const BARS = 48;
const MIN_BAR = 0.08;

export async function computeWaveform(
  url: string,
  bars = BARS
): Promise<number[]> {
  const response = await fetch(url);
  const buffer = await response.arrayBuffer();
  const ctx = new AudioContext();
  try {
    const audio = await ctx.decodeAudioData(buffer);
    const data = audio.getChannelData(0);
    const block = Math.max(1, Math.floor(data.length / bars));
    const peaks: number[] = [];
    for (let i = 0; i < bars; i++) {
      const start = i * block;
      let max = 0;
      for (let j = 0; j < block; j++) {
        const value = Math.abs(data[start + j] ?? 0);
        if (value > max) {
          max = value;
        }
      }
      peaks.push(max);
    }
    const norm = Math.max(...peaks, 0.0001);
    return peaks.map((peak) => Math.max(MIN_BAR, peak / norm));
  } finally {
    await ctx.close();
  }
}

export function flatWaveform(bars = BARS): number[] {
  return Array.from({ length: bars }, () => 0.3);
}