// 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 pub.source.hosted;

import 'dart:async';
import 'dart:io' as io;
import "dart:convert";

import 'package:http/http.dart' as http;
import 'package:path/path.dart' as path;

import '../http.dart';
import '../io.dart';
import '../log.dart' as log;
import '../package.dart';
import '../pubspec.dart';
import '../source.dart';
import '../utils.dart';
import '../version.dart';

/// A package source that gets packages from a package hosting site that uses
/// the same API as pub.dartlang.org.
class HostedSource extends Source {

  final name = "hosted";
  final shouldCache = true;

  /// Gets the default URL for the package server for hosted dependencies.
  static String get defaultUrl {
    var url = io.Platform.environment["PUB_HOSTED_URL"];
    if (url != null) {
      log.fine("Got server $url from PUB_HOSTED_URL.");
      return url;
    }

    return "https://pub.dartlang.org";
  }

  /// Downloads a list of all versions of a package that are available from the
  /// site.
  Future<List<Version>> getVersions(String name, description) {
    var url = _makeUrl(description,
        (server, package) => "$server/api/packages/$package");

    log.io("Get versions from $url.");
    return httpClient.read(url, headers: PUB_API_HEADERS).then((body) {
      var doc = JSON.decode(body);
      return doc['versions']
          .map((version) => new Version.parse(version['version']))
          .toList();
    }).catchError((ex, stackTrace) {
      var parsed = _parseDescription(description);
      _throwFriendlyError(ex, stackTrace, parsed.first, parsed.last);
    });
  }

  /// Downloads and parses the pubspec for a specific version of a package that
  /// is available from the site.
  Future<Pubspec> describeUncached(PackageId id) {
    // Request it from the server.
    var url = _makeVersionUrl(id, (server, package, version) =>
        "$server/api/packages/$package/versions/$version");

    log.io("Describe package at $url.");
    return httpClient.read(url, headers: PUB_API_HEADERS).then((version) {
      version = JSON.decode(version);

      // TODO(rnystrom): After this is pulled down, we could place it in
      // a secondary cache of just pubspecs. This would let us have a
      // persistent cache for pubspecs for packages that haven't actually
      // been downloaded.
      return new Pubspec.fromMap(version['pubspec'], systemCache.sources,
          expectedName: id.name, location: url);
    }).catchError((ex, stackTrace) {
      var parsed = _parseDescription(id.description);
      _throwFriendlyError(ex, stackTrace, id, parsed.last);
    });
  }

  /// Downloads a package from the site and unpacks it.
  Future<bool> get(PackageId id, String destPath) {
    return new Future.sync(() {
      var url = _makeVersionUrl(id, (server, package, version) =>
          "$server/packages/$package/versions/$version.tar.gz");
      log.io("Get package from $url.");

      log.message('Downloading $id...');

      // Download and extract the archive to a temp directory.
      var tempDir = systemCache.createTempDir();
      return httpClient.send(new http.Request("GET", url))
          .then((response) => response.stream)
          .then((stream) {
        return timeout(extractTarGz(stream, tempDir), HTTP_TIMEOUT,
            'fetching URL "$url"');
      }).then((_) {
        // Now that the get has succeeded, move it to the real location in the
        // cache. This ensures that we don't leave half-busted ghost
        // directories in the user's pub cache if a get fails.
        renameDir(tempDir, destPath);
        return true;
      });
    });
  }

  /// The system cache directory for the hosted source contains subdirectories
  /// for each separate repository URL that's used on the system. Each of these
  /// subdirectories then contains a subdirectory for each package downloaded
  /// from that site.
  Future<String> systemCacheDirectory(PackageId id) {
    var parsed = _parseDescription(id.description);
    var dir = _getSourceDirectory(parsed.last);

    return new Future.value(
        path.join(systemCacheRoot, dir, "${parsed.first}-${id.version}"));
  }

  String packageName(description) => _parseDescription(description).first;

  bool descriptionsEqual(description1, description2) =>
      _parseDescription(description1) == _parseDescription(description2);

  /// Ensures that [description] is a valid hosted package description.
  ///
  /// There are two valid formats. A plain string refers to a package with the
  /// given name from the default host, while a map with keys "name" and "url"
  /// refers to a package with the given name from the host at the given URL.
  dynamic parseDescription(String containingPath, description,
                           {bool fromLockFile: false}) {
    _parseDescription(description);
    return description;
  }

  List<Package> getCachedPackages([String url]) {
    if (url == null) url = defaultUrl;

    var cacheDir = path.join(systemCacheRoot,
                             _getSourceDirectory(url));
    if (!dirExists(cacheDir)) return [];

    return listDir(path.join(cacheDir)).map((entry) {
      // TODO(keertip): instead of catching exception in pubspec parse with
      // sdk dependency, fix to parse and report usage of sdk dependency.
      // dartbug.com/10190
      try {
        return new Package.load(null, entry, systemCache.sources);
      }  on ArgumentError catch (e) {
        log.error(e);
      }
    }).where((package) => package != null).toList();
  }

  /// When an error occurs trying to read something about [package] from [url],
  /// this tries to translate into a more user friendly error message. Always
  /// throws an error, either the original one or a better one.
  void _throwFriendlyError(error, StackTrace stackTrace, String package,
      String url) {
    if (error is PubHttpException &&
        error.response.statusCode == 404) {
      fail('Could not find package "$package" at $url.', error, stackTrace);
    }

    if (error is TimeoutException) {
      fail('Timed out trying to find package "$package" at $url.',
          error, stackTrace);
    }

    if (error is io.SocketException) {
      fail('Got socket error trying to find package "$package" at $url.',
           error, stackTrace);
    }

    // Otherwise re-throw the original exception.
    throw error;
  }
}

/// This is the modified hosted source used when pub get or upgrade are run
/// with "--offline". This uses the system cache to get the list of available
/// packages and does no network access.
class OfflineHostedSource extends HostedSource {
  /// Gets the list of all versions of [name] that are in the system cache.
  Future<List<Version>> getVersions(String name, description) {
    return newFuture(() {
      var parsed = _parseDescription(description);
      var server = parsed.last;
      log.io("Finding versions of $name in "
             "${systemCache.rootDir}/${_getSourceDirectory(server)}");
      return getCachedPackages(server)
          .where((package) => package.name == name)
          .map((package) => package.version)
          .toList();
    }).then((versions) {
      // If there are no versions in the cache, report a clearer error.
      if (versions.isEmpty) fail('Could not find package "$name" in cache.');

      return versions;
    });
  }

  Future<bool> get(PackageId id, String destPath) {
    // Since HostedSource returns `true` for [shouldCache], install will only
    // be called for uncached packages.
    throw new UnsupportedError("Cannot get packages when offline.");
  }

  Future<Pubspec> describeUncached(PackageId id) {
    // [getVersions()] will only return packages that are already cached.
    // Source should only call [describeUncached()] on a package after it has
    // failed to find it in the cache, so this code should not be reached.
    throw new UnsupportedError("Cannot describe packages when offline.");
  }
}

String _getSourceDirectory(String url) {
  url = url.replaceAll(new RegExp(r"^https?://"), "");
  return replace(url, new RegExp(r'[<>:"\\/|?*%]'),
      (match) => '%${match[0].codeUnitAt(0)}');
}

/// Parses [description] into its server and package name components, then
/// converts that to a Uri given [pattern]. Ensures the package name is
/// properly URL encoded.
Uri _makeUrl(description, String pattern(String server, String package)) {
  var parsed = _parseDescription(description);
  var server = parsed.last;
  var package = Uri.encodeComponent(parsed.first);
  return Uri.parse(pattern(server, package));
}

/// Parses [id] into its server, package name, and version components, then
/// converts that to a Uri given [pattern]. Ensures the package name is
/// properly URL encoded.
Uri _makeVersionUrl(PackageId id,
    String pattern(String server, String package, String version)) {
  var parsed = _parseDescription(id.description);
  var server = parsed.last;
  var package = Uri.encodeComponent(parsed.first);
  var version = Uri.encodeComponent(id.version.toString());
  return Uri.parse(pattern(server, package, version));
}

/// Parses the description for a package.
///
/// If the package parses correctly, this returns a (name, url) pair. If not,
/// this throws a descriptive FormatException.
Pair<String, String> _parseDescription(description) {
  if (description is String) {
    return new Pair<String, String>(description, HostedSource.defaultUrl);
  }

  if (description is! Map) {
    throw new FormatException(
        "The description must be a package name or map.");
  }

  if (!description.containsKey("name")) {
    throw new FormatException(
    "The description map must contain a 'name' key.");
  }

  var name = description["name"];
  if (name is! String) {
    throw new FormatException("The 'name' key must have a string value.");
  }

  var url = description["url"];
  if (url == null) url = HostedSource.defaultUrl;

  return new Pair<String, String>(name, url);
}