// 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.

/// Message logging.
library pub.log;

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

import 'package:path/path.dart' as p;
import 'package:stack_trace/stack_trace.dart';

import 'io.dart';
import 'progress.dart';
import 'transcript.dart';
import 'utils.dart';

/// The singleton instance so that we can have a nice api like:
///
///     log.json.error(...);
final json = new _JsonLogger();

typedef LogFn(Entry entry);
final Map<Level, LogFn> _loggers = new Map<Level, LogFn>();

/// In cases where there's a ton of log spew, make sure we don't eat infinite
/// memory.
///
/// This can occur when the backtracking solver stumbles into a pathological
/// dependency graph. It generally will find a solution, but it may log
/// thousands and thousands of entries to get there.
const _MAX_TRANSCRIPT = 10000;

/// The list of recorded log messages. Will only be recorded if
/// [recordTranscript()] is called.
Transcript<Entry> _transcript;

/// The currently-running progress indicator or `null` if there is none.
Progress _progress;

final _cyan = getSpecial('\u001b[36m');
final _green = getSpecial('\u001b[32m');
final _magenta = getSpecial('\u001b[35m');
final _red = getSpecial('\u001b[31m');
final _yellow = getSpecial('\u001b[33m');
final _gray = getSpecial('\u001b[1;30m');
final _none = getSpecial('\u001b[0m');
final _bold = getSpecial('\u001b[1m');

/// An enum type for defining the different logging levels. By default, [ERROR]
/// and [WARNING] messages are printed to sterr. [MESSAGE] messages are printed
/// to stdout, and others are ignored.
class Level {
  /// An error occurred and an operation could not be completed. Usually shown
  /// to the user on stderr.
  static const ERROR = const Level._("ERR ");

  /// Something unexpected happened, but the program was able to continue,
  /// though possibly in a degraded fashion.
  static const WARNING = const Level._("WARN");

  /// A message intended specifically to be shown to the user.
  static const MESSAGE = const Level._("MSG ");

  /// Some interaction with the external world occurred, such as a network
  /// operation, process spawning, or file IO.
  static const IO = const Level._("IO  ");

  /// Incremental output during pub's version constraint solver.
  static const SOLVER = const Level._("SLVR");

  /// Fine-grained and verbose additional information. Can be used to provide
  /// program state context for other logs (such as what pub was doing when an
  /// IO operation occurred) or just more detail for an operation.
  static const FINE = const Level._("FINE");

  const Level._(this.name);
  final String name;

  String toString() => name;
  int get hashCode => name.hashCode;
}

/// A single log entry.
class Entry {
  final Level level;
  final List<String> lines;

  Entry(this.level, this.lines);
}

/// Logs [message] at [Level.ERROR].
void error(message, [error]) {
  if (error != null) {
    message = "$message: $error";
    var trace;
    if (error is Error) trace = error.stackTrace;
    if (trace != null) {
      message = "$message\nStackTrace: $trace";
    }
  }
  write(Level.ERROR, message);
}

/// Logs [message] at [Level.WARNING].
void warning(message) => write(Level.WARNING, message);

/// Logs [message] at [Level.MESSAGE].
void message(message) => write(Level.MESSAGE, message);

/// Logs [message] at [Level.IO].
void io(message) => write(Level.IO, message);

/// Logs [message] at [Level.SOLVER].
void solver(message) => write(Level.SOLVER, message);

/// Logs [message] at [Level.FINE].
void fine(message) => write(Level.FINE, message);

/// Logs [message] at [level].
void write(Level level, message) {
  if (_loggers.isEmpty) showNormal();

  var lines = splitLines(message.toString());

  // Discard a trailing newline. This is useful since StringBuffers often end
  // up with an extra newline at the end from using [writeln].
  if (lines.isNotEmpty && lines.last == "") {
    lines.removeLast();
  }

  var entry = new Entry(level, lines);

  var logFn = _loggers[level];
  if (logFn != null) logFn(entry);

  if (_transcript != null) _transcript.add(entry);
}

/// Logs an asynchronous IO operation. Logs [startMessage] before the operation
/// starts, then when [operation] completes, invokes [endMessage] with the
/// completion value and logs the result of that. Returns a future that
/// completes after the logging is done.
///
/// If [endMessage] is omitted, then logs "Begin [startMessage]" before the
/// operation and "End [startMessage]" after it.
Future ioAsync(String startMessage, Future operation,
               [String endMessage(value)]) {
  if (endMessage == null) {
    io("Begin $startMessage.");
  } else {
    io(startMessage);
  }

  return operation.then((result) {
    if (endMessage == null) {
      io("End $startMessage.");
    } else {
      io(endMessage(result));
    }
    return result;
  });
}

/// Logs the spawning of an [executable] process with [arguments] at [IO]
/// level.
void process(String executable, List<String> arguments,
    String workingDirectory) {
  io("Spawning \"$executable ${arguments.join(' ')}\" in "
      "${p.absolute(workingDirectory)}");
}

/// Logs the results of running [executable].
void processResult(String executable, PubProcessResult result) {
  // Log it all as one message so that it shows up as a single unit in the logs.
  var buffer = new StringBuffer();
  buffer.writeln("Finished $executable. Exit code ${result.exitCode}.");

  dumpOutput(String name, List<String> output) {
    if (output.length == 0) {
      buffer.writeln("Nothing output on $name.");
    } else {
      buffer.writeln("$name:");
      var numLines = 0;
      for (var line in output) {
        if (++numLines > 1000) {
          buffer.writeln('[${output.length - 1000}] more lines of output '
              'truncated...]');
          break;
        }

        buffer.writeln("| $line");
      }
    }
  }

  dumpOutput("stdout", result.stdout);
  dumpOutput("stderr", result.stderr);

  io(buffer.toString().trim());
}

/// Enables recording of log entries.
void recordTranscript() {
  _transcript = new Transcript<Entry>(_MAX_TRANSCRIPT);
}

/// If [recordTranscript()] was called, then prints the previously recorded log
/// transcript to stderr.
void dumpTranscript() {
  if (_transcript == null) return;

  stderr.writeln('---- Log transcript ----');
  _transcript.forEach((entry) {
    _printToStream(stderr, entry, showLabel: true);
  }, (discarded) {
    stderr.writeln('---- ($discarded discarded) ----');
  });
  stderr.writeln('---- End log transcript ----');
}

/// Prints [message] then displays an updated elapsed time until the future
/// returned by [callback] completes. If anything else is logged during this
/// (include another call to [progress]) that cancels the progress.
Future progress(String message, Future callback()) {
  _stopProgress();
  _progress = new Progress(message);
  return callback().whenComplete(() {
    var message = _stopProgress();

    // Add the progress message to the transcript.
    if (_transcript != null && message != null) {
      _transcript.add(new Entry(Level.MESSAGE, [message]));
    }
  });
}

/// Stops the running progress indicator, if currently running.
///
/// Returns the final progress message, if any, otherwise `null`.
String _stopProgress() {
  if (_progress == null) return null;
  var message = _progress.stop();
  _progress = null;
  return message;
}

/// Wraps [text] in the ANSI escape codes to make it bold when on a platform
/// that supports that.
///
/// Use this to highlight the most important piece of a long chunk of text.
String bold(text) => "$_bold$text$_none";

/// Wraps [text] in the ANSI escape codes to make it gray when on a platform
/// that supports that.
///
/// Use this for text that's less important than the text around it.
String gray(text) => "$_gray$text$_none";

/// Wraps [text] in the ANSI escape codes to color it cyan when on a platform
/// that supports that.
///
/// Use this to highlight something interesting but neither good nor bad.
String cyan(text) => "$_cyan$text$_none";

/// Wraps [text] in the ANSI escape codes to color it green when on a platform
/// that supports that.
///
/// Use this to highlight something successful or otherwise positive.
String green(text) => "$_green$text$_none";

/// Wraps [text] in the ANSI escape codes to color it magenta when on a
/// platform that supports that.
///
/// Use this to highlight something risky that the user should be aware of but
/// may intend to do.
String magenta(text) => "$_magenta$text$_none";

/// Wraps [text] in the ANSI escape codes to color it red when on a platform
/// that supports that.
///
/// Use this to highlight unequivocal errors, problems, or failures.
String red(text) => "$_red$text$_none";

/// Wraps [text] in the ANSI escape codes to color it yellow when on a platform
/// that supports that.
///
/// Use this to highlight warnings, cautions or other things that are bad but
/// do not prevent the user's goal from being reached.
String yellow(text) => "$_yellow$text$_none";

/// Sets the verbosity to "normal", which shows errors, warnings, and messages.
void showNormal() {
  _loggers[Level.ERROR]   = _logToStderr;
  _loggers[Level.WARNING] = _logToStderr;
  _loggers[Level.MESSAGE] = _logToStdout;
  _loggers[Level.IO]      = null;
  _loggers[Level.SOLVER]  = null;
  _loggers[Level.FINE]    = null;
}

/// Sets the verbosity to "io", which shows errors, warnings, messages, and IO
/// event logs.
void showIO() {
  _loggers[Level.ERROR]   = _logToStderrWithLabel;
  _loggers[Level.WARNING] = _logToStderrWithLabel;
  _loggers[Level.MESSAGE] = _logToStdoutWithLabel;
  _loggers[Level.IO]      = _logToStderrWithLabel;
  _loggers[Level.SOLVER]  = null;
  _loggers[Level.FINE]    = null;
}

/// Sets the verbosity to "solver", which shows errors, warnings, messages, and
/// solver logs.
void showSolver() {
  _loggers[Level.ERROR]   = _logToStderr;
  _loggers[Level.WARNING] = _logToStderr;
  _loggers[Level.MESSAGE] = _logToStdout;
  _loggers[Level.IO]      = null;
  _loggers[Level.SOLVER]  = _logToStdout;
  _loggers[Level.FINE]    = null;
}

/// Sets the verbosity to "all", which logs ALL the things.
void showAll() {
  _loggers[Level.ERROR]   = _logToStderrWithLabel;
  _loggers[Level.WARNING] = _logToStderrWithLabel;
  _loggers[Level.MESSAGE] = _logToStdoutWithLabel;
  _loggers[Level.IO]      = _logToStderrWithLabel;
  _loggers[Level.SOLVER]  = _logToStderrWithLabel;
  _loggers[Level.FINE]    = _logToStderrWithLabel;
}

/// Log function that prints the message to stdout.
void _logToStdout(Entry entry) {
  _logToStream(stdout, entry, showLabel: false);
}

/// Log function that prints the message to stdout with the level name.
void _logToStdoutWithLabel(Entry entry) {
  _logToStream(stdout, entry, showLabel: true);
}

/// Log function that prints the message to stderr.
void _logToStderr(Entry entry) {
  _logToStream(stderr, entry, showLabel: false);
}

/// Log function that prints the message to stderr with the level name.
void _logToStderrWithLabel(Entry entry) {
  _logToStream(stderr, entry, showLabel: true);
}

void _logToStream(IOSink sink, Entry entry, {bool showLabel}) {
  if (json.enabled) return;

  _printToStream(sink, entry, showLabel: showLabel);
}

void _printToStream(IOSink sink, Entry entry, {bool showLabel}) {
  _stopProgress();

  bool firstLine = true;
  for (var line in entry.lines) {
    if (showLabel) {
      if (firstLine) {
        sink.write('${entry.level.name}: ');
      } else {
        sink.write('    | ');
      }
    }

    sink.writeln(line);

    firstLine = false;
  }
}

/// Namespace-like class for collecting the methods for JSON logging.
class _JsonLogger {
  /// Whether logging should use machine-friendly JSON output or human-friendly
  /// text.
  ///
  /// If set to `true`, then no regular logging is printed. Logged messages
  /// will still be recorded and displayed if the transcript is printed.
  bool enabled = false;

  /// Creates an error JSON object for [error] and prints it if JSON output
  /// is enabled.
  ///
  /// Always prints to stdout.
  void error(error, [stackTrace]) {
    var errorJson = {"error": error.toString()};

    if (stackTrace == null && error is Error) stackTrace = error.stackTrace;
    if (stackTrace != null) {
      errorJson["stackTrace"] = new Chain.forTrace(stackTrace).toString();
    }

    this.message(errorJson);
  }

  /// Encodes [message] to JSON and prints it if JSON output is enabled.
  void message(message) {
    if (!enabled) return;

    print(JSON.encode(message));
  }
}