/**
 * fc_writer.c — Framecache slot writer for deltacast-bridge.
 *
 * Uses only POSIX + libc — no external dependencies beyond what the bridge
 * already links.  HTTP calls are done with raw sockets (tiny GET/POST/DELETE)
 * to avoid pulling in libcurl.
 */
#include "fc_writer.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdatomic.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <semaphore.h>
#include <time.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/* Re-use the shared memory layout from the framecache service */
#define FC_MAGIC          0x46524D43u
#define FC_VERSION        1u
#define FC_RING_DEPTH     120u
#define FC_HEADER_SIZE    4096u
#define FC_FRAME_HDR_SIZE 24u

typedef struct {
    uint32_t magic;
    uint32_t version;
    uint32_t width;
    uint32_t height;
    uint32_t fps_num;
    uint32_t fps_den;
    uint32_t pixel_format;
    uint32_t frame_size;
    uint32_t ring_depth;
    uint32_t _reserved;
    _Atomic uint64_t write_cursor;
    _Atomic uint64_t dropped_frames;
    char source_type[32];
    char slot_id[64];
    uint8_t _pad[FC_HEADER_SIZE - 112];
} fc_hdr_t;

typedef struct {
    uint64_t pts_us;
    uint64_t wall_us;
    uint32_t size;
    uint32_t _pad;
    uint8_t  data[];
} fc_frm_t;

struct fc_writer {
    void    *base;
    size_t   shm_size;
    int      shm_fd;
    sem_t   *sem;
    char     slot_id[64];
    char     fc_url[256];   /* base URL for DELETE on close */
    char     shm_path[128];
    char     sem_name[128];
};

/* ── tiny HTTP helper ──────────────────────────────────────────────── */

static int http_request(const char *method,
                         const char *host, int port, const char *path,
                         const char *body,   /* NULL for GET/DELETE */
                         char *resp_buf, size_t resp_len)
{
    struct sockaddr_in sa;
    memset(&sa, 0, sizeof sa);
    sa.sin_family = AF_INET;
    sa.sin_port   = htons((uint16_t)port);

    struct hostent *he = gethostbyname(host);
    if (!he) return -1;
    memcpy(&sa.sin_addr, he->h_addr_list[0], (size_t)he->h_length);

    int fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0) return -1;

    struct timeval tv = { .tv_sec = 5 };
    setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof tv);
    setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof tv);

    if (connect(fd, (struct sockaddr *)&sa, sizeof sa) < 0) {
        close(fd); return -1;
    }

    char req[4096];
    int  req_len;
    if (body) {
        req_len = snprintf(req, sizeof req,
            "%s %s HTTP/1.0\r\n"
            "Host: %s:%d\r\n"
            "Content-Type: application/json\r\n"
            "Content-Length: %zu\r\n"
            "Connection: close\r\n\r\n"
            "%s",
            method, path, host, port, strlen(body), body);
    } else {
        req_len = snprintf(req, sizeof req,
            "%s %s HTTP/1.0\r\n"
            "Host: %s:%d\r\n"
            "Connection: close\r\n\r\n",
            method, path, host, port);
    }

    if (send(fd, req, (size_t)req_len, 0) < 0) { close(fd); return -1; }

    int status = -1;
    size_t got = 0;
    char buf[8192];
    ssize_t n;
    while ((n = recv(fd, buf + got, sizeof buf - got - 1, 0)) > 0)
        got += (size_t)n;
    buf[got] = '\0';

    /* Parse status line */
    if (sscanf(buf, "HTTP/%*s %d", &status) != 1) status = -1;

    /* Copy body (after \r\n\r\n) into resp_buf */
    if (resp_buf && resp_len > 0) {
        const char *body_start = strstr(buf, "\r\n\r\n");
        if (body_start) {
            strncpy(resp_buf, body_start + 4, resp_len - 1);
            resp_buf[resp_len - 1] = '\0';
        }
    }

    close(fd);
    return status;
}

/* Parse "host:port" or just "host" from a URL like "http://host:port" */
static void parse_url(const char *url, char *host, size_t hlen, int *port)
{
    const char *p = url;
    if (strncmp(p, "http://", 7) == 0) p += 7;
    *port = 7435;
    const char *colon = strchr(p, ':');
    if (colon) {
        size_t n = (size_t)(colon - p);
        if (n >= hlen) n = hlen - 1;
        strncpy(host, p, n);
        host[n] = '\0';
        *port = atoi(colon + 1);
    } else {
        strncpy(host, p, hlen - 1);
        host[hlen - 1] = '\0';
    }
}

static int json_str(const char *json, const char *key, char *out, size_t len)
{
    char pat[128];
    snprintf(pat, sizeof pat, "\"%s\":", key);
    const char *p = strstr(json, pat);
    if (!p) return -1;
    p += strlen(pat);
    while (*p == ' ') p++;
    if (*p != '"') return -1;
    p++;
    size_t i = 0;
    while (*p && *p != '"' && i < len - 1) out[i++] = *p++;
    out[i] = '\0';
    return 0;
}

/* ── public API ────────────────────────────────────────────────────── */

fc_writer_t *fc_writer_open(const char *fc_url,
                              const char *slot_id,
                              uint32_t width, uint32_t height,
                              uint32_t fps_num, uint32_t fps_den)
{
    char host[128]; int port;
    parse_url(fc_url, host, sizeof host, &port);

    /* POST /slots */
    char body[512];
    snprintf(body, sizeof body,
        "{\"slot_id\":\"%s\","
        "\"width\":%u,\"height\":%u,"
        "\"fps_num\":%u,\"fps_den\":%u,"
        "\"source_type\":\"deltacast\"}",
        slot_id, width, height, fps_num, fps_den);

    char resp[1024] = {0};
    int status = http_request("POST", host, port, "/slots", body, resp, sizeof resp);
    if (status != 201) {
        fprintf(stderr, "[fc_writer:%s] POST /slots failed (HTTP %d): %s\n",
                slot_id, status, resp);
        return NULL;
    }

    char shm_path[128] = {0}, sem_name[128] = {0};
    json_str(resp, "shm_path", shm_path, sizeof shm_path);
    json_str(resp, "sem_name", sem_name, sizeof sem_name);

    if (!shm_path[0] || !sem_name[0]) {
        fprintf(stderr, "[fc_writer:%s] bad response (missing shm_path/sem_name)\n", slot_id);
        return NULL;
    }

    /* mmap the shm file */
    int fd = open(shm_path, O_RDWR);
    if (fd < 0) {
        fprintf(stderr, "[fc_writer:%s] open %s: %s\n", slot_id, shm_path, strerror(errno));
        return NULL;
    }
    /* Read header to get frame_size */
    fc_hdr_t hdr;
    if (pread(fd, &hdr, sizeof hdr, 0) != sizeof hdr || hdr.magic != FC_MAGIC) {
        fprintf(stderr, "[fc_writer:%s] bad shm header\n", slot_id);
        close(fd); return NULL;
    }
    size_t total = (size_t)FC_HEADER_SIZE
                 + (size_t)FC_RING_DEPTH * ((size_t)FC_FRAME_HDR_SIZE + hdr.frame_size);

    void *base = mmap(NULL, total, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (base == MAP_FAILED) {
        fprintf(stderr, "[fc_writer:%s] mmap: %s\n", slot_id, strerror(errno));
        close(fd); return NULL;
    }

    sem_t *sem = sem_open(sem_name, 0);
    if (sem == SEM_FAILED) {
        fprintf(stderr, "[fc_writer:%s] sem_open %s: %s\n", slot_id, sem_name, strerror(errno));
        munmap(base, total); close(fd); return NULL;
    }

    fc_writer_t *w = calloc(1, sizeof *w);
    if (!w) { sem_close(sem); munmap(base, total); close(fd); return NULL; }

    w->base     = base;
    w->shm_size = total;
    w->shm_fd   = fd;
    w->sem      = sem;
    strncpy(w->slot_id,  slot_id,  sizeof w->slot_id  - 1);
    strncpy(w->fc_url,   fc_url,   sizeof w->fc_url   - 1);
    strncpy(w->shm_path, shm_path, sizeof w->shm_path - 1);
    strncpy(w->sem_name, sem_name, sizeof w->sem_name - 1);

    fprintf(stderr, "[fc_writer:%s] slot open (%ux%u %.2ffps shm=%s)\n",
            slot_id, width, height,
            fps_den ? (double)fps_num / fps_den : 0.0, shm_path);
    return w;
}

void fc_writer_write(fc_writer_t *w,
                      const uint8_t *data, uint32_t size,
                      uint64_t pts_us)
{
    fc_hdr_t *hdr = (fc_hdr_t *)w->base;
    uint64_t cur  = atomic_load_explicit(&hdr->write_cursor, memory_order_relaxed);
    uint64_t idx  = cur % FC_RING_DEPTH;

    /* Locate frame in ring */
    uint8_t  *frames = (uint8_t *)w->base + FC_HEADER_SIZE;
    fc_frm_t *frame  = (fc_frm_t *)(frames + idx * ((size_t)FC_FRAME_HDR_SIZE + hdr->frame_size));

    struct timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
    uint64_t wall = (uint64_t)ts.tv_sec * 1000000ULL + ts.tv_nsec / 1000ULL;

    frame->pts_us  = pts_us;
    frame->wall_us = wall;
    frame->size    = size < hdr->frame_size ? size : hdr->frame_size;
    memcpy(frame->data, data, frame->size);

    atomic_store_explicit(&hdr->write_cursor, cur + 1, memory_order_release);
    sem_post(w->sem);
}

void fc_writer_close(fc_writer_t *w)
{
    if (!w) return;

    /* DELETE /slots/:id */
    char host[128]; int port;
    parse_url(w->fc_url, host, sizeof host, &port);
    char path[192];
    snprintf(path, sizeof path, "/slots/%s", w->slot_id);
    http_request("DELETE", host, port, path, NULL, NULL, 0);

    sem_close(w->sem);
    munmap(w->base, w->shm_size);
    close(w->shm_fd);
    fprintf(stderr, "[fc_writer:%s] slot closed\n", w->slot_id);
    free(w);
}