import { renderSignal } from "./signal.js";

export const MAX_MIX_WORKING_BYTES = 384 * 1024 * 1024;
export const MAX_MIX_SAMPLE_OPERATIONS = 250_000_000;

export function estimateSceneMix(scene, assetBuffers = new Map()) {
  const sampleCount = Math.ceil(scene.duration * scene.sampleRate);
  const entryCount = scene.sources.length + (scene.ambient?.length ?? 0);
  let assetBytes = 0;
  for (const asset of assetBuffers.values()) {
    for (const channel of asset.channels ?? []) assetBytes += channel.byteLength ?? 0;
  }
  return {
    sampleCount,
    entryCount,
    assetBytes,
    workingBytes: sampleCount * Float32Array.BYTES_PER_ELEMENT * 2 + assetBytes,
    sampleOperations: sampleCount * entryCount,
  };
}

export function renderSceneMix(scene, assetBuffers = new Map()) {
  const estimate = estimateSceneMix(scene, assetBuffers);
  if (!Number.isSafeInteger(estimate.sampleCount) || estimate.sampleCount <= 0) {
    throw new Error("장면 sample 수가 올바르지 않습니다.");
  }
  if (estimate.workingBytes > MAX_MIX_WORKING_BYTES) {
    throw new Error(
      `확인용 mix 작업 메모리 ${(estimate.workingBytes / 1024 ** 2).toFixed(1)} MiB가 ` +
        `${(MAX_MIX_WORKING_BYTES / 1024 ** 2).toFixed(0)} MiB 한도를 넘습니다. duration 또는 sample rate를 줄이세요.`,
    );
  }
  if (estimate.sampleOperations > MAX_MIX_SAMPLE_OPERATIONS) {
    throw new Error(
      `확인용 mix 연산량 ${estimate.sampleOperations.toLocaleString()} samples가 ` +
        `${MAX_MIX_SAMPLE_OPERATIONS.toLocaleString()} 한도를 넘습니다. duration 또는 음원 수를 줄이세요.`,
    );
  }
  const { sampleCount } = estimate;
  const samples = new Float32Array(sampleCount);
  for (const source of scene.sources) {
    const sourceSamples = renderSignal(source, scene, assetBuffers);
    for (let index = 0; index < sampleCount; index += 1) samples[index] += sourceSamples[index];
  }
  for (const ambient of scene.ambient ?? []) {
    const ambientSamples = renderSignal(ambient, scene, assetBuffers);
    for (let index = 0; index < sampleCount; index += 1) samples[index] += ambientSamples[index];
  }

  let preNormalizationPeak = 0;
  for (const value of samples) preNormalizationPeak = Math.max(preNormalizationPeak, Math.abs(value));
  const appliedScale =
    scene.mix?.normalization === "peak" && preNormalizationPeak > 0
      ? scene.mix.targetPeak / preNormalizationPeak
      : 1;
  let peak = 0;
  let clippedSampleCount = 0;
  for (let index = 0; index < samples.length; index += 1) {
    samples[index] *= appliedScale;
    peak = Math.max(peak, Math.abs(samples[index]));
    if (Math.abs(samples[index]) > 1) clippedSampleCount += 1;
  }
  return { samples, sampleRate: scene.sampleRate, preNormalizationPeak, appliedScale, peak, clippedSampleCount };
}