// 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.

/// Generic utility functions. Stuff that should possibly be in core.
import 'dart:async';
import "dart:convert";
import 'dart:io';
import 'dart:math' as math;

import "package:crypto/crypto.dart" as crypto;
import 'package:meta/meta.dart';
import "package:stack_trace/stack_trace.dart";

import 'exceptions.dart';
import 'io.dart';
import 'log.dart' as log;

/// Whether Pub is running its own tests under Travis.CI.
final isTravis = Platform.environment["TRAVIS_REPO_SLUG"] == "dart-lang/pub";

/// A regular expression matching a Dart identifier.
///
/// This also matches a package name, since they must be Dart identifiers.
final identifierRegExp = new RegExp(r"[a-zA-Z_]\w*");

/// Like [identifierRegExp], but anchored so that it only matches strings that
/// are *just* Dart identifiers.
final onlyIdentifierRegExp = new RegExp("^${identifierRegExp.pattern}\$");

/// Dart reserved words, from the Dart spec.
const reservedWords = const [
  "assert",
  "break",
  "case",
  "catch",
  "class",
  "const",
  "continue",
  "default",
  "do",
  "else",
  "extends",
  "false",
  "final",
  "finally",
  "for",
  "if",
  "in",
  "is",
  "new",
  "null",
  "return",
  "super",
  "switch",
  "this",
  "throw",
  "true",
  "try",
  "var",
  "void",
  "while",
  "with"
];

/// An cryptographically secure instance of [math.Random].
final random = new math.Random.secure();

/// The maximum line length for output.
///
/// If pub isn't attached to a terminal, uses an infinite line length and does
/// not wrap text.
final int _lineLength = () {
  try {
    return stdout.terminalColumns;
  } on StdoutException {
    return null;
  }
}();

/// A pair of values.
class Pair<E, F> {
  E first;
  F last;

  Pair(this.first, this.last);

  String toString() => '($first, $last)';

  bool operator ==(other) {
    if (other is! Pair) return false;
    return other.first == first && other.last == last;
  }

  int get hashCode => first.hashCode ^ last.hashCode;
}

/// Runs [callback] in an error zone and pipes any unhandled error to the
/// returned [Future].
///
/// If the returned [Future] produces an error, its stack trace will always be a
/// [Chain]. By default, this chain will contain only the local stack trace, but
/// if [captureStackChains] is passed, it will contain the full stack chain for
/// the error.
Future captureErrors(Future callback(), {bool captureStackChains: false}) {
  var completer = new Completer();
  var wrappedCallback = () {
    new Future.sync(callback)
        .then(completer.complete)
        .catchError((e, stackTrace) {
      // [stackTrace] can be null if we're running without [captureStackChains],
      // since dart:io will often throw errors without stack traces.
      if (stackTrace != null) {
        stackTrace = new Chain.forTrace(stackTrace);
      } else {
        stackTrace = new Chain([]);
      }
      if (!completer.isCompleted) completer.completeError(e, stackTrace);
    });
  };

  if (captureStackChains) {
    Chain.capture(wrappedCallback, onError: (error, stackTrace) {
      if (!completer.isCompleted) completer.completeError(error, stackTrace);
    });
  } else {
    runZoned(wrappedCallback, onError: (e, stackTrace) {
      if (stackTrace == null) {
        stackTrace = new Chain.current();
      } else {
        stackTrace = new Chain([new Trace.from(stackTrace)]);
      }
      if (!completer.isCompleted) completer.completeError(e, stackTrace);
    });
  }

  return completer.future;
}

/// Like [Future.wait], but prints all errors from the futures as they occur and
/// only returns once all Futures have completed, successfully or not.
///
/// This will wrap the first error thrown in a [SilentException] and rethrow it.
Future<List<T>> waitAndPrintErrors<T>(Iterable<Future<T>> futures) {
  return Future.wait(futures.map((future) {
    return future.catchError((error, stackTrace) {
      log.exception(error, stackTrace);
      throw error;
    });
  })).catchError((error, stackTrace) {
    throw new SilentException(error, stackTrace);
  });
}

/// Returns a [StreamTransformer] that will call [onDone] when the stream
/// completes.
///
/// The stream will be passed through unchanged.
StreamTransformer<T, T> onDoneTransformer<T>(void onDone()) {
  return new StreamTransformer<T, T>.fromHandlers(handleDone: (sink) {
    onDone();
    sink.close();
  });
}

/// Pads [source] to [length] by adding [char]s at the beginning.
///
/// If [char] is `null`, it defaults to a space.
String _padLeft(String source, int length, [String char]) {
  if (char == null) char = ' ';
  if (source.length >= length) return source;

  return char * (length - source.length) + source;
}

/// Returns a labelled sentence fragment starting with [name] listing the
/// elements [iter].
///
/// If [iter] does not have one item, name will be pluralized by adding "s" or
/// using [plural], if given.
String namedSequence(String name, Iterable iter, [String plural]) {
  if (iter.length == 1) return "$name ${iter.single}";

  if (plural == null) plural = "${name}s";
  return "$plural ${toSentence(iter)}";
}

/// Returns a sentence fragment listing the elements of [iter].
///
/// This converts each element of [iter] to a string and separates them with
/// commas and/or [conjunction] (`"and"` by default) where appropriate.
String toSentence(Iterable iter, {String conjunction}) {
  if (iter.length == 1) return iter.first.toString();
  conjunction ??= 'and';
  return iter.take(iter.length - 1).join(", ") + " $conjunction ${iter.last}";
}

/// Returns [name] if [number] is 1, or the plural of [name] otherwise.
///
/// By default, this just adds "s" to the end of [name] to get the plural. If
/// [plural] is passed, that's used instead.
String pluralize(String name, int number, {String plural}) {
  if (number == 1) return name;
  if (plural != null) return plural;
  return '${name}s';
}

/// Returns [text] with the first letter capitalized.
String capitalize(String text) =>
    text.substring(0, 1).toUpperCase() + text.substring(1);

/// Escapes any regex metacharacters in [string] so that using as a [RegExp]
/// pattern will match the string literally.
// TODO(rnystrom): Remove when #4706 is fixed.
String quoteRegExp(String string) {
  // Note: make sure "\" is done first so that we don't escape the other
  // escaped characters. We could do all of the replaces at once with a regexp
  // but string literal for regex that matches all regex metacharacters would
  // be a bit hard to read.
  for (var metacharacter in r"\^$.*+?()[]{}|".split("")) {
    string = string.replaceAll(metacharacter, "\\$metacharacter");
  }

  return string;
}

/// Returns whether [host] is a host for a localhost or loopback URL.
///
/// Unlike [InternetAddress.isLoopback], this hostnames from URLs as well as
/// from [InternetAddress]es, including "localhost".
bool isLoopback(String host) {
  if (host == 'localhost') return true;

  // IPv6 hosts in URLs are surrounded by square brackets.
  if (host.startsWith("[") && host.endsWith("]")) {
    host = host.substring(1, host.length - 1);
  }

  try {
    return new InternetAddress(host).isLoopback;
  } on ArgumentError catch (_) {
    // The host isn't an IP address and isn't "localhost', so it's almost
    // certainly not a loopback host.
    return false;
  }
}

/// Randomly chooses a single element in [elements].
T choose<T>(List<T> elements) => elements[random.nextInt(elements.length)];

/// Returns a list containing the sorted elements of [iter].
List<T> ordered<T extends Comparable<T>>(Iterable<T> iter) {
  var list = iter.toList();
  list.sort();
  return list;
}

/// Given a list of filenames, returns a set of patterns that can be used to
/// filter for those filenames.
///
/// For a given path, that path ends with some string in the returned set if
/// and only if that path's basename is in [files].
Set<String> createFileFilter(Iterable<String> files) {
  return files.expand<String>((file) {
    var result = ["/$file"];
    if (Platform.operatingSystem == 'windows') result.add("\\$file");
    return result;
  }).toSet();
}

/// Given a blacklist of directory names, returns a set of patterns that can
/// be used to filter for those directory names.
///
/// For a given path, that path contains some string in the returned set if
/// and only if one of that path's components is in [dirs].
Set<String> createDirectoryFilter(Iterable<String> dirs) {
  return dirs.expand<String>((dir) {
    var result = ["/$dir/"];
    if (Platform.operatingSystem == 'windows') {
      result..add("/$dir\\")..add("\\$dir/")..add("\\$dir\\");
    }
    return result;
  }).toSet();
}

/// Returns the maximum value in [iter] by [compare].
///
/// [compare] defaults to [Comparable.compare].
T maxAll<T extends Comparable>(Iterable<T> iter,
    [int compare(T element1, T element2)]) {
  if (compare == null) compare = Comparable.compare;
  return iter
      .reduce((max, element) => compare(element, max) > 0 ? element : max);
}

/// Like [minBy], but with an asynchronous [orderBy] callback.
Future<S> minByAsync<S, T>(
    Iterable<S> values, Future<T> orderBy(S element)) async {
  S minValue;
  T minOrderBy;
  for (var element in values) {
    var elementOrderBy = await orderBy(element);
    if (minOrderBy == null ||
        (elementOrderBy as Comparable).compareTo(minOrderBy) < 0) {
      minValue = element;
      minOrderBy = elementOrderBy;
    }
  }
  return minValue;
}

/// Like [List.sublist], but for any iterable.
Iterable<T> slice<T>(Iterable<T> values, int start, int end) {
  if (end <= start) {
    throw new RangeError.range(
        end, start + 1, null, "end", "must be greater than start");
  }
  return values.skip(start).take(end - start);
}

/// Like [Iterable.fold], but for an asynchronous [combine] function.
Future<S> foldAsync<S, T>(Iterable<T> values, S initialValue,
        Future<S> combine(S previous, T element)) =>
    values.fold(
        new Future.value(initialValue),
        (previousFuture, element) =>
            previousFuture.then((previous) => combine(previous, element)));

/// Replace each instance of [matcher] in [source] with the return value of
/// [fn].
String replace(String source, Pattern matcher, String fn(Match match)) {
  var buffer = new StringBuffer();
  var start = 0;
  for (var match in matcher.allMatches(source)) {
    buffer.write(source.substring(start, match.start));
    start = match.end;
    buffer.write(fn(match));
  }
  buffer.write(source.substring(start));
  return buffer.toString();
}

/// Returns the hex-encoded sha1 hash of [source].
String sha1(String source) =>
    crypto.sha1.convert(utf8.encode(source)).toString();

/// Configures [future] so that its result (success or exception) is passed on
/// to [completer].
void chainToCompleter(Future future, Completer completer) {
  future.then(completer.complete, onError: completer.completeError);
}

// TODO(nweiz): remove this when issue 7964 is fixed.
/// Returns a [Future] that will complete to the first element of [stream].
///
/// Unlike [Stream.first], this is safe to use with single-subscription streams.
Future<T> streamFirst<T>(Stream<T> stream) {
  var completer = new Completer();
  var subscription;
  subscription = stream.listen((value) {
    subscription.cancel();
    completer.complete(value);
  }, onError: (e, [StackTrace stackTrace]) {
    completer.completeError(e, stackTrace);
  }, onDone: () {
    completer.completeError(new StateError("No elements"), new Chain.current());
  }, cancelOnError: true);
  return completer.future;
}

/// A regular expression matching a trailing CR character.
final _trailingCR = new RegExp(r"\r$");

// TODO(nweiz): Use `text.split(new RegExp("\r\n?|\n\r?"))` when issue 9360 is
// fixed.
/// Splits [text] on its line breaks in a Windows-line-break-friendly way.
List<String> splitLines(String text) =>
    text.split("\n").map((line) => line.replaceFirst(_trailingCR, "")).toList();

/// Converts a stream of arbitrarily chunked strings into a line-by-line stream.
///
/// The lines don't include line termination characters. A single trailing
/// newline is ignored.
Stream<String> streamToLines(Stream<String> stream) {
  var buffer = new StringBuffer();
  return stream
      .transform(new StreamTransformer.fromHandlers(handleData: (chunk, sink) {
    var lines = splitLines(chunk);
    var leftover = lines.removeLast();
    for (var line in lines) {
      if (buffer.isNotEmpty) {
        buffer.write(line);
        line = buffer.toString();
        buffer = new StringBuffer();
      }

      sink.add(line);
    }
    buffer.write(leftover);
  }, handleDone: (sink) {
    if (buffer.isNotEmpty) sink.add(buffer.toString());
    sink.close();
  }));
}

// TODO(nweiz): unify the following functions with the utility functions in
// pkg/http.

/// Like [String.split], but only splits on the first occurrence of the pattern.
///
/// This always returns an array of two elements or fewer.
List<String> split1(String toSplit, String pattern) {
  if (toSplit.isEmpty) return <String>[];

  var index = toSplit.indexOf(pattern);
  if (index == -1) return [toSplit];
  return [
    toSplit.substring(0, index),
    toSplit.substring(index + pattern.length)
  ];
}

/// Convert a URL query string (or `application/x-www-form-urlencoded` body)
/// into a [Map] from parameter names to values.
Map<String, String> queryToMap(String queryList) {
  var map = <String, String>{};
  for (var pair in queryList.split("&")) {
    var split = split1(pair, "=");
    if (split.isEmpty) continue;
    var key = _urlDecode(split[0]);
    var value = split.length > 1 ? _urlDecode(split[1]) : "";
    map[key] = value;
  }
  return map;
}

/// Returns a human-friendly representation of [duration].
String niceDuration(Duration duration) {
  var hasMinutes = duration.inMinutes > 0;
  var result = hasMinutes ? "${duration.inMinutes}:" : "";

  var s = duration.inSeconds % 60;
  var ms = duration.inMilliseconds % 1000;

  // If we're using verbose logging, be more verbose but more accurate when
  // reporting timing information.
  var msString = log.verbosity.isLevelVisible(log.Level.FINE)
      ? _padLeft(ms.toString(), 3, '0')
      : (ms ~/ 100).toString();

  return "$result${hasMinutes ? _padLeft(s.toString(), 2, '0') : s}"
      ".${msString}s";
}

/// Decodes a URL-encoded string.
///
/// Unlike [Uri.decodeComponent], this includes replacing `+` with ` `.
String _urlDecode(String encoded) =>
    Uri.decodeComponent(encoded.replaceAll("+", " "));

/// Whether "special" strings such as Unicode characters or color escapes are
/// safe to use.
///
/// On Windows or when not printing to a terminal, only printable ASCII
/// characters should be used.
bool get canUseSpecialChars =>
    !runningFromTest &&
    !runningAsTest &&
    Platform.operatingSystem != 'windows' &&
    stdioType(stdout) == StdioType.TERMINAL;

/// Gets a "special" string (ANSI escape or Unicode).
///
/// On Windows or when not printing to a terminal, returns something else since
/// those aren't supported.
String getSpecial(String special, [String onWindows = '']) =>
    canUseSpecialChars ? special : onWindows;

/// Prepends each line in [text] with [prefix].
///
/// If [firstPrefix] is passed, the first line is prefixed with that instead.
String prefixLines(String text, {String prefix: '| ', String firstPrefix}) {
  var lines = text.split('\n');
  if (firstPrefix == null) {
    return lines.map((line) => '$prefix$line').join('\n');
  }

  var firstLine = "$firstPrefix${lines.first}";
  lines = lines.skip(1).map((line) => '$prefix$line').toList();
  lines.insert(0, firstLine);
  return lines.join('\n');
}

/// Whether today is April Fools' day.
bool get isAprilFools {
  // Tests should never see April Fools' output.
  if (runningFromTest) return false;

  var date = new DateTime.now();
  return date.month == 4 && date.day == 1;
}

/// The subset of strings that don't need quoting in YAML.
///
/// This pattern does not strictly follow the plain scalar grammar of YAML,
/// which means some strings may be unnecessarily quoted, but it's much simpler.
final _unquotableYamlString = new RegExp(r"^[a-zA-Z_-][a-zA-Z_0-9-]*$");

/// Converts [data], which is a parsed YAML object, to a pretty-printed string,
/// using indentation for maps.
String yamlToString(data) {
  var buffer = new StringBuffer();

  _stringify(bool isMapValue, String indent, data) {
    // TODO(nweiz): Serialize using the YAML library once it supports
    // serialization.

    // Use indentation for (non-empty) maps.
    if (data is Map && data.isNotEmpty) {
      if (isMapValue) {
        buffer.writeln();
        indent += '  ';
      }

      // Sort the keys. This minimizes deltas in diffs.
      var keys = data.keys.toList();
      keys.sort((a, b) => a.toString().compareTo(b.toString()));

      var first = true;
      for (var key in keys) {
        if (!first) buffer.writeln();
        first = false;

        var keyString = key;
        if (key is! String || !_unquotableYamlString.hasMatch(key)) {
          keyString = jsonEncode(key);
        }

        buffer.write('$indent$keyString:');
        _stringify(true, indent, data[key]);
      }

      return;
    }

    // Everything else we just stringify using JSON to handle escapes in
    // strings and number formatting.
    var string = data;

    // Don't quote plain strings if not needed.
    if (data is! String || !_unquotableYamlString.hasMatch(data)) {
      string = jsonEncode(data);
    }

    if (isMapValue) {
      buffer.write(' $string');
    } else {
      buffer.write('$indent$string');
    }
  }

  _stringify(false, '', data);
  return buffer.toString();
}

/// Throw a [ApplicationException] with [message].
@alwaysThrows
void fail(String message, [innerError, StackTrace innerTrace]) {
  if (innerError != null) {
    throw new WrappedException(message, innerError, innerTrace);
  } else {
    throw new ApplicationException(message);
  }
}

/// Throw a [DataException] with [message] to indicate that the command has
/// failed because of invalid input data.
///
/// This will report the error and cause pub to exit with [exit_codes.DATA].
void dataError(String message) => throw new DataException(message);

/// Returns a UUID in v4 format as a `String`.
///
/// If [bytes] is provided, it must be length 16 and have values between `0` and
/// `255` inclusive.
///
/// If [bytes] is not provided, it is generated using `Random.secure`.
String createUuid([List<int> bytes]) {
  var rnd = new math.Random.secure();

  // See http://www.cryptosys.net/pki/uuid-rfc4122.html for notes
  bytes ??= new List<int>.generate(16, (_) => rnd.nextInt(256));
  bytes[6] = (bytes[6] & 0x0F) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;

  var chars = bytes
      .map((b) => b.toRadixString(16).padLeft(2, '0'))
      .join()
      .toUpperCase();

  return '${chars.substring(0, 8)}-${chars.substring(8, 12)}-'
      '${chars.substring(12, 16)}-${chars.substring(16, 20)}-${chars.substring(20, 32)}';
}

/// Wraps [text] so that it fits within [_lineLength], if there is a line length.
///
/// This preserves existing newlines and doesn't consider terminal color escapes
/// part of a word's length. It only splits words on spaces, not on other sorts
/// of whitespace.
///
/// If [prefix] is passed, it's added at the beginning of any wrapped lines.
String wordWrap(String text, {String prefix}) {
  // If there is no limit, don't wrap.
  if (_lineLength == null) return text;

  prefix ??= "";
  return text.split("\n").map((originalLine) {
    var buffer = new StringBuffer();
    var lengthSoFar = 0;
    var firstLine = true;
    for (var word in originalLine.split(" ")) {
      var wordLength = _withoutColors(word).length;
      if (wordLength > _lineLength) {
        if (lengthSoFar != 0) buffer.writeln();
        if (!firstLine) buffer.write(prefix);
        buffer.writeln(word);
        firstLine = false;
      } else if (lengthSoFar == 0) {
        if (!firstLine) buffer.write(prefix);
        buffer.write(word);
        lengthSoFar = wordLength + prefix.length;
      } else if (lengthSoFar + 1 + wordLength > _lineLength) {
        buffer.writeln();
        buffer.write(prefix);
        buffer.write(word);
        lengthSoFar = wordLength + prefix.length;
        firstLine = false;
      } else {
        buffer.write(" $word");
        lengthSoFar += 1 + wordLength;
      }
    }
    return buffer.toString();
  }).join("\n");
}

/// A regular expression matching terminal color codes.
final _colorCode = new RegExp('\u001b\\[[0-9;]+m');

/// Returns [str] without any color codes.
String _withoutColors(String str) => str.replaceAll(_colorCode, '');

/// A regular expression to match the exception prefix that some exceptions'
/// [Object.toString] values contain.
final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');

/// Get a string description of an exception.
///
/// Many exceptions include the exception class name at the beginning of their
/// [toString], so we remove that if it exists.
String getErrorMessage(error) =>
    error.toString().replaceFirst(_exceptionPrefix, '');