/* play/meta_gate.c — 见 meta_gate.h 头注释（M10 媒体会话 META 上报闸）。 */
#include "meta_gate.h"
#include <string.h>

static void gate_cp(char *dst, size_t cap, const char *src)
{
    size_t i = 0;
    if (!dst || cap == 0) return;
    if (src) {
        for (; src[i] && i + 1 < cap; i++) dst[i] = src[i];
    }
    dst[i] = 0;
}

void ncm_meta_gate_init(ncm_meta_gate *g)
{
    if (g) memset(g, 0, sizeof *g);
}

static void gate_record(ncm_meta_gate *g, const ncm_meta_snap *s, int64_t now_ms)
{
    g->inited = 1;
    g->state = s->state;
    g->dur_ms = s->dur_ms;
    g->flags = s->flags;
    g->last_pos_ms = s->pos_ms;
    g->last_send_ms = now_ms;
    gate_cp(g->title, sizeof g->title, s->title);
    gate_cp(g->artist, sizeof g->artist, s->artist);
    gate_cp(g->album, sizeof g->album, s->album);
    gate_cp(g->artwork, sizeof g->artwork, s->artwork);
}

/* 只比较「会被发送的那部分」：发送侧同样按 cap 截断，超长串不得因截断而恒判「变了」。 */
static int str_diff(const char *stored, size_t cap, const char *now)
{
    size_t i = 0;
    if (!now) now = "";
    for (; i + 1 < cap && stored[i] && stored[i] == now[i]; i++) { }
    if (i + 1 >= cap) return 0;   /* 前 cap-1 字符一致且已到截断长度 → 相同 */
    return stored[i] != now[i];
}

int ncm_meta_gate_should_send(ncm_meta_gate *g, const ncm_meta_snap *s, int64_t now_ms)
{
    if (!g || !s) return 0;
    if (!g->inited) { gate_record(g, s, now_ms); return 1; }   /* 首帧：注册媒体源 */

    int64_t gap = now_ms - g->last_send_ms;
    if (gap < 0) {              /* 时钟回退/异常：重定基准，差值按 0 处理（防下溢成「恒该发」） */
        g->last_send_ms = now_ms;
        gap = 0;
    }

    int changed = (s->state  != g->state) ||
                  (s->dur_ms != g->dur_ms) ||
                  (s->flags  != g->flags) ||
                  str_diff(g->title,   sizeof g->title,   s->title) ||
                  str_diff(g->artist,  sizeof g->artist,  s->artist) ||
                  str_diff(g->album,   sizeof g->album,   s->album) ||
                  str_diff(g->artwork, sizeof g->artwork, s->artwork);

    int64_t dpos = (int64_t)s->pos_ms - (int64_t)g->last_pos_ms;
    if (dpos < 0) dpos = -dpos;   /* seek 前后跳都算偏移 */

    int playing = (s->state == NCM_META_ST_PLAYING || s->state == NCM_META_ST_BUFFER);
    int64_t hb = playing ? NCM_META_HB_PLAY_MS : NCM_META_HB_IDLE_MS;

    if (!changed && dpos < NCM_META_POS_RESEND_MS && gap < hb) return 0;
    if (gap < NCM_META_MIN_GAP_MS) return 0;   /* 硬下限：变化挂起，下一轮再发（不快于 4 帧/秒） */

    gate_record(g, s, now_ms);
    return 1;
}