/**
 * SPL Meter tiles.
 *
 * Four kinds, all fed by one SSE stream from the module's server:
 *
 *   readout      the number, big
 *   bars         one level bar per channel, with peak hold
 *   rta          spectrum now, folded to the banding this tile wants
 *   spectrogram  the same bands over time, either axis
 *
 * Nothing here measures anything. The capture child already sent every
 * averaging and the finest banding, and each tile folds that down to the
 * view it was configured for. That is the whole design: two dashboards can
 * watch one room through different settings without either disturbing the
 * measurement or the other dashboard.
 */

const FLOOR = -200;

/**
 * A dead input reads as a number, and a number on a wall is believed. Every
 * tile therefore refuses to draw a level while the server says the input is
 * digitally silent, and says why instead.
 */
function silentFor(payload) {
  return payload && payload.silentSec ? payload.silentSec : 0;
}

function silentText(sec) {
  if (sec < 90) return `No audio — ${sec} s`;
  const m = Math.round(sec / 60);
  return m < 90 ? `No audio — ${m} min` : `No audio — ${(m / 60).toFixed(1)} hours`;
}

/** Retention per frame for the RTA's smoothing setting. */
const SMOOTHING = { off: 0, light: 0.45, medium: 0.72, heavy: 0.9 };

export default function create({ root, moduleApi }) {
  const variant = moduleApi.variant || 'readout';
  let stream = null;
  let latest = null;
  let raf = 0;

  root.classList.add('spl');
  root.dataset.variant = variant;

  const view = buildView(variant, root, moduleApi);

  function onState(payload) {
    latest = payload;
    if (payload.error) {
      moduleApi.setStatus('error', payload.error);
    } else if (!payload.frame) {
      moduleApi.setStatus('connecting', 'waiting for the first reading');
    } else if (silentFor(payload)) {
      moduleApi.setStatus('error',
        `No audio on the chosen input — digital silence for ${silentText(silentFor(payload)).replace('No audio — ', '')}`);
    } else if (!payload.calibrated) {
      moduleApi.setStatus('ok', 'Measuring, but uncalibrated — these are dBFS, not dB SPL');
    } else {
      moduleApi.setStatus('ok', '');
    }
    // Frames land 20×/s; paint on a frame the browser was going to draw
    // anyway rather than fighting it for every one.
    if (!raf) raf = requestAnimationFrame(() => { raf = 0; view.render(latest); });
  }

  return {
    start() {
      moduleApi.setStatus('connecting', 'connecting');
      moduleApi.fetch('/state')
        .then((r) => r.json())
        .then(onState)
        .catch(() => { /* the stream will bring it */ });
      // Named events go under `events` — a top-level `state(ev)` is silently
      // never registered, and the tile just sits on whatever /state gave it.
      stream = moduleApi.sse('/stream', {
        events: {
          state(ev) {
            try { onState(JSON.parse(ev.data)); } catch { /* keep the last good frame */ }
          },
        },
        error() { moduleApi.setStatus('connecting', 'reconnecting'); },
      });
    },
    stop() {
      if (stream) { stream.close(); stream = null; }
      if (raf) { cancelAnimationFrame(raf); raf = 0; }
      view.destroy();
    },
    onResize() { view.resize(); },
  };
}

/* ── shared helpers ─────────────────────────────────────────────────── */

function pickChannel(payload, settings) {
  if (!payload || !payload.frame) return null;
  const want = Number(settings.channel);
  return payload.frame.ch.find((c) => c.i === want) || payload.frame.ch[0] || null;
}

/**
 * The level this tile asked for: an averaging, or one of the fixed metrics.
 *
 * Tiles saved by an earlier version carry metrics that no longer exist —
 * "spl" became an averaging, "leq" became Inf. A layout on a wall somewhere
 * must not start reading dashes because a setting was renamed, so those map
 * forward instead of falling through to undefined.
 */
const LEGACY_METRIC = { spl: 'level', leq: 'level' };
const LEGACY_AVERAGING = { leq: 'inf' };

function readValue(ch, settings) {
  const raw = settings.metric || 'level';
  const metric = LEGACY_METRIC[raw] || raw;
  if (metric !== 'level') {
    return metric in ch ? ch[metric] : ch.fast;
  }
  const avg = LEGACY_AVERAGING[raw] || settings.averaging || 'fast';
  return avg in ch ? ch[avg] : ch.fast;
}

function fmt(db) {
  if (!Number.isFinite(db) || db <= FLOOR) return '––.–';
  return db.toFixed(1);
}

function themeColor(el, name, fallback) {
  const v = getComputedStyle(el).getPropertyValue(name).trim();
  return v || fallback;
}

function hzLabel(f) {
  if (f >= 1000) {
    const k = f / 1000;
    return (k >= 10 ? Math.round(k) : Math.round(k * 10) / 10) + 'k';
  }
  return String(f >= 100 ? Math.round(f) : Math.round(f * 10) / 10);
}

/**
 * Fold the 1/48-octave bands on the wire down to this tile's banding.
 *
 * Every banding offered divides 48, so a coarser band is an exact sum of
 * finer ones in the power domain — no interpolation, no resampling. Groups
 * are keyed on the 1 kHz band (n = 0), which is what keeps folded centres on
 * the values an RTA is expected to show.
 *
 * @returns {{freq:number[], db:number[]}}
 */
function foldBands(bands, bandN0, perOctave, denom) {
  const g = Math.max(1, Math.round(perOctave / denom));
  const power = new Map();
  for (let i = 0; i < bands.length; i++) {
    const n = bandN0 + i;
    const k = Math.round(n / g);
    const p = 10 ** (bands[i] / 10);
    power.set(k, (power.get(k) || 0) + p);
  }
  const keys = [...power.keys()].sort((a, b) => a - b);
  return {
    freq: keys.map((k) => 1000 * 2 ** ((k * g) / perOctave)),
    db: keys.map((k) => 10 * Math.log10(Math.max(power.get(k), 1e-20))),
  };
}

/**
 * Which frequency labels fit, most important first.
 *
 * Decades earn their place before octaves, octaves before thirds, and
 * anything that would collide with a label already placed is dropped. That
 * is what makes the axis thin out as a tile shrinks instead of turning into
 * a smear.
 */
const LABEL_TIERS = [
  [100, 1000, 10000],
  [31.5, 63, 250, 500, 2000, 4000, 8000, 20000],
  [20, 40, 50, 80, 125, 160, 200, 315, 400, 630, 800, 1250, 1600, 2500, 3150, 5000, 6300, 12500, 16000],
];

function chooseLabels(freqs, positionOf, extent, minGapPx) {
  const placed = [];
  for (const tier of LABEL_TIERS) {
    for (const f of tier) {
      if (f < freqs[0] * 0.92 || f > freqs[freqs.length - 1] * 1.08) continue;
      const pos = positionOf(f);
      if (pos < 0 || pos > extent) continue;
      if (placed.some((p) => Math.abs(p.pos - pos) < minGapPx)) continue;
      placed.push({ f, pos });
    }
  }
  return placed.sort((a, b) => a.pos - b.pos);
}

/* ── views ──────────────────────────────────────────────────────────── */

function buildView(variant, root, moduleApi) {
  switch (variant) {
    case 'bars': return barsView(root, moduleApi);
    case 'rta': return spectrumView(root, moduleApi, false);
    case 'spectrogram': return spectrumView(root, moduleApi, true);
    default: return readoutView(root, moduleApi);
  }
}

function readoutView(root, moduleApi) {
  root.innerHTML = `
    <div class="spl-readout">
      <div class="spl-value"><span class="spl-num">––.–</span><span class="spl-unit">dB</span></div>
      <div class="spl-sub"></div>
    </div>`;
  const num = root.querySelector('.spl-num');
  const unit = root.querySelector('.spl-unit');
  const sub = root.querySelector('.spl-sub');
  const box = root.querySelector('.spl-readout');
  const value = root.querySelector('.spl-value');
  let fitKey = '';

  /**
   * Grow the number until it fills the tile, measuring the text we actually
   * have rather than assuming a digit count.
   *
   * The CSS can only guess at width — it has to pick a cqw coefficient for
   * some number of characters, and then "-100.5" overflows the tile that
   * "-45.9" merely filled. Measuring costs one layout read, and only when
   * the tile size or the length of the reading changes.
   */
  function fit() {
    const w = root.clientWidth, h = root.clientHeight;
    const key = `${w}x${h}:${num.textContent.length}:${unit.textContent}:${sub.hidden}`;
    if (key === fitKey || w < 2 || h < 2) return;
    fitKey = key;

    const TRIAL = 100;
    num.style.fontSize = `${TRIAL}px`;
    unit.style.fontSize = `${TRIAL * 0.26}px`;
    const natural = value.scrollWidth || 1;

    // Leave the caption its room when it is showing, and a little air either
    // way so descenders and the tile's padding never clip.
    const subH = sub.offsetParent ? sub.getBoundingClientRect().height + 6 : 0;
    const byHeight = (h - subH) * 0.92;
    const byWidth = ((w - 8) * TRIAL) / natural;
    const size = Math.max(12, Math.min(byHeight, byWidth));
    num.style.fontSize = `${size}px`;
    unit.style.fontSize = `${size * 0.26}px`;
  }

  return {
    render(payload) {
      const s = moduleApi.instanceSettings;
      const ch = pickChannel(payload, s);
      const quiet = silentFor(payload);
      if (quiet && ch) {
        num.textContent = '––.–';
        unit.textContent = '';
        sub.hidden = false;
        sub.textContent = silentText(quiet);
        box.dataset.level = 'dead';
        fit();
        return;
      }
      if (!payload || payload.error || !ch) {
        num.textContent = '––.–';
        sub.textContent = payload && payload.error ? payload.error : '';
        box.dataset.level = 'idle';
        fit();
        return;
      }
      const value = readValue(ch, s);
      num.textContent = fmt(value);
      unit.textContent = payload.calibrated ? 'dB' : 'dBFS';

      const warn = Number(s.warnAt), alarm = Number(s.alarmAt);
      box.dataset.level = !payload.calibrated ? 'idle'
        : value >= alarm ? 'alarm' : value >= warn ? 'warn' : 'ok';

      const raw = s.metric || 'level';
      const metric = LEGACY_METRIC[raw] || raw;
      const avg = LEGACY_AVERAGING[raw] || s.averaging || 'fast';
      const label = metric === 'level'
        ? ({ fast: 'Fast', slow: 'Slow', inf: 'Inf', none: 'No avg' }[avg] || 'Fast')
        : ({ leq1m: 'Leq 1 min', leq10m: 'Leq 10 min', peakC: 'Peak C' }[metric] || metric);
      const parts = [`${payload.weighting || '?'} · ${label}`, `ch ${ch.i}`];
      if (ch.clip) parts.push('CLIP');
      if (!payload.calibrated) parts.push('uncalibrated');
      sub.hidden = s.caption === false;
      sub.textContent = parts.join('  ·  ');
      fit();
    },
    resize() { fitKey = ''; fit(); },
    destroy() { root.innerHTML = ''; },
  };
}

function barsView(root, moduleApi) {
  root.innerHTML = '<div class="spl-bars"></div>';
  const host = root.querySelector('.spl-bars');
  let built = '';

  return {
    render(payload) {
      if (!payload || !payload.frame) { host.textContent = payload?.error || ''; built = ''; return; }
      const chans = payload.frame.ch;
      const key = chans.map((c) => c.i).join(',');
      if (key !== built) {
        built = key;
        host.innerHTML = chans.map((c) => `
          <div class="spl-bar" data-ch="${c.i}">
            <div class="spl-bar-label">${c.i}</div>
            <div class="spl-bar-track"><div class="spl-bar-fill"></div><div class="spl-bar-peak"></div></div>
            <div class="spl-bar-value">––.–</div>
          </div>`).join('');
      }
      const s = moduleApi.instanceSettings;
      const quiet = silentFor(payload);
      const warn = Number(s.warnAt), alarm = Number(s.alarmAt);
      const showPeak = s.peakHold !== false;
      const lo = payload.calibrated ? 40 : -80;
      const hi = payload.calibrated ? 110 : 0;
      for (const c of chans) {
        const el = host.querySelector(`.spl-bar[data-ch="${c.i}"]`);
        if (!el) continue;
        const value = readValue(c, { averaging: s.averaging });
        const pct = (v) => Math.max(0, Math.min(100, ((v - lo) / (hi - lo)) * 100));
        el.querySelector('.spl-bar-fill').style.width = quiet ? '0%' : `${pct(value)}%`;
        const peak = el.querySelector('.spl-bar-peak');
        peak.style.display = showPeak ? '' : 'none';
        if (showPeak) peak.style.left = `${pct(c.peakC)}%`;
        el.querySelector('.spl-bar-value').textContent = quiet ? '––.–' : fmt(value);
        el.dataset.level = quiet ? 'dead' : !payload.calibrated ? 'idle'
          : value >= alarm ? 'alarm' : value >= warn ? 'warn' : 'ok';
        el.classList.toggle('clip', !!c.clip);
      }
    },
    resize() {},
    destroy() { root.innerHTML = ''; },
  };
}

/**
 * RTA bars, or the same folded bands scrolling as a spectrogram.
 *
 * Canvas for both, because both redraw wholesale many times a second and a
 * few hundred animating DOM nodes is how a dashboard starts dropping frames
 * on the machine that is also running the service.
 */
function spectrumView(root, moduleApi, scrolling) {
  root.innerHTML = '<canvas class="spl-canvas"></canvas>';
  const canvas = root.querySelector('.spl-canvas');
  const ctx = canvas.getContext('2d', { alpha: false });
  /**
   * The spectrogram's scrolling history, on its own surface.
   *
   * It used to scroll by copying the visible canvas onto itself, which also
   * copied whatever had been drawn on top of it — so every frame dragged the
   * frequency labels and gridlines one step further along and left a smear.
   * Only measured pixels belong on a surface that scrolls; annotations are
   * drawn fresh over the top of it, every frame, and never into it.
   */
  let history = null;
  let historyCtx = null;
  let painted = false;          // spectrogram: has the history been cleared yet
  let smoothed = null;          // RTA: displayed values, damped toward the real ones
  let smoothedFor = '';
  let axisBtn = null;
  let axisOverride = null;      // set by the title-bar toggle, which never remounts us

  function axis() {
    return axisOverride || moduleApi.instanceSettings.axis || 'x';
  }

  if (scrolling) {
    // The axis lives here and nowhere else (rule 11): a tile does not offer
    // the same action twice. Icon only, tooltip carries the words (rule 9).
    // saveInstanceSettings deliberately does not remount us, so the new
    // value is held here as well and read back by axis().
    const swapIcon = '<svg viewBox="0 0 16 16" width="13" height="13" fill="none" '
      + 'stroke="currentColor" stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round">'
      + '<path d="M2 5h9M8.5 2 11.5 5 8.5 8"/><path d="M14 11H5M7.5 8 4.5 11 7.5 14"/></svg>';
    const describe = () => (axis() === 'x' ? 'Time left to right' : 'Time top to bottom');
    axisBtn = moduleApi.header.addButton({
      icon: swapIcon,
      title: describe(),
      onClick() {
        axisOverride = axis() === 'x' ? 'y' : 'x';
        moduleApi.saveInstanceSettings({ axis: axisOverride });
        painted = false;         // the picture means nothing in the other orientation
        axisBtn.title = describe();
      },
    });
  }

  function sizeCanvas() {
    const dpr = window.devicePixelRatio || 1;
    const w = Math.max(1, Math.floor(root.clientWidth));
    const h = Math.max(1, Math.floor(root.clientHeight));
    if (canvas.width === Math.floor(w * dpr) && canvas.height === Math.floor(h * dpr)) return false;
    canvas.width = Math.floor(w * dpr);
    canvas.height = Math.floor(h * dpr);
    canvas.style.width = `${w}px`;
    canvas.style.height = `${h}px`;
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    painted = false;
    return true;
  }
  sizeCanvas();

  function norm(db, calibrated) {
    const lo = calibrated ? 30 : -100;
    const hi = calibrated ? 110 : -10;
    return Math.max(0, Math.min(1, (db - lo) / (hi - lo)));
  }

  function heat(v) {
    const stops = [[10, 12, 20], [30, 90, 150], [90, 180, 140], [230, 190, 80], [220, 80, 60]];
    const x = Math.max(0, Math.min(0.999, v)) * (stops.length - 1);
    const i = Math.floor(x), t = x - i;
    const a = stops[i], b = stops[i + 1] || stops[i];
    return `rgb(${Math.round(a[0] + (b[0] - a[0]) * t)},${Math.round(a[1] + (b[1] - a[1]) * t)},${Math.round(a[2] + (b[2] - a[2]) * t)})`;
  }

  return {
    render(payload) {
      sizeCanvas();
      const w = canvas.clientWidth, h = canvas.clientHeight;
      const bg = themeColor(root, '--panel', '#141414');
      const muted = themeColor(root, '--muted', '#888');
      const border = themeColor(root, '--border', '#333');

      const quiet = silentFor(payload);
      if (quiet || !payload || !payload.frame || !payload.frame.bands) {
        ctx.fillStyle = bg; ctx.fillRect(0, 0, w, h);
        ctx.fillStyle = muted; ctx.font = '12px system-ui'; ctx.textAlign = 'center';
        ctx.fillText(quiet ? silentText(quiet)
                     : (payload?.error || 'Spectrum analysis is off'), w / 2, h / 2);
        painted = false;
        return;
      }

      const s = moduleApi.instanceSettings;
      const want = Number(s.channel);
      const idx = Math.max(0, payload.frame.ch.findIndex((c) => c.i === want));
      const raw = payload.frame.bands[idx] || payload.frame.bands[0] || [];
      if (!raw.length) return;

      const denom = Number(s.banding) || 3;
      const folded = foldBands(raw, payload.bandN0 || 0, payload.bandsPerOctave || 48, denom);
      const freqs = folded.freq;
      let values = folded.db;
      const grid = s.gridlines === true;
      const showLabels = s.labels !== false;
      const axisPad = showLabels || grid ? 13 : 0;

      if (!scrolling) {
        // Damp the bars toward the measurement. Cosmetic: `values` is what
        // gets drawn, never what gets reported.
        const keep = SMOOTHING[s.smoothing] ?? SMOOTHING.medium;
        const key = `${denom}:${values.length}`;
        if (smoothedFor !== key || !smoothed || smoothed.length !== values.length) {
          smoothed = values.slice();
          smoothedFor = key;
        } else if (keep > 0) {
          for (let i = 0; i < values.length; i++) {
            smoothed[i] = smoothed[i] * keep + values[i] * (1 - keep);
          }
        } else {
          smoothed = values.slice();
        }
        values = smoothed;

        ctx.fillStyle = bg; ctx.fillRect(0, 0, w, h);
        const plotH = h - axisPad;
        const bw = w / values.length;

        const xOf = (f) => (Math.log2(f / freqs[0]) / Math.log2(freqs[freqs.length - 1] / freqs[0])) * w;
        const labels = chooseLabels(freqs, xOf, w, 34);

        if (grid) {
          ctx.strokeStyle = border; ctx.lineWidth = 1; ctx.globalAlpha = 0.5;
          ctx.beginPath();
          for (const l of labels) {
            const x = Math.round(l.pos) + 0.5;
            ctx.moveTo(x, 0); ctx.lineTo(x, plotH);
          }
          for (let g = 0.2; g < 1; g += 0.2) {
            const y = Math.round(plotH * g) + 0.5;
            ctx.moveTo(0, y); ctx.lineTo(w, y);
          }
          ctx.stroke(); ctx.globalAlpha = 1;
        }

        for (let i = 0; i < values.length; i++) {
          const v = norm(values[i], payload.calibrated);
          const bh = v * plotH;
          ctx.fillStyle = heat(v);
          ctx.fillRect(i * bw, plotH - bh, Math.max(1, bw - (bw > 3 ? 1 : 0)), bh);
        }

        if (showLabels) {
          ctx.fillStyle = muted; ctx.font = '9px system-ui'; ctx.textAlign = 'center';
          for (const l of labels) ctx.fillText(hzLabel(l.f), l.pos, h - 3);
        }
        return;
      }

      // ── spectrogram ──
      const timeX = axis() === 'x';
      const colW = 2;
      // A label along the bottom needs only its line height; one down the
      // side has to fit "12.5k" beside the plot rather than on top of it.
      const gutter = (showLabels || grid) ? (timeX ? 30 : axisPad) : 0;
      // Labels belong beside the frequency axis: down the left when frequency
      // runs vertically, along the bottom when it runs horizontally.
      const plotX = timeX ? gutter : 0;
      const plotW = timeX ? w - gutter : w;
      const plotH = timeX ? h : h - gutter;
      const freqExtent = timeX ? plotH : plotW;
      const timeExtent = timeX ? plotW : plotH;
      if (plotW < 4 || plotH < 4) return;

      // The history surface is sized to the plot, in device pixels, and is
      // thrown away whenever that geometry changes — a scroll buffer means
      // nothing once it is being stretched into a different shape.
      const dpr = window.devicePixelRatio || 1;
      const needW = Math.max(1, Math.round(plotW * dpr));
      const needH = Math.max(1, Math.round(plotH * dpr));
      if (!history || history.width !== needW || history.height !== needH) {
        history = document.createElement('canvas');
        history.width = needW;
        history.height = needH;
        historyCtx = history.getContext('2d', { alpha: false });
        historyCtx.setTransform(dpr, 0, 0, dpr, 0, 0);
        painted = false;
      }
      if (!painted) {
        historyCtx.fillStyle = bg;
        historyCtx.fillRect(0, 0, plotW, plotH);
        painted = true;
      }

      // Scroll the history, then add the newest column. The source rectangle
      // is in device pixels and the destination in CSS pixels, because the
      // context carries the dpr transform but the canvas as an image source
      // does not.
      historyCtx.drawImage(history, 0, 0, history.width, history.height,
                           timeX ? -colW : 0, timeX ? 0 : -colW, plotW, plotH);

      const bandExtent = freqExtent / values.length;
      for (let i = 0; i < values.length; i++) {
        historyCtx.fillStyle = heat(norm(values[i], payload.calibrated));
        if (timeX) {
          // Low frequencies at the bottom, as every spectrogram has them.
          historyCtx.fillRect(timeExtent - colW, freqExtent - (i + 1) * bandExtent,
                              colW, Math.ceil(bandExtent) + 1);
        } else {
          // Low frequencies at the left.
          historyCtx.fillRect(i * bandExtent, timeExtent - colW,
                              Math.ceil(bandExtent) + 1, colW);
        }
      }

      // Repaint the visible canvas from scratch every frame: history first,
      // annotations over it. Nothing drawn here can ever reach the scroll.
      ctx.fillStyle = bg; ctx.fillRect(0, 0, w, h);
      ctx.drawImage(history, 0, 0, history.width, history.height,
                    plotX, 0, plotW, plotH);

      if (!grid && !showLabels) return;

      const span = Math.log2(freqs[freqs.length - 1] / freqs[0]);
      const posOf = (f) => {
        const t = Math.log2(f / freqs[0]) / span;
        return timeX ? plotH - t * plotH : plotX + t * plotW;
      };
      const labels = chooseLabels(freqs, posOf, timeX ? plotH : w, timeX ? 14 : 34);

      if (grid) {
        ctx.strokeStyle = border; ctx.lineWidth = 1; ctx.globalAlpha = 0.35;
        ctx.beginPath();
        for (const l of labels) {
          if (timeX) {
            const y = Math.round(l.pos) + 0.5;
            ctx.moveTo(plotX, y); ctx.lineTo(w, y);
          } else {
            const x = Math.round(l.pos) + 0.5;
            ctx.moveTo(x, 0); ctx.lineTo(x, plotH);
          }
        }
        ctx.stroke(); ctx.globalAlpha = 1;
      }

      if (showLabels) {
        ctx.fillStyle = muted; ctx.font = '9px system-ui';
        ctx.textAlign = timeX ? 'right' : 'center';
        for (const l of labels) {
          if (timeX) {
            ctx.fillText(hzLabel(l.f), gutter - 2,
                         Math.max(7, Math.min(h - 2, l.pos + 3)));
          } else {
            ctx.fillText(hzLabel(l.f), l.pos, h - 3);
          }
        }
      }
    },
    resize() { sizeCanvas(); },
    destroy() { root.innerHTML = ''; },
  };
}