declare global {
  interface Window {
    webkitAudioContext?: typeof AudioContext;
  }
}

let audioCtx: AudioContext | null = null;

function getCtx(): AudioContext | null {
  if (typeof window === "undefined") return null;
  const AudioCtor = window.AudioContext ?? window.webkitAudioContext;
  if (!AudioCtor) return null;
  if (!audioCtx) audioCtx = new AudioCtor();
  if (audioCtx.state === "suspended") void audioCtx.resume();
  return audioCtx;
}

type ToneOptions = {
  readonly frequency: number;
  readonly endFrequency?: number;
  readonly duration: number;
  readonly type?: OscillatorType;
  readonly volume?: number;
  readonly delay?: number;
};

function playTone(ctx: AudioContext, options: ToneOptions): void {
  const { frequency, endFrequency, duration, type = "sine", volume = 0.2, delay = 0 } = options;
  const oscillator = ctx.createOscillator();
  const gain = ctx.createGain();
  const startAt = ctx.currentTime + delay;
  oscillator.type = type;
  oscillator.frequency.setValueAtTime(Math.max(frequency, 1), startAt);
  if (endFrequency !== undefined && endFrequency !== frequency) {
    oscillator.frequency.exponentialRampToValueAtTime(
      Math.max(endFrequency, 1),
      startAt + duration,
    );
  }
  gain.gain.setValueAtTime(0.0001, startAt);
  gain.gain.exponentialRampToValueAtTime(volume, startAt + 0.012);
  gain.gain.exponentialRampToValueAtTime(0.0001, startAt + duration);
  oscillator.connect(gain);
  gain.connect(ctx.destination);
  oscillator.start(startAt);
  oscillator.stop(startAt + duration + 0.05);
}

function playNoise(
  ctx: AudioContext,
  options: { readonly duration: number; readonly volume?: number; readonly lowpass?: number },
): void {
  const { duration, volume = 0.2, lowpass = 800 } = options;
  const bufferSize = Math.max(1, Math.floor(ctx.sampleRate * duration));
  const buffer = ctx.createBuffer(1, bufferSize, ctx.sampleRate);
  const data = buffer.getChannelData(0);
  for (let index = 0; index < bufferSize; index += 1) {
    data[index] = Math.random() * 2 - 1;
  }
  const source = ctx.createBufferSource();
  source.buffer = buffer;
  const filter = ctx.createBiquadFilter();
  filter.type = "lowpass";
  filter.frequency.setValueAtTime(lowpass, ctx.currentTime);
  const gain = ctx.createGain();
  gain.gain.setValueAtTime(0.0001, ctx.currentTime);
  gain.gain.exponentialRampToValueAtTime(volume, ctx.currentTime + 0.005);
  gain.gain.exponentialRampToValueAtTime(0.0001, ctx.currentTime + duration);
  source.connect(filter);
  filter.connect(gain);
  gain.connect(ctx.destination);
  source.start();
}

export function playFire(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, {
    frequency: 180,
    endFrequency: 90,
    duration: 0.055,
    type: "square",
    volume: 0.12,
  });
}

export function playHeadshot(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, {
    frequency: 720,
    endFrequency: 1180,
    duration: 0.12,
    type: "triangle",
    volume: 0.16,
  });
  playTone(ctx, { frequency: 1040, duration: 0.16, type: "sine", volume: 0.12, delay: 0.06 });
}

export function playTorsoHit(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, {
    frequency: 360,
    endFrequency: 220,
    duration: 0.1,
    type: "triangle",
    volume: 0.15,
  });
}

export function playCivilianHit(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, {
    frequency: 300,
    endFrequency: 140,
    duration: 0.22,
    type: "sawtooth",
    volume: 0.16,
  });
  playNoise(ctx, { duration: 0.12, volume: 0.12, lowpass: 520 });
}

export function playMiss(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, {
    frequency: 120,
    endFrequency: 55,
    duration: 0.18,
    type: "sawtooth",
    volume: 0.14,
  });
  playNoise(ctx, { duration: 0.11, volume: 0.11, lowpass: 480 });
}

export function playCountdownTick(critical = false): void {
  const ctx = getCtx();
  if (!ctx) return;
  const frequency = critical ? 880 : 520;
  playTone(ctx, { frequency, duration: critical ? 0.09 : 0.06, type: "square", volume: 0.1 });
}

export function playRoundComplete(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, { frequency: 420, duration: 0.12, type: "triangle", volume: 0.14 });
  playTone(ctx, { frequency: 630, duration: 0.12, type: "triangle", volume: 0.14, delay: 0.1 });
  playTone(ctx, { frequency: 940, duration: 0.24, type: "sine", volume: 0.16, delay: 0.2 });
}

export function playXp(): void {
  const ctx = getCtx();
  if (!ctx) return;
  playTone(ctx, { frequency: 660, duration: 0.09, type: "sine", volume: 0.18 });
  playTone(ctx, { frequency: 880, duration: 0.16, type: "sine", volume: 0.18, delay: 0.09 });
}