// Where the develop's white level comes from (src/engine/sensorWhite.ts). The
// probe reads the frame instead of trusting a constant: the plane's ceiling is
// 1.89-2.00x `maximum - black` and which one depends on the body, and a frame
// that sat below the desaturation's 0.95 start came out tinted (Fuji X-Trans,
// measured 1.892). These pin the two states it has to tell apart — a blown
// plateau (spike plus gap) and a bright smooth sky (a top bin no bigger than the
// ones under it) — and the fall-backs on frames with nothing to measure.
//
//   node scripts/white-level-check.mjs
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import ts from 'typescript';

const src = readFileSync(new URL('../src/engine/sensorWhite.ts', import.meta.url), 'utf8');
const js = ts.transpileModule(src, {
  compilerOptions: { module: ts.ModuleKind.ESNext, target: ts.ScriptTarget.ES2022 },
}).outputText;
const { sensorWhite } = await import(`data:text/javascript,${encodeURIComponent(js)}`);

const N = 1_000_000;
const MAXIMUM = 16383;
const BLACK = 512;
const LEGACY = 2 * (MAXIMUM - BLACK);
const FLOOR = 8192; // an unremarkable mid-tone the frame is mostly made of

// A frame of `N` mid-tone samples plus `counts` of them sitting in the nine bins
// from top-8 up to top: counts[8] is the top bin, counts[0] the one eight below.
function plane(top, counts) {
  const data = new Uint16Array(N);
  data.fill(FLOOR);
  let i = 0;
  for (let d = 0; d < 9; d++) for (let k = 0; k < counts[d]; k++) data[i++] = top - 8 + d;
  return data;
}

// The sensor's own plateau: a pile at the top with nine near-empty bins under it.
assert.equal(sensorWhite(plane(30995, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), 30995, 'X-Trans plateau missed');
assert.equal(sensorWhite(plane(31779, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), 31779, 'Sony plateau missed');
// ...and the body that really does sit at twice the white level is read as such,
// not as the constant it used to be. Same answer either way, which is the point:
// the probe does not need to know which body it has.
assert.equal(sensorWhite(plane(LEGACY, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), LEGACY);

// A smooth sky fills the bins around the top far more than a clipped one does,
// and its top bin is a tail, not a step: no gap, no clip, no move of the white.
assert.equal(
  sensorWhite(plane(30995, [400, 900, 1500, 2000, 2400, 2600, 2600, 2400, 2000]), MAXIMUM, BLACK),
  LEGACY,
  'a smooth top read as a clip'
);
// A bright flat wall sits exactly on one value with a big pile — but the bins
// under it are empty too, so that one IS a clip and is meant to move the white.
assert.equal(sensorWhite(plane(30995, [0, 0, 0, 0, 0, 0, 0, 0, 5000]), MAXIMUM, BLACK), 30995);

// Nothing to measure: a frame that never reached the plane's ceiling, and one
// whose only pile is a handful of hot pixels, both stay on the fixed factor two.
assert.equal(sensorWhite(plane(9000, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), LEGACY, 'an unblown frame moved the white');
assert.equal(sensorWhite(plane(30995, [0, 0, 0, 0, 0, 0, 0, 0, 5]), MAXIMUM, BLACK), LEGACY, 'hot pixels moved the white');

// A hot pixel above the plateau is not the ceiling: the window is hung off the
// pile, not off the frame's largest sample. Measured on a Panasonic DMC-LX10 RW2
// — a pile of 3.1M at 13855 with one sample at 15993 over it — reading the stray
// as the top left the nine bins under it empty, the frame fell back on the factor
// two (7908 against its own 13855) and opened 0.8 of a stop bright with its
// highlights clipped flat.
const strayed = new Uint16Array(N);
strayed.fill(FLOOR);
for (let i = 0; i < 400_000; i++) strayed[i] = 30995;
strayed[600_000] = 34000;
strayed[700_000] = 32400;
assert.equal(sensorWhite(strayed, MAXIMUM, BLACK), 30995, 'a stray sample above the plateau moved the white');

// The pile is a fraction of the plane, not a fixed count, so a small sensor with
// the same clipping is read the same way as a large one.
const small = new Uint16Array(100_000);
small.fill(FLOOR);
for (let i = 0; i < 40; i++) small[i] = 30995;
assert.equal(sensorWhite(small, MAXIMUM, BLACK), 30995, 'a small plane moved the threshold');

console.log('white-level-check ok');