// Copyright (c) 2013, 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 'package:graphs/graphs.dart';

import 'entrypoint.dart';
import 'package.dart';
import 'solver.dart';
import 'source/cached.dart';
import 'source/sdk.dart';
import 'utils.dart';

/// A holistic view of the entire transitive dependency graph for an entrypoint.
class PackageGraph {
  /// The entrypoint.
  final Entrypoint entrypoint;

  /// The transitive dependencies of the entrypoint (including itself).
  ///
  /// This may not include all transitive dependencies of the entrypoint if the
  /// creator of the package graph knows only a subset of the packages are
  /// relevant in the current context.
  final Map<String, Package> packages;

  /// A map of transitive dependencies for each package.
  Map<String, Set<Package>>? _transitiveDependencies;

  PackageGraph(this.entrypoint, this.packages);

  /// Creates a package graph using the data from [result].
  ///
  /// This is generally faster than loading a package graph from scratch, since
  /// the packages' pubspecs are already fully-parsed.
  factory PackageGraph.fromSolveResult(
    Entrypoint entrypoint,
    SolveResult result,
  ) {
    final packages = {
      for (final package in entrypoint.workspaceRoot.transitiveWorkspace)
        package.name: package,
      for (final id in result.packages.where((p) => !p.isRoot))
        id.name: Package(
          result.pubspecs[id.name]!,
          entrypoint.cache.getDirectory(id),
          [],
        ),
    };

    return PackageGraph(entrypoint, packages);
  }

  /// Returns all transitive dependencies of [package].
  ///
  /// For the entrypoint this returns all packages in [packages], which includes
  /// dev and override. For any other package, it ignores dev and override
  /// dependencies.
  Set<Package> transitiveDependencies(String package) {
    if (package == entrypoint.workspaceRoot.name) {
      return packages.values.toSet();
    }

    if (_transitiveDependencies == null) {
      final graph = mapMap<String, Package, String, Iterable<String>>(
        packages,
        value: (_, package) => package.dependencies.keys,
      );
      final closure = transitiveClosure(graph.keys, (n) => graph[n]!);
      _transitiveDependencies =
          mapMap<String, Set<String>, String, Set<Package>>(
            closure,
            value: (depender, names) {
              final set = names.map((name) => packages[name]!).toSet();
              set.add(packages[depender]!);
              return set;
            },
          );
    }
    return _transitiveDependencies![package]!;
  }

  bool _isPackageFromImmutableSource(String package) {
    final id = entrypoint.lockFile.packages[package];
    if (id == null) {
      return false; // This is a root package.
    }
    return id.source is CachedSource || id.source is SdkSource;
  }

  /// Returns whether [package] is mutable.
  ///
  /// A package is considered to be mutable if it or any of its dependencies
  /// don't come from a cached source, since the user can change its contents
  /// without modifying the pub cache. Information generated from mutable
  /// packages is generally not safe to cache, since it may change frequently.
  bool isPackageMutable(String package) {
    if (!_isPackageFromImmutableSource(package)) return true;

    return transitiveDependencies(
      package,
    ).any((dep) => !_isPackageFromImmutableSource(dep.name));
  }
}