// 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.

import 'dart:async';

import 'package:pub_semver/pub_semver.dart';

import '../entrypoint.dart';
import '../log.dart' as log;
import '../package.dart';
import '../source/hosted.dart';
import '../validator.dart';

/// The range of all pub versions that don't support `^` version constraints.
///
/// This is the actual range of pub versions, whereas [_postCaretPubVersions] is
/// the nicer-looking range that doesn't include a prerelease tag.
final _preCaretPubVersions = new VersionConstraint.parse("<1.8.0-dev.3.0");

/// The range of all pub versions that do support `^` version constraints.
///
/// This is intersected with the user's SDK constraint to provide a suggested
/// constraint.
final _postCaretPubVersions = new VersionConstraint.parse("^1.8.0");

/// A validator that validates a package's dependencies.
class DependencyValidator extends Validator {
  /// Whether the SDK constraint guarantees that `^` version constraints are
  /// safe.
  bool get _caretAllowed => entrypoint.root.pubspec.environment.sdkVersion
      .intersect(_preCaretPubVersions).isEmpty;

  DependencyValidator(Entrypoint entrypoint)
    : super(entrypoint);

  Future validate() async {
    var caretDeps = [];

    for (var dependency in entrypoint.root.pubspec.dependencies) {
      if (dependency.source != "hosted") {
        await _warnAboutSource(dependency);
      } else if (dependency.constraint.isAny) {
        _warnAboutNoConstraint(dependency);
      } else if (dependency.constraint is Version) {
        _warnAboutSingleVersionConstraint(dependency);
      } else if (dependency.constraint is VersionRange) {
        if (dependency.constraint.min == null) {
          _warnAboutNoConstraintLowerBound(dependency);
        } else if (dependency.constraint.max == null) {
          _warnAboutNoConstraintUpperBound(dependency);
        }

        if (dependency.constraint.toString().startsWith("^")) {
          caretDeps.add(dependency);
        }
      }
    }

    if (caretDeps.isNotEmpty && !_caretAllowed) {
      _errorAboutCaretConstraints(caretDeps);
    }
  }

  /// Warn that dependencies should use the hosted source.
  Future _warnAboutSource(PackageDep dep) async {
    var versions;
    try {
      var ids = await entrypoint.cache.sources['hosted']
          .getVersions(HostedSource.refFor(dep.name));
      versions = ids.map((id) => id.version).toList();
    } catch (error) {
      versions = [];
    }

    var constraint;
    var primary = Version.primary(versions);
    if (primary != null) {
      constraint = _constraintForVersion(primary);
    } else {
      constraint = dep.constraint.toString();
      if (!dep.constraint.isAny && dep.constraint is! Version) {
        constraint = '"$constraint"';
      }
    }

    // Path sources are errors. Other sources are just warnings.
    var messages = warnings;
    if (dep.source == "path") {
      messages = errors;
    }

    messages.add('Don\'t depend on "${dep.name}" from the ${dep.source} '
            'source. Use the hosted source instead. For example:\n'
        '\n'
        'dependencies:\n'
        '  ${dep.name}: $constraint\n'
        '\n'
        'Using the hosted source ensures that everyone can download your '
            'package\'s dependencies along with your package.');
  }

  /// Warn that dependencies should have version constraints.
  void _warnAboutNoConstraint(PackageDep dep) {
    var message = 'Your dependency on "${dep.name}" should have a version '
        'constraint.';
    var locked = entrypoint.lockFile.packages[dep.name];
    if (locked != null) {
      message = '$message For example:\n'
        '\n'
        'dependencies:\n'
        '  ${dep.name}: ${_constraintForVersion(locked.version)}\n';
    }
    warnings.add("$message\n"
        'Without a constraint, you\'re promising to support ${log.bold("all")} '
            'future versions of "${dep.name}".');
  }

  /// Warn that dependencies should allow more than a single version.
  void _warnAboutSingleVersionConstraint(PackageDep dep) {
    warnings.add(
        'Your dependency on "${dep.name}" should allow more than one version. '
            'For example:\n'
        '\n'
        'dependencies:\n'
        '  ${dep.name}: ${_constraintForVersion(dep.constraint)}\n'
        '\n'
        'Constraints that are too tight will make it difficult for people to '
            'use your package\n'
        'along with other packages that also depend on "${dep.name}".');
  }

  /// Warn that dependencies should have lower bounds on their constraints.
  void _warnAboutNoConstraintLowerBound(PackageDep dep) {
    var message = 'Your dependency on "${dep.name}" should have a lower bound.';
    var locked = entrypoint.lockFile.packages[dep.name];
    if (locked != null) {
      var constraint;
      if (locked.version == (dep.constraint as VersionRange).max) {
        constraint = _constraintForVersion(locked.version);
      } else {
        constraint = '">=${locked.version} ${dep.constraint}"';
      }

      message = '$message For example:\n'
        '\n'
        'dependencies:\n'
        '  ${dep.name}: $constraint\n';
    }
    warnings.add("$message\n"
        'Without a constraint, you\'re promising to support ${log.bold("all")} '
            'previous versions of "${dep.name}".');
  }

  /// Warn that dependencies should have upper bounds on their constraints.
  void _warnAboutNoConstraintUpperBound(PackageDep dep) {
    var constraint;
    if ((dep.constraint as VersionRange).includeMin) {
      constraint = _constraintForVersion((dep.constraint as VersionRange).min);
    } else {
      constraint = '"${dep.constraint} '
          '<${(dep.constraint as VersionRange).min.nextBreaking}"';
    }

    warnings.add(
        'Your dependency on "${dep.name}" should have an upper bound. For '
            'example:\n'
        '\n'
        'dependencies:\n'
        '  ${dep.name}: $constraint\n'
        '\n'
        'Without an upper bound, you\'re promising to support '
            '${log.bold("all")} future versions of ${dep.name}.');
  }

  /// Emits an error for any version constraints that use `^` without an
  /// appropriate SDK constraint.
  void _errorAboutCaretConstraints(List<PackageDep> caretDeps) {
    var newSdkConstraint = entrypoint.root.pubspec.environment.sdkVersion
        .intersect(_postCaretPubVersions);

    if (newSdkConstraint.isEmpty) newSdkConstraint = _postCaretPubVersions;

    var buffer = new StringBuffer(
        "Older versions of pub don't support ^ version constraints.\n"
        "Make sure your SDK constraint excludes those old versions:\n"
        "\n"
        "environment:\n"
        "  sdk: \"$newSdkConstraint\"\n"
        "\n");

    if (caretDeps.length == 1) {
      buffer.writeln("Or use a fully-expanded constraint:");
    } else {
      buffer.writeln("Or use fully-expanded constraints:");
    }

    buffer.writeln();
    buffer.writeln("dependencies:");

    caretDeps.forEach((dep) {
      VersionRange constraint = dep.constraint;
      buffer.writeln(
          "  ${dep.name}: \">=${constraint.min} <${constraint.max}\"");
    });

    errors.add(buffer.toString().trim());
  }

  /// Returns the suggested version constraint for a dependency that was tested
  /// against [version].
  String _constraintForVersion(Version version) {
    if (_caretAllowed) return "^$version";
    return '">=$version <${version.nextBreaking}"';
  }
}