// Copyright (c) 2017, 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:front_end/compilation_message.dart';
import 'package:front_end/byte_store.dart';
import 'package:front_end/compiler_options.dart';
import 'package:front_end/file_system.dart';
import 'package:front_end/src/base/performance_logger.dart';
import 'package:front_end/src/fasta/fasta_codes.dart';
import 'package:front_end/src/fasta/problems.dart' show unimplemented;
import 'package:front_end/src/fasta/severity.dart';
import 'package:front_end/src/fasta/ticker.dart';
import 'package:front_end/src/fasta/uri_translator.dart';
import 'package:front_end/src/fasta/uri_translator_impl.dart';
import 'package:front_end/src/multi_root_file_system.dart';
import 'package:kernel/kernel.dart' show Program, CanonicalName;
import 'package:kernel/target/targets.dart';
import 'package:kernel/target/vm.dart';
import 'package:package_config/packages.dart' show Packages;
import 'package:package_config/src/packages_impl.dart'
    show NonFilePackagesDirectoryPackages, MapPackages;
import 'package:package_config/packages_file.dart' as package_config;
import 'package:source_span/source_span.dart' show SourceSpan, SourceLocation;
import 'package:front_end/src/fasta/command_line_reporting.dart'
    as command_line_reporting;

import 'package:kernel/binary/ast_from_binary.dart' show BinaryBuilder;

import 'libraries_specification.dart';

/// All options needed for the front end implementation.
///
/// This includes: all of [CompilerOptions] in a form useful to the
/// implementation, default values for options that were not provided,
/// and information derived from how the compiler was invoked (like the
/// entry-points given to the compiler and whether a modular or whole-program
/// API was used).
///
/// The intent is that the front end should immediately wrap any incoming
/// [CompilerOptions] object in this class before doing further processing, and
/// should thereafter access all options via the wrapper.  This ensures that
/// options are interpreted in a consistent way and that data derived from
/// options is not unnecessarily recomputed.
class ProcessedOptions {
  /// The raw [CompilerOptions] which this class wraps.
  final CompilerOptions _raw;

  /// The package map derived from the options, or `null` if the package map has
  /// not been computed yet.
  Packages _packages;

  /// The object that knows how to resolve "package:" and "dart:" URIs,
  /// or `null` if it has not been computed yet.
  UriTranslatorImpl _uriTranslator;

  /// The SDK summary, or `null` if it has not been read yet.
  ///
  /// A summary, also referred to as "outline" internally, is a [Program] where
  /// all method bodies are left out. In essence, it contains just API
  /// signatures and constants. When strong-mode is enabled, the summary already
  /// includes inferred types.
  Program _sdkSummaryProgram;

  /// The summary for each uri in `options.inputSummaries`.
  ///
  /// A summary, also referred to as "outline" internally, is a [Program] where
  /// all method bodies are left out. In essence, it contains just API
  /// signatures and constants. When strong-mode is enabled, the summary already
  /// includes inferred types.
  List<Program> _inputSummariesPrograms;

  /// Other programs that are meant to be linked and compiled with the input
  /// sources.
  List<Program> _linkedDependencies;

  /// The location of the SDK, or `null` if the location hasn't been determined
  /// yet.
  Uri _sdkRoot;
  Uri get sdkRoot {
    _ensureSdkDefaults();
    return _sdkRoot;
  }

  Uri _sdkSummary;
  Uri get sdkSummary {
    _ensureSdkDefaults();
    return _sdkSummary;
  }

  List<int> _sdkSummaryBytes;

  /// Get the bytes of the SDK outline, if any.
  Future<List<int>> loadSdkSummaryBytes() async {
    if (_sdkSummaryBytes == null) {
      if (sdkSummary == null) return null;
      var entry = fileSystem.entityForUri(sdkSummary);
      _sdkSummaryBytes = await entry.readAsBytes();
    }
    return _sdkSummaryBytes;
  }

  Uri _librariesSpecificationUri;
  Uri get librariesSpecificationUri {
    _ensureSdkDefaults();
    return _librariesSpecificationUri;
  }

  Ticker ticker;

  bool get verbose => _raw.verbose;

  bool get verify => _raw.verify;

  bool get debugDump => _raw.debugDump;

  bool get setExitCodeOnProblem => _raw.setExitCodeOnProblem;

  bool get embedSourceText => _raw.embedSourceText;

  bool get throwOnErrorsForDebugging => _raw.throwOnErrorsForDebugging;

  bool get throwOnWarningsForDebugging => _raw.throwOnWarningsForDebugging;

  bool get throwOnNitsForDebugging => _raw.throwOnNitsForDebugging;

  /// Like [CompilerOptions.chaseDependencies] but with the appropriate default
  /// value filled in.
  bool get chaseDependencies => _raw.chaseDependencies ?? !_modularApi;

  /// Whether the compiler was invoked with a modular API.
  ///
  /// Used to determine the default behavior for [chaseDependencies].
  final bool _modularApi;

  /// The entry-points provided to the compiler.
  final List<Uri> inputs;

  /// The Uri where output is generated, may be null.
  final Uri output;

  /// Initializes a [ProcessedOptions] object wrapping the given [rawOptions].
  ProcessedOptions(CompilerOptions rawOptions,
      [this._modularApi = false, this.inputs = const [], this.output])
      : this._raw = rawOptions,
        // TODO(sigmund, ahe): create ticker even earlier or pass in a stopwatch
        // collecting time since the start of the VM.
        ticker = new Ticker(isVerbose: rawOptions.verbose);

  /// The logger to report compilation progress.
  PerformanceLog get logger {
    return _raw.logger;
  }

  /// The byte storage to get and put serialized data.
  ByteStore get byteStore {
    return _raw.byteStore;
  }

  bool get _reportMessages => _raw.reportMessages ?? (_raw.onError == null);

  void report(LocatedMessage message, Severity severity) {
    if (_raw.onError != null) {
      _raw.onError(new _CompilationMessage(message, severity));
    }

    if (_reportMessages) command_line_reporting.report(message, severity);
  }

  void reportWithoutLocation(Message message, Severity severity) {
    if (_raw.onError != null) {
      _raw.onError(
          new _CompilationMessage(message.withLocation(null, -1), severity));
    }

    if (_reportMessages) {
      command_line_reporting.reportWithoutLocation(message, severity);
    }
  }

  /// Runs various validations checks on the input options. For instance,
  /// if an option is a path to a file, it checks that the file exists.
  Future<bool> validateOptions() async {
    if (verbose) print(debugString());

    if (inputs.isEmpty) {
      reportWithoutLocation(messageMissingInput, Severity.error);
      return false;
    }

    for (var source in inputs) {
      // Note: we don't translate Uris at this point because some of the
      // validation further below must be done before we even construct an
      // UriTranslator
      // TODO(sigmund): consider validating dart/packages uri right after we
      // build the uri translator.
      if (source.scheme != 'dart' &&
          source.scheme != 'package' &&
          !await fileSystem.entityForUri(source).exists()) {
        reportWithoutLocation(
            templateInputFileNotFound.withArguments(source), Severity.error);
        return false;
      }
    }

    if (_raw.sdkRoot != null &&
        !await fileSystem.entityForUri(sdkRoot).exists()) {
      reportWithoutLocation(
          templateSdkRootNotFound.withArguments(sdkRoot), Severity.error);
      return false;
    }

    var summary = sdkSummary;
    if (summary != null && !await fileSystem.entityForUri(summary).exists()) {
      reportWithoutLocation(
          templateSdkSummaryNotFound.withArguments(summary), Severity.error);
      return false;
    }

    if (compileSdk && summary != null) {
      reportWithoutLocation(
          messageInternalProblemProvidedBothCompileSdkAndSdkSummary,
          Severity.internalProblem);
      return false;
    }
    return true;
  }

  /// Determine whether to generate code for the SDK when compiling a
  /// whole-program.
  bool get compileSdk => _raw.compileSdk;

  FileSystem _fileSystem;

  /// Get the [FileSystem] which should be used by the front end to access
  /// files.
  ///
  /// If the client supplied roots using [CompilerOptions.multiRoots], the
  /// returned [FileSystem] will automatically perform the appropriate mapping.
  FileSystem get fileSystem => _fileSystem ??= _createFileSystem();

  /// Whether to interpret Dart sources in strong-mode.
  bool get strongMode => _raw.strongMode;

  Target _target;
  Target get target => _target ??=
      _raw.target ?? new VmTarget(new TargetFlags(strongMode: strongMode));

  /// Get an outline program that summarizes the SDK, if any.
  // TODO(sigmund): move, this doesn't feel like an "option".
  Future<Program> loadSdkSummary(CanonicalName nameRoot) async {
    if (_sdkSummaryProgram == null) {
      if (sdkSummary == null) return null;
      var bytes = await loadSdkSummaryBytes();
      _sdkSummaryProgram = loadProgram(bytes, nameRoot);
    }
    return _sdkSummaryProgram;
  }

  /// Get the summary programs for each of the underlying `inputSummaries`
  /// provided via [CompilerOptions].
  // TODO(sigmund): move, this doesn't feel like an "option".
  Future<List<Program>> loadInputSummaries(CanonicalName nameRoot) async {
    if (_inputSummariesPrograms == null) {
      var uris = _raw.inputSummaries;
      if (uris == null || uris.isEmpty) return const <Program>[];
      // TODO(sigmund): throttle # of concurrent opreations.
      var allBytes = await Future
          .wait(uris.map((uri) => fileSystem.entityForUri(uri).readAsBytes()));
      _inputSummariesPrograms =
          allBytes.map((bytes) => loadProgram(bytes, nameRoot)).toList();
    }
    return _inputSummariesPrograms;
  }

  /// Load each of the [CompilerOptions.linkedDependencies] programs.
  // TODO(sigmund): move, this doesn't feel like an "option".
  Future<List<Program>> loadLinkDependencies(CanonicalName nameRoot) async {
    if (_linkedDependencies == null) {
      var uris = _raw.linkedDependencies;
      if (uris == null || uris.isEmpty) return const <Program>[];
      // TODO(sigmund): throttle # of concurrent opreations.
      var allBytes = await Future
          .wait(uris.map((uri) => fileSystem.entityForUri(uri).readAsBytes()));
      _linkedDependencies =
          allBytes.map((bytes) => loadProgram(bytes, nameRoot)).toList();
    }
    return _linkedDependencies;
  }

  /// Helper to load a .dill file from [uri] using the existing [nameRoot].
  Program loadProgram(List<int> bytes, CanonicalName nameRoot) {
    Program program = new Program(nameRoot: nameRoot);
    // TODO(ahe): Pass file name to BinaryBuilder.
    // TODO(ahe): Control lazy loading via an option.
    new BinaryBuilder(bytes, null, false).readProgram(program);
    return program;
  }

  /// Get the [UriTranslator] which resolves "package:" and "dart:" URIs.
  ///
  /// This is an asynchronous method since file system operations may be
  /// required to locate/read the packages file as well as SDK metadata.
  Future<UriTranslatorImpl> getUriTranslator() async {
    if (_uriTranslator == null) {
      ticker.logMs("Started building UriTranslator");
      var libraries = await _computeLibrarySpecification();
      ticker.logMs("Read libraries file");
      var packages = await _getPackages();
      ticker.logMs("Read packages file");
      _uriTranslator = new UriTranslatorImpl(libraries, packages);
    }
    return _uriTranslator;
  }

  Future<TargetLibrariesSpecification> _computeLibrarySpecification() async {
    var name = target.name;
    // TODO(sigmund): Eek! We should get to the point where there is no
    // fasta-specific targets and the target names are meaningful.
    if (name.endsWith('_fasta')) name = name.substring(0, name.length - 6);

    if (librariesSpecificationUri == null ||
        !await fileSystem.entityForUri(librariesSpecificationUri).exists()) {
      if (compileSdk) {
        reportWithoutLocation(
            templateSdkSpecificationNotFound
                .withArguments(librariesSpecificationUri),
            Severity.error);
      }
      return new TargetLibrariesSpecification(name);
    }

    var json =
        await fileSystem.entityForUri(librariesSpecificationUri).readAsString();
    try {
      var spec =
          await LibrariesSpecification.parse(librariesSpecificationUri, json);
      return spec.specificationFor(name);
    } on LibrariesSpecificationException catch (e) {
      reportWithoutLocation(
          templateCannotReadSdkSpecification.withArguments('${e.error}'),
          Severity.error);
      return new TargetLibrariesSpecification(name);
    }
  }

  /// Get the package map which maps package names to URIs.
  ///
  /// This is an asynchronous getter since file system operations may be
  /// required to locate/read the packages file.
  Future<Packages> _getPackages() async {
    if (_packages != null) return _packages;
    if (_raw.packagesFileUri != null) {
      return _packages = await createPackagesFromFile(_raw.packagesFileUri);
    }

    if (inputs.length > 1) {
      // TODO(sigmund): consider not reporting an error if we would infer
      // the same .packages file from all of the inputs.
      reportWithoutLocation(
          messageCantInferPackagesFromManyInputs, Severity.error);
      return _packages = Packages.noPackages;
    }

    var input = inputs.first;

    // When compiling the SDK the input files are normaly `dart:` URIs.
    if (input.scheme == 'dart') return _packages = Packages.noPackages;

    if (input.scheme == 'packages') {
      report(messageCantInferPackagesFromPackageUri.withLocation(input, -1),
          Severity.error);
      return _packages = Packages.noPackages;
    }

    return _packages = await _findPackages(inputs.first);
  }

  /// Create a [Packages] given the Uri to a `.packages` file.
  Future<Packages> createPackagesFromFile(Uri file) async {
    try {
      List<int> contents = await fileSystem.entityForUri(file).readAsBytes();
      Map<String, Uri> map = package_config.parse(contents, file);
      return new MapPackages(map);
    } catch (e) {
      report(
          templateCannotReadPackagesFile
              .withArguments("$e")
              .withLocation(file, -1),
          Severity.error);
      return Packages.noPackages;
    }
  }

  /// Finds a package resolution strategy using a [FileSystem].
  ///
  /// The [scriptUri] points to a Dart script with a valid scheme accepted by
  /// the [FileSystem].
  ///
  /// This function first tries to locate a `.packages` file in the `scriptUri`
  /// directory. If that is not found, it instead checks for the presence of a
  /// `packages/` directory in the same place.  If that also fails, it starts
  /// checking parent directories for a `.packages` file, and stops if it finds
  /// it.  Otherwise it gives up and returns [Packages.noPackages].
  ///
  /// Note: this is a fork from `package:package_config/discovery.dart` to adapt
  /// it to use [FileSystem]. The logic here is a mix of the logic in the
  /// `findPackagesFromFile` and `findPackagesFromNonFile`:
  ///
  ///    * Like `findPackagesFromFile` resolution searches for parent
  ///    directories
  ///
  ///    * Like `findPackagesFromNonFile` if we resolve packages as the
  ///    `packages/` directory, we can't provide a list of packages that are
  ///    visible.
  Future<Packages> _findPackages(Uri scriptUri) async {
    var dir = scriptUri.resolve('.');
    if (!dir.isAbsolute) {
      reportWithoutLocation(
          templateInternalProblemUnsupported
              .withArguments("Expected input Uri to be absolute: $scriptUri."),
          Severity.internalProblem);
      return Packages.noPackages;
    }

    Future<Uri> checkInDir(Uri dir) async {
      Uri candidate = dir.resolve('.packages');
      if (await fileSystem.entityForUri(candidate).exists()) return candidate;
      return null;
    }

    // Check for $cwd/.packages
    var candidate = await checkInDir(dir);
    if (candidate != null) return createPackagesFromFile(candidate);

    // Check for $cwd/packages/
    var packagesDir = dir.resolve("packages/");
    if (await fileSystem.entityForUri(packagesDir).exists()) {
      return new NonFilePackagesDirectoryPackages(packagesDir);
    }

    // Check for cwd(/..)+/.packages
    var parentDir = dir.resolve('..');
    while (parentDir.path != dir.path) {
      candidate = await checkInDir(parentDir);
      if (candidate != null) break;
      dir = parentDir;
      parentDir = dir.resolve('..');
    }

    if (candidate != null) return createPackagesFromFile(candidate);
    return Packages.noPackages;
  }

  bool _computedSdkDefaults = false;

  /// Ensure [_sdkRoot], [_sdkSummary] and [_librarySpecUri] are initialized.
  ///
  /// If they are not set explicitly, they are infered based on the default
  /// behavior described in [CompilerOptions].
  void _ensureSdkDefaults() {
    if (_computedSdkDefaults) return;
    _computedSdkDefaults = true;
    var root = _raw.sdkRoot;
    if (root != null) {
      // Normalize to always end in '/'
      if (!root.path.endsWith('/')) {
        root = root.replace(path: root.path + '/');
      }
      _sdkRoot = root;
    } else if (compileSdk) {
      // TODO(paulberry): implement the algorithm for finding the SDK
      // automagically.
      unimplemented('infer the default sdk location', -1, null);
    }

    if (_raw.sdkSummary != null) {
      _sdkSummary = _raw.sdkSummary;
    } else if (!compileSdk) {
      // Infer based on the sdkRoot, but only when `compileSdk` is false,
      // otherwise the default intent was to compile the sdk from sources and
      // not to load an sdk summary file.
      _sdkSummary = root?.resolve("vm_outline.dill");
    }

    if (_raw.librariesSpecificationUri != null) {
      _librariesSpecificationUri = _raw.librariesSpecificationUri;
    } else if (compileSdk) {
      _librariesSpecificationUri = sdkRoot.resolve('lib/libraries.json');
    }
  }

  /// Create a [FileSystem] specific to the current options.
  ///
  /// If `_raw.multiRoots` is not empty, the file-system will implement the
  /// semantics of multiple roots. If [chaseDependencies] is false, the
  /// resulting file system will be hermetic.
  FileSystem _createFileSystem() {
    var result = _raw.fileSystem;
    // Note: hermetic checks are done before translating multi-root URIs, so
    // the order in which we create the file systems below is relevant.
    if (!_raw.multiRoots.isEmpty) {
      result = new MultiRootFileSystem('multi-root', _raw.multiRoots, result);
    }
    if (!chaseDependencies) {
      var allInputs = inputs.toSet();
      allInputs.addAll(_raw.inputSummaries);
      allInputs.addAll(_raw.linkedDependencies);

      if (sdkSummary != null) allInputs.add(sdkSummary);

      if (_raw.sdkRoot != null) {
        // TODO(sigmund): refine this, we should be more explicit about when
        // sdkRoot and libraries.json are allowed to be used.
        allInputs.add(sdkRoot);
        allInputs.add(sdkRoot.resolve("lib/libraries.json"));
      }

      /// Note: Searching the file-system for the package-config is not
      /// supported in hermetic builds.
      if (_raw.packagesFileUri != null) allInputs.add(_raw.packagesFileUri);
      result = new HermeticFileSystem(allInputs, result);
    }
    return result;
  }

  String debugString() {
    var sb = new StringBuffer();
    writeList(String name, List elements) {
      if (elements.isEmpty) {
        sb.writeln('$name: <empty>');
        return;
      }
      sb.writeln('$name:');
      elements.forEach((s) {
        sb.writeln('  - $s');
      });
    }

    sb.writeln('Inputs: ${inputs}');
    sb.writeln('Output: ${output}');

    sb.writeln('Was error handler provided: '
        '${_raw.onError == null ? "no" : "yes"}');

    sb.writeln('FileSystem: ${_fileSystem.runtimeType} '
        '(provided: ${_raw.fileSystem.runtimeType})');

    writeList('Input Summaries', _raw.inputSummaries);
    writeList('Linked Dependencies', _raw.linkedDependencies);
    writeList('Multiroots', _raw.multiRoots);

    sb.writeln('Modular: ${_modularApi}');
    sb.writeln('Hermetic: ${!chaseDependencies} (provided: '
        '${_raw.chaseDependencies == null ? null : !_raw.chaseDependencies})');
    sb.writeln('Packages uri: ${_raw.packagesFileUri}');
    sb.writeln('Packages: ${_packages}');

    sb.writeln('Compile SDK: ${compileSdk}');
    sb.writeln('SDK root: ${_sdkRoot} (provided: ${_raw.sdkRoot})');
    sb.writeln('SDK specification: ${_librariesSpecificationUri} '
        '(provided: ${_raw.librariesSpecificationUri})');
    sb.writeln('SDK summary: ${_sdkSummary} (provided: ${_raw.sdkSummary})');

    sb.writeln('Strong: ${strongMode}');
    sb.writeln('Target: ${_target?.name} (provided: ${_raw.target?.name})');

    sb.writeln('throwOnErrorsForDebugging: ${throwOnErrorsForDebugging}');
    sb.writeln('throwOnWarningsForDebugging: ${throwOnWarningsForDebugging}');
    sb.writeln('throwOnNitsForDebugging: ${throwOnNitsForDebugging}');
    sb.writeln('exit on problem: ${setExitCodeOnProblem}');
    sb.writeln('Embed sources: ${embedSourceText}');
    sb.writeln('debugDump: ${debugDump}');
    sb.writeln('verbose: ${verbose}');
    sb.writeln('verify: ${verify}');
    return '$sb';
  }
}

/// A [FileSystem] that only allows access to files that have been explicitly
/// whitelisted.
class HermeticFileSystem implements FileSystem {
  final Set<Uri> includedFiles;
  final FileSystem _realFileSystem;

  HermeticFileSystem(this.includedFiles, this._realFileSystem);

  FileSystemEntity entityForUri(Uri uri) {
    if (includedFiles.contains(uri)) return _realFileSystem.entityForUri(uri);
    throw new HermeticAccessException(uri);
  }
}

class HermeticAccessException extends FileSystemException {
  HermeticAccessException(Uri uri)
      : super(
            uri,
            'Invalid access to $uri: '
            'the file is accessed in a modular hermetic build, '
            'but it was not explicitly listed as an input.');

  @override
  String toString() => message;
}

/// Wraps a [LocatedMessage] to implement the public [CompilationMessage] API.
class _CompilationMessage implements CompilationMessage {
  final LocatedMessage _original;
  final Severity severity;

  String get message => _original.message;

  String get tip => _original.tip;

  String get analyzerCode => _original.code.analyzerCode;

  String get dart2jsCode => _original.code.dart2jsCode;

  SourceSpan get span {
    if (_original.charOffset == -1) {
      if (_original.uri == null) return null;
      return new SourceLocation(0, sourceUrl: _original.uri).pointSpan();
    }
    return new SourceLocation(_original.charOffset, sourceUrl: _original.uri)
        .pointSpan();
  }

  _CompilationMessage(this._original, this.severity);

  String toString() => message;
}