// Copyright (c) 2016, 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:js_runtime/shared/embedded_names.dart';
import 'package:kernel/ast.dart' as ir;

import '../constants/expressions.dart';
import '../common.dart';
import '../common/names.dart';
import '../compiler.dart';
import '../constants/values.dart';
import '../dart_types.dart';
import '../elements/elements.dart';
import '../js/js.dart' as js;
import '../js_backend/backend_helpers.dart';
import '../js_backend/js_backend.dart';
import '../kernel/kernel.dart';
import '../kernel/kernel_debug.dart';
import '../native/native.dart' as native;
import '../resolution/tree_elements.dart';
import '../tree/tree.dart' as ast;
import '../types/masks.dart';
import '../types/types.dart';
import '../universe/call_structure.dart';
import '../universe/selector.dart';
import '../universe/side_effects.dart';
import '../world.dart';
import 'locals_handler.dart';
import 'types.dart';

/// A helper class that abstracts all accesses of the AST from Kernel nodes.
///
/// The goal is to remove all need for the AST from the Kernel SSA builder.
class KernelAstAdapter {
  final Kernel kernel;
  final JavaScriptBackend _backend;
  final ResolvedAst _resolvedAst;
  final Map<ir.Node, ast.Node> _nodeToAst;
  final Map<ir.Node, Element> _nodeToElement;
  final Map<ir.VariableDeclaration, SyntheticLocal> _syntheticLocals =
      <ir.VariableDeclaration, SyntheticLocal>{};
  DartTypeConverter _typeConverter;

  KernelAstAdapter(this.kernel, this._backend, this._resolvedAst,
      this._nodeToAst, this._nodeToElement) {
    // TODO(het): Maybe just use all of the kernel maps directly?
    for (FieldElement fieldElement in kernel.fields.keys) {
      _nodeToElement[kernel.fields[fieldElement]] = fieldElement;
    }
    for (FunctionElement functionElement in kernel.functions.keys) {
      _nodeToElement[kernel.functions[functionElement]] = functionElement;
    }
    for (ClassElement classElement in kernel.classes.keys) {
      _nodeToElement[kernel.classes[classElement]] = classElement;
    }
    for (LibraryElement libraryElement in kernel.libraries.keys) {
      _nodeToElement[kernel.libraries[libraryElement]] = libraryElement;
    }
    for (LocalFunctionElement localFunction in kernel.localFunctions.keys) {
      _nodeToElement[kernel.localFunctions[localFunction]] = localFunction;
    }
    _typeConverter = new DartTypeConverter(this);
  }

  Compiler get _compiler => _backend.compiler;
  TreeElements get elements => _resolvedAst.elements;
  DiagnosticReporter get reporter => _compiler.reporter;
  Element get _target => _resolvedAst.element;

  GlobalTypeInferenceElementResult _resultOf(Element e) =>
      _compiler.globalInference.results.resultOf(e);

  ConstantValue getConstantForSymbol(ir.SymbolLiteral node) {
    ast.Node astNode = getNode(node);
    ConstantValue constantValue = _backend.constants
        .getConstantValueForNode(astNode, _resolvedAst.elements);
    assert(invariant(astNode, constantValue != null,
        message: 'No constant computed for $node'));
    return constantValue;
  }

  // TODO(johnniwinther): Use the more precise functions below.
  Element getElement(ir.Node node) {
    Element result = _nodeToElement[node];
    assert(invariant(CURRENT_ELEMENT_SPANNABLE, result != null,
        message: "No element found for $node."));
    return result;
  }

  MemberElement getMember(ir.Node node) => getElement(node).declaration;

  MethodElement getMethod(ir.Node node) => getElement(node).declaration;

  ClassElement getClass(ir.Node node) => getElement(node).declaration;

  ast.Node getNode(ir.Node node) {
    ast.Node result = _nodeToAst[node];
    assert(invariant(CURRENT_ELEMENT_SPANNABLE, result != null,
        message: "No node found for $node"));
    return result;
  }

  Local getLocal(ir.VariableDeclaration variable) {
    // If this is a synthetic local, return the synthetic local
    if (variable.name == null) {
      return _syntheticLocals.putIfAbsent(
          variable, () => new SyntheticLocal("x", null));
    }
    return getElement(variable) as LocalElement;
  }

  bool getCanThrow(ir.Node procedure) {
    FunctionElement function = getElement(procedure);
    return !_compiler.closedWorld.getCannotThrow(function);
  }

  TypeMask returnTypeOf(ir.Member node) {
    return TypeMaskFactory.inferredReturnTypeForElement(
        getElement(node), _compiler);
  }

  SideEffects getSideEffects(ir.Node node) {
    return _compiler.closedWorld.getSideEffectsOfElement(getElement(node));
  }

  CallStructure getCallStructure(ir.Arguments arguments) {
    int argumentCount = arguments.positional.length + arguments.named.length;
    List<String> namedArguments = arguments.named.map((e) => e.name).toList();
    return new CallStructure(argumentCount, namedArguments);
  }

  FunctionSignature getFunctionSignature(ir.FunctionNode function) {
    return getElement(function).asFunctionElement().functionSignature;
  }

  Name getName(ir.Name name) {
    return new Name(
        name.name, name.isPrivate ? getElement(name.library) : null);
  }

  ir.Field getFieldFromElement(FieldElement field) {
    return kernel.fields[field];
  }

  Selector getSelector(ir.Expression node) {
    if (node is ir.PropertyGet) return getGetterSelector(node);
    if (node is ir.PropertySet) return getSetterSelector(node);
    if (node is ir.InvocationExpression) return getInvocationSelector(node);
    _compiler.reporter.internalError(getNode(node),
        "Can only get the selector for a property get or an invocation.");
    return null;
  }

  Selector getInvocationSelector(ir.InvocationExpression invocation) {
    Name name = getName(invocation.name);
    SelectorKind kind;
    if (Elements.isOperatorName(invocation.name.name)) {
      if (name == Names.INDEX_NAME || name == Names.INDEX_SET_NAME) {
        kind = SelectorKind.INDEX;
      } else {
        kind = SelectorKind.OPERATOR;
      }
    } else {
      kind = SelectorKind.CALL;
    }

    CallStructure callStructure = getCallStructure(invocation.arguments);
    return new Selector(kind, name, callStructure);
  }

  Selector getGetterSelector(ir.PropertyGet getter) {
    ir.Name irName = getter.name;
    Name name = new Name(
        irName.name, irName.isPrivate ? getElement(irName.library) : null);
    return new Selector.getter(name);
  }

  Selector getSetterSelector(ir.PropertySet setter) {
    ir.Name irName = setter.name;
    Name name = new Name(
        irName.name, irName.isPrivate ? getElement(irName.library) : null);
    return new Selector.setter(name);
  }

  TypeMask typeOfInvocation(ir.Expression send) {
    ast.Node operatorNode = kernel.nodeToAstOperator[send];
    if (operatorNode != null) {
      return _resultOf(_target).typeOfOperator(operatorNode);
    }
    return _resultOf(_target).typeOfSend(getNode(send));
  }

  TypeMask typeOfGet(ir.PropertyGet getter) {
    return _resultOf(_target).typeOfSend(getNode(getter));
  }

  TypeMask typeOfSet(ir.PropertySet setter) {
    return _compiler.closedWorld.commonMasks.dynamicType;
  }

  TypeMask typeOfSend(ir.Expression send) {
    assert(send is ir.InvocationExpression || send is ir.PropertyGet);
    return _resultOf(_target).typeOfSend(getNode(send));
  }

  TypeMask typeOfNewList(Element owner, ir.ListLiteral listLiteral) {
    return _resultOf(owner).typeOfNewList(getNode(listLiteral)) ??
        _compiler.closedWorld.commonMasks.dynamicType;
  }

  TypeMask typeOfIterator(ir.ForInStatement forInStatement) {
    return _resultOf(_target).typeOfIterator(getNode(forInStatement));
  }

  TypeMask typeOfIteratorCurrent(ir.ForInStatement forInStatement) {
    return _resultOf(_target).typeOfIteratorCurrent(getNode(forInStatement));
  }

  TypeMask typeOfIteratorMoveNext(ir.ForInStatement forInStatement) {
    return _resultOf(_target).typeOfIteratorMoveNext(getNode(forInStatement));
  }

  bool isJsIndexableIterator(ir.ForInStatement forInStatement) {
    TypeMask mask = typeOfIterator(forInStatement);
    ClosedWorld closedWorld = _compiler.closedWorld;
    return mask != null &&
        mask.satisfies(_backend.helpers.jsIndexableClass, closedWorld) &&
        // String is indexable but not iterable.
        !mask.satisfies(_backend.helpers.jsStringClass, closedWorld);
  }

  bool isFixedLength(TypeMask mask) {
    ClosedWorld closedWorld = _compiler.closedWorld;
    JavaScriptBackend backend = _compiler.backend;
    if (mask.isContainer && (mask as ContainerTypeMask).length != null) {
      // A container on which we have inferred the length.
      return true;
    }
    // TODO(sra): Recognize any combination of fixed length indexables.
    if (mask.containsOnly(backend.helpers.jsFixedArrayClass) ||
        mask.containsOnly(backend.helpers.jsUnmodifiableArrayClass) ||
        mask.containsOnlyString(closedWorld) ||
        backend.isTypedArray(mask)) {
      return true;
    }
    return false;
  }

  TypeMask inferredIndexType(ir.ForInStatement forInStatement) {
    return TypeMaskFactory.inferredTypeForSelector(
        new Selector.index(), typeOfIterator(forInStatement), _compiler);
  }

  TypeMask inferredTypeOf(ir.Member node) {
    return TypeMaskFactory.inferredTypeForElement(getElement(node), _compiler);
  }

  TypeMask selectorTypeOf(Selector selector, TypeMask mask) {
    return TypeMaskFactory.inferredTypeForSelector(selector, mask, _compiler);
  }

  TypeMask typeFromNativeBehavior(native.NativeBehavior nativeBehavior) {
    return TypeMaskFactory.fromNativeBehavior(nativeBehavior, _compiler);
  }

  ConstantValue getConstantFor(ir.Node node) {
    ConstantValue constantValue =
        _backend.constants.getConstantValueForNode(getNode(node), elements);
    assert(invariant(getNode(node), constantValue != null,
        message: 'No constant computed for $node'));
    return constantValue;
  }

  ConstantValue getConstantForType(ir.DartType irType) {
    DartType type = getDartType(irType);
    return _backend.constantSystem.createType(_compiler, type.asRaw());
  }

  bool isIntercepted(ir.Node node) {
    Selector selector = getSelector(node);
    return _backend.isInterceptedSelector(selector);
  }

  bool isInterceptedSelector(Selector selector) {
    return _backend.isInterceptedSelector(selector);
  }

  LibraryElement get jsHelperLibrary => _backend.helpers.jsHelperLibrary;

  JumpTarget getTargetDefinition(ir.Node node) =>
      elements.getTargetDefinition(getNode(node));

  ir.Class get mapLiteralClass =>
      kernel.classes[_backend.helpers.mapLiteralClass];

  ir.Procedure get mapLiteralConstructor =>
      kernel.functions[_backend.helpers.mapLiteralConstructor];

  ir.Procedure get mapLiteralConstructorEmpty =>
      kernel.functions[_backend.helpers.mapLiteralConstructorEmpty];

  ir.Procedure get mapLiteralUntypedEmptyMaker =>
      kernel.functions[_backend.helpers.mapLiteralUntypedEmptyMaker];

  ir.Procedure get mapLiteralUntypedMaker =>
      kernel.functions[_backend.helpers.mapLiteralUntypedMaker];

  MemberElement get jsIndexableLength => _backend.helpers.jsIndexableLength;

  ir.Procedure get checkConcurrentModificationError =>
      kernel.functions[_backend.helpers.checkConcurrentModificationError];

  TypeMask get checkConcurrentModificationErrorReturnType =>
      TypeMaskFactory.inferredReturnTypeForElement(
          _backend.helpers.checkConcurrentModificationError, _compiler);

  ir.Procedure get assertHelper =>
      kernel.functions[_backend.helpers.assertHelper];

  TypeMask get throwTypeErrorType => TypeMaskFactory
      .inferredReturnTypeForElement(_backend.helpers.throwTypeError, _compiler);

  TypeMask get assertHelperReturnType => TypeMaskFactory
      .inferredReturnTypeForElement(_backend.helpers.assertHelper, _compiler);

  ir.Procedure get assertTest => kernel.functions[_backend.helpers.assertTest];

  TypeMask get assertTestReturnType => TypeMaskFactory
      .inferredReturnTypeForElement(_backend.helpers.assertTest, _compiler);

  ir.Procedure get assertThrow =>
      kernel.functions[_backend.helpers.assertThrow];

  ir.Procedure get setRuntimeTypeInfo =>
      kernel.functions[_backend.helpers.setRuntimeTypeInfo];

  TypeMask get assertThrowReturnType => TypeMaskFactory
      .inferredReturnTypeForElement(_backend.helpers.assertThrow, _compiler);

  ir.Class get objectClass => kernel.classes[_compiler.coreClasses.objectClass];

  ir.Procedure get currentIsolate =>
      kernel.functions[_backend.helpers.currentIsolate];

  bool isInForeignLibrary(ir.Member member) =>
      _backend.isForeign(getElement(member));

  native.NativeBehavior getNativeBehavior(ir.Node node) {
    return elements.getNativeData(getNode(node));
  }

  js.Name getNameForJsGetName(ir.Node argument, ConstantValue constant) {
    int index = _extractEnumIndexFromConstantValue(
        constant, _backend.helpers.jsGetNameEnum);
    if (index == null) return null;
    return _backend.namer
        .getNameForJsGetName(getNode(argument), JsGetName.values[index]);
  }

  js.Template getJsBuiltinTemplate(ConstantValue constant) {
    int index = _extractEnumIndexFromConstantValue(
        constant, _backend.helpers.jsBuiltinEnum);
    if (index == null) return null;
    return _backend.emitter.builtinTemplateFor(JsBuiltin.values[index]);
  }

  int _extractEnumIndexFromConstantValue(
      ConstantValue constant, Element classElement) {
    if (constant is ConstructedConstantValue) {
      if (constant.type.element == classElement) {
        assert(constant.fields.length == 1);
        ConstantValue indexConstant = constant.fields.values.single;
        if (indexConstant is IntConstantValue) {
          return indexConstant.primitiveValue;
        }
      }
    }
    return null;
  }

  DartType getDartType(ir.DartType type) {
    return type.accept(_typeConverter);
  }

  List<DartType> getDartTypes(List<ir.DartType> types) {
    return types.map(getDartType).toList();
  }

  DartType getFunctionReturnType(ir.FunctionNode node) {
    return getDartType(node.returnType);
  }

  /// Computes the function type corresponding the signature of [node].
  FunctionType getFunctionType(ir.FunctionNode node) {
    DartType returnType = getFunctionReturnType(node);
    List<DartType> parameterTypes = <DartType>[];
    List<DartType> optionalParameterTypes = <DartType>[];
    for (ir.VariableDeclaration variable in node.positionalParameters) {
      if (parameterTypes.length == node.requiredParameterCount) {
        optionalParameterTypes.add(getDartType(variable.type));
      } else {
        parameterTypes.add(getDartType(variable.type));
      }
    }
    List<String> namedParameters = <String>[];
    List<DartType> namedParameterTypes = <DartType>[];
    List<ir.VariableDeclaration> sortedNamedParameters =
        node.namedParameters.toList()..sort((a, b) => a.name.compareTo(b.name));
    for (ir.VariableDeclaration variable in sortedNamedParameters) {
      namedParameters.add(variable.name);
      namedParameterTypes.add(getDartType(variable.type));
    }
    return new FunctionType.synthesized(returnType, parameterTypes,
        optionalParameterTypes, namedParameters, namedParameterTypes);
  }

  /// Converts [annotations] into a list of [ConstantExpression]s.
  List<ConstantExpression> getMetadata(List<ir.Expression> annotations) {
    List<ConstantExpression> metadata = <ConstantExpression>[];
    annotations.forEach((ir.Expression node) {
      ConstantExpression constant = node.accept(new Constantifier(this));
      if (constant == null) {
        throw new UnsupportedError(
            'No constant for ${DebugPrinter.prettyPrint(node)}');
      }
      metadata.add(constant);
    });
    return metadata;
  }

  /// Compute the kind of foreign helper function called by [node], if any.
  ForeignKind getForeignKind(ir.StaticInvocation node) {
    if (isForeignLibrary(node.target.enclosingLibrary)) {
      switch (node.target.name.name) {
        case BackendHelpers.JS:
          return ForeignKind.JS;
        case BackendHelpers.JS_BUILTIN:
          return ForeignKind.JS_BUILTIN;
        case BackendHelpers.JS_EMBEDDED_GLOBAL:
          return ForeignKind.JS_EMBEDDED_GLOBAL;
        case BackendHelpers.JS_INTERCEPTOR_CONSTANT:
          return ForeignKind.JS_INTERCEPTOR_CONSTANT;
      }
    }
    return ForeignKind.NONE;
  }

  /// Return `true` if [node] is the `dart:_foreign_helper` library.
  bool isForeignLibrary(ir.Library node) {
    return node.importUri == BackendHelpers.DART_FOREIGN_HELPER;
  }

  /// Looks up [typeName] for use in the spec-string of a `JS` called.
  // TODO(johnniwinther): Use this in [native.NativeBehavior] instead of calling the
  // `ForeignResolver`.
  // TODO(johnniwinther): Cache the result to avoid redundant lookups?
  native.TypeLookup _typeLookup({bool resolveAsRaw: true}) {
    return (String typeName) {
      DartType findIn(Uri uri) {
        LibraryElement library = _compiler.libraryLoader.lookupLibrary(uri);
        if (library != null) {
          Element element = library.find(typeName);
          if (element != null && element.isClass) {
            ClassElement cls = element;
            // TODO(johnniwinther): Align semantics.
            return resolveAsRaw ? cls.rawType : cls.thisType;
          }
        }
        return null;
      }

      DartType type = findIn(Uris.dart_core);
      type ??= findIn(BackendHelpers.DART_JS_HELPER);
      type ??= findIn(BackendHelpers.DART_INTERCEPTORS);
      type ??= findIn(BackendHelpers.DART_ISOLATE_HELPER);
      type ??= findIn(Uris.dart_collection);
      type ??= findIn(Uris.dart_html);
      type ??= findIn(Uris.dart_svg);
      type ??= findIn(Uris.dart_web_audio);
      type ??= findIn(Uris.dart_web_gl);
      return type;
    };
  }

  String _getStringArgument(ir.StaticInvocation node, int index) {
    return node.arguments.positional[index].accept(new Stringifier());
  }

  /// Computes the [native.NativeBehavior] for a call to the [JS] function.
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForJsCall(ir.StaticInvocation node) {
    if (node.arguments.positional.length < 2 ||
        node.arguments.named.isNotEmpty) {
      reporter.reportErrorMessage(
          CURRENT_ELEMENT_SPANNABLE, MessageKind.WRONG_ARGUMENT_FOR_JS);
      return new native.NativeBehavior();
    }
    String specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.reportErrorMessage(
          CURRENT_ELEMENT_SPANNABLE, MessageKind.WRONG_ARGUMENT_FOR_JS_FIRST);
      return new native.NativeBehavior();
    }

    String codeString = _getStringArgument(node, 1);
    if (codeString == null) {
      reporter.reportErrorMessage(
          CURRENT_ELEMENT_SPANNABLE, MessageKind.WRONG_ARGUMENT_FOR_JS_SECOND);
      return new native.NativeBehavior();
    }

    return native.NativeBehavior.ofJsCall(
        specString,
        codeString,
        _typeLookup(resolveAsRaw: true),
        CURRENT_ELEMENT_SPANNABLE,
        reporter,
        _compiler.coreTypes);
  }

  /// Computes the [native.NativeBehavior] for a call to the [JS_BUILTIN] function.
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForJsBuiltinCall(
      ir.StaticInvocation node) {
    if (node.arguments.positional.length < 1) {
      reporter.internalError(
          CURRENT_ELEMENT_SPANNABLE, "JS builtin expression has no type.");
      return new native.NativeBehavior();
    }
    if (node.arguments.positional.length < 2) {
      reporter.internalError(
          CURRENT_ELEMENT_SPANNABLE, "JS builtin is missing name.");
      return new native.NativeBehavior();
    }
    String specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.internalError(
          CURRENT_ELEMENT_SPANNABLE, "Unexpected first argument.");
      return new native.NativeBehavior();
    }
    return native.NativeBehavior.ofJsBuiltinCall(
        specString,
        _typeLookup(resolveAsRaw: true),
        CURRENT_ELEMENT_SPANNABLE,
        reporter,
        _compiler.coreTypes);
  }

  /// Computes the [native.NativeBehavior] for a call to the [JS_EMBEDDED_GLOBAL]
  /// function.
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForJsEmbeddedGlobalCall(
      ir.StaticInvocation node) {
    if (node.arguments.positional.length < 1) {
      reporter.internalError(CURRENT_ELEMENT_SPANNABLE,
          "JS embedded global expression has no type.");
      return new native.NativeBehavior();
    }
    if (node.arguments.positional.length < 2) {
      reporter.internalError(
          CURRENT_ELEMENT_SPANNABLE, "JS embedded global is missing name.");
      return new native.NativeBehavior();
    }
    if (node.arguments.positional.length > 2 ||
        node.arguments.named.isNotEmpty) {
      reporter.internalError(CURRENT_ELEMENT_SPANNABLE,
          "JS embedded global has more than 2 arguments.");
      return new native.NativeBehavior();
    }
    String specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.internalError(
          CURRENT_ELEMENT_SPANNABLE, "Unexpected first argument.");
      return new native.NativeBehavior();
    }
    return native.NativeBehavior.ofJsEmbeddedGlobalCall(
        specString,
        _typeLookup(resolveAsRaw: true),
        CURRENT_ELEMENT_SPANNABLE,
        reporter,
        _compiler.coreTypes);
  }

  /// Returns `true` is [node] has a `@Native(...)` annotation.
  // TODO(johnniwinther): Cache this for later use.
  bool isNative(ir.Class node) {
    for (ir.Expression annotation in node.annotations) {
      if (annotation is ir.ConstructorInvocation) {
        ConstructorElement target = getElement(annotation.target).declaration;
        if (target.enclosingClass ==
            _compiler.commonElements.nativeAnnotationClass) {
          return true;
        }
      }
    }
    return false;
  }

  /// Computes the native behavior for reading the native [field].
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForFieldLoad(ir.Field field) {
    DartType type = getDartType(field.type);
    List<ConstantExpression> metadata = getMetadata(field.annotations);
    return native.NativeBehavior.ofFieldLoad(CURRENT_ELEMENT_SPANNABLE, type,
        metadata, _typeLookup(resolveAsRaw: false), _compiler,
        isJsInterop: false);
  }

  /// Computes the native behavior for writing to the native [field].
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForFieldStore(ir.Field field) {
    DartType type = getDartType(field.type);
    return native.NativeBehavior.ofFieldStore(type, _compiler.resolution);
  }

  /// Computes the native behavior for calling [procedure].
  // TODO(johnniwinther): Cache this for later use.
  native.NativeBehavior getNativeBehaviorForMethod(ir.Procedure procedure) {
    DartType type = getFunctionType(procedure.function);
    List<ConstantExpression> metadata = getMetadata(procedure.annotations);
    return native.NativeBehavior.ofMethod(CURRENT_ELEMENT_SPANNABLE, type,
        metadata, _typeLookup(resolveAsRaw: false), _compiler,
        isJsInterop: false);
  }
}

/// Kinds of foreign functions.
enum ForeignKind {
  JS,
  JS_BUILTIN,
  JS_EMBEDDED_GLOBAL,
  JS_INTERCEPTOR_CONSTANT,
  NONE,
}

/// Visitor that converts kernel dart types into [DartType].
class DartTypeConverter extends ir.DartTypeVisitor<DartType> {
  final KernelAstAdapter astAdapter;

  DartTypeConverter(this.astAdapter);

  DartType visitType(ir.DartType type) => type.accept(this);

  List<DartType> visitTypes(List<ir.DartType> types) {
    return new List.generate(
        types.length, (int index) => types[index].accept(this));
  }

  @override
  DartType visitTypeParameterType(ir.TypeParameterType node) {
    if (node.parameter.parent is ir.Class) {
      ir.Class cls = node.parameter.parent;
      int index = cls.typeParameters.indexOf(node.parameter);
      ClassElement classElement = astAdapter.getElement(cls);
      return classElement.typeVariables[index];
    } else if (node.parameter.parent is ir.FunctionNode) {
      ir.FunctionNode func = node.parameter.parent;
      int index = func.typeParameters.indexOf(node.parameter);
      ConstructorElement constructorElement = astAdapter.getElement(func);
      ClassElement classElement = constructorElement.enclosingClass;
      return classElement.typeVariables[index];
    }
    throw new UnsupportedError('Unsupported type parameter type node $node.');
  }

  @override
  DartType visitFunctionType(ir.FunctionType node) {
    return new FunctionType.synthesized(
        visitType(node.returnType),
        visitTypes(node.positionalParameters
            .take(node.requiredParameterCount)
            .toList()),
        visitTypes(node.positionalParameters
            .skip(node.requiredParameterCount)
            .toList()),
        node.namedParameters.map((n) => n.name).toList(),
        node.namedParameters.map((n) => visitType(n.type)).toList());
  }

  @override
  DartType visitInterfaceType(ir.InterfaceType node) {
    ClassElement cls = astAdapter.getElement(node.classNode);
    return new InterfaceType(cls, visitTypes(node.typeArguments));
  }

  @override
  DartType visitVoidType(ir.VoidType node) {
    return const VoidType();
  }

  @override
  DartType visitDynamicType(ir.DynamicType node) {
    return const DynamicType();
  }

  @override
  DartType visitInvalidType(ir.InvalidType node) {
    throw new UnimplementedError("Invalid types not currently supported");
  }
}

/// Visitor that converts string literals and concatenations of string literals
/// into the string value.
class Stringifier extends ir.ExpressionVisitor<String> {
  @override
  String visitStringLiteral(ir.StringLiteral node) => node.value;

  @override
  String visitStringConcatenation(ir.StringConcatenation node) {
    StringBuffer sb = new StringBuffer();
    for (ir.Expression expression in node.expressions) {
      String value = expression.accept(this);
      if (value == null) return null;
      sb.write(value);
    }
    return sb.toString();
  }
}

/// Visitor that converts a kernel constant expression into a
/// [ConstantExpression].
class Constantifier extends ir.ExpressionVisitor<ConstantExpression> {
  final KernelAstAdapter astAdapter;

  Constantifier(this.astAdapter);

  @override
  ConstantExpression visitConstructorInvocation(ir.ConstructorInvocation node) {
    ConstructorElement constructor =
        astAdapter.getElement(node.target).declaration;
    List<DartType> typeArguments = <DartType>[];
    for (ir.DartType type in node.arguments.types) {
      typeArguments.add(astAdapter.getDartType(type));
    }
    List<ConstantExpression> arguments = <ConstantExpression>[];
    List<String> argumentNames = <String>[];
    for (ir.Expression argument in node.arguments.positional) {
      ConstantExpression constant = argument.accept(this);
      if (constant == null) return null;
      arguments.add(constant);
    }
    for (ir.NamedExpression argument in node.arguments.named) {
      argumentNames.add(argument.name);
      ConstantExpression constant = argument.value.accept(this);
      if (constant == null) return null;
      arguments.add(constant);
    }
    return new ConstructedConstantExpression(
        constructor.enclosingClass.thisType.createInstantiation(typeArguments),
        constructor,
        new CallStructure(
            node.arguments.positional.length + argumentNames.length,
            argumentNames),
        arguments);
  }

  @override
  ConstantExpression visitStaticGet(ir.StaticGet node) {
    Element element = astAdapter.getMember(node.target);
    if (element.isField) {
      return new VariableConstantExpression(element);
    }
    astAdapter.reporter.internalError(
        CURRENT_ELEMENT_SPANNABLE, "Unexpected constant target: $element.");
    return null;
  }

  @override
  ConstantExpression visitStringLiteral(ir.StringLiteral node) {
    return new StringConstantExpression(node.value);
  }
}