/**
 * Sleep Timer Store (Backend-First Architecture)
 *
 * This store reflects sleep timer state from the backend.
 * All logic is in the Rust backend (PlayerController).
 *
 * The backend emits SleepTimerChanged events to update this store.
 * Components call store methods which invoke the backend API.
 *
 * TRACES: UR-026 | DR-029
 */

import { writable, derived } from "svelte/store";
import { commands } from "$lib/api/bindings";

export type SleepTimerMode =
  | { kind: "off" }
  | { kind: "time"; endTime: number }
  | { kind: "endOfTrack" }
  | { kind: "episodes"; remaining: number };

interface SleepTimerState {
  mode: SleepTimerMode;
  remainingSeconds: number;
}

function createSleepTimerStore() {
  const initialState: SleepTimerState = {
    mode: { kind: "off" },
    remainingSeconds: 0,
  };

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

  return {
    subscribe,
    set, // Updated by playerEvents.ts when backend emits SleepTimerChanged event

    // Methods that invoke the backend API
    async setTimeTimer(minutes: number): Promise<void> {
      const endTime = Date.now() + minutes * 60 * 1000;
      await commands.playerSetSleepTimer({ kind: "time", endTime });
    },

    async setEndOfTrackTimer(): Promise<void> {
      await commands.playerSetSleepTimer({ kind: "endOfTrack" });
    },

    async setEpisodesTimer(count: number): Promise<void> {
      await commands.playerSetSleepTimer({ kind: "episodes", remaining: count });
    },

    async cancel(): Promise<void> {
      await commands.playerCancelSleepTimer();
    },
  };
}

export const sleepTimer = createSleepTimerStore();

/**
 * Incremented each time the backend reports the time-based sleep timer
 * expired. The backend stops its own (MPV/ExoPlayer) playback itself, but
 * HTML5 video on Linux plays in the webview outside the backend's control —
 * VideoPlayer watches this signal and pauses the <video> element.
 */
export const sleepTimerExpiredSignal = writable(0);

// Derived stores for convenient access
export const sleepTimerMode = derived(sleepTimer, ($s) => $s.mode);

export const sleepTimerActive = derived(
  sleepTimer,
  ($s) => $s.mode.kind !== "off"
);

export const sleepTimerRemainingSeconds = derived(
  sleepTimer,
  ($s) => $s.remainingSeconds
);

export const sleepTimerRemainingEpisodes = derived(sleepTimer, ($s) =>
  $s.mode.kind === "episodes" ? $s.mode.remaining : 0
);