// 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 kernel.canonical_name;

import 'ast.dart';

/// A string sequence that identifies a library, class, or member.
///
/// Canonical names are organized in a prefix tree.  Each node knows its
/// parent, children, and the AST node it is currently bound to.
///
/// The following schema specifies how the canonical name of a given object
/// is defined:
///
///      Library:
///         URI of library
///
///      Class:
///         Canonical name of enclosing library
///         Name of class
///
///      Extension:
///         Canonical name of enclosing library
///         Name of extension
///
///      Constructor:
///         Canonical name of enclosing class or library
///         "@constructors"
///         Qualified name
///
///      Field:
///         Canonical name of enclosing class or library
///         "@fields"
///         Qualified name
///
///      Typedef:
///         Canonical name of enclosing class
///         "@typedefs"
///         Name text
///
///      Procedure that is not an accessor or factory:
///         Canonical name of enclosing class or library
///         "@methods"
///         Qualified name
///
///      Procedure that is a getter:
///         Canonical name of enclosing class or library
///         "@getters"
///         Qualified name
///
///      Procedure that is a setter:
///         Canonical name of enclosing class or library
///         "@setters"
///         Qualified name
///
///      Procedure that is a factory:
///         Canonical name of enclosing class
///         "@factories"
///         Qualified name
///
///      Qualified name:
///         if private: URI of library
///         Name text
///
/// The "qualified name" allows a member to have a name that is private to
/// a library other than the one containing that member.
class CanonicalName {
  CanonicalName? _parent;

  CanonicalName? get parent => _parent;

  final String name;
  CanonicalName? _nonRootTop;

  Map<String, CanonicalName>? _children;

  /// The library, class, or member bound to this name.
  Reference? reference;

  /// Temporary index used during serialization.
  int index = -1;

  CanonicalName._(CanonicalName parent, this.name) : _parent = parent {
    // ignore: unnecessary_null_comparison
    assert(name != null);
    // ignore: unnecessary_null_comparison
    assert(parent != null);
    _nonRootTop = parent.isRoot ? this : parent._nonRootTop;
  }

  CanonicalName.root()
      : _parent = null,
        _nonRootTop = null,
        name = '';

  bool get isRoot => _parent == null;

  CanonicalName? get nonRootTop => _nonRootTop;

  Iterable<CanonicalName> get children =>
      _children?.values ?? const <CanonicalName>[];

  Iterable<CanonicalName>? get childrenOrNull => _children?.values;

  bool hasChild(String name) {
    return _children != null && _children!.containsKey(name);
  }

  CanonicalName getChild(String name) {
    Map<String, CanonicalName> map = _children ??= <String, CanonicalName>{};
    return map[name] ??= new CanonicalName._(this, name);
  }

  CanonicalName getChildFromUri(Uri uri) {
    // Note that the Uri class caches its string representation, and all library
    // URIs will be stringified for serialization anyway, so there is no
    // significant cost for converting the Uri to a string here.
    return getChild('$uri');
  }

  CanonicalName getChildFromQualifiedName(Name name) {
    return name.isPrivate
        ? getChildFromUri(name.library!.importUri).getChild(name.text)
        : getChild(name.text);
  }

  CanonicalName getChildFromProcedure(Procedure procedure) {
    return getChild(getProcedureQualifier(procedure))
        .getChildFromQualifiedName(procedure.name!);
  }

  CanonicalName getChildFromField(Field field) {
    return getChild('@fields').getChildFromQualifiedName(field.name!);
  }

  CanonicalName getChildFromFieldSetter(Field field) {
    return getChild('@=fields').getChildFromQualifiedName(field.name!);
  }

  CanonicalName getChildFromConstructor(Constructor constructor) {
    return getChild('@constructors')
        .getChildFromQualifiedName(constructor.name!);
  }

  CanonicalName getChildFromRedirectingFactoryConstructor(
      RedirectingFactoryConstructor redirectingFactoryConstructor) {
    return getChild('@factories')
        .getChildFromQualifiedName(redirectingFactoryConstructor.name!);
  }

  CanonicalName getChildFromFieldWithName(Name name) {
    return getChild('@fields').getChildFromQualifiedName(name);
  }

  CanonicalName getChildFromFieldSetterWithName(Name name) {
    return getChild('@=fields').getChildFromQualifiedName(name);
  }

  CanonicalName getChildFromTypedef(Typedef typedef_) {
    return getChild('@typedefs').getChild(typedef_.name);
  }

  /// Take ownership of a child canonical name and its subtree.
  ///
  /// The child name is removed as a child of its current parent and this name
  /// becomes the new parent.  Note that this moves the entire subtree rooted at
  /// the child.
  ///
  /// This method can be used to move subtrees within a canonical name tree or
  /// else move them between trees.  It is safe to call this method if the child
  /// name is already a child of this name.
  ///
  /// The precondition is that this name cannot have a (different) child with
  /// the same name.
  void adoptChild(CanonicalName child) {
    if (child._parent == this) return;
    if (_children != null && _children!.containsKey(child.name)) {
      throw 'Cannot add a child to $this because this name already has a '
          'child named ${child.name}';
    }
    child._parent?.removeChild(child.name);
    child._parent = this;
    _children ??= <String, CanonicalName>{};
    _children![child.name] = child;
  }

  void removeChild(String name) {
    if (_children != null) {
      _children!.remove(name);
      if (_children!.isEmpty) {
        _children = null;
      }
    }
  }

  void bindTo(Reference target) {
    // ignore: unnecessary_null_comparison
    if (target == null) {
      throw '$this cannot be bound to null';
    }
    if (reference == target) return;
    if (reference != null) {
      throw '$this is already bound';
    }
    if (target.canonicalName != null) {
      throw 'Cannot bind $this to ${target.node}, target is already bound to '
          '${target.canonicalName}';
    }
    target.canonicalName = this;
    this.reference = target;
  }

  void unbind() {
    _unbindInternal();
    // TODO(johnniwinther): To support replacement of fields with getters and
    // setters (and the reverse) we need to remove canonical names from the
    // canonical name tree. We need to establish better invariants about the
    // state of the canonical name tree, since for instance [unbindAll] doesn't
    // remove unneeded leaf nodes.
    _parent?.removeChild(name);
  }

  void _unbindInternal() {
    if (reference == null) return;
    assert(reference!.canonicalName == this);
    if (reference!.node is Class) {
      // TODO(jensj): Get rid of this. This is only needed because pkg:vm does
      // weird stuff in transformations. `unbind` should probably be private.
      Class c = reference!.asClass;
      c.ensureLoaded();
    }
    reference!.canonicalName = null;
    reference = null;
  }

  void unbindAll() {
    _unbindInternal();
    Iterable<CanonicalName>? children_ = childrenOrNull;
    if (children_ != null) {
      for (CanonicalName child in children_) {
        child.unbindAll();
      }
    }
  }

  String toString() => _parent == null ? 'root' : '$parent::$name';
  String toStringInternal() {
    if (isRoot) return "";
    if (parent!.isRoot) return "$name";
    return "${parent!.toStringInternal()}::$name";
  }

  Reference getReference() {
    return reference ??= (new Reference()..canonicalName = this);
  }

  static String getProcedureQualifier(Procedure procedure) {
    if (procedure.isGetter) return '@getters';
    if (procedure.isSetter) return '@setters';
    if (procedure.isFactory) return '@factories';
    return '@methods';
  }
}