arthur/frontend/test/parity/oracle.mjs

// Runs the JS prototype — the numeric oracle — and writes its answers to JSON
// for arthur.parity-test to diff against the CLJS port.
//
// DELETABLE. This file and arthur.parity-test go together, in one commit, once
// the CLJS player renders the synthetic take correctly (port-plan step 5). A
// parity test pins behaviour while the code moves; keeping it afterwards would
// bake the prototype's mistakes into the rewrite and make them permanent.
//
// Math.random is stubbed to a constant so both sides get the IDENTICAL track:
// js/synth.js reads Math.random at call time, not at import time, so assigning
// it here — before synthDense is called below — is enough, and js/ stays
// untouched. 0.5 makes every (Math.random() - 0.5) jitter term exactly zero,
// which is also what `:rand-fn (constantly 0.5)` does on the CLJS side.
Math.random = () => 0.5;

import { writeFileSync } from 'node:fs';
import { fileURLToPath } from 'node:url';
import { dirname, join } from 'node:path';

import { RIGID, LIPS_OUTER, EYE_R_RING, BROW_A_RING, FACE_OVAL,
         subsampleSlots } from '../../../js/landmarks.js';
import { fitSimilarity, applySim, fitResidual, procrustesMean,
         movingAverage, smoothTransforms, offsetRing } from '../../../js/mathutil.js';
import { synthDense } from '../../../js/synth.js';
import { IndexedRaster, hexToRgb } from '../../../js/raster.js';

const FRAMES = 72;
const track = synthDense(FRAMES);
const rigid = track.map((f) => RIGID.map((i) => f[i]));

// The two the port plan names explicitly, plus everything else in mathutil.js:
// a function nobody diffed is a function nobody ported.
const ref = procrustesMean(rigid);
const tfs = rigid.map((r) => fitSimilarity(r, ref));

const strip = (p) => ({ x: p.x, y: p.y, z: p.z ?? 0 });
const stripTf = (t) => ({ s: t.s, theta: t.theta, tx: t.tx, ty: t.ty });

// A known transform recovered exactly, which is the same case the CLJS unit test
// asserts — here so a disagreement can be localised to the fit rather than to
// the track.
const knownSrc = [{ x: 0, y: 0 }, { x: 1, y: 0 }, { x: 0, y: 1 }, { x: 2, y: 3 }];
const knownTruth = { s: 1.7, theta: 0.6, tx: 4, ty: -2 };
const knownDst = knownSrc.map((p) => applySim(knownTruth, p));

const out = {
  frames: FRAMES,
  track: track.map((f) => f.map(strip)),
  rigidRef: ref.map(strip),
  transforms: tfs.map(stripTf),
  residuals: rigid.map((r, i) => fitResidual(tfs[i], r, ref)),
  smoothed: [0, 1, 2, 5].map((radius) => ({
    radius, tfs: smoothTransforms(tfs, radius).map(stripTf),
  })),
  known: { src: knownSrc, truth: knownTruth, dst: knownDst,
           fit: stripTf(fitSimilarity(knownSrc, knownDst)) },
  // tx over the shot is the sway; it is the one-dimensional series the smoothing
  // knob actually acts on, so it is what movingAverage gets diffed on.
  movingAverage: [0, 1, 2, 3, 7].map((radius) => ({
    radius, vals: movingAverage(tfs.map((t) => t.tx), radius),
  })),
  offsetRing: [0, 0.5, 2, -1].map((d) => ({
    d,
    ring: offsetRing(LIPS_OUTER.map((i) => track[0][i]), d).map(strip),
    // The degenerate case: a shut lid is a flat sliver and must still open into
    // a band, and a ring collapsed onto its own centroid must not emit NaN.
    shutLid: offsetRing([{ x: -10, y: 0 }, { x: 0, y: -0.02 },
                         { x: 10, y: 0 }, { x: 0, y: 0.02 }], d).map(strip),
    collapsed: offsetRing([{ x: 0, y: 0 }, { x: 0, y: 0 }, { x: 0, y: 0 }], d).map(strip),
  })),
  subsampleSlots: Object.fromEntries(
    [[20, 4], [20, 6], [20, 8], [20, 10], [20, 16], [16, 4], [16, 6], [16, 12],
     [10, 4], [10, 6], [10, 10], [36, 8]]
      .map(([len, n]) => [`${len}/${n}`, subsampleSlots(len, n)])),
  tables: { RIGID, LIPS_OUTER, EYE_R_RING, BROW_A_RING, FACE_OVAL },
  // The raster is integer output, so parity here is EXACT equality, not 1e-9.
  // One scanline drawn one pixel wide of the JS would read as a seam between two
  // parts rather than as an error, which is why the whole buffer is diffed and
  // not a pixel count.
  //
  // toImageData is not exercised: it needs an ImageData, the CLJS side returns
  // plain bytes on purpose so domain/ stays DOM-free, and the palette expansion
  // is asserted directly in arthur.domain.raster-test instead.
  raster: (() => {
    const r = new IndexedRaster(64, 48);
    r.clear(0);
    // A real mouth ring at raster scale, so the scanline fill is diffed on a
    // shape with fractional coordinates and non-convex spans rather than on an
    // axis-aligned box that would agree even if the rounding were wrong.
    r.fillPoly(LIPS_OUTER.map((i) => ({ x: track[0][i].x * 320 - 100,
                                        y: track[0][i].y * 200 - 40 })), 2);
    r.fillPoly([{ x: 8.5, y: 8.5 }, { x: 56.25, y: 8.5 },
                { x: 56.25, y: 40.75 }, { x: 8.5, y: 40.75 }], 1);
    r.fillDisc(30.4, 24.6, 9.2, 3, 1);        // stencilled by the box
    r.fillDisc(5.5, 44.5, 4, 4);              // unstencilled, clipped by the edge
    r.fillRect(30.49, 24.51, 3, 5, 3);        // stencilled by the disc
    r.fillRect(1, 1, 0, 6);                   // size 0 draws nothing
    return { w: r.w, h: r.h, buf: Array.from(r.buf) };
  })(),
  paletteRgb: ['#12141c', '#b07a5a', '#7a4f3a', '#24161a', '#d9cfc2',
               '#c9c3b4', '#4a5468', '#171a22', '#3a2a22'].map(hexToRgb),
};

const here = dirname(fileURLToPath(import.meta.url));
const path = join(here, 'oracle.json');
writeFileSync(path, JSON.stringify(out));
console.log(`oracle: ${FRAMES} frames -> ${path}`);