/*
 * Copyright (c) Double Symmetry GmbH
 * Commercial use requires a license. See https://rntp.dev/pricing
 */

package com.doublesymmetry.trackplayer

import androidx.media3.common.MediaItem
import androidx.media3.exoplayer.source.ForwardingMediaSourceFactory
import androidx.media3.exoplayer.source.MediaSource
import androidx.media3.exoplayer.source.WrappingMediaSource
import java.util.IdentityHashMap

/**
 * Forces an explicitly marked item replacement to create a new source holder.
 *
 * A URI fragment or custom cache key would also make some Media3 sources reject
 * an in-place update, but would change app-visible request/cache semantics and
 * does not work consistently across source types. This identity-scoped token
 * leaves every [MediaItem] field untouched and uses Media3's update contract.
 */
internal class LiveRefreshMediaSourceFactory(
  delegate: MediaSource.Factory,
) : ForwardingMediaSourceFactory(delegate) {
  override fun createMediaSource(mediaItem: MediaItem): MediaSource =
    TokenAwareMediaSource(super.createMediaSource(mediaItem), LiveRefreshTokens.consume(mediaItem))

  private class TokenAwareMediaSource(
    source: MediaSource,
    private val token: Long?,
  ) : WrappingMediaSource(source) {
    override fun canUpdateMediaItem(mediaItem: MediaItem): Boolean {
      val requestedToken = LiveRefreshTokens.peek(mediaItem)
      return (requestedToken == null || requestedToken == token) && super.canUpdateMediaItem(mediaItem)
    }
  }
}

internal object LiveRefreshTokens {
  private val tokens = IdentityHashMap<MediaItem, Long>()

  fun mark(mediaItem: MediaItem, generation: Long) = synchronized(tokens) {
    tokens[mediaItem] = generation
  }

  fun peek(mediaItem: MediaItem): Long? = synchronized(tokens) { tokens[mediaItem] }

  fun consume(mediaItem: MediaItem): Long? = synchronized(tokens) { tokens.remove(mediaItem) }

  fun discard(mediaItem: MediaItem) = synchronized(tokens) {
    tokens.remove(mediaItem)
    Unit
  }
}