// Copyright (c) 2014, 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.

part of dart2js.js_emitter;

class TypeTestProperties {
  /// The index of the function type into the metadata.
  ///
  /// If the class doesn't have a function type this field is `null`.
  ///
  /// If the is tests were generated with `storeFunctionTypeInMetadata` set to
  /// `false`, this field is `null`, and the [properties] contain a property
  /// that encodes the function type.
  int functionTypeIndex;

  /// The properties that must be installed on the prototype of the
  /// JS constructor of the [ClassElement] for which the is checks were
  /// generated.
  final Map<String, jsAst.Node> properties = <String, jsAst.Node>{};
}

class TypeTestGenerator {
  final Compiler compiler;
  final CodeEmitterTask emitterTask;
  final Namer namer;

  TypeTestGenerator(this.compiler, this.emitterTask, this.namer);

  JavaScriptBackend get backend => compiler.backend;
  OldEmitter get oldEmitter => emitterTask.oldEmitter;
  TypeTestRegistry get typeTestRegistry => emitterTask.typeTestRegistry;

  Set<ClassElement> get checkedClasses =>
      typeTestRegistry.checkedClasses;

  Iterable<ClassElement> get classesUsingTypeVariableTests =>
      typeTestRegistry.classesUsingTypeVariableTests;

  Set<FunctionType> get checkedFunctionTypes =>
      typeTestRegistry.checkedFunctionTypes;

  /// Generates all properties necessary for is-checks on the [classElement].
  ///
  /// Returns an instance of [TypeTestProperties] that contains the properties
  /// that must be installed on the prototype of the JS constructor of the
  /// [classElement].
  ///
  /// If [storeFunctionTypeInMetadata] is `true`, stores the reified function
  /// type (if class has one) in the metadata object and stores its index in
  /// the result. This is only possible for function types that do not contain
  /// type variables.
  TypeTestProperties generateIsTests(
      ClassElement classElement,
      { bool storeFunctionTypeInMetadata: true}) {
    assert(invariant(classElement, classElement.isDeclaration));

    TypeTestProperties result = new TypeTestProperties();

    void generateIsTest(Element other) {
      if (other == compiler.objectClass && other != classElement) {
        // Avoid emitting `$isObject` on all classes but [Object].
        return;
      }
      result.properties[namer.operatorIs(other)] = js('true');
    }

    void generateFunctionTypeSignature(FunctionElement method,
                                       FunctionType type) {
      assert(method.isImplementation);
      jsAst.Expression thisAccess = new jsAst.This();
      Node node = method.node;
      ClosureClassMap closureData =
          compiler.closureToClassMapper.closureMappingCache[node];
      if (closureData != null) {
        ClosureFieldElement thisLocal =
            closureData.freeVariableMap[closureData.thisLocal];
        if (thisLocal != null) {
          String thisName = namer.instanceFieldPropertyName(thisLocal);
          thisAccess = js('this.#', thisName);
        }
      }

      if (storeFunctionTypeInMetadata && !type.containsTypeVariables) {
        result.functionTypeIndex = oldEmitter.metadataEmitter.reifyType(type);
      } else {
        RuntimeTypes rti = backend.rti;
        jsAst.Expression encoding = rti.getSignatureEncoding(type, thisAccess);
        String operatorSignature = namer.operatorSignature;
        result.properties[operatorSignature] = encoding;
      }
    }

    void generateSubstitution(ClassElement cls, {bool emitNull: false}) {
      if (cls.typeVariables.isEmpty) return;
      RuntimeTypes rti = backend.rti;
      jsAst.Expression expression;
      bool needsNativeCheck =
          oldEmitter.nativeEmitter.requiresNativeIsCheck(cls);
      expression = rti.getSupertypeSubstitution(classElement, cls);
      if (expression == null && (emitNull || needsNativeCheck)) {
        expression = new jsAst.LiteralNull();
      }
      if (expression != null) {
        result.properties[namer.substitutionName(cls)] = expression;
      }
    }

    void generateTypeCheck(TypeCheck check) {
      ClassElement checkedClass = check.cls;
      // We must not call [generateIsTest] since we also want is$Object.
      result.properties[namer.operatorIs(checkedClass)] = js('true');
      Substitution substitution = check.substitution;
      if (substitution != null) {
        jsAst.Expression body = substitution.getCode(backend.rti);
        result.properties[namer.substitutionName(checkedClass)] = body;
      }
    }

    _generateIsTestsOn(classElement, generateIsTest,
        generateFunctionTypeSignature,
        generateSubstitution,
        generateTypeCheck);

    return result;
  }

  /**
   * Generate "is tests" for [cls] itself, and the "is tests" for the
   * classes it implements and type argument substitution functions for these
   * tests.   We don't need to add the "is tests" of the super class because
   * they will be inherited at runtime, but we may need to generate the
   * substitutions, because they may have changed.
   */
  void _generateIsTestsOn(
      ClassElement cls,
      void generateIsTest(Element element),
      FunctionTypeSignatureEmitter generateFunctionTypeSignature,
      SubstitutionEmitter generateSubstitution,
      void emitTypeCheck(TypeCheck check)) {
    Setlet<Element> generated = new Setlet<Element>();

    if (checkedClasses.contains(cls)) {
      generateIsTest(cls);
      generateSubstitution(cls);
      generated.add(cls);
    }

    // Precomputed is checks.
    TypeChecks typeChecks = backend.rti.requiredChecks;
    Iterable<TypeCheck> classChecks = typeChecks[cls];
    if (classChecks != null) {
      for (TypeCheck check in classChecks) {
        if (!generated.contains(check.cls)) {
          emitTypeCheck(check);
          generated.add(check.cls);
        }
      }
    }

    RuntimeTypes rti = backend.rti;
    ClassElement superclass = cls.superclass;

    bool haveSameTypeVariables(ClassElement a, ClassElement b) {
      if (a.isClosure) return true;
      return backend.rti.isTrivialSubstitution(a, b);
    }

    if (superclass != null && superclass != compiler.objectClass &&
        !haveSameTypeVariables(cls, superclass)) {
      // We cannot inherit the generated substitutions, because the type
      // variable layout for this class is different.  Instead we generate
      // substitutions for all checks and make emitSubstitution a NOP for the
      // rest of this function.

      // TODO(karlklose): move the computation of these checks to
      // RuntimeTypeInformation.
      while (superclass != null) {
        if (backend.classNeedsRti(superclass)) {
          generateSubstitution(superclass, emitNull: true);
          generated.add(superclass);
        }
        superclass = superclass.superclass;
      }
      for (DartType supertype in cls.allSupertypes) {
        ClassElement superclass = supertype.element;
        if (generated.contains(superclass)) continue;

        if (classesUsingTypeVariableTests.contains(superclass) ||
            checkedClasses.contains(superclass)) {
          // Generate substitution.  If no substitution is necessary, emit
          // `null` to overwrite a (possibly) existing substitution from the
          // super classes.
          generateSubstitution(superclass, emitNull: true);
        }
      }

      void emitNothing(_, {emitNull}) {};

      generateSubstitution = emitNothing;
    }

    // A class that defines a `call` method implicitly implements
    // [Function] and needs checks for all typedefs that are used in is-checks.
    if (checkedClasses.contains(compiler.functionClass) ||
        checkedFunctionTypes.isNotEmpty) {
      Element call = cls.lookupLocalMember(Compiler.CALL_OPERATOR_NAME);
      if (call == null) {
        // If [cls] is a closure, it has a synthetic call operator method.
        call = cls.lookupBackendMember(Compiler.CALL_OPERATOR_NAME);
      }
      if (call != null && call.isFunction) {
        // A superclass might already implement the Function interface. In such
        // a case, we can avoid emiting the is test here.
        if (!cls.superclass.implementsFunction(compiler)) {
          _generateInterfacesIsTests(compiler.functionClass,
                                    generateIsTest,
                                    generateSubstitution,
                                    generated);
        }
        FunctionType callType = call.computeType(compiler);
        generateFunctionTypeSignature(call, callType);
      }
    }

    for (DartType interfaceType in cls.interfaces) {
      _generateInterfacesIsTests(interfaceType.element, generateIsTest,
                                 generateSubstitution, generated);
    }
  }

  /**
   * Generate "is tests" where [cls] is being implemented.
   */
  void _generateInterfacesIsTests(ClassElement cls,
                                  void generateIsTest(ClassElement element),
                                  SubstitutionEmitter generateSubstitution,
                                  Set<Element> alreadyGenerated) {
    void tryEmitTest(ClassElement check) {
      if (!alreadyGenerated.contains(check) && checkedClasses.contains(check)) {
        alreadyGenerated.add(check);
        generateIsTest(check);
        generateSubstitution(check);
      }
    };

    tryEmitTest(cls);

    for (DartType interfaceType in cls.interfaces) {
      Element element = interfaceType.element;
      tryEmitTest(element);
      _generateInterfacesIsTests(element, generateIsTest, generateSubstitution,
                                 alreadyGenerated);
    }

    // We need to also emit "is checks" for the superclass and its supertypes.
    ClassElement superclass = cls.superclass;
    if (superclass != null) {
      tryEmitTest(superclass);
      _generateInterfacesIsTests(superclass, generateIsTest,
                                 generateSubstitution, alreadyGenerated);
    }
  }
}