mdg-filius/packages/core/test/virtualFileSystem.test.ts

// The virtual file system against the Swift core: every case in
// vfs.cases.json runs in Swift (vfs.swift.json, tools/swift-oracle --vfs);
// each step's result or error and the final entries must match. The cases
// include the three Swift tests on the file system, ported as cases.

import { createHash } from 'node:crypto';
import { readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { describe, expect, it } from 'vitest';
import {
  VirtualFileSystem,
  VirtualFileSystemError,
  normalizedAbsolutePath,
  type VirtualFileContent,
  type VirtualFileEntry,
} from '../src/index.js';

interface Step {
  op: string;
  path?: string;
  to?: string;
  name?: string;
  text?: string;
  size?: number;
  byte?: number;
  mediaType?: string;
  recursive?: boolean;
  overwrite?: boolean;
  entries?: { path: string; kind: string; text?: string }[];
}

const here = dirname(fileURLToPath(import.meta.url));
const cases = JSON.parse(readFileSync(join(here, 'vfs.cases.json'), 'utf8')) as { name: string; steps: Step[] }[];
const swift = JSON.parse(readFileSync(join(here, 'vfs.swift.json'), 'utf8')) as {
  name: string;
  results: unknown[];
  entries: unknown[];
}[];

function describeEntries(entries: VirtualFileEntry[]): unknown[] {
  return entries.map(({ path, content }) => ({ path, ...describeContent(content) }));
}

function describeContent(content: VirtualFileContent): Record<string, unknown> {
  switch (content.kind) {
    case 'directory':
      return { kind: 'directory' };
    case 'text':
      return { kind: 'text', text: content.text };
    case 'binary':
    case 'image':
      return {
        kind: content.kind,
        bytes: content.data.length,
        mediaType: content.mediaType ?? null,
        sha256: createHash('sha256').update(content.data).digest('hex'),
      };
  }
}

function run(steps: Step[]) {
  let fileSystem = new VirtualFileSystem();
  const results: unknown[] = [];
  for (const step of steps) {
    const path = step.path ?? '/';
    const bytes = () => new Uint8Array(step.size ?? 0).fill(step.byte ?? 0);
    try {
      switch (step.op) {
        case 'createDirectory':
          fileSystem.createDirectory(path, step.recursive ?? false);
          break;
        case 'writeText':
          fileSystem.writeTextFile(path, step.text ?? '', step.overwrite ?? true);
          break;
        case 'writeBinary':
          fileSystem.writeBinaryFile(path, bytes(), step.mediaType, step.overwrite ?? true);
          break;
        case 'writeImage':
          fileSystem.writeImageFile(path, bytes(), step.mediaType ?? 'image/png', step.overwrite ?? true);
          break;
        case 'copy':
          fileSystem.copyItem(path, step.to ?? '/', step.overwrite ?? false);
          break;
        case 'move':
          fileSystem.moveItem(path, step.to ?? '/', step.overwrite ?? false);
          break;
        case 'rename':
          results.push({ ok: fileSystem.renameItem(path, step.name ?? '') });
          continue;
        case 'delete':
          fileSystem.deleteItem(path, step.recursive ?? false);
          break;
        case 'entry':
          results.push({ ok: describeEntries([fileSystem.entry(path)])[0] });
          continue;
        case 'entries':
          results.push({ ok: describeEntries(fileSystem.entries(path)) });
          continue;
        case 'text':
          results.push({ ok: fileSystem.textFile(path) });
          continue;
        case 'contains':
          results.push({ ok: fileSystem.contains(path) });
          continue;
        case 'normalize':
          results.push({ ok: normalizedAbsolutePath(path) });
          continue;
        case 'default':
          fileSystem = VirtualFileSystem.defaultForDevice();
          break;
        case 'fromEntries':
          fileSystem = VirtualFileSystem.fromEntries(
            (step.entries ?? []).map((entry) => ({
              path: entry.path,
              content: entry.kind === 'directory' ? { kind: 'directory' } : { kind: 'text', text: entry.text ?? '' },
            })),
          );
          break;
        default:
          throw new Error(`unknown step ${step.op}`);
      }
      results.push({ ok: true });
    } catch (error) {
      if (!(error instanceof VirtualFileSystemError)) throw error;
      results.push({ error: error.code, values: error.values });
    }
  }
  return { results, entries: describeEntries(fileSystem.allEntries()) };
}

describe('virtual file system against Swift', () => {
  it('covers every case', () => {
    expect(swift.map((result) => result.name)).toEqual(cases.map((item) => item.name));
  });

  cases.forEach((item, index) => {
    it(item.name, () => {
      const { results, entries } = run(item.steps);
      const expected = swift[index]!;
      results.forEach((result, step) => {
        expect(result, `step ${step + 1}: ${JSON.stringify(item.steps[step])}`).toEqual(expected.results[step]);
      });
      expect(entries).toEqual(expected.entries);
    });
  });
});

describe('virtual file system', () => {
  it('leaves itself unchanged when a copy breaks a quota (Swift test)', () => {
    const fileSystem = new VirtualFileSystem();
    const maximum = new Uint8Array(8 * 1024 * 1024).fill(0x41);
    for (const name of ['source', 'destination', 'third', 'fourth']) {
      fileSystem.writeBinaryFile(`/${name}.bin`, maximum, 'application/octet-stream');
    }
    const before = fileSystem.clone();

    expect(() => fileSystem.copyItem('/source.bin', '/new.bin', true)).toThrow(VirtualFileSystemError);
    expect(fileSystem.equals(before)).toBe(true);
  });

  it('upgrades the 1×1 black images of older versions, and only those', () => {
    const fileSystem = VirtualFileSystem.defaultForDevice();
    expect(fileSystem.upgradeLegacyDefaultImages()).toBe(0);
  });
});

describe("a file system's revision", () => {
  it('changes with every change, a removal too, and not with a reading', () => {
    const files = new VirtualFileSystem();
    const seen = [files.revision];
    files.createDirectory('/a');
    seen.push(files.revision);
    files.writeTextFile('/a/b.txt', 'x');
    seen.push(files.revision);
    files.renameInPlace('/a/b.txt', 'c.txt');
    seen.push(files.revision);
    files.deleteItem('/a/c.txt');
    seen.push(files.revision);
    files.allEntries();
    files.contains('/a');
    seen.push(files.revision);
    expect(new Set(seen.slice(0, 5)).size).toBe(5);
    expect(seen[5]).toBe(seen[4]);
  });
});