// The WB preset table's two colour decisions, checked where they are made.
//
// A preset button is filled with temperatureSwatch(kelvin) and labelled in
// readableInk(fill). Both are one formula over the whole range, and both fail
// quietly in the direction nobody notices: a swatch that stops moving with K
// still looks like a swatch, and an ink that is merely the theme's text colour
// on a mid-grey fill is legible to whoever picked the theme and unreadable to
// everyone on the other one. So this walks the ruler and holds every swatch to
// WCAG's 4.5:1 against the ink it was given — plus the direction of the cast,
// which is the whole reason the fill is a colour rather than a name.
//
//   node scripts/wb-table-check.mjs
import assert from 'node:assert/strict';
import { mkdtempSync, readFileSync, writeFileSync } from 'node:fs';
import { tmpdir } from 'node:os';
import { join } from 'node:path';
import { fileURLToPath, pathToFileURL } from 'node:url';
import ts from 'typescript';

const transpile = (path) =>
  ts.transpileModule(readFileSync(new URL(path, import.meta.url), 'utf8'), {
    compilerOptions: { module: ts.ModuleKind.ESNext, target: ts.ScriptTarget.ES2022 },
  }).outputText;

// colorUtils imports types only, so the compiler drops that line itself.
const dir = mkdtempSync(join(tmpdir(), 'wb-table-check-'));
writeFileSync(join(dir, 'colorUtils.mjs'), transpile('../shared/utils/colorUtils.ts'));
const { readableInk, temperatureSwatch } = await import(pathToFileURL(join(dir, 'colorUtils.mjs')).href);

// WCAG contrast ratio between two #rrggbb colours.
const channel = (c) => (c <= 0.04045 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4));
const rel = (hex) => {
  const n = parseInt(hex.slice(1), 16);
  return 0.2126 * channel(((n >> 16) & 255) / 255) + 0.7152 * channel(((n >> 8) & 255) / 255) + 0.0722 * channel((n & 255) / 255);
};
const ratio = (a, b) => {
  const [hi, lo] = [rel(a), rel(b)].sort((x, y) => y - x);
  return (hi + 0.05) / (lo + 0.05);
};

const PRESETS = [5500, 5500, 5500, 6500, 7500, 3200, 4000]; // AUTO..FLUOR, WB_PRESETS' kelvins
const RULER = [...Array(151).keys()].map((i) => 2500 + i * 50);

// 1. The ink is always one of the two, and always the one that reads better.
const inkOf = (k) => readableInk(temperatureSwatch(k));
assert.ok(['#0b0e12', '#ffffff'].includes(readableInk('#808080')));
assert.ok(['#0b0e12', '#ffffff'].includes(readableInk('#000000')));
assert.ok(['#0b0e12', '#ffffff'].includes(readableInk('#ffffff')));
assert.equal(readableInk('#ffffff'), '#0b0e12', 'a white fill carries dark ink');
assert.equal(readableInk('#000000'), '#ffffff', 'a black fill carries light ink');
for (const fill of ['#7f7f7f', '#808080', '#517eff', '#947d61', '#e8e8e8', '#101010']) {
  const ink = readableInk(fill);
  const other = ink === '#ffffff' ? '#0b0e12' : '#ffffff';
  assert.ok(ratio(fill, ink) >= ratio(fill, other), `${fill}: ${ink} is not the better of the two`);
}

// 2. Every swatch on the ruler, and every preset's, clears 4.5:1 under its ink.
for (const k of [...RULER, ...PRESETS]) {
  const bg = temperatureSwatch(k);
  assert.match(bg, /^#[0-9a-f]{6}$/, `${k}K paints ${bg}`);
  const ink = readableInk(bg);
  const r = ratio(bg, ink);
  assert.ok(r >= 4.5, `${k}K: ${ink} on ${bg} is ${r.toFixed(2)}:1`);
}

// 3. The fill runs the way the ruler does: warmer as K rises, i.e. red up and
// blue down, so the table reads as a scale rather than seven greys.
const low = temperatureSwatch(2500);
const high = temperatureSwatch(10000);
const chan = (hex, shift) => (parseInt(hex.slice(1), 16) >> shift) & 255;
assert.ok(chan(low, 16) < chan(high, 16), `red does not rise: ${low} -> ${high}`);
assert.ok(chan(low, 0) > chan(high, 0), `blue does not fall: ${low} -> ${high}`);

// 4. And the fills collapse the way the kelvins do — five over the seven, since
// the three 5500K presets differ by TINT and the swatch is the temperature's.
const fills = new Set(PRESETS.map(temperatureSwatch));
assert.equal(fills.size, 5, `the presets paint ${fills.size} different fills`);

console.log(`wb table: ${RULER.length} swatches >= 4.5:1 under readableInk, ${low} -> ${high} across the ruler, ${fills.size} fills over 7 presets`);