// Summary numbers of a rendered clip.

import { FFT } from "../audio/fft.ts";

export interface ClipMetrics {
  peakPa: number;
  peakDbSpl: number;
  rmsPa: number;
  /** Spectral centroid [Hz] of the sound between 0.2 s and 1.2 s. */
  centroidHz: number;
  /** Fitted 60 dB decay times [s] per band, from 0.2 s to the end (Infinity when not decaying). */
  t60: Record<string, number>;
  /** Band levels [dB] relative to the 100-500 Hz band, at 0.1 s. */
  bandLevelsDb: Record<string, number>;
}

const BANDS: [string, number, number][] = [["20-100", 20, 100], ["100-500", 100, 500], ["500-2k", 500, 2000], ["2k-8k", 2000, 8000]];

export function clipMetrics(a: Float32Array, fs: number): ClipMetrics {
  let peak = 0, sum = 0;
  for (let k = 0; k < a.length; k++) { peak = Math.max(peak, Math.abs(a[k])); sum += a[k] * a[k]; }
  const rms = Math.sqrt(sum / Math.max(1, a.length));
  const win = Math.round(0.1 * fs);
  const n = Math.floor(a.length / win);
  const N = 1 << Math.ceil(Math.log2(win));
  const fft = new FFT(N);
  const re = new Float32Array(N), im = new Float32Array(N);
  const rows: number[][] = [];
  for (let i = 0; i < n; i++) {
    re.fill(0); im.fill(0);
    for (let k = 0; k < win; k++) re[k] = a[i * win + k] * (0.5 - 0.5 * Math.cos((2 * Math.PI * k) / win));
    fft.transform(re, im);
    const row: number[] = [];
    for (const [, lo, hi] of BANDS) {
      let e = 0;
      for (let b = Math.floor((lo * N) / fs); b < Math.min(N / 2, Math.ceil((hi * N) / fs)); b++) e += re[b] * re[b] + im[b] * im[b];
      row.push(10 * Math.log10(e + 1e-20));
    }
    rows.push(row);
  }
  const t60: Record<string, number> = {};
  const bandLevelsDb: Record<string, number> = {};
  BANDS.forEach(([name], k) => {
    const pts = rows.slice(2).map((r, i) => [(i + 2) * 0.1, r[k]]);
    let slope = 0;
    if (pts.length >= 3) {
      const mx = pts.reduce((s, p) => s + p[0], 0) / pts.length, my = pts.reduce((s, p) => s + p[1], 0) / pts.length;
      slope = pts.reduce((s, p) => s + (p[0] - mx) * (p[1] - my), 0) / pts.reduce((s, p) => s + (p[0] - mx) ** 2, 0);
    }
    t60[name] = slope < 0 ? 60 / -slope : Infinity;
    bandLevelsDb[name] = rows.length > 1 ? rows[1][k] - rows[1][1] : 0;
  });
  // Spectral centroid, 0.2 to 1.2 s.
  const seg = a.subarray(Math.round(0.2 * fs), Math.min(a.length, Math.round(1.2 * fs)));
  const M = 1 << Math.ceil(Math.log2(Math.max(2, seg.length)));
  const fft2 = new FFT(M);
  const r2 = new Float32Array(M), i2 = new Float32Array(M);
  r2.set(seg);
  fft2.transform(r2, i2);
  let num = 0, den = 0;
  for (let b = 1; b < M / 2; b++) {
    const p = r2[b] * r2[b] + i2[b] * i2[b];
    num += ((b * fs) / M) * p; den += p;
  }
  return { peakPa: peak, peakDbSpl: peak > 0 ? 20 * Math.log10(peak / 2e-5) : -Infinity, rmsPa: rms, centroidHz: den > 0 ? num / den : 0, t60, bandLevelsDb };
}