import { useEffect, useMemo, useRef, useState } from "react";
import { encodeWav, prepareAudio, toAudioBuffer } from "@plate-lab/core";

export interface AudioPlayerProps {
  /** Pressure signal [Pa] */
  p: Float64Array;
  fs: number;
  label?: string;
  /** Base name for the exported .wav file (no extension) */
  filename?: string;
}

/**
 * Plays the radiated-pressure estimate once, exactly as long as it is, and
 * offers the same clip as a 16-bit mono WAV download. Playback and export level
 * are normalized; the displayed peak is not. A clip of a few milliseconds
 * sounds like a click, and is labelled as such rather than repeated.
 */
export function AudioPlayer({ p, fs, label, filename = "plate-sound" }: AudioPlayerProps) {
  const prep = useMemo(() => prepareAudio(p, fs), [p, fs]);
  const ctxRef = useRef<AudioContext | null>(null);
  const srcRef = useRef<AudioBufferSourceNode | null>(null);
  const [playing, setPlaying] = useState(false);
  useEffect(() => () => stop(), []);

  const stop = () => {
    srcRef.current?.stop();
    srcRef.current = null;
    setPlaying(false);
  };
  const play = () => {
    if (!ctxRef.current) ctxRef.current = new AudioContext();
    const ctx = ctxRef.current;
    void ctx.resume();
    stop();
    const src = ctx.createBufferSource();
    src.buffer = toAudioBuffer(ctx, prep);
    src.connect(ctx.destination);
    src.start();
    src.onended = () => setPlaying(false);
    srcRef.current = src;
    setPlaying(true);
  };
  const download = () => {
    // The exported file carries the same normalized signal that is played, at the
    // simulation's own sample rate; the peak in Pa is reported alongside it.
    const blob = new Blob([encodeWav(prep.samples, Math.round(prep.fs)) as BlobPart], {
      type: "audio/wav",
    });
    const url = URL.createObjectURL(blob);
    const a = document.createElement("a");
    a.href = url;
    a.download = `${filename}.wav`;
    a.click();
    setTimeout(() => URL.revokeObjectURL(url), 0);
  };

  const short = prep.durationS < 0.1;
  return (
    <div className="pl-row pl-small">
      <button className="pl-btn" onClick={playing ? stop : play} disabled={p.length < 2}>
        {playing ? "Stop" : `Play${label ? ` ${label}` : ""}`}
      </button>
      <button
        className="pl-btn"
        onClick={download}
        disabled={p.length < 2}
        title="Download as a 16-bit mono WAV file"
      >
        Save .wav
      </button>
      <span className="pl-muted">
        {(prep.durationS * 1000).toFixed(1)} ms at {fs} Hz, peak {prep.peakPa.toExponential(2)} Pa;
        normalized for playback, played once
        {short
          ? ". This excerpt is too short to hear as a note; lengthen the simulated window for a longer clip"
          : ""}
      </span>
    </div>
  );
}