// 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.

library fasta.verifier;

import 'dart:core' hide MapEntry;

import 'package:_fe_analyzer_shared/src/messages/severity.dart' show Severity;

import 'package:kernel/ast.dart';

import 'package:kernel/transformations/flags.dart' show TransformerFlag;

import 'package:kernel/verifier.dart' show VerifyingVisitor;

import '../compiler_context.dart' show CompilerContext;

import '../fasta_codes.dart'
    show
        LocatedMessage,
        messageVerificationErrorOriginContext,
        noLength,
        templateInternalProblemVerificationError;

import '../type_inference/type_schema.dart' show UnknownType;

import 'redirecting_factory_body.dart'
    show RedirectingFactoryBody, getRedirectingFactoryBody;

List<LocatedMessage> verifyComponent(Component component,
    {bool isOutline, bool afterConst, bool skipPlatform: false}) {
  FastaVerifyingVisitor verifier =
      new FastaVerifyingVisitor(isOutline, afterConst, skipPlatform);
  component.accept(verifier);
  return verifier.errors;
}

class FastaVerifyingVisitor extends VerifyingVisitor {
  final List<LocatedMessage> errors = <LocatedMessage>[];

  Uri fileUri;
  final List<TreeNode> treeNodeStack = <TreeNode>[];
  final bool skipPlatform;

  FastaVerifyingVisitor(bool isOutline, bool afterConst, this.skipPlatform)
      : super(isOutline: isOutline, afterConst: afterConst);

  /// Invoked by all visit methods if the visited node is a [TreeNode].
  void enterTreeNode(TreeNode node) {
    treeNodeStack.add(node);
  }

  /// Invoked by all visit methods if the visited node is a [TreeNode].
  void exitTreeNode(TreeNode node) {
    if (treeNodeStack.isEmpty) {
      throw new StateError("Attempting to exit tree node '${node}' "
          "when the tree node stack is empty.");
    }
    if (!identical(treeNodeStack.last, node)) {
      throw new StateError("Attempting to exit tree node '${node}' "
          "when another node '${treeNodeStack.last}' is active.");
    }
    treeNodeStack.removeLast();
  }

  TreeNode getLastSeenTreeNode({bool withLocation = false}) {
    assert(treeNodeStack.isNotEmpty);
    for (int i = treeNodeStack.length - 1; i >= 0; --i) {
      TreeNode node = treeNodeStack[i];
      if (withLocation && !_hasLocation(node)) continue;
      return node;
    }
    return null;
  }

  TreeNode getSameLibraryLastSeenTreeNode({bool withLocation = false}) {
    if (treeNodeStack.isEmpty) return null;
    if (currentLibrary == null || currentLibrary.fileUri == null) return null;

    for (int i = treeNodeStack.length - 1; i >= 0; --i) {
      TreeNode node = treeNodeStack[i];
      if (withLocation && !_hasLocation(node)) continue;
      if (node.location?.file != null &&
          node.location.file == currentLibrary.fileUri) {
        return node;
      }
    }
    return null;
  }

  static bool _hasLocation(TreeNode node) {
    return node.location != null &&
        node.location.file != null &&
        node.fileOffset != null &&
        node.fileOffset != -1;
  }

  static bool _isInSameLibrary(Library library, TreeNode node) {
    if (library == null) return false;
    if (library.fileUri == null) return false;
    if (node.location == null) return false;
    if (node.location.file == null) return false;

    return library.fileUri == node.location.file;
  }

  TreeNode get localContext {
    TreeNode result = getSameLibraryLastSeenTreeNode(withLocation: true);
    if (result == null &&
        currentClassOrMember != null &&
        _isInSameLibrary(currentLibrary, currentClassOrMember)) {
      result = currentClassOrMember;
    }
    return result;
  }

  TreeNode get remoteContext {
    TreeNode result = getLastSeenTreeNode(withLocation: true);
    if (result != null && _isInSameLibrary(currentLibrary, result)) {
      result = null;
    }
    return result;
  }

  Uri checkLocation(TreeNode node, String name, Uri fileUri) {
    if (name == null || name.contains("#")) {
      // TODO(ahe): Investigate if these checks can be enabled:
      // if (node.fileUri != null && node is! Library) {
      //   problem(node, "A synthetic node shouldn't have a fileUri",
      //       context: node);
      // }
      // if (node.fileOffset != -1) {
      //   problem(node, "A synthetic node shouldn't have a fileOffset",
      //       context: node);
      // }
      return fileUri;
    } else {
      if (fileUri == null) {
        problem(node, "'$name' has no fileUri", context: node);
        return fileUri;
      }
      if (node.fileOffset == -1 && node is! Library) {
        problem(node, "'$name' has no fileOffset", context: node);
      }
      return fileUri;
    }
  }

  void checkSuperInvocation(TreeNode node) {
    Member containingMember = getContainingMember(node);
    if (containingMember == null) {
      problem(node, 'Super call outside of any member');
    } else {
      if (containingMember.transformerFlags & TransformerFlag.superCalls == 0) {
        problem(
            node, 'Super call in a member lacking TransformerFlag.superCalls');
      }
    }
  }

  Member getContainingMember(TreeNode node) {
    while (node != null) {
      if (node is Member) return node;
      node = node.parent;
    }
    return null;
  }

  @override
  problem(TreeNode node, String details, {TreeNode context, TreeNode origin}) {
    node ??= (context ?? currentClassOrMember);
    int offset = node?.fileOffset ?? -1;
    Uri file = node?.location?.file ?? fileUri;
    Uri uri = file == null ? null : file;
    LocatedMessage message = templateInternalProblemVerificationError
        .withArguments(details)
        .withLocation(uri, offset, noLength);
    List<LocatedMessage> contextMessages;
    if (origin != null) {
      contextMessages = [
        messageVerificationErrorOriginContext.withLocation(
            origin.location.file, origin.fileOffset, noLength)
      ];
    }
    CompilerContext.current
        .report(message, Severity.error, context: contextMessages);
    errors.add(message);
  }

  @override
  void visitAsExpression(AsExpression node) {
    enterTreeNode(node);
    super.visitAsExpression(node);
    if (node.fileOffset == -1) {
      TreeNode parent = node.parent;
      while (parent != null) {
        if (parent.fileOffset != -1) break;
        parent = parent.parent;
      }
      problem(parent, "No offset for $node", context: node);
    }
    exitTreeNode(node);
  }

  @override
  void visitExpressionStatement(ExpressionStatement node) {
    // Bypass verification of the [StaticGet] in [RedirectingFactoryBody] as
    // this is a static get without a getter.
    if (node is! RedirectingFactoryBody) {
      enterTreeNode(node);
      super.visitExpressionStatement(node);
      exitTreeNode(node);
    }
  }

  @override
  void visitLibrary(Library node) {
    // Issue(http://dartbug.com/32530)
    if (skipPlatform && node.importUri.scheme == 'dart') {
      return;
    }

    enterTreeNode(node);
    fileUri = checkLocation(node, node.name, node.fileUri);
    currentLibrary = node;
    super.visitLibrary(node);
    currentLibrary = null;
    exitTreeNode(node);
  }

  @override
  void visitClass(Class node) {
    enterTreeNode(node);
    fileUri = checkLocation(node, node.name, node.fileUri);
    super.visitClass(node);
    exitTreeNode(node);
  }

  @override
  void visitField(Field node) {
    enterTreeNode(node);
    fileUri = checkLocation(node, node.name.text, node.fileUri);
    super.visitField(node);
    exitTreeNode(node);
  }

  @override
  void visitProcedure(Procedure node) {
    enterTreeNode(node);
    fileUri = checkLocation(node, node.name.text, node.fileUri);
    super.visitProcedure(node);
    exitTreeNode(node);
  }

  bool isNullType(DartType node) {
    if (node is InterfaceType) {
      Uri importUri = node.classNode.enclosingLibrary.importUri;
      return node.classNode.name == "Null" &&
          importUri.scheme == "dart" &&
          importUri.path == "core";
    }
    return false;
  }

  bool isObjectClass(Class c) {
    return c.name == "Object" &&
        c.enclosingLibrary.importUri.scheme == "dart" &&
        c.enclosingLibrary.importUri.path == "core";
  }

  bool isTopType(DartType node) {
    return node is DynamicType ||
        node is VoidType ||
        node is InterfaceType &&
            isObjectClass(node.classNode) &&
            (node.nullability == Nullability.nullable ||
                node.nullability == Nullability.legacy) ||
        node is FutureOrType && isTopType(node.typeArgument);
  }

  bool isFutureOrNull(DartType node) {
    return isNullType(node) ||
        node is FutureOrType && isFutureOrNull(node.typeArgument);
  }

  @override
  void defaultDartType(DartType node) {
    final TreeNode localContext = this.localContext;
    final TreeNode remoteContext = this.remoteContext;

    if (node is UnknownType) {
      problem(localContext, "Unexpected appearance of the unknown type.",
          origin: remoteContext);
    }

    bool isTypeCast = localContext != null &&
        localContext is AsExpression &&
        localContext.isTypeError;
    // Don't check cases like foo(x as{TypeError} T).  In cases where foo comes
    // from a library with a different opt-in status than the current library,
    // the check may not be necessary.  For now, just skip all type-error casts.
    // TODO(dmitryas): Implement a more precise analysis.
    bool isFromAnotherLibrary = remoteContext != null || isTypeCast;

    // Checking for non-legacy types in opt-out libraries.
    {
      bool neverLegacy = isNullType(node) ||
          isFutureOrNull(node) ||
          isTopType(node) ||
          node is InvalidType ||
          node is NeverType ||
          node is BottomType;
      // TODO(dmitryas): Consider checking types coming from other libraries.
      bool expectedLegacy = !isFromAnotherLibrary &&
          !currentLibrary.isNonNullableByDefault &&
          !neverLegacy;
      if (expectedLegacy && node.nullability != Nullability.legacy) {
        problem(localContext,
            "Found a non-legacy type '${node}' in an opted-out library.",
            origin: remoteContext);
      }
    }

    // Checking for legacy types in opt-in libraries.
    {
      Nullability nodeNullability =
          node is InvalidType ? Nullability.undetermined : node.nullability;
      // TODO(dmitryas): Consider checking types coming from other libraries.
      if (!isFromAnotherLibrary &&
          currentLibrary.isNonNullableByDefault &&
          nodeNullability == Nullability.legacy) {
        problem(localContext,
            "Found a legacy type '${node}' in an opted-in library.",
            origin: remoteContext);
      }
    }

    super.defaultDartType(node);
  }

  @override
  void visitFunctionType(FunctionType node) {
    if (node.typeParameters.isNotEmpty) {
      for (TypeParameter typeParameter in node.typeParameters) {
        if (typeParameter.parent != null) {
          problem(
              localContext,
              "Type parameters of function types shouldn't have parents: "
              "$node.");
        }
      }
    }
    super.visitFunctionType(node);
  }

  @override
  void visitInterfaceType(InterfaceType node) {
    if (isNullType(node) && node.nullability != Nullability.nullable) {
      problem(localContext, "Found a not nullable Null type: ${node}");
    }
    super.visitInterfaceType(node);
  }

  @override
  void visitSuperMethodInvocation(SuperMethodInvocation node) {
    enterTreeNode(node);
    checkSuperInvocation(node);
    super.visitSuperMethodInvocation(node);
    exitTreeNode(node);
  }

  @override
  void visitSuperPropertyGet(SuperPropertyGet node) {
    enterTreeNode(node);
    checkSuperInvocation(node);
    super.visitSuperPropertyGet(node);
    exitTreeNode(node);
  }

  @override
  void visitSuperPropertySet(SuperPropertySet node) {
    enterTreeNode(node);
    checkSuperInvocation(node);
    super.visitSuperPropertySet(node);
    exitTreeNode(node);
  }

  @override
  void visitStaticInvocation(StaticInvocation node) {
    enterTreeNode(node);
    super.visitStaticInvocation(node);
    RedirectingFactoryBody body = getRedirectingFactoryBody(node.target);
    if (body != null) {
      problem(node, "Attempt to invoke redirecting factory.");
    }
    exitTreeNode(node);
  }

  @override
  void defaultTreeNode(TreeNode node) {
    enterTreeNode(node);
    super.defaultTreeNode(node);
    exitTreeNode(node);
  }
}