT_FILENO, F_GETFL, 0) & ~O_NONBLOCK);

    fprintf(stderr, "[fc_pipe] opening slot '%s' (wait %llums)\n",
            slot_id, (unsigned long long)wait_ms);

    fc_consumer_t *c = fc_consumer_open(slot_id, wait_ms);
    if (!c) {
        fprintf(stderr, "[fc_pipe] slot '%s' not found within %llums\n",
                slot_id, (unsigned long long)wait_ms);
        return 1;
    }

    fprintf(stderr, "[fc_pipe] slot open, streaming to stdout\n");

    uint64_t frames_out = 0;
    uint64_t total_dropped = 0;

    while (!g_stop) {
        fc_frame_ref_t ref;
        int rc = fc_consumer_read(c, &ref, 2000 /* 2s timeout */);

        if (rc == FC_TIMEOUT) continue;
        if (rc == FC_ERROR)   break;

        if (rc == FC_LAPPED) {
            /* Copy was torn (writer lapped us mid-read). No valid frame to
             * write — log and read again. */
            total_dropped = fc_consumer_dropped(c);
            fprintf(stderr, "[fc_pipe] WARNING: frame lapped mid-read — total dropped: %llu\n",
                    (unsigned long long)total_dropped);
            continue;
        }

        if (rc == FC_DROPPED) {
            /* Skipped one or more older frames, but THIS frame is valid — log
             * and write it (do NOT continue). */
            total_dropped = fc_consumer_dropped(c);
            fprintf(stderr, "[fc_pipe] WARNING: consumer fell behind — total dropped: %llu\n",
                    (unsigned long long)total_dropped);
        }

        /* Write frame data to stdout (ref.data is a stable consumer-owned copy) */
        if (write_all_fd(STDOUT_FILENO, ref.data, ref.size) < 0) {
            if (!g_stop)
                fprintf(stderr, "[fc_pipe] stdout EPIPE — ffmpeg exited\n");
            break;
        }
        frames_out++;

        /* Periodic stats to stderr (every 300 frames ≈ 5s at 60fps) */
        if (frames_out % 300 == 0) {
            fprintf(stderr, "[fc_pipe] frames=%llu dropped=%llu\n",
                    (unsigned long long)frames_out,
                    (unsigned long long)total_dropped);
        }
    }

    fc_consumer_close(c);
    fprintf(stderr, "[fc_pipe] done frames=%llu dropped=%llu\n",
            (unsigned long long)frames_out,
            (unsigned long long)total_dropped);
    return 0;
}