/**
 * ShimmerCue — the READY-RESEARCH attention cue, shared by the two
 * surfaces that wear it (the scene arms exactly one at a time — GameScene
 *._applyResearchCue keeps the cue on one screen):
 *
 *   - the command deck's RESEARCH slot (ActionBar.setShimmer) — while a
 *     tech can start, a yellow band sweeps the button's FACE, then a
 *     comet runs its cut-corner EDGE (face + edge);
 *   - the research console's category tabs (ResearchWindow._paintCues) —
 *     the same edge comet on every tab whose tree still holds an
 *     available tech (edge only; the tabs are the deck's button in
 *     miniature, without the face sweep).
 *
 * The cycle is a PURE function of the absolute clock (the PerimeterShimmer
 * idiom — a repaint mid-cycle never makes the cue jump):
 *
 *   periodMs = faceMs + gapMs + edgeMs + rest (the rest is silence);
 *   face — a soft yellow band + white-hot core crossing the face L→R;
 *   edge — a faint full-rim glow + a bright dash with a fading tail
 *          running one full lap around the cut-corner outline.
 *
 * `shimmerPhase` is pure (node-testable, dev/research-cue.test.mjs). The
 * draw helpers take ANY object with the Phaser Graphics surface they use
 * (fillStyle/fillRect/lineStyle/strokePoints) — a recorder suffices for
 * the tests; the arc math is PerimeterShimmer's own (perimeterPath /
 * arcPolyline), so the comet traces the SAME cut-corner polygon as the
 * plates (top-left + bottom-right notched).
 */
import { perimeterPath, arcPolyline } from './PerimeterShimmer.js';

/** `Number(v)` when finite, else `fallback` (config-safe). */
const num = (v, fallback) => {
  const n = Number(v);
  return Number.isFinite(n) ? n : fallback;
};

/**
 * The cycle's phase at `time` (see the header). Pure.
 * Returns { faceU, faceA, edgeU, edgeA } — `*U` the 0..1 position,
 * `*A` the 0..1 envelope (sine — zero at both ends of its window);
 * the inactive half carries a null position + zero envelope.
 * @param {number} time ms (the scene clock)
 * @param {object} cfg { periodMs, faceMs, gapMs, edgeMs }
 * @param {number} [offsetMs] a per-target phase offset (staggered rows)
 */
export function shimmerPhase(time, cfg = {}, offsetMs = 0) {
  const P = Math.max(400, num(cfg.periodMs, 4200));
  const faceMs = Math.max(0, num(cfg.faceMs, 700));
  const gapMs = Math.max(0, num(cfg.gapMs, 140));
  const edgeMs = Math.max(200, num(cfg.edgeMs, 1500));
  const ct = (((num(time, 0) + num(offsetMs, 0)) % P) + P) % P;
  const out = { faceU: null, faceA: 0, edgeU: null, edgeA: 0 };
  if (faceMs > 0 && ct < faceMs) {
    out.faceU = ct / faceMs;
    out.faceA = Math.sin(Math.PI * out.faceU);
  }
  const e0 = faceMs + gapMs;
  if (ct >= e0 && ct < e0 + edgeMs) {
    out.edgeU = (ct - e0) / edgeMs;
    out.edgeA = Math.sin(Math.PI * out.edgeU);
  }
  return out;
}

/**
 * One shimmer pass over the plate rect (x, y = top-left; w, h; `notch`
 * the corner-cut size, 0 = plain rectangle) into `g` (a Graphics, or a
 * recorder with fillStyle/fillRect/lineStyle/strokePoints).
 * @param {object} o { face?: boolean (default true — pass false for the
 *   tabs), dashFrac?: the comet's dash as a fraction of the perimeter }
 */
export function drawShimmer(g, x, y, w, h, notch, color, ph, o = {}) {
  if (!ph || w <= 0 || h <= 0) return;

  // FACE — the sweep band: a soft wide pass + a hot core + a 2 px white
  // line at the band's centre. The band travels from just off the left
  // edge to just off the right; its visible part is clamped to the face
  // (a Graphics has no clip — clamping IS the clip).
  if (o.face !== false && ph.faceA > 0.01) {
    const margin = Math.max(18, w * 0.25);
    const bx = x - margin + (w + 2 * margin) * ph.faceU;
    const band = Math.max(10, w * 0.18);
    let lo = Math.max(x, bx - band);
    let hi = Math.min(x + w, bx + band);
    if (hi > lo) {
      g.fillStyle(color, 0.16 * ph.faceA);
      g.fillRect(lo, y, hi - lo, h);
      lo = Math.max(x, bx - 3);
      hi = Math.min(x + w, bx + 3);
      if (hi > lo) {
        g.fillStyle(color, 0.5 * ph.faceA);
        g.fillRect(lo, y, hi - lo, h);
      }
      const c0 = Math.max(x, Math.min(x + w, bx - 1));
      const cw = Math.min(2, x + w - c0);
      if (cw > 0) {
        g.fillStyle(0xffffff, 0.55 * ph.faceA);
        g.fillRect(c0, y, cw, h);
      }
    }
  }

  // EDGE — the faint full-rim glow (the rim is "armed" while the comet
  // passes) + the comet itself: 3 tail→head bands of falling alpha, the
  // same comet as PerimeterShimmer's READY rim, one lap per cycle.
  if (o.edge !== false && ph.edgeA > 0.01) {
    const n = Math.max(0, Math.min(num(notch, 0), w / 2, h / 2));
    const { segs, P } = perimeterPath(x, y, w, h, n);
    const pts = [{ x: segs[0].ax, y: segs[0].ay }];
    for (const s of segs) pts.push({ x: s.bx, y: s.by });
    g.lineStyle(2, color, 0.28 * ph.edgeA);
    g.strokePoints(pts, true);
    const dashFrac = Math.min(0.5, Math.max(0.08, num(o.dashFrac, 0.3)));
    const head = (((ph.edgeU * P) % P) + P) % P;
    drawComet(g, segs, P, head, dashFrac * P, color, ph.edgeA);
  }
}

/** The comet: 3 tail→head bands, each a halo pass + a core pass. */
const BANDS = [0.16, 0.45, 1.0];
function drawComet(g, segs, P, head, dashLen, color, env) {
  const bandLen = dashLen / BANDS.length;
  for (let i = 0; i < BANDS.length; i++) {
    const d0 = head - dashLen + i * bandLen;
    const poly = arcPolyline(segs, P, d0, bandLen + 1e-6);
    if (poly.length < 2) continue;
    const a = env * BANDS[i];
    if (a < 0.004) continue;
    g.lineStyle(3.5, color, a * 0.3); // the halo (soft width, low alpha)
    g.strokePoints(poly, false);
    g.lineStyle(1.8, color, a); // the core
    g.strokePoints(poly, false);
  }
}