// Web Audio player for the challenge wav files. The files are exact, unnormalized signals with a
// large crest factor (a strike transient followed by a much quieter ring), so this player applies a
// page-wide gain, with a per-challenge default, and an optional fast limiter so that the ring can be
// brought up without the transient clipping. Presentation only: nothing here touches the files.
//
// Usage: <div class="cplayer" data-src="audio/x.wav"></div> elements, then
//   ChallengePlayer.mount();                       upgrade every .cplayer on the page
//   ChallengePlayer.controls(el, {gainDb, limiter}) render the gain slider and limiter switch into el
//
// Each player can also show a spectrogram of its file, computed in the browser from the decoded
// samples (periodic Hann window of 2048 samples, hop 512, the same analysis as the spectrogram error
// measure), drawn in dB relative to the file's own maximum with a page-wide frequency limit and
// dynamic range. The playhead is drawn over it during playback.
(function () {
  "use strict";
  let audioCtx = null;
  let bus = null; // all players feed this
  let limiter = null;
  let limiterOn = true;
  let gainDb = 20;
  const players = [];
  const spec = { nfft: 2048, hop: 512, fmax: 12000, rangeDb: 80 };

  // ---------------------------------------------------------------- spectrogram analysis
  function fftReal(re, im) {
    // in-place iterative radix-2 complex FFT (re, im of equal power-of-two length)
    const n = re.length;
    for (let i = 1, j = 0; i < n; i++) {
      let bit = n >> 1;
      for (; j & bit; bit >>= 1) j ^= bit;
      j ^= bit;
      if (i < j) { let t = re[i]; re[i] = re[j]; re[j] = t; t = im[i]; im[i] = im[j]; im[j] = t; }
    }
    for (let len = 2; len <= n; len <<= 1) {
      const ang = -2 * Math.PI / len, wr = Math.cos(ang), wi = Math.sin(ang);
      for (let i = 0; i < n; i += len) {
        let cr = 1, ci = 0;
        for (let k = 0; k < len / 2; k++) {
          const a = i + k, b = a + len / 2;
          const tr = re[b] * cr - im[b] * ci, ti = re[b] * ci + im[b] * cr;
          re[b] = re[a] - tr; im[b] = im[a] - ti; re[a] += tr; im[a] += ti;
          const ncr = cr * wr - ci * wi; ci = cr * wi + ci * wr; cr = ncr;
        }
      }
    }
  }

  function spectrogramDb(samples, sampleRate) {
    const { nfft, hop } = spec;
    const nframes = Math.max(0, Math.floor((samples.length - nfft) / hop) + 1);
    const nbins = nfft / 2 + 1;
    const win = new Float32Array(nfft);
    for (let i = 0; i < nfft; i++) win[i] = 0.5 * (1 - Math.cos(2 * Math.PI * i / nfft));
    const db = new Float32Array(nframes * nbins);
    const re = new Float64Array(nfft), im = new Float64Array(nfft);
    let max = -Infinity;
    for (let f = 0; f < nframes; f++) {
      const o = f * hop;
      for (let i = 0; i < nfft; i++) { re[i] = samples[o + i] * win[i]; im[i] = 0; }
      fftReal(re, im);
      for (let k = 0; k < nbins; k++) {
        const v = 10 * Math.log10(re[k] * re[k] + im[k] * im[k] + 1e-30);
        db[f * nbins + k] = v;
        if (v > max) max = v;
      }
    }
    return { db, nframes, nbins, max, binHz: sampleRate / nfft, frameSec: hop / sampleRate, duration: samples.length / sampleRate };
  }

  // a compact inferno-like colormap: anchors interpolated linearly
  const CMAP = [[0, 0, 4], [40, 11, 84], [101, 21, 110], [159, 42, 99], [212, 72, 66], [245, 125, 21], [250, 193, 39], [252, 255, 164]];
  function color(u) {
    u = Math.max(0, Math.min(0.99999, u)) * (CMAP.length - 1);
    const i = Math.floor(u), t = u - i;
    const a = CMAP[i], b = CMAP[i + 1];
    return [a[0] + (b[0] - a[0]) * t, a[1] + (b[1] - a[1]) * t, a[2] + (b[2] - a[2]) * t];
  }

  function ctx() {
    if (!audioCtx) {
      audioCtx = new (window.AudioContext || window.webkitAudioContext)();
      bus = audioCtx.createGain();
      limiter = audioCtx.createDynamicsCompressor();
      limiter.threshold.value = -1;
      limiter.knee.value = 0;
      limiter.ratio.value = 20;
      limiter.attack.value = 0.001;
      limiter.release.value = 0.08;
      route();
    }
    return audioCtx;
  }

  function route() {
    bus.disconnect();
    limiter.disconnect();
    if (limiterOn) { bus.connect(limiter); limiter.connect(audioCtx.destination); }
    else bus.connect(audioCtx.destination);
  }

  function fmt(t) {
    if (!isFinite(t)) return "0.00";
    return t.toFixed(2);
  }

  class Player {
    constructor(el) {
      this.el = el;
      this.src = el.dataset.src;
      this.buffer = null;
      this.source = null;
      this.gain = null;
      this.startCtxTime = 0;
      this.offset = 0;
      this.playing = false;
      el.classList.add("cplayer-ready");
      el.innerHTML =
        '<button class="cp-btn" type="button" title="Play">&#9654;</button>' +
        '<input class="cp-seek" type="range" min="0" max="1000" value="0" step="1">' +
        '<span class="cp-time">0.00 / …</span>';
      el.insertAdjacentHTML("beforeend", '<button class="cp-spec-btn" type="button" title="Show or hide the spectrogram">spectrogram</button>');
      this.btn = el.querySelector(".cp-btn");
      this.seek = el.querySelector(".cp-seek");
      this.time = el.querySelector(".cp-time");
      this.specBtn = el.querySelector(".cp-spec-btn");
      this.specPanel = null; // created on demand, inserted after the player element
      this.specData = null;
      this.specImage = null; // {canvas, fmax, rangeDb}
      this.specBtn.addEventListener("click", () => this.toggleSpectrogram());
      this.btn.addEventListener("click", () => (this.playing ? this.pause() : this.play()));
      this.seek.addEventListener("input", () => {
        if (!this.buffer) return;
        const t = (this.seek.value / 1000) * this.buffer.duration;
        const was = this.playing;
        if (was) this.stopSource();
        this.offset = t;
        this.updateTime();
        if (was) this.startSource();
      });
      players.push(this);
    }

    async load() {
      if (this.buffer) return this.buffer;
      this.time.textContent = "loading…";
      const resp = await fetch(this.src);
      const data = await resp.arrayBuffer();
      this.buffer = await ctx().decodeAudioData(data);
      this.updateTime();
      return this.buffer;
    }

    startSource() {
      const c = ctx();
      this.gain = c.createGain();
      this.gain.gain.value = Math.pow(10, gainDb / 20);
      this.source = c.createBufferSource();
      this.source.buffer = this.buffer;
      this.source.connect(this.gain);
      this.gain.connect(bus);
      this.startCtxTime = c.currentTime;
      this.source.start(0, this.offset);
      this.playing = true;
      this.btn.innerHTML = "&#10074;&#10074;";
      this.btn.title = "Pause";
      this.source.onended = () => {
        if (this.playing && this.position() >= this.buffer.duration - 0.01) {
          this.playing = false;
          this.offset = 0;
          this.btn.innerHTML = "&#9654;";
          this.btn.title = "Play";
          this.updateTime();
        }
      };
      this.tick();
    }

    stopSource() {
      if (this.source) {
        this.offset = this.position();
        try { this.source.stop(); } catch (_) {}
        this.source.disconnect();
        this.gain.disconnect();
        this.source = null;
      }
      this.playing = false;
      this.btn.innerHTML = "&#9654;";
      this.btn.title = "Play";
    }

    position() {
      if (!this.playing || !this.source) return this.offset;
      return Math.min(this.buffer.duration, this.offset + (ctx().currentTime - this.startCtxTime));
    }

    async play() {
      for (const p of players) if (p !== this && p.playing) p.pause();
      await this.load();
      if (ctx().state === "suspended") await ctx().resume();
      if (this.offset >= this.buffer.duration - 0.01) this.offset = 0;
      this.startSource();
    }

    pause() { this.stopSource(); this.updateTime(); }

    setGain() { if (this.gain) this.gain.gain.value = Math.pow(10, gainDb / 20); }

    updateTime() {
      if (!this.buffer) return;
      const pos = this.position();
      this.seek.value = String(Math.round((pos / this.buffer.duration) * 1000));
      this.time.textContent = fmt(pos) + " / " + fmt(this.buffer.duration) + " s";
      if (!this.playing && this.specImage && this.specPanel.style.display !== "none") this.drawPlayhead();
    }

    tick() {
      if (!this.playing) return;
      this.updateTime();
      if (this.specPanel && this.specPanel.style.display !== "none") this.drawPlayhead();
      requestAnimationFrame(() => this.tick());
    }

    // ---------------------------------------------------------------- spectrogram display
    async toggleSpectrogram(force) {
      const show = typeof force === "boolean" ? force : !(this.specPanel && this.specPanel.style.display !== "none");
      if (!show) {
        if (this.specPanel) this.specPanel.style.display = "none";
        return;
      }
      if (!this.specPanel) {
        this.specPanel = document.createElement("div");
        this.specPanel.className = "cp-spec";
        this.specPanel.innerHTML = '<canvas class="cp-spec-canvas"></canvas><div class="cp-spec-note">computing…</div>';
        this.el.insertAdjacentElement("afterend", this.specPanel);
        this.canvas = this.specPanel.querySelector(".cp-spec-canvas");
        this.canvas.addEventListener("click", (ev) => {
          if (!this.buffer) return;
          const r = this.canvas.getBoundingClientRect();
          const t = ((ev.clientX - r.left - LEFT) / (r.width - LEFT)) * this.buffer.duration;
          if (t < 0) return;
          const was = this.playing;
          if (was) this.stopSource();
          this.offset = Math.min(this.buffer.duration, t);
          this.updateTime();
          if (was) this.startSource(); else this.drawPlayhead();
        });
      }
      this.specPanel.style.display = "";
      if (!this.specData) {
        await this.load();
        // yield so the "computing" note paints before the analysis runs
        await new Promise((r) => setTimeout(r, 0));
        this.specData = spectrogramDb(this.buffer.getChannelData(0), this.buffer.sampleRate);
      }
      this.renderSpectrogram();
    }

    renderSpectrogram() {
      if (!this.specData || !this.specPanel || this.specPanel.style.display === "none") return;
      const d = this.specData;
      const rows = Math.min(d.nbins, Math.ceil(spec.fmax / d.binHz));
      const img = document.createElement("canvas");
      img.width = d.nframes;
      img.height = rows;
      const ictx = img.getContext("2d");
      const data = ictx.createImageData(d.nframes, rows);
      const lo = d.max - spec.rangeDb;
      for (let f = 0; f < d.nframes; f++) {
        for (let k = 0; k < rows; k++) {
          const u = (d.db[f * d.nbins + k] - lo) / spec.rangeDb;
          const c = color(u);
          const o = 4 * ((rows - 1 - k) * d.nframes + f);
          data.data[o] = c[0]; data.data[o + 1] = c[1]; data.data[o + 2] = c[2]; data.data[o + 3] = 255;
        }
      }
      ictx.putImageData(data, 0, 0);
      this.specImage = { canvas: img, rows };
      this.drawPlayhead();
      this.specPanel.querySelector(".cp-spec-note").textContent =
        "Hann 2048, hop 512; 0 to " + (rows * d.binHz / 1000).toFixed(1) + " kHz; " + spec.rangeDb + " dB below the file's maximum. Click to seek.";
    }

    drawPlayhead() {
      if (!this.specImage) return;
      const c = this.canvas;
      const W = Math.max(300, Math.floor(c.parentElement.clientWidth || 600)), H = 170;
      if (c.width !== W || c.height !== H) { c.width = W; c.height = H; }
      const g = c.getContext("2d");
      const d = this.specData, rows = this.specImage.rows;
      const x0 = LEFT, y1 = H - BOTTOM, pw = W - x0, ph = y1;
      g.fillStyle = getComputedStyle(document.body).backgroundColor || "#fff";
      g.fillRect(0, 0, W, H);
      g.imageSmoothingEnabled = false;
      g.drawImage(this.specImage.canvas, x0, 0, pw, ph);
      // axes
      const fg = getComputedStyle(document.body).color || "#000";
      g.fillStyle = fg; g.strokeStyle = fg; g.font = "10px system-ui, sans-serif";
      g.textAlign = "right"; g.textBaseline = "middle";
      const fmaxShown = rows * d.binHz;
      const fstep = fmaxShown > 15000 ? 5000 : fmaxShown > 7000 ? 2000 : 1000;
      for (let fr = 0; fr <= fmaxShown + 1; fr += fstep) {
        const y = y1 - (fr / fmaxShown) * ph;
        if (y < 6) continue;
        g.fillText((fr / 1000).toFixed(0) + "k", x0 - 3, y);
        g.beginPath(); g.moveTo(x0 - 2, y); g.lineTo(x0, y); g.stroke();
      }
      g.textAlign = "center"; g.textBaseline = "top";
      const tstep = d.duration > 4 ? 1 : 0.5;
      const tspan = d.nframes * d.frameSec;
      for (let t = 0; t <= tspan + 1e-9; t += tstep) {
        const x = x0 + (t / tspan) * pw;
        g.fillText(t.toFixed(tstep < 1 ? 1 : 0) + " s", x, y1 + 3);
        g.beginPath(); g.moveTo(x, y1); g.lineTo(x, y1 + 2); g.stroke();
      }
      // playhead
      if (this.buffer) {
        const x = x0 + (this.position() / tspan) * pw;
        g.strokeStyle = "rgba(255,255,255,0.9)"; g.lineWidth = 1.5;
        g.beginPath(); g.moveTo(x, 0); g.lineTo(x, y1); g.stroke();
        g.lineWidth = 1;
      }
    }
  }
  const LEFT = 30, BOTTOM = 16;
  window.addEventListener("resize", () => { for (const p of players) if (p.specImage) p.drawPlayhead(); });

  const style = document.createElement("style");
  style.textContent =
    ".cplayer{display:inline-flex;align-items:center;gap:6px;font-size:0.85em;white-space:nowrap}" +
    ".cp-btn{font:inherit;width:2em;padding:2px 0;cursor:pointer}.cp-seek{width:110px}" +
    ".cp-controls{display:flex;flex-wrap:wrap;gap:14px;align-items:center;margin:8px 0}.cp-controls label{display:flex;gap:6px;align-items:center}" +
    ".cp-spec-btn{font:inherit;font-size:0.9em;padding:2px 6px;cursor:pointer}" +
    ".cp-spec{display:block;margin:4px 0 6px;min-width:320px}.cp-spec canvas{display:block;width:100%;height:170px;cursor:crosshair}" +
    ".cp-spec-note{font-size:0.78em;opacity:0.7;margin-top:2px}";
  document.head.appendChild(style);

  window.ChallengePlayer = {
    mount(root) {
      (root || document).querySelectorAll(".cplayer:not(.cplayer-ready)").forEach((el) => new Player(el));
    },
    setGain(db) {
      gainDb = db;
      for (const p of players) p.setGain();
    },
    setLimiter(on) {
      limiterOn = !!on;
      if (audioCtx) route();
    },
    setSpectrogram(opts) {
      if (typeof opts.fmax === "number") spec.fmax = opts.fmax;
      if (typeof opts.rangeDb === "number") spec.rangeDb = opts.rangeDb;
      for (const p of players) p.renderSpectrogram();
    },
    showSpectrograms(on) {
      for (const p of players) p.toggleSpectrogram(!!on);
    },
    controls(el, opts) {
      opts = opts || {};
      if (typeof opts.gainDb === "number") gainDb = opts.gainDb;
      if (typeof opts.limiter === "boolean") limiterOn = opts.limiter;
      el.classList.add("cp-controls");
      el.innerHTML =
        '<label>Playback gain <input class="cp-gain" type="range" min="0" max="60" step="1"> <span class="cp-gain-label"></span></label>' +
        '<label><input class="cp-lim" type="checkbox"> limiter</label>' +
        '<span class="cp-note">The wav files are exact physical signals with a loud strike and a quiet ring; the gain and limiter apply to playback only.</span>' +
        '<span class="cp-break" style="flex-basis:100%;height:0"></span>' +
        '<label>Spectrograms <button class="cp-spec-all" type="button">show all</button> <button class="cp-spec-none" type="button">hide all</button></label>' +
        '<label>up to <select class="cp-spec-fmax"><option value="3000">3 kHz</option><option value="6000">6 kHz</option><option value="12000" selected>12 kHz</option><option value="24000">24 kHz</option></select></label>' +
        '<label>range <select class="cp-spec-range"><option value="60">60 dB</option><option value="80" selected>80 dB</option><option value="100">100 dB</option><option value="120">120 dB</option></select></label>';
      const g = el.querySelector(".cp-gain"), gl = el.querySelector(".cp-gain-label"), lim = el.querySelector(".cp-lim");
      el.querySelector(".cp-spec-all").addEventListener("click", () => window.ChallengePlayer.showSpectrograms(true));
      el.querySelector(".cp-spec-none").addEventListener("click", () => window.ChallengePlayer.showSpectrograms(false));
      const fm = el.querySelector(".cp-spec-fmax"), rg = el.querySelector(".cp-spec-range");
      fm.value = String(spec.fmax); rg.value = String(spec.rangeDb);
      fm.addEventListener("change", () => window.ChallengePlayer.setSpectrogram({ fmax: parseFloat(fm.value) }));
      rg.addEventListener("change", () => window.ChallengePlayer.setSpectrogram({ rangeDb: parseFloat(rg.value) }));
      g.value = String(gainDb);
      lim.checked = limiterOn;
      const upd = () => { gl.textContent = "+" + g.value + " dB"; };
      g.addEventListener("input", () => { upd(); window.ChallengePlayer.setGain(parseFloat(g.value)); });
      lim.addEventListener("change", () => window.ChallengePlayer.setLimiter(lim.checked));
      upd();
    },
  };
})();