// The walk that reads a picked folder (src/engine/rollWalk.ts) is the part of a
// scan that can run for minutes, and its order is what the reader sees: the
// picked folder with its own frames, then every folder one layer down with
// theirs, then the layer below that — and the folder they just clicked in front
// of everything. None of that can be watched in a browser, so it is walked here
// over a stand-in tree.
//
//   node scripts/roll-walk-check.mjs
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import ts from 'typescript';

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

// A directory handle is only ever read for `values()` and `getDirectoryHandle()`,
// so a stand-in tree needs nothing else: `{ name: { … } }` for folders and
// `name: null` for a file. `@eaDir` and `.thumbnails` are the folders a real roll
// drags along.
const dir = (name, children) => ({
  kind: 'directory',
  name,
  values: async function* () {
    for (const [child, kids] of Object.entries(children)) {
      yield kids === null ? { kind: 'file', name: child } : dir(child, kids);
    }
  },
  getDirectoryHandle: async (part) => {
    if (!(part in children) || children[part] === null) throw new DOMException('not a folder', 'NotFoundError');
    return dir(part, children[part]);
  },
});
const keep = (name) => /\.(jpe?g|rw2)$/i.test(name);
// A walk is its root, its queue, and the folders it has read.
const at = (root, pending) => ({ root, pending, walked: new Set() });

const roll = dir('CheckRoll', {
  '.thumbnails': { hidden: null },
  '@eaDir': { junk: null },
  'P1.JPG': null,
  'Empty': { 'notes.txt': null },
  '2026': { 'P2.JPG': null, '04': { 'P3.RW2': null, 'notes.txt': null } },
  '2025': { 'P4.JPG': null },
});

// Walks to the end, one click per pass, which is what the browser does between
// passes: whatever the reader clicked last is what `jump` names. `seen` is the
// folders each pass named, which is what the column draws.
const walk = async (jumps = []) => {
  const tree = at(roll, [{ dir: roll, rel: '' }]);
  const out = [];
  let clicked = 0;
  let passes = 0;
  let walked = false;
  let seen = null;
  while (!walked) {
    const names = [];
    walked = await walkPass(tree, out, names, keep, () => jumps[clicked++] ?? null);
    passes++;
    seen ??= names;
  }
  return { out, names: seen, passes };
};

// Nothing clicked: the picked folder's own frames, then a layer down, then the
// deepest — a folder is never read before the folder that holds it. Every folder
// is named in the pass that finds it, which is how a row exists before its own
// frames do.
const { out, names, passes } = await walk();
const rels = out.map((f) => f.rel);
assert.deepEqual(rels, ['P1.JPG', '2025/P4.JPG', '2026/P2.JPG', '2026/04/P3.RW2'], 'layer by layer from the parent down');
assert.ok(
  rels.every((rel, i) => i === 0 || rel.split('/').length >= rels[i - 1].split('/').length),
  'no deeper frame is read before a shallower one'
);
assert.ok(!rels.some((rel) => /\.thumbnails|@eaDir|notes\.txt/.test(rel)), 'hidden and unsupported names are skipped');
assert.deepEqual(
  names,
  ['2025/', '2026/', 'Empty/', '2026/04/'],
  'the first pass names every folder it walked into, frames or no frames'
);
assert.ok(names.includes('Empty/'), 'a folder holding no frame at all is still a row');
assert.equal(passes, 1, 'a roll this size is one pass, and the names are in it');

// A click on a folder one layer down, while that layer is still to be read, puts
// it first: the frames the reader is looking at are read before the branch beside
// them.
const clicked = await walk([null, '2026/']);
assert.deepEqual(
  clicked.out.map((f) => f.rel),
  ['P1.JPG', '2026/P2.JPG', '2025/P4.JPG', '2026/04/P3.RW2'],
  'the clicked folder jumps the queue'
);

// A folder the walk has not reached yet — a row on screen from the parent pass —
// is opened from the picked folder and read next: `getDirectoryHandle` walks the
// path, and a path that will not open is left where it was.
const deep = at(roll, [{ dir: dir('Other', { 'X.JPG': null }), rel: 'other/' }]);
const deepOut = [];
await walkPass(deep, deepOut, [], keep, () => '2026/04/');
assert.deepEqual(
  deepOut.map((f) => f.rel),
  ['2026/04/P3.RW2', 'other/X.JPG'],
  'a folder the queue never held is opened and read first'
);
const missing = at(roll, [{ dir: roll, rel: '' }]);
await jumpQueue(missing, '2026/nope/');
assert.equal(missing.pending.length, 1, 'a path that does not open leaves the queue alone');

// And the rule without a browser around it: a pass reads the queue in its own
// order unless the click says otherwise.
const wide = dir('Wide', { a: { 'A.JPG': null }, b: { 'B.JPG': null } });
const before = [];
await walkPass(at(wide, [{ dir: wide, rel: '' }]), before, [], keep, () => null);
assert.deepEqual(before.map((f) => f.rel), ['a/A.JPG', 'b/B.JPG'], 'untouched, the folders are read in the order they were found');
const after = [];
await walkPass(at(wide, [{ dir: wide, rel: '' }]), after, [], keep, () => 'b/');
assert.deepEqual(after.map((f) => f.rel), ['b/B.JPG', 'a/A.JPG'], 'the folder the reader clicked is read first');

// A pass is bounded: a library wider than the budget is read over several passes,
// and the rest waits in the queue rather than in a loop that never yields.
const children = {};
for (let i = 0; i < DIRS_PER_PASS + 5; i++) children[`d${String(i).padStart(3, '0')}`] = { 'x.jpg': null };
const many = at(dir('Many', children), [{ dir: dir('Many', children), rel: '' }]);
const found = [];
assert.equal(await walkPass(many, found, [], keep, () => null), false, 'the queue is not empty after one pass');
assert.equal(found.length, DIRS_PER_PASS - 1, `one pass read the picked folder and ${DIRS_PER_PASS - 1} below it`);
assert.equal(many.pending.length, 6, 'the rest is left in the queue, for the next pass');

console.log(`ok   roll walk — ${rels.length} frames layer by layer, names a pass ahead, click jumps the queue, ${DIRS_PER_PASS} folders a pass`);