/* app/reader_ipc.c — 系统翻页信号接收（见 app/reader_ipc.h）。 */
#include "reader_ipc.h"
#include "../reader_internal.h"   /* reader_page_key() */
#include "meow_ipc.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <poll.h>
#include <pthread.h>
#include <sys/socket.h>
#include <sys/un.h>

static pthread_mutex_t g_mu   = PTHREAD_MUTEX_INITIALIZER;
static int             g_fd   = -1;
static pthread_t       g_thr;
static int             g_thr_on = 0;
static volatile int    g_quit  = 0;

static const char *sock_path(void)
{
    const char *e = getenv("MEOW_IPC_SOCK");
    return (e && e[0]) ? e : MEOW_IPC_PATH;
}

static void app_id_of(char *out, int outsz)
{
    const char *e = getenv("MEOW_LOG_APP");
    snprintf(out, (size_t)outsz, "%s", (e && e[0]) ? e : "os.meow.reader");
}

static int connect_path(const char *path)
{
    int fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd < 0) return -1;
    struct sockaddr_un a;
    memset(&a, 0, sizeof a);
    a.sun_family = AF_UNIX;
    strncpy(a.sun_path, path, sizeof a.sun_path - 1);
    if (connect(fd, (struct sockaddr *)&a, sizeof a) < 0) { close(fd); return -1; }
    return fd;
}

static int write_all(int fd, const uint8_t *p, size_t n)
{
    size_t off = 0;
    while (off < n) {
        ssize_t w = write(fd, p + off, n - off);
        if (w < 0) { if (errno == EINTR) continue; return 0; }
        if (w == 0) return 0;
        off += (size_t)w;
    }
    return 1;
}

static int read_all(int fd, uint8_t *p, size_t n)
{
    size_t off = 0;
    while (off < n) {
        ssize_t r = read(fd, p + off, n - off);
        if (r < 0) { if (errno == EINTR) continue; return 0; }
        if (r == 0) return 0;
        off += (size_t)r;
    }
    return 1;
}

static int send_frame(int fd, uint16_t type, uint32_t req_id,
                      const void *payload, uint32_t len)
{
    uint8_t hdr[MEOW_IPC_HDR_LEN];
    uint32_t magic = MEOW_IPC_MAGIC;
    uint16_t ver   = MEOW_IPC_VERSION;
    memcpy(hdr + 0, &magic, 4);
    memcpy(hdr + 4, &ver, 2);
    memcpy(hdr + 6, &type, 2);
    memcpy(hdr + 8, &req_id, 4);
    memcpy(hdr + 12, &len, 4);
    if (!write_all(fd, hdr, sizeof hdr)) return -1;
    if (len && payload && !write_all(fd, payload, len)) return -1;
    return 0;
}

static int read_frame(int fd, uint16_t *type, uint8_t *rbuf, uint32_t rcap)
{
    uint8_t hdr[MEOW_IPC_HDR_LEN];
    if (!read_all(fd, hdr, sizeof hdr)) return -1;
    uint32_t magic, len; uint16_t ver;
    memcpy(&magic, hdr, 4); memcpy(&ver, hdr + 4, 2); memcpy(type, hdr + 6, 2);
    memcpy(&len, hdr + 12, 4);
    if (magic != MEOW_IPC_MAGIC || ver != MEOW_IPC_VERSION) return -1;
    if (len > rcap) len = rcap;
    if (len > 0 && !read_all(fd, rbuf, len)) return -1;
    return (int)len;
}

static int conn_locked(void)
{
    if (g_fd >= 0) return g_fd;
    int fd = connect_path(sock_path());
    if (fd < 0) return -1;
    char app[MEOW_APP_ID_MAX];
    app_id_of(app, (int)sizeof app);
    m_hello_t h;
    memset(&h, 0, sizeof h);
    snprintf(h.app_id, sizeof h.app_id, "%s", app);
    h.version = 1;
    h.flags = 0;                      /* 非媒体源；仅声明存在，收系统翻页信号 */
    if (send_frame(fd, MSG_HELLO, 1, &h, sizeof h) != 0) { close(fd); return -1; }
    uint8_t rbuf[256];
    uint16_t rt;
    if (read_frame(fd, &rt, rbuf, sizeof rbuf) < 0 ||
        (rt != MSG_ACK && rt != MSG_ERR)) { close(fd); return -1; }
    g_fd = fd;
    return fd;
}

static void mark_dead_locked(void)
{
    if (g_fd >= 0) { close(g_fd); g_fd = -1; }
}

static void *ipc_thread_main(void *arg)
{
    (void)arg;
    while (!g_quit) {
        pthread_mutex_lock(&g_mu);
        int fd = g_fd;
        if (fd < 0) fd = conn_locked();   /* 懒连/重连（best-effort；失败则重试） */
        pthread_mutex_unlock(&g_mu);
        if (fd < 0) { usleep(500000); continue; }

        struct pollfd p;
        p.fd = fd; p.events = POLLIN; p.revents = 0;
        int pr = poll(&p, 1, 200);
        if (pr < 0 && errno != EINTR) {
            pthread_mutex_lock(&g_mu); mark_dead_locked(); pthread_mutex_unlock(&g_mu);
            continue;
        }
        if (pr > 0 && (p.revents & (POLLHUP | POLLERR | POLLNVAL))) {
            pthread_mutex_lock(&g_mu); mark_dead_locked(); pthread_mutex_unlock(&g_mu);
            continue;
        }
        if (pr > 0 && (p.revents & POLLIN)) {
            uint8_t rbuf[MEOW_IPC_MAX];
            uint16_t type;
            int n = read_frame(fd, &type, rbuf, sizeof rbuf);
            if (n < 0) {
                pthread_mutex_lock(&g_mu); mark_dead_locked(); pthread_mutex_unlock(&g_mu);
                continue;
            }
            /* UI 线程经 reader_on_tick 消费（跨线程仅置 pending 计数，不直接改页） */
            if (type == MSG_KEY_PAGEUP)   reader_page_key(-1);
            else if (type == MSG_KEY_PAGEDOWN) reader_page_key(1);
        }
    }
    pthread_mutex_lock(&g_mu); mark_dead_locked(); pthread_mutex_unlock(&g_mu);
    return NULL;
}

void reader_ipc_start(void)
{
    pthread_mutex_lock(&g_mu);
    int need = !g_thr_on;
    if (need) { g_quit = 0; g_thr_on = 1; }
    pthread_mutex_unlock(&g_mu);
    if (need) {
        pthread_attr_t at;
        pthread_attr_init(&at);
        pthread_attr_setstacksize(&at, 64 * 1024);   /* 小栈：阅读态 ≤8MB 纪律 */
        pthread_create(&g_thr, &at, ipc_thread_main, NULL);
        pthread_attr_destroy(&at);
        pthread_detach(g_thr);
    }
}

void reader_ipc_stop(void)
{
    pthread_mutex_lock(&g_mu);
    g_quit = 1;
    mark_dead_locked();
    g_thr_on = 0;
    pthread_mutex_unlock(&g_mu);
}