import { useCallback, useEffect, useRef, useState } from "react";

export type AudioAnnouncementStatus = "locked" | "enabling" | "ready" | "error";

const AUDIO_BASE_PATH = "/audio/queue-voice";
const ANNOUNCEMENT_REPEAT_COUNT = 3;
const GAP_AUDIO = `${AUDIO_BASE_PATH}/gap.wav`;

const DIGIT_AUDIO: Record<string, string> = {
  零: `${AUDIO_BASE_PATH}/digit-0.wav`,
  一: `${AUDIO_BASE_PATH}/digit-1.wav`,
  二: `${AUDIO_BASE_PATH}/digit-2.wav`,
  三: `${AUDIO_BASE_PATH}/digit-3.wav`,
  四: `${AUDIO_BASE_PATH}/digit-4.wav`,
  五: `${AUDIO_BASE_PATH}/digit-5.wav`,
  六: `${AUDIO_BASE_PATH}/digit-6.wav`,
  七: `${AUDIO_BASE_PATH}/digit-7.wav`,
  八: `${AUDIO_BASE_PATH}/digit-8.wav`,
  九: `${AUDIO_BASE_PATH}/digit-9.wav`,
};

const PHRASE_AUDIO = [
  ["前往入口", `${AUDIO_BASE_PATH}/entrance.wav`],
  ["请", `${AUDIO_BASE_PATH}/please.wav`],
  ["号", `${AUDIO_BASE_PATH}/number.wav`],
  ["至", `${AUDIO_BASE_PATH}/through.wav`],
] as const;

function clipsForAnnouncement(announcement: string): string[] {
  const callStart = announcement.indexOf("请");
  if (callStart < 0) return [];

  const callText = announcement.slice(callStart);
  const clips: string[] = [];
  for (let index = 0; index < callText.length;) {
    const phrase = PHRASE_AUDIO.find(([text]) => callText.startsWith(text, index));
    if (phrase) {
      clips.push(phrase[1]);
      index += phrase[0].length;
      continue;
    }

    const digit = DIGIT_AUDIO[callText[index]];
    if (digit) clips.push(digit);
    index += 1;
  }

  return clips.length ? [...clips, GAP_AUDIO] : [];
}

export function announcementAudioQueue(announcements: string[]): string[] {
  const queue: string[] = [];
  for (const announcement of announcements) {
    const clips = clipsForAnnouncement(announcement);
    for (let repeat = 0; repeat < ANNOUNCEMENT_REPEAT_COUNT; repeat += 1) {
      queue.push(...clips);
    }
  }
  return queue;
}

export function useAudioAnnouncements() {
  const audioRef = useRef<HTMLAudioElement | null>(null);
  const playbackIdRef = useRef(0);
  const [status, setStatus] = useState<AudioAnnouncementStatus>("locked");

  const playQueue = useCallback((sources: string[], onStarted?: () => void) => {
    const audio = audioRef.current;
    if (!audio || !sources.length) {
      setStatus("error");
      return;
    }

    const playbackId = ++playbackIdRef.current;
    audio.pause();
    audio.onended = null;
    audio.onerror = null;

    let cursor = 0;
    let started = false;
    const markStarted = () => {
      if (started || playbackIdRef.current !== playbackId) return;
      started = true;
      onStarted?.();
    };
    const fail = (error?: unknown) => {
      if (playbackIdRef.current !== playbackId) return;
      if (error instanceof DOMException && error.name === "AbortError") return;
      audio.onended = null;
      audio.onerror = null;
      setStatus("error");
    };
    const playNext = () => {
      if (playbackIdRef.current !== playbackId) return;
      if (cursor >= sources.length) {
        audio.onended = null;
        audio.onerror = null;
        return;
      }

      audio.src = sources[cursor];
      cursor += 1;
      audio.currentTime = 0;
      audio.onended = playNext;
      audio.onerror = () => fail();

      try {
        const result = audio.play();
        if (result && typeof result.then === "function") {
          void result.then(markStarted).catch(fail);
        } else {
          markStarted();
        }
      } catch (error) {
        fail(error);
      }
    };

    playNext();
  }, []);

  const enable = useCallback(() => {
    setStatus("enabling");
    playQueue([`${AUDIO_BASE_PATH}/ready.wav`], () => setStatus("ready"));
  }, [playQueue]);

  const announce = useCallback((announcements: string[]) => {
    if (status !== "ready" || !announcements.length) return;
    const queue = announcementAudioQueue(announcements);
    if (queue.length) playQueue(queue);
  }, [playQueue, status]);

  useEffect(() => () => {
    playbackIdRef.current += 1;
    const audio = audioRef.current;
    if (!audio) return;
    audio.pause();
    audio.onended = null;
    audio.onerror = null;
  }, []);

  return { announce, audioRef, enable, status };
}