/**
 * SYNTHETIC meeting stand-in (spec 001 "Measurement fallback", coordination
 * plan 001-0): no real meeting recording exists, so this joins the repo's
 * own English clips with meeting-like pauses. Built at test time from
 * tests/audio_files — nothing new is checked in. Every number measured on it
 * is labelled synthetic.
 *
 * Layout (≈ 2 min 45 s): 2 s lead-in, en_aiproblem (whole), then three
 * en_alien excerpts, each clip followed by a pause of 3, 8, 2 and 5 s. Pauses and lead-in carry
 * deterministic room noise at about −60 dBFS (a real recording is never
 * digital silence). Excerpts are cut on reference-line boundaries; their
 * times were read once from a timestamped Large v3 Turbo transcript of
 * en_alien (2026-10-29) and land in the pause before the line, so each
 * excerpt's reference is exactly its lines of en_alien.txt.
 */

import { decodeClip, readReference } from "./clips";

const RATE = 16_000;
const LEAD_IN_SECONDS = 2;
const PAUSES_SECONDS = [3, 8, 2, 5];
const NOISE_AMPLITUDE = 0.001; // ≈ −60 dBFS

/** en_alien excerpts: [start s, end s) and the 1-based reference lines they contain. */
export const ALIEN_EXCERPTS: { start: number; end: number; firstLine: number; lastLine: number }[] = [
  { start: 0, end: 36.8, firstLine: 1, lastLine: 9 },
  { start: 36.8, end: 99.0, firstLine: 10, lastLine: 28 },
  { start: 165.4, end: 196.1, firstLine: 45, lastLine: 58 },
];

function roomNoise(seconds: number, seed: number): Float32Array {
  let state = seed;
  return new Float32Array(Math.round(seconds * RATE)).map(() => {
    state = (state * 1_103_515_245 + 12_345) % 2 ** 31;
    return NOISE_AMPLITUDE * (state / 2 ** 30 - 1);
  });
}

export async function buildMeetingFixture(): Promise<{ audio: Float32Array; reference: string }> {
  const aiproblem = await decodeClip("en_aiproblem.m4a");
  const alien = await decodeClip("en_alien.opus");
  const alienLines = (await readReference("en_alien")).split("\n");

  const speech: Float32Array[] = [aiproblem];
  const references: string[] = [(await readReference("en_aiproblem")).trim()];
  for (const excerpt of ALIEN_EXCERPTS) {
    speech.push(alien.subarray(Math.round(excerpt.start * RATE), Math.round(excerpt.end * RATE)));
    references.push(alienLines.slice(excerpt.firstLine - 1, excerpt.lastLine).join(" ").trim());
  }

  const parts: Float32Array[] = [roomNoise(LEAD_IN_SECONDS, 1)];
  // A pause after every clip — the last one is the meeting's trailing room tone.
  speech.forEach((clip, i) => {
    parts.push(clip);
    parts.push(roomNoise(PAUSES_SECONDS[i % PAUSES_SECONDS.length]!, i + 2));
  });
  const audio = new Float32Array(parts.reduce((n, p) => n + p.length, 0));
  let at = 0;
  for (const part of parts) {
    audio.set(part, at);
    at += part.length;
  }
  return { audio, reference: references.join(" ") };
}