package top.yeij.hearth.media

import android.content.ComponentName
import android.content.Context
import android.media.MediaMetadata
import android.media.session.MediaController
import android.media.session.MediaSessionManager
import android.media.session.PlaybackState
import android.util.Log

// 监听系统活跃媒体会话，取第一个 controller 的 metadata + playbackState 构造 MediaInfo 回调
// Watch active media sessions; build MediaInfo from the first controller's metadata + playbackState
class MediaSessionSource(context: Context) {
    private val msm = context.getSystemService(Context.MEDIA_SESSION_SERVICE) as MediaSessionManager

    // 通知监听组件作为授权凭据传入 addOnActiveSessionsChangedListener，
    // 取代依赖 MEDIA_CONTENT_CONTROL 系统权限的 null 方案。
    // The notification listener component is passed as the authorization credential,
    // replacing the null-based approach that relied on the MEDIA_CONTENT_CONTROL permission.
    private val listenerComponent = ComponentName(context, HearthNotificationListenerService::class.java)

    private var callback: ((MediaInfo?) -> Unit)? = null
    private var registered = false

    // 具名监听器字段：会话列表变化时回调
    // Named listener field: fires when the active-session list changes
    private val activeSessionsListener =
        MediaSessionManager.OnActiveSessionsChangedListener { controllers ->
            val cb = callback ?: return@OnActiveSessionsChangedListener
            notifyMedia(controllers?.firstOrNull(), cb)
        }

    // 注册监听：幂等——先移除旧监听再注册，避免重复 start 累积监听器。
    // 注册后主动拉取一次当前活跃会话：注册前已开始的播放不会触发变化回调，
    // 主动拉取保证启动时媒体卡即可显示。
    // Register the listener: idempotent — remove the old one first to avoid accumulation.
    // After registering, actively pull the current sessions once: playback that started
    // before registration never fires the change callback, so the active pull makes the
    // media card show immediately on startup.
    fun start(cb: (MediaInfo?) -> Unit) {
        stop()
        callback = cb
        try {
            msm.addOnActiveSessionsChangedListener(activeSessionsListener, listenerComponent)
            registered = true
            Log.d(TAG, "start: media session listener registered")
            val current = msm.getActiveSessions(listenerComponent).firstOrNull()
            notifyMedia(current, cb)
        } catch (e: SecurityException) {
            // 未授权「通知使用权」时系统抛 SecurityException：媒体监听降级为不可用，不崩溃。
            // 用户在系统设置开启通知使用权后，重启 Hearth 才会恢复媒体卡。
            // MediaSessionService throws SecurityException without notification access;
            // degrade to media listening disabled instead of crashing. Media card recovers
            // after the user grants notification access and restarts Hearth.
            Log.w(TAG, "start: no notification access, media listener disabled: ${e.message}")
            registered = false
        }
    }

    // 注销监听：释放回调引用，供 Activity onDestroy 调用
    // Unregister the listener: release the callback, call from Activity onDestroy
    fun stop() {
        if (registered) {
            msm.removeOnActiveSessionsChangedListener(activeSessionsListener)
            registered = false
            Log.d(TAG, "stop: media session listener removed")
        }
        callback = null
    }

    // 从 controller 提取 metadata + playbackState 构造 MediaInfo 并回调
    // Build MediaInfo from the controller's metadata + playbackState and invoke the callback
    private fun notifyMedia(controller: MediaController?, cb: (MediaInfo?) -> Unit) {
        if (controller == null) {
            Log.d(TAG, "no active media session")
            cb(null)
            return
        }
        val meta = controller.metadata
        val state = controller.playbackState
        cb(
            MediaInfo(
                meta?.getString(MediaMetadata.METADATA_KEY_TITLE) ?: "",
                meta?.getString(MediaMetadata.METADATA_KEY_ARTIST) ?: "",
                meta?.getString(MediaMetadata.METADATA_KEY_ALBUM) ?: "",
                state?.state == PlaybackState.STATE_PLAYING,
                state?.position ?: 0L,
                meta?.getLong(MediaMetadata.METADATA_KEY_DURATION) ?: 0L,
                controller.packageName,
            )
        )
        Log.d(TAG, "media: ${controller.packageName}")
    }

    companion object {
        private const val TAG = "HearthMedia"
    }
}