/**
 * FIT-001: no core package imports a concrete extension.
 *
 * Architecture guard (CI-enforced, see .gitea/workflows/ci.yml):
 *   - a "concrete extension" is any workspace package under extensions/
 *   - code under packages/ (the core packages) must never import one, neither
 *     by package name nor by a relative path that resolves into extensions/
 *
 * The rule is discovered from the filesystem, so adding an extension package
 * under extensions/ automatically extends the guard; no manifest edits needed.
 */
import { describe, expect, it } from 'vitest';
import { readdirSync, readFileSync, existsSync } from 'node:fs';
import { dirname, isAbsolute, join, relative, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';

const repoRoot = resolve(fileURLToPath(new URL('..', import.meta.url)));
const packagesRoot = join(repoRoot, 'packages');
const extensionsRoot = join(repoRoot, 'extensions');

interface ExtensionInfo {
  /** Absolute path of the extension package directory. */
  dir: string;
  /** Package name from its manifest (e.g. "@personal-blog/example-extension"). */
  name: string;
}

/** True when `candidate` is `parent` itself or lies inside it. */
function isWithin(parent: string, candidate: string): boolean {
  const rel = relative(parent, candidate);
  return rel === '' || (!rel.startsWith('..') && !isAbsolute(rel));
}

function findExtensionPackages(): ExtensionInfo[] {
  if (!existsSync(extensionsRoot)) {
    return [];
  }
  return readdirSync(extensionsRoot, { withFileTypes: true })
    .filter((entry) => entry.isDirectory())
    .map((entry): ExtensionInfo | null => {
      const manifestPath = join(extensionsRoot, entry.name, 'package.json');
      if (!existsSync(manifestPath)) {
        return null;
      }
      const manifest = JSON.parse(readFileSync(manifestPath, 'utf8')) as {
        name?: string;
      };
      return manifest.name ? { dir: join(extensionsRoot, entry.name), name: manifest.name } : null;
    })
    .filter((info): info is ExtensionInfo => info !== null);
}

/** Matches static imports, side-effect imports, dynamic imports and require. */
const IMPORT_SPECIFIER_RE = /(?:from\s*|import\s*\(\s*|require\s*\(\s*|import\s+)(['"])([^'"]+)\1/g;

function extractImportSpecifiers(source: string): string[] {
  return [...source.matchAll(IMPORT_SPECIFIER_RE)]
    .map((match) => match[2] ?? '')
    .filter((specifier) => specifier.length > 0);
}

/** True when `specifier` targets a concrete extension from `importerFile`. */
function isExtensionImport(
  specifier: string,
  importerFile: string,
  extensions: ExtensionInfo[],
): boolean {
  for (const ext of extensions) {
    if (specifier === ext.name || specifier.startsWith(`${ext.name}/`)) {
      return true;
    }
  }
  if (specifier.startsWith('.')) {
    const resolved = resolve(dirname(importerFile), specifier);
    if (isWithin(extensionsRoot, resolved)) {
      return true;
    }
  }
  return false;
}

function listSourceFiles(dir: string): string[] {
  if (!existsSync(dir)) {
    return [];
  }
  const files: string[] = [];
  for (const entry of readdirSync(dir, { withFileTypes: true })) {
    const path = join(dir, entry.name);
    if (entry.isDirectory()) {
      files.push(...listSourceFiles(path));
    } else if (entry.isFile() && /\.(?:[cm]?ts|tsx)$/.test(entry.name) && !entry.name.endsWith('.d.ts')) {
      files.push(path);
    }
  }
  return files;
}

describe('FIT-001: no core package imports a concrete extension', () => {
  const extensions = findExtensionPackages();

  it('finds at least one concrete extension package to check against', () => {
    // Guards against a vacuous pass when extensions/ is empty.
    expect(extensions.length).toBeGreaterThan(0);
  });

  it('packages/* sources import no concrete extension', () => {
    const violations: string[] = [];
    for (const file of listSourceFiles(packagesRoot)) {
      const source = readFileSync(file, 'utf8');
      for (const specifier of extractImportSpecifiers(source)) {
        if (isExtensionImport(specifier, file, extensions)) {
          violations.push(
            `${relative(repoRoot, file)}: import "${specifier}" targets concrete extension "${extensions
              .filter((ext) => isExtensionImport(specifier, file, [ext]))
              .map((ext) => ext.name)
              .join(', ')}"`,
          );
        }
      }
    }
    expect(violations).toEqual([]);
  });

  it('detector rejects extension imports and accepts benign imports (sanity)', () => {
    const ext = extensions[0];
    expect(ext, 'expected at least one extension package').toBeDefined();
    if (!ext) {
      return;
    }
    const importer = join(packagesRoot, 'core', 'src', 'index.ts');

    // By package name (bare and subpath).
    expect(isExtensionImport(ext.name, importer, extensions)).toBe(true);
    expect(isExtensionImport(`${ext.name}/server`, importer, extensions)).toBe(true);
    // By relative path resolving into extensions/.
    expect(
      isExtensionImport(relative(dirname(importer), join(ext.dir, 'src', 'index.js')), importer, extensions),
    ).toBe(true);
    // Benign imports must pass.
    expect(isExtensionImport('node:test', importer, extensions)).toBe(false);
    expect(isExtensionImport('vitest', importer, extensions)).toBe(false);
    expect(isExtensionImport('@personal-blog/core', importer, extensions)).toBe(false);
    expect(isExtensionImport('./site.js', importer, extensions)).toBe(false);
  });
});