// 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 dart2js.library_loader;

import 'dart:async';

import 'package:front_end/src/fasta/kernel/utils.dart';
import 'package:kernel/ast.dart' as ir;
import 'package:kernel/binary/ast_from_binary.dart' show BinaryBuilder;

import 'package:front_end/src/api_unstable/dart2js.dart' as fe;
import 'package:kernel/kernel.dart' hide LibraryDependency, Combinator;
import 'package:kernel/target/targets.dart';

import '../../compiler_new.dart' as api;
import '../common/tasks.dart' show CompilerTask, Measurer;
import '../common.dart';
import '../options.dart';

import 'front_end_adapter.dart';
import 'dart2js_target.dart' show Dart2jsTarget;

/// A task that produces the kernel IR representation of the application.
///
/// It supports loading both .dart source files or pre-compiled .dill files.
/// When given .dart source files, it invokes the common front-end (CFE)
/// to produce the corresponding kernel IR representation.
class KernelLoaderTask extends CompilerTask {
  final DiagnosticReporter _reporter;

  final api.CompilerInput _compilerInput;

  final CompilerOptions _options;

  /// Shared state between compilations.
  fe.InitializedCompilerState initializedCompilerState;

  // TODO(johnniwinther): Remove this when #34942 is fixed.
  /// Force in-memory serialization/deserialization of the loaded component.
  ///
  /// This is used for testing.
  bool forceSerialization = false;

  KernelLoaderTask(
      this._options, this._compilerInput, this._reporter, Measurer measurer)
      : initializedCompilerState = _options.kernelInitializedCompilerState,
        super(measurer);

  String get name => 'kernel loader';

  /// Loads an entire Kernel [Component] from a file on disk.
  Future<KernelResult> load(Uri resolvedUri) {
    return measure(() async {
      var isDill = resolvedUri.path.endsWith('.dill');
      ir.Component component;
      if (isDill) {
        api.Input input = await _compilerInput.readFromUri(resolvedUri,
            inputKind: api.InputKind.binary);
        component = new ir.Component();
        new BinaryBuilder(input.data).readComponent(component);
      } else {
        String targetName =
            _options.compileForServer ? "dart2js_server" : "dart2js";
        String platform = '${targetName}_platform.dill';
        initializedCompilerState = fe.initializeCompiler(
            initializedCompilerState,
            new Dart2jsTarget(targetName, new TargetFlags()),
            _options.librariesSpecificationUri,
            _options.platformBinaries.resolve(platform),
            _options.packageConfig);
        component = await fe.compile(
            initializedCompilerState,
            false,
            new CompilerFileSystem(_compilerInput),
            (e) => reportFrontEndMessage(_reporter, e),
            resolvedUri);
      }
      if (component == null) return null;
      if (forceSerialization) {
        // TODO(johnniwinther): Remove this when #34942 is fixed.
        List<int> data = serializeComponent(component);
        component = new ir.Component();
        new BinaryBuilder(data).readComponent(component);
      }
      return _toResult(component);
    });
  }

  KernelResult _toResult(ir.Component component) {
    Uri rootLibraryUri = null;
    Iterable<ir.Library> libraries = component.libraries;
    if (component.mainMethod != null) {
      var root = component.mainMethod.enclosingLibrary;
      rootLibraryUri = root.importUri;

      // Filter unreachable libraries: [Component] was built by linking in the
      // entire SDK libraries, not all of them are used. We include anything
      // that is reachable from `main`. Note that all internal libraries that
      // the compiler relies on are reachable from `dart:core`.
      var seen = new Set<Library>();
      search(ir.Library current) {
        if (!seen.add(current)) return;
        for (ir.LibraryDependency dep in current.dependencies) {
          search(dep.targetLibrary);
        }
      }

      search(root);

      // Libraries dependencies do not show implicit imports to `dart:core`.
      var dartCore = component.libraries.firstWhere((lib) {
        return lib.importUri.scheme == 'dart' && lib.importUri.path == 'core';
      });
      search(dartCore);

      libraries = libraries.where(seen.contains);
    }
    return new KernelResult(component, rootLibraryUri,
        libraries.map((lib) => lib.importUri).toList());
  }
}

/// Result of invoking the CFE to produce the kernel IR.
class KernelResult {
  final ir.Component component;

  /// The [Uri] of the root library containing main.
  final Uri rootLibraryUri;

  /// Returns the [Uri]s of all libraries that have been loaded that are
  /// reachable from the [rootLibraryUri].
  ///
  /// Note that [component] may contain some libraries that are excluded here.
  final Iterable<Uri> libraries;

  KernelResult(this.component, this.rootLibraryUri, this.libraries) {
    assert(rootLibraryUri != null);
  }

  String toString() => 'root=$rootLibraryUri,libraries=${libraries}';
}