// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:io';

import 'package:package_config/package_config.dart';
import 'package:path/path.dart' as p;

/// [Resolver] resolves imports with respect to a given environment.
class Resolver {
  @Deprecated('Use Resolver.create')
  Resolver({this.packagesPath, this.sdkRoot})
      : _packages = packagesPath != null ? _parsePackages(packagesPath) : null,
        packagePath = null;

  Resolver._(
      {this.packagesPath,
      this.packagePath,
      this.sdkRoot,
      Map<String, Uri>? packages})
      : _packages = packages;

  static Future<Resolver> create({
    String? packagesPath,
    String? packagePath,
    String? sdkRoot,
  }) async {
    return Resolver._(
      packagesPath: packagesPath,
      packagePath: packagePath,
      sdkRoot: sdkRoot,
      packages: packagesPath != null
          ? _parsePackages(packagesPath)
          : (packagePath != null ? await _parsePackage(packagePath) : null),
    );
  }

  final String? packagesPath;
  final String? packagePath;
  final String? sdkRoot;
  final List<String> failed = [];
  final Map<String, Uri>? _packages;

  /// Returns the absolute path wrt. to the given environment or null, if the
  /// import could not be resolved.
  String? resolve(String scriptUri) {
    final uri = Uri.parse(scriptUri);
    if (uri.scheme == 'dart') {
      final sdkRoot = this.sdkRoot;
      if (sdkRoot == null) {
        // No sdk-root given, do not resolve dart: URIs.
        return null;
      }
      String filePath;
      if (uri.pathSegments.length > 1) {
        var path = uri.pathSegments[0];
        // Drop patch files, since we don't have their source in the compiled
        // SDK.
        if (path.endsWith('-patch')) {
          failed.add('$uri');
          return null;
        }
        // Canonicalize path. For instance: _collection-dev => _collection_dev.
        path = path.replaceAll('-', '_');
        final pathSegments = [
          sdkRoot,
          path,
          ...uri.pathSegments.sublist(1),
        ];
        filePath = p.joinAll(pathSegments);
      } else {
        // Resolve 'dart:something' to be something/something.dart in the SDK.
        final lib = uri.path;
        filePath = p.join(sdkRoot, lib, '$lib.dart');
      }
      return resolveSymbolicLinks(filePath);
    }
    if (uri.scheme == 'package') {
      final packages = _packages;
      if (packages == null) {
        return null;
      }

      final packageName = uri.pathSegments[0];
      final packageUri = packages[packageName];
      if (packageUri == null) {
        failed.add('$uri');
        return null;
      }
      final packagePath = p.fromUri(packageUri);
      final pathInPackage = p.joinAll(uri.pathSegments.sublist(1));
      return resolveSymbolicLinks(p.join(packagePath, pathInPackage));
    }
    if (uri.scheme == 'file') {
      return resolveSymbolicLinks(p.fromUri(uri));
    }
    // We cannot deal with anything else.
    failed.add('$uri');
    return null;
  }

  /// Returns a canonicalized path, or `null` if the path cannot be resolved.
  String? resolveSymbolicLinks(String path) {
    final normalizedPath = p.normalize(path);
    final type = FileSystemEntity.typeSync(normalizedPath, followLinks: true);
    if (type == FileSystemEntityType.notFound) return null;
    return File(normalizedPath).resolveSymbolicLinksSync();
  }

  static Map<String, Uri> _parsePackages(String packagesPath) {
    final content = File(packagesPath).readAsStringSync();
    final packagesUri = p.toUri(packagesPath);
    final parsed =
        PackageConfig.parseString(content, Uri.base.resolveUri(packagesUri));
    return {
      for (var package in parsed.packages) package.name: package.packageUriRoot
    };
  }

  static Future<Map<String, Uri>?> _parsePackage(String packagePath) async {
    final parsed = await findPackageConfig(Directory(packagePath));
    if (parsed == null) return null;
    return {
      for (var package in parsed.packages) package.name: package.packageUriRoot
    };
  }
}

/// Bazel URI resolver.
class BazelResolver extends Resolver {
  /// Creates a Bazel resolver with the specified workspace path, if any.
  BazelResolver({this.workspacePath = ''});

  final String workspacePath;

  /// Returns the absolute path wrt. to the given environment or null, if the
  /// import could not be resolved.
  @override
  String? resolve(String scriptUri) {
    final uri = Uri.parse(scriptUri);
    if (uri.scheme == 'dart') {
      // Ignore the SDK
      return null;
    }
    if (uri.scheme == 'package') {
      // TODO(cbracken) belongs in a Bazel package
      return _resolveBazelPackage(uri.pathSegments);
    }
    if (uri.scheme == 'file') {
      final runfilesPathSegment =
          '.runfiles/$workspacePath'.replaceAll(RegExp(r'/*$'), '/');
      final runfilesPos = uri.path.indexOf(runfilesPathSegment);
      if (runfilesPos >= 0) {
        final pathStart = runfilesPos + runfilesPathSegment.length;
        return uri.path.substring(pathStart);
      }
      return null;
    }
    if (uri.scheme == 'https' || uri.scheme == 'http') {
      return _extractHttpPath(uri);
    }
    // We cannot deal with anything else.
    failed.add('$uri');
    return null;
  }

  String _extractHttpPath(Uri uri) {
    final packagesPos = uri.pathSegments.indexOf('packages');
    if (packagesPos >= 0) {
      final workspacePath = uri.pathSegments.sublist(packagesPos + 1);
      return _resolveBazelPackage(workspacePath);
    }
    return uri.pathSegments.join('/');
  }

  String _resolveBazelPackage(List<String> pathSegments) {
    // TODO(cbracken) belongs in a Bazel package
    final packageName = pathSegments[0];
    final pathInPackage = pathSegments.sublist(1).join('/');
    final packagePath = packageName.contains('.')
        ? packageName.replaceAll('.', '/')
        : 'third_party/dart/$packageName';
    return '$packagePath/lib/$pathInPackage';
  }
}

/// Loads the lines of imported resources.
class Loader {
  final List<String> failed = [];

  /// Loads an imported resource and returns a [Future] with a [List] of lines.
  /// Returns `null` if the resource could not be loaded.
  Future<List<String>?> load(String path) async {
    try {
      // Ensure `readAsLines` runs within the try block so errors are caught.
      return await File(path).readAsLines();
    } catch (_) {
      failed.add(path);
      return null;
    }
  }

  /// Loads an imported resource and returns a [List] of lines.
  /// Returns `null` if the resource could not be loaded.
  List<String>? loadSync(String path) {
    try {
      // Ensure `readAsLinesSync` runs within the try block so errors are
      // caught.
      return File(path).readAsLinesSync();
    } catch (_) {
      failed.add(path);
      return null;
    }
  }
}