/**
 * Player state store - Thin wrapper over Rust PlayerController
 *
 * This store is display-only for most fields, receiving updates from
 * backend events via playerEvents.ts. User actions are sent as commands
 * to the Rust backend, which drives state changes.
 *
 * @req: UR-005 - Control media playback (pause, play, skip, scrub)
 * @req: DR-001 - Player state machine (idle, loading, playing, paused, seeking, error)
 * @req: DR-009 - Audio player UI (mini player, full screen)
 */

import { writable, derived } from "svelte/store";
import type { MediaItem } from "$lib/api/types";
import { isRemoteMode } from "./playbackMode";
import { selectedSession } from "./sessions";
import { ticksToSeconds } from "$lib/utils/playbackUnits";

// Merged media item from backend (matches Rust MergedMediaItem)
export interface MergedMediaItem {
  id: string;
  title: string;
  artist: string | null;
  album: string | null;
  albumId: string | null;
  duration: number | null;
  primaryImageTag: string | null;
  mediaType: "audio" | "video";
}

export type PlayerState =
  | { kind: "idle" }
  | { kind: "loading"; media: MediaItem }
  | { kind: "playing"; media: MediaItem; position: number; duration: number }
  | { kind: "paused"; media: MediaItem; position: number; duration: number }
  | { kind: "seeking"; media: MediaItem; target: number }
  | { kind: "error"; media: MediaItem | null; error: string };

export type RepeatMode = "off" | "all" | "one";

interface PlayerStore {
  state: PlayerState;
  volume: number;
  muted: boolean;
}

function createPlayerStore() {
  const initialState: PlayerStore = {
    state: { kind: "idle" },
    volume: 1.0,
    muted: false,
  };

  const { subscribe, set, update } = writable<PlayerStore>(initialState);

  function setIdle() {
    update((s) => ({ ...s, state: { kind: "idle" } }));
  }

  function setLoading(media: MediaItem) {
    update((s) => ({ ...s, state: { kind: "loading", media } }));
  }

  function setPlaying(media: MediaItem, position: number, duration: number) {
    update((s) => ({
      ...s,
      state: { kind: "playing", media, position, duration },
    }));
  }

  function setPaused(media: MediaItem, position: number, duration: number) {
    update((s) => ({
      ...s,
      state: { kind: "paused", media, position, duration },
    }));
  }

  function setSeeking(media: MediaItem, target: number) {
    update((s) => ({ ...s, state: { kind: "seeking", media, target } }));
  }

  function setError(error: string, media: MediaItem | null = null) {
    update((s) => ({ ...s, state: { kind: "error", media, error } }));
  }

  function updatePosition(position: number, duration?: number) {
    update((s) => {
      if (s.state.kind === "playing" || s.state.kind === "paused") {
        return {
          ...s,
          state: {
            ...s.state,
            position,
            // Update duration if provided and valid
            duration: duration !== undefined && duration > 0 ? duration : s.state.duration
          },
        };
      }
      return s;
    });
  }

  function setVolume(volume: number) {
    update((s) => ({ ...s, volume: Math.max(0, Math.min(1, volume)) }));
  }

  function setMuted(muted: boolean) {
    update((s) => ({ ...s, muted }));
  }

  function toggleMute() {
    update((s) => ({ ...s, muted: !s.muted }));
  }

  return {
    subscribe,
    setIdle,
    setLoading,
    setPlaying,
    setPaused,
    setSeeking,
    setError,
    updatePosition,
    setVolume,
    setMuted,
    toggleMute,
  };
}

export const player = createPlayerStore();

// Derived stores
export const playerState = derived(player, ($p) => $p.state);
export const currentMedia = derived(player, ($p) => {
  const state = $p.state;
  if (state.kind === "idle") return null;
  return state.media;
});
export const isPlaying = derived(player, ($p) => $p.state.kind === "playing");
export const isPaused = derived(player, ($p) => $p.state.kind === "paused");
export const isLoading = derived(player, ($p) => $p.state.kind === "loading");
export const playbackPosition = derived(player, ($p) => {
  const state = $p.state;
  if (state.kind === "playing" || state.kind === "paused") {
    return state.position;
  }
  return 0;
});
export const playbackDuration = derived(player, ($p) => {
  const state = $p.state;
  if (state.kind === "playing" || state.kind === "paused") {
    return state.duration;
  }
  return 0;
});
export const volume = derived(player, ($p) => $p.volume);
export const isMuted = derived(player, ($p) => $p.muted);

// Merged playback state (combines local and remote based on playback mode)
// These stores replace the mergedPlaybackState.ts helper functions

/**
 * Merged media item - prefers remote session when in remote mode
 */
export const mergedMedia = derived(
  [isRemoteMode, selectedSession, currentMedia],
  ([$isRemote, $session, $local]) => {
    if ($isRemote && $session?.nowPlayingItem) {
      return $session.nowPlayingItem;
    }
    return $local;
  }
);

/**
 * Merged isPlaying state - prefers remote session when in remote mode
 */
export const mergedIsPlaying = derived(
  [isRemoteMode, selectedSession, isPlaying],
  ([$isRemote, $session, $localIsPlaying]) => {
    if ($isRemote && $session?.playState) {
      return !$session.playState.isPaused;
    }
    return $localIsPlaying;
  }
);

/**
 * Merged position - prefers remote session when in remote mode
 */
export const mergedPosition = derived(
  [isRemoteMode, selectedSession, playbackPosition],
  ([$isRemote, $session, $localPosition]) => {
    if ($isRemote && $session?.playState) {
      return ticksToSeconds($session.playState.positionTicks ?? 0);
    }
    return $localPosition;
  }
);

/**
 * Merged duration - prefers remote session when in remote mode
 */
export const mergedDuration = derived(
  [isRemoteMode, selectedSession, playbackDuration],
  ([$isRemote, $session, $localDuration]) => {
    if ($isRemote && $session?.nowPlayingItem?.runTimeTicks) {
      return ticksToSeconds($session.nowPlayingItem.runTimeTicks);
    }
    return $localDuration;
  }
);

/**
 * Merged volume - prefers remote session when in remote mode
 * Both local and remote use 0-1 normalized range
 */
export const mergedVolume = derived(
  [isRemoteMode, selectedSession, volume],
  ([$isRemote, $session, $localVolume]) => {
    if ($isRemote && $session?.playState) {
      // Convert remote 0-100 to normalized 0-1
      return ($session.playState.volumeLevel ?? 100) / 100;
    }
    return $localVolume;
  }
);

/**
 * Should show audio miniplayer - state machine gated
 * Only true when:
 * 1. Player is in playing or paused state (not idle, loading, error)
 * 2. Current media is audio (not video: Movie or Episode)
 */
export const shouldShowAudioMiniPlayer = derived(
  [player, currentMedia],
  ([$player, $media]) => {
    const state = $player.state;

    // Only show when actively playing or paused
    if (state.kind !== "playing" && state.kind !== "paused") {
      return false;
    }

    // Don't show for video content
    const mediaType = $media?.type;
    if (mediaType === "Movie" || mediaType === "Episode") {
      return false;
    }

    // Show for audio content
    return true;
  }
);