// Copyright (c) 2012, 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.

library package;

import 'io.dart';
import 'pubspec.dart';
import 'source.dart';
import 'source_registry.dart';
import 'version.dart';

/**
 * A named, versioned, unit of code and resource reuse.
 */
class Package {
  /**
   * Loads the package whose root directory is [packageDir]. [name] is the
   * expected name of that package (e.g. the name given in the dependency), or
   * null if the package being loaded is the entrypoint package.
   */
  static Future<Package> load(String name, String packageDir,
      SourceRegistry sources) {
    var pubspecPath = join(packageDir, 'pubspec.yaml');

    return fileExists(pubspecPath).chain((exists) {
      if (!exists) throw new PubspecNotFoundException(name);
      return readTextFile(pubspecPath);
    }).transform((contents) {
      var pubspec = new Pubspec.parse(contents, sources);
      if (pubspec.name == null) throw new PubspecHasNoNameException(name);
      if (name != null && pubspec.name != name) {
        throw new PubspecNameMismatchException(name, pubspec.name);
      }
      return new Package._(packageDir, pubspec);
    });
  }

  /**
   * The path to the directory containing the package.
   */
  final String dir;

  /**
   * The name of the package.
   */
  String get name {
    if (pubspec.name != null) return pubspec.name;
    if (dir != null) return basename(dir);
    return null;
  }

  /**
   * The package's version.
   */
  Version get version => pubspec.version;

  /**
   * The parsed pubspec associated with this package.
   */
  final Pubspec pubspec;

  /**
   * The ids of the packages that this package depends on. This is what is
   * specified in the pubspec when this package depends on another.
   */
  Collection<PackageRef> get dependencies => pubspec.dependencies;

  /**
   * Constructs a package with the given pubspec. The package will have no
   * directory associated with it.
   */
  Package.inMemory(this.pubspec)
    : dir = null;

  /**
   * Constructs a package. This should not be called directly. Instead, acquire
   * packages from [load()].
   */
  Package._(this.dir, this.pubspec);

  /**
   * Returns a debug string for the package.
   */
  String toString() => '$name $version ($dir)';
}

/**
 * An unambiguous resolved reference to a package. A package ID contains enough
 * information to correctly install the package.
 *
 * Note that it's possible for multiple distinct package IDs to point to
 * different directories that happen to contain identical packages. For example,
 * the same package may be available from multiple sources. As far as Pub is
 * concerned, those packages are different.
 */
class PackageId implements Comparable {
  /// The name of the package being identified.
  final String name;

  /**
   * The [Source] used to look up this package given its [description].
   */
  final Source source;

  /**
   * The package's version.
   */
  final Version version;

  /**
   * The metadata used by the package's [source] to identify and locate it. It
   * contains whatever [Source]-specific data it needs to be able to install
   * the package. For example, the description of a git sourced package might
   * by the URL "git://github.com/dart/uilib.git".
   */
  final description;

  PackageId(this.name, this.source, this.version, this.description);

  int hashCode() => name.hashCode() ^
                    source.name.hashCode() ^
                    version.hashCode();

  bool operator ==(other) {
    if (other is! PackageId) return false;
    // TODO(rnystrom): We're assuming here the name/version/source tuple is
    // enough to uniquely identify the package and that we don't need to delve
    // into the description.
    return other.name == name &&
           other.source.name == source.name &&
           other.version == version;
  }

  String toString() => "$name $version from ${source.name}";

  int compareTo(Comparable other) {
    if (other is! PackageId) throw new ArgumentError(other);

    var sourceComp = source.name.compareTo(other.source.name);
    if (sourceComp != 0) return sourceComp;

    var nameComp = name.compareTo(other.name);
    if (nameComp != 0) return nameComp;

    return version.compareTo(other.version);
  }

  /**
   * Returns the pubspec for this package.
   */
  Future<Pubspec> describe() => source.describe(this);

  /**
   * Returns a future that completes to the resovled [PackageId] for this id.
   */
  Future<PackageId> get resolved => source.resolveId(this);
}

/**
 * A reference to a package. Unlike a [PackageId], a PackageRef may not
 * unambiguously refer to a single package. It may describe a range of allowed
 * packages.
 */
class PackageRef {
  /// The name of the package being identified.
  final String name;

  /**
   * The [Source] used to look up the package.
   */
  final Source source;

  /**
   * The allowed package versions.
   */
  final VersionConstraint constraint;

  /**
   * The metadata used to identify the package being referenced. The
   * interpretation of this will vary based on the [source].
   */
  final description;

  PackageRef(this.name, this.source, this.constraint, this.description);

  String toString() => "$name $constraint from $source ($description)";

  /**
   * Returns a [PackageId] generated from this [PackageRef] with the given
   * concrete version.
   */
  PackageId atVersion(Version version) =>
    new PackageId(name, source, version, description);
}

class PubspecNotFoundException implements Exception {
  final String name;

  PubspecNotFoundException(this.name);

  String toString() => 'Package "$name" doesn\'t have a pubspec.yaml file.';
}

class PubspecHasNoNameException implements Exception {
  final String name;

  PubspecHasNoNameException(this.name);

  String toString() => 'Package "$name"\'s pubspec.yaml file is missing the '
    'required "name" field (e.g. "name: $name").';
}

class PubspecNameMismatchException implements Exception {
  final String expectedName;
  final String actualName;

  PubspecNameMismatchException(this.expectedName, this.actualName);

  String toString() => 'The name you specified for your dependency, '
    '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
}