pkg/front_end/lib/src/incremental/combine.dart

// 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 'package:kernel/kernel.dart';

/// Given the list of full and partial [outlines] of libraries, combine them
/// into a new [Program].  Different outlines can define the same node multiple
/// times, just one is kept, and all references to synonyms are replaced with
/// the reference to the kept version.  Call [CombineResult.undo] after
/// finishing using the combined [Program] to restore [outlines] into their
/// original state.
CombineResult combine(List<Program> outlines) {
  var combiner = new _Combiner(outlines);
  combiner.perform();
  return combiner.result;
}

/// The result of outlines combining; call [undo] after using to restore
/// partial outlines into their original state.
class CombineResult {
  final Program program;

  final Map<Library, Program> _undoLibraryToProgram = {};

  final Map<Class, Library> _undoClassToLibrary = {};
  final Map<Field, Library> _undoFieldToLibrary = {};
  final Map<Procedure, Library> _undoProcedureToLibrary = {};

  final Map<Library, int> _undoLibraryToClasses = {};
  final Map<Library, int> _undoLibraryToFields = {};
  final Map<Library, int> _undoLibraryToProcedures = {};

  final Map<Program, Map<Reference, Reference>> _undoReferenceMap = {};

  bool _undone = false;

  CombineResult(this.program);

  /// Undo changes applied to partial outlines by [combine].
  void undo() {
    if (_undone) {
      throw new StateError('This result has already been undone.');
    }
    _undone = true;

    _undoLibraryToProgram.forEach((library, program) {
      program.root.adoptChild(library.canonicalName);
      library.parent = program;
    });

    _undoClassToLibrary.forEach((child, parent) {
      parent.canonicalName.adoptChild(child.canonicalName);
      child.parent = parent;
    });
    _undoFieldToLibrary.forEach((child, parent) {
      var parentName = parent.canonicalName.getChild('@fields');
      parentName.adoptChild(child.canonicalName);
      child.parent = parent;
    });
    _undoProcedureToLibrary.forEach((child, parent) {
      var qualifier = CanonicalName.getMemberQualifier(child);
      var parentName = parent.canonicalName.getChild(qualifier);
      parentName.adoptChild(child.canonicalName);
      child.parent = parent;
    });

    _undoLibraryToClasses.forEach((library, classesLength) {
      library.classes.length = classesLength;
    });
    _undoLibraryToFields.forEach((library, fieldsLength) {
      library.fields.length = fieldsLength;
    });
    _undoLibraryToProcedures.forEach((library, fieldsLength) {
      library.procedures.length = fieldsLength;
    });

    _undoReferenceMap.forEach((outline, map) {
      outline.accept(new _ReplaceReferencesVisitor(map, null));
    });
  }
}

/// Keeps the state during combining and contains the result.
class _Combiner {
  final List<Program> outlines;
  final CombineResult result = new CombineResult(new Program());

  /// We record here during [_combineOutline], that keys should be replaced
  /// with values in all places that can use [Reference]s.
  Map<Reference, Reference> _referenceMap;

  _Combiner(this.outlines);

  /// Combine the [outlines] into a new [Program].
  void perform() {
    for (var outline in outlines) {
      _combineOutline(outline);
    }
  }

  /// If the [target] does not have a child with the same name as the [source],
  /// adopt the [source] and return `null`.  Otherwise return the existing
  /// name.
  CanonicalName _adoptMemberName(NamedNode target, Member source) {
    String qualifier = CanonicalName.getMemberQualifier(source);
    CanonicalName parentName = target.canonicalName.getChild(qualifier);
    String sourceName = source.canonicalName.name;
    if (parentName.hasChild(sourceName)) {
      return parentName.getChild(sourceName);
    }
    parentName.adoptChild(source.canonicalName);
    return null;
  }

  /// If [source] is the first node with a particular name, we remember its
  /// original parent into [CombineResult._undoClassToLibrary], and add it
  /// into the [target].
  ///
  /// If [source] is not the first node with this name, we don't add it,
  /// instead we remember that references to this node should be replaced
  /// with the reference to the first node.
  void _combineClass(Library target, Class source) {
    String name = source.name;
    if (target.canonicalName.hasChild(name)) {
      // TODO(scheglov): combine members
    } else {
      result._undoClassToLibrary[source] = source.parent;
      target.canonicalName.adoptChild(source.canonicalName);
      target.addClass(source);
    }
  }

  /// If [source] is the first node with a particular name, we remember its
  /// original parent into [CombineResult._undoFieldToLibrary], and add it
  /// into the [target].
  ///
  /// If [source] is not the first node with this name, we don't add it,
  /// instead we remember that references to this node should be replaced
  /// with the reference to the first node.
  void _combineField(Library target, Field source) {
    CanonicalName existing = _adoptMemberName(target, source);
    if (existing == null) {
      result._undoFieldToLibrary[source] = source.parent;
      target.addField(source);
    } else {
      _referenceMap[source.reference] = existing.reference;
    }
  }

  /// If [source] is the first node with a particular name, we remember its
  /// original parent into [CombineResult._undoFieldToLibrary], and add it
  /// into the [target].
  ///
  /// If [source] is not the first node with this name, we don't add it,
  /// instead we remember that references to this node should be replaced
  /// with the reference to the first node.  Then we continue merging children
  /// of the node into the first node.
  ///
  /// The first nodes are updated by adding more children into them.  We
  /// remember the original lengths of their [Library.classes],
  /// [Library.fields], and [Library.procedures] lists.  So, to undo the
  /// changes and get rid of added children it is enough to set their lengths.
  void _combineLibrary(Program target, Library source) {
    String name = source.importUri.toString();
    if (target.root.hasChild(name)) {
      var existingReference = target.root.getChild(name).reference;
      _referenceMap[source.reference] = existingReference;
      Library existingNode = existingReference.node;
      for (var class_ in source.classes) {
        _combineClass(existingNode, class_);
      }
      for (var field in source.fields) {
        _combineField(existingNode, field);
      }
      for (var procedure in source.procedures) {
        _combineProcedure(existingNode, procedure);
      }
    } else {
      result._undoLibraryToProgram[source] = source.parent;
      result._undoLibraryToClasses[source] = source.classes.length;
      result._undoLibraryToFields[source] = source.fields.length;
      result._undoLibraryToProcedures[source] = source.procedures.length;
      target.root.adoptChild(source.canonicalName);
      source.parent = target;
      target.libraries.add(source);
    }
  }

  void _combineOutline(Program outline) {
    _referenceMap = {};
    for (var library in outline.libraries) {
      _combineLibrary(result.program, library);
    }
    var undoMap = <Reference, Reference>{};
    result._undoReferenceMap[outline] = undoMap;
    outline.accept(new _ReplaceReferencesVisitor(_referenceMap, undoMap));
    _referenceMap = null;
  }

  /// If [source] is the first node with a particular name, we remember its
  /// original parent into [CombineResult._undoProcedureToLibrary], and add it
  /// into the [target].
  ///
  /// If [source] is not the first node with this name, we don't add it,
  /// instead we remember that references to this node should be replaced
  /// with the reference to the first node.
  void _combineProcedure(Library target, Procedure source) {
    CanonicalName existing = _adoptMemberName(target, source);
    if (existing == null) {
      result._undoProcedureToLibrary[source] = source.parent;
      target.addProcedure(source);
    } else {
      _referenceMap[source.reference] = existing.reference;
    }
  }
}

class _ReplaceReferencesVisitor extends RecursiveVisitor {
  final Map<Reference, Reference> map;
  final Map<Reference, Reference> undoMap;

  _ReplaceReferencesVisitor(this.map, this.undoMap);

  @override
  void visitLibraryDependency(LibraryDependency node) {
    var reference = node.importedLibraryReference;
    var newReference = map[reference];
    if (newReference != null) {
      node.importedLibraryReference = newReference;
      if (undoMap != null) {
        undoMap[newReference] = reference;
      }
    }
  }

  @override
  void visitStaticGet(StaticGet node) {
    var reference = node.targetReference;
    var newReference = map[reference];
    if (newReference != null) {
      node.targetReference = newReference;
      if (undoMap != null) {
        undoMap[newReference] = reference;
      }
    }
  }

  @override
  void visitStaticInvocation(StaticInvocation node) {
    var reference = node.targetReference;
    var newReference = map[reference];
    if (newReference != null) {
      node.targetReference = newReference;
      if (undoMap != null) {
        undoMap[newReference] = reference;
      }
    }
  }

  @override
  void visitStaticSet(StaticSet node) {
    var reference = node.targetReference;
    var newReference = map[reference];
    if (newReference != null) {
      node.targetReference = newReference;
      if (undoMap != null) {
        undoMap[newReference] = reference;
      }
    }
  }
}