// Copyright (c) 2012, 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;

import '../common.dart';
import '../common/elements.dart' show CommonElements;
import '../elements/entities.dart';
import '../elements/types.dart';
import '../deferred_load/output_unit.dart' show OutputUnit;
import '../js/js.dart' as js;
import '../universe/record_shape.dart';
import '../util/util.dart';

enum ConstantValueKind {
  function,
  null_,
  int,
  double,
  bool,
  string,
  list,
  set,
  map,
  constructed,
  record,
  type,
  interceptor,
  javaScriptObject,
  jsName,
  dummyInterceptor,
  lateSentinel,
  unreachable,
  instantiation,
  deferredGlobal,
}

abstract class ConstantValueVisitor<R, A> {
  const ConstantValueVisitor();

  R visitFunction(covariant FunctionConstantValue constant, covariant A arg);
  R visitNull(covariant NullConstantValue constant, covariant A arg);
  R visitInt(covariant IntConstantValue constant, covariant A arg);
  R visitDouble(covariant DoubleConstantValue constant, covariant A arg);
  R visitBool(covariant BoolConstantValue constant, covariant A arg);
  R visitString(covariant StringConstantValue constant, covariant A arg);
  R visitList(covariant ListConstantValue constant, covariant A arg);
  R visitSet(covariant SetConstantValue constant, covariant A arg);
  R visitMap(covariant MapConstantValue constant, covariant A arg);
  R visitConstructed(
    covariant ConstructedConstantValue constant,
    covariant A arg,
  );
  R visitRecord(covariant RecordConstantValue constant, covariant A arg);
  R visitType(covariant TypeConstantValue constant, covariant A arg);
  R visitInterceptor(
    covariant InterceptorConstantValue constant,
    covariant A arg,
  );
  R visitJavaScriptObject(
    covariant JavaScriptObjectConstantValue constant,
    covariant A arg,
  );
  R visitDummyInterceptor(
    covariant DummyInterceptorConstantValue constant,
    covariant A arg,
  );
  R visitLateSentinel(
    covariant LateSentinelConstantValue constant,
    covariant A arg,
  );
  R visitUnreachable(
    covariant UnreachableConstantValue constant,
    covariant A arg,
  );
  R visitJsName(covariant JsNameConstantValue constant, covariant A arg);
  R visitDeferredGlobal(
    covariant DeferredGlobalConstantValue constant,
    covariant A arg,
  );
  R visitInstantiation(
    covariant InstantiationConstantValue constant,
    covariant A arg,
  );
}

abstract class ConstantValue {
  const ConstantValue();

  /// `true` if this is a valid constant value.
  bool get isConstant => true;

  /// Returns true if the constant is a list, a map or a constructed object.
  bool get isDummy => false;

  bool get isNaN => false;
  bool get isMinusZero => false;
  bool get isZero => false;
  bool get isOne => false;
  bool get isPositiveInfinity => false;
  bool get isNegativeInfinity => false;

  // TODO(johnniwinther): Replace with a 'type' getter.
  DartType getType(CommonElements types);

  List<ConstantValue> getDependencies();

  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg);

  /// The value of this constant in Dart syntax, if possible.
  ///
  /// For [ConstructedConstantValue]s there is no way to create a valid const
  /// expression from the value so the unparse of these is best effort.
  ///
  /// For the synthetic constants, [DeferredConstantValue],
  /// [DeferredGlobalConstantValue], [SyntheticConstantValue],
  /// [InterceptorConstantValue] the unparse is descriptive only.
  String toDartText(DartTypes? dartTypes);

  /// Returns a structured representation of this constant suited for debugging.
  String toStructuredText(DartTypes? dartTypes);

  ConstantValueKind get kind;

  @override
  String toString() {
    assertDebugMode(
      "Use ConstantValue.toDartText() or "
      "ConstantValue.toStructuredText() "
      "instead of ConstantValue.toString().",
    );
    return toStructuredText(null);
  }
}

bool _listsEqual(List<ConstantValue> a, List<ConstantValue> b) {
  if (a.length != b.length) return false;
  for (int i = 0; i < a.length; i++) {
    if (a[i] != b[i]) return false;
  }
  return true;
}

class FunctionConstantValue extends ConstantValue {
  final FunctionEntity element;
  // TODO(johnniwinther): Should the type be derived from [element].
  final FunctionType type;

  FunctionConstantValue(this.element, this.type);

  @override
  bool operator ==(var other) {
    if (other is! FunctionConstantValue) return false;
    return identical(other.element, element);
  }

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  FunctionType getType(CommonElements types) => type;

  @override
  int get hashCode => (17 * element.hashCode) & 0x7fffffff;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitFunction(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.function;

  @override
  String toDartText(DartTypes? dartTypes) {
    if (element.enclosingClass != null) {
      return '${element.enclosingClass!.name}.${element.name}';
    } else {
      return '${element.name}';
    }
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    return 'FunctionConstant(${toDartText(dartTypes)})';
  }
}

abstract class PrimitiveConstantValue extends ConstantValue {
  const PrimitiveConstantValue();

  @override
  bool operator ==(var other) {
    // Making this method abstract does not give us an error.
    throw UnsupportedError('PrimitiveConstant.==');
  }

  @override
  int get hashCode => throw UnsupportedError('PrimitiveConstant.hashCode');

  // Primitive constants don't have dependencies.
  @override
  List<ConstantValue> getDependencies() => const [];
}

class NullConstantValue extends PrimitiveConstantValue {
  /// The value a Dart null is compiled to in JavaScript.
  static const String jsNull = "null";

  const factory NullConstantValue() = NullConstantValue._internal;

  const NullConstantValue._internal();

  @override
  DartType getType(CommonElements types) => types.nullType;

  @override
  bool operator ==(other) => other is NullConstantValue;

  // The magic constant has no meaning. It is just a random value.
  @override
  int get hashCode => 785965825;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitNull(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.null_;

  @override
  String toStructuredText(DartTypes? dartTypes) => 'NullConstant';

  @override
  String toDartText(DartTypes? dartTypes) => 'null';
}

abstract class NumConstantValue extends PrimitiveConstantValue {
  double get doubleValue;

  const NumConstantValue();
}

class IntConstantValue extends NumConstantValue {
  final BigInt intValue;

  // Caching IntConstantValues representing -2 through 10 so that we don't have
  // to create new ones every time those values are used.
  static final Map<BigInt, IntConstantValue> _cachedValues = {};

  @override
  double get doubleValue => intValue.toDouble();

  factory IntConstantValue(BigInt value) {
    var existing = _cachedValues[value];
    if (existing != null) return existing;
    var intConstantVal = IntConstantValue._internal(value);
    var intValue = value.toInt();
    if (intValue <= -2 && intValue >= 10) {
      _cachedValues[value] = intConstantVal;
    }
    return intConstantVal;
  }

  const IntConstantValue._internal(this.intValue);

  bool isUInt31() => intValue.toUnsigned(31) == intValue;

  bool isUInt32() => intValue.toUnsigned(32) == intValue;

  bool isPositive() => intValue >= BigInt.zero;

  @override
  bool get isZero => intValue == BigInt.zero;

  @override
  bool get isOne => intValue == BigInt.one;

  @override
  DartType getType(CommonElements types) => types.intType;

  @override
  bool operator ==(var other) {
    // Ints and doubles are treated as separate constants.
    if (other is! IntConstantValue) return false;
    IntConstantValue otherInt = other;
    return intValue == otherInt.intValue;
  }

  @override
  int get hashCode => intValue.hashCode & Hashing.smiMask;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitInt(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.int;

  @override
  String toStructuredText(DartTypes? dartTypes) =>
      'IntConstant(${toDartText(dartTypes)})';

  @override
  String toDartText(DartTypes? dartTypes) => intValue.toString();
}

class DoubleConstantValue extends NumConstantValue {
  @override
  final double doubleValue;

  factory DoubleConstantValue(double value) {
    if (value.isNaN) {
      return const DoubleConstantValue._internal(double.nan);
    } else if (value == double.infinity) {
      return const DoubleConstantValue._internal(double.infinity);
    } else if (value == -double.infinity) {
      return const DoubleConstantValue._internal(-double.infinity);
    } else if (value == 0.0 && !value.isNegative) {
      return const DoubleConstantValue._internal(0.0);
    } else if (value == 1.0) {
      return const DoubleConstantValue._internal(1.0);
    } else {
      return DoubleConstantValue._internal(value);
    }
  }

  const DoubleConstantValue._internal(this.doubleValue);

  @override
  bool get isNaN => doubleValue.isNaN;

  // We need to check for the negative sign since -0.0 == 0.0.
  @override
  bool get isMinusZero => doubleValue == 0.0 && doubleValue.isNegative;

  @override
  bool get isZero => doubleValue == 0.0;

  @override
  bool get isOne => doubleValue == 1.0;

  @override
  bool get isPositiveInfinity => doubleValue == double.infinity;

  @override
  bool get isNegativeInfinity => doubleValue == -double.infinity;

  @override
  DartType getType(CommonElements types) => types.doubleType;

  @override
  bool operator ==(var other) {
    if (other is! DoubleConstantValue) return false;
    DoubleConstantValue otherDouble = other;
    double otherValue = otherDouble.doubleValue;
    if (doubleValue == 0.0 && otherValue == 0.0) {
      return doubleValue.isNegative == otherValue.isNegative;
    } else if (doubleValue.isNaN) {
      return otherValue.isNaN;
    } else {
      return doubleValue == otherValue;
    }
  }

  @override
  int get hashCode => doubleValue.hashCode;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitDouble(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.double;

  @override
  String toStructuredText(DartTypes? dartTypes) =>
      'DoubleConstant(${toDartText(dartTypes)})';

  @override
  String toDartText(DartTypes? dartTypes) => doubleValue.toString();
}

abstract class BoolConstantValue extends PrimitiveConstantValue {
  factory BoolConstantValue(bool value) {
    return value ? TrueConstantValue() : FalseConstantValue();
  }

  const BoolConstantValue._internal();

  bool get boolValue;

  @override
  DartType getType(CommonElements types) => types.boolType;

  BoolConstantValue negate();

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitBool(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.bool;

  @override
  String toStructuredText(DartTypes? dartTypes) =>
      'BoolConstant(${toDartText(dartTypes)})';
}

class TrueConstantValue extends BoolConstantValue {
  factory TrueConstantValue() => const TrueConstantValue._internal();

  const TrueConstantValue._internal() : super._internal();

  @override
  bool get boolValue => true;

  @override
  FalseConstantValue negate() => FalseConstantValue();

  @override
  bool operator ==(var other) => identical(this, other);

  // The magic constant is just a random value. It does not have any
  // significance.
  @override
  int get hashCode => 499;

  @override
  String toDartText(DartTypes? dartTypes) => boolValue.toString();
}

class FalseConstantValue extends BoolConstantValue {
  factory FalseConstantValue() => const FalseConstantValue._internal();

  const FalseConstantValue._internal() : super._internal();

  @override
  bool get boolValue => false;

  @override
  TrueConstantValue negate() => TrueConstantValue();

  @override
  bool operator ==(var other) => identical(this, other);

  // The magic constant is just a random value. It does not have any
  // significance.
  @override
  int get hashCode => 536555975;

  @override
  String toDartText(DartTypes? dartTypes) => boolValue.toString();
}

class StringConstantValue extends PrimitiveConstantValue {
  final String stringValue;

  @override
  final int hashCode;

  // TODO(floitsch): cache StringConstants.
  StringConstantValue(String value)
    : stringValue = value,
      hashCode = value.hashCode;

  @override
  DartType getType(CommonElements types) => types.stringType;

  @override
  bool operator ==(var other) {
    if (identical(this, other)) return true;
    if (other is! StringConstantValue) return false;
    StringConstantValue otherString = other;
    return hashCode == otherString.hashCode &&
        stringValue == otherString.stringValue;
  }

  String toDartString() => stringValue;

  int get length => stringValue.length;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitString(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.string;

  // TODO(johnniwinther): Ensure correct escaping.
  @override
  String toDartText(DartTypes? dartTypes) => '"$stringValue"';

  @override
  String toStructuredText(DartTypes? dartTypes) =>
      'StringConstant(${toDartText(dartTypes)})';
}

abstract class ObjectConstantValue extends ConstantValue {
  final InterfaceType type;

  ObjectConstantValue(this.type);

  @override
  DartType getType(CommonElements types) => type;

  void _unparseTypeArguments(DartTypes? dartTypes, StringBuffer sb) {
    if (dartTypes == null || !dartTypes.treatAsRawType(type)) {
      sb.write('<');
      sb.write(type.typeArguments.join(', '));
      sb.write('>');
    }
  }
}

class TypeConstantValue extends ObjectConstantValue {
  /// The user type that this constant represents.
  final DartType representedType;

  TypeConstantValue(this.representedType, InterfaceType type) : super(type);

  @override
  bool operator ==(other) {
    return other is TypeConstantValue &&
        representedType == other.representedType;
  }

  @override
  int get hashCode => representedType.hashCode * 13;

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitType(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.type;

  @override
  String toDartText(DartTypes? dartTypes) => '$representedType';

  @override
  String toStructuredText(DartTypes? dartTypes) =>
      'TypeConstant($representedType)';
}

class ListConstantValue extends ObjectConstantValue {
  final List<ConstantValue> entries;
  @override
  final int hashCode;

  ListConstantValue(super.type, this.entries)
    : hashCode = Hashing.listHash(entries, Hashing.objectHash(type));

  @override
  bool operator ==(var other) {
    if (identical(this, other)) return true;
    if (other is! ListConstantValue) return false;
    ListConstantValue otherList = other;
    if (hashCode != otherList.hashCode) return false;
    if (type != otherList.type) return false;
    if (entries.length != otherList.entries.length) return false;
    for (int i = 0; i < entries.length; i++) {
      if (entries[i] != otherList.entries[i]) return false;
    }
    return true;
  }

  @override
  List<ConstantValue> getDependencies() => entries;

  int get length => entries.length;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitList(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.list;

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    _unparseTypeArguments(dartTypes, sb);
    sb.write('[');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(',');
      sb.write(entries[i].toDartText(dartTypes));
    }
    sb.write(']');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('ListConstant(');
    _unparseTypeArguments(dartTypes, sb);
    sb.write('[');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(', ');
      sb.write(entries[i].toStructuredText(dartTypes));
    }
    sb.write('])');
    return sb.toString();
  }
}

abstract class SetConstantValue extends ObjectConstantValue {
  final List<ConstantValue> values;
  @override
  final int hashCode;

  SetConstantValue(super.type, this.values)
    : hashCode = Hashing.listHash(values, Hashing.objectHash(type));

  @override
  bool operator ==(var other) {
    if (identical(this, other)) return true;
    if (other is! SetConstantValue) return false;
    SetConstantValue otherSet = other;
    if (hashCode != otherSet.hashCode) return false;
    if (type != otherSet.type) return false;
    if (length != otherSet.length) return false;
    for (int i = 0; i < values.length; i++) {
      if (values[i] != otherSet.values[i]) return false;
    }
    return true;
  }

  @override
  List<ConstantValue> getDependencies() => values;

  int get length => values.length;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitSet(this, arg);

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    _unparseTypeArguments(dartTypes, sb);
    sb.write('{');
    sb.writeAll(values.map((v) => v.toDartText(dartTypes)), ',');
    sb.write('}');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('SetConstant(');
    _unparseTypeArguments(dartTypes, sb);
    sb.write('{');
    sb.writeAll(values.map((v) => v.toStructuredText(dartTypes)), ', ');
    sb.write('})');
    return sb.toString();
  }

  @override
  ConstantValueKind get kind => ConstantValueKind.set;
}

abstract class MapConstantValue extends ObjectConstantValue {
  final List<ConstantValue> keys;
  final List<ConstantValue> values;
  @override
  final int hashCode;
  Map<ConstantValue, ConstantValue>? _lookupMap;

  MapConstantValue(super.type, this.keys, this.values)
    : hashCode = Hashing.listHash(
        values,
        Hashing.listHash(keys, Hashing.objectHash(type)),
      ) {
    assert(keys.length == values.length);
  }

  @override
  bool operator ==(var other) {
    if (identical(this, other)) return true;
    if (other is! MapConstantValue) return false;
    MapConstantValue otherMap = other;
    if (hashCode != otherMap.hashCode) return false;
    if (type != other.type) return false;
    if (length != other.length) return false;
    for (int i = 0; i < length; i++) {
      if (keys[i] != otherMap.keys[i]) return false;
      if (values[i] != otherMap.values[i]) return false;
    }
    return true;
  }

  @override
  List<ConstantValue> getDependencies() => [...keys, ...values];

  int get length => keys.length;

  ConstantValue? lookup(ConstantValue key) {
    var lookupMap = _lookupMap ??= Map.fromIterables(keys, values);
    return lookupMap[key];
  }

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitMap(this, arg);

  @override
  ConstantValueKind get kind => ConstantValueKind.map;

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    _unparseTypeArguments(dartTypes, sb);
    sb.write('{');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(',');
      sb.write(keys[i].toDartText(dartTypes));
      sb.write(':');
      sb.write(values[i].toDartText(dartTypes));
    }
    sb.write('}');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('MapConstant(');
    _unparseTypeArguments(dartTypes, sb);
    sb.write('{');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(', ');
      sb.write(keys[i].toStructuredText(dartTypes));
      sb.write(': ');
      sb.write(values[i].toStructuredText(dartTypes));
    }
    sb.write('})');
    return sb.toString();
  }
}

class InterceptorConstantValue extends ConstantValue {
  /// The class for which this interceptor holds the methods.  The constant
  /// is a dispatch table for this class.
  final ClassEntity cls;

  InterceptorConstantValue(this.cls);

  @override
  bool operator ==(other) {
    return other is InterceptorConstantValue && cls == other.cls;
  }

  @override
  int get hashCode => cls.hashCode * 43;

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitInterceptor(this, arg);
  }

  @override
  DartType getType(CommonElements types) => types.dynamicType;

  @override
  ConstantValueKind get kind => ConstantValueKind.interceptor;

  @override
  String toDartText(DartTypes? dartTypes) {
    return 'interceptor($cls)';
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    return 'InterceptorConstant(${cls.name})';
  }
}

class JsNameConstantValue extends ConstantValue {
  final js.LiteralString name;

  JsNameConstantValue(this.name);

  @override
  bool get isDummy => true;

  @override
  bool operator ==(other) {
    return other is JsNameConstantValue && name == other.name;
  }

  @override
  int get hashCode => name.hashCode * 17;

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitJsName(this, arg);
  }

  @override
  DartType getType(CommonElements types) => types.dynamicType;

  @override
  ConstantValueKind get kind => ConstantValueKind.jsName;

  @override
  String toDartText(DartTypes? dartTypes) {
    if (name.isFinalized) 'js_name($name)';
    return 'js_name(name.nonfinalizedDebugText())';
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    if (name.isFinalized) return 'JsNameConstant($name)';
    return 'JsNameConstant(name.nonfinalizedDebugText())';
  }
}

/// A constant used as the dummy receiver value for intercepted calls with
/// a known non-interceptor target.
// TODO(sra): Rename fo 'DummyReceiverConstantValue'.
class DummyInterceptorConstantValue extends ConstantValue {
  factory DummyInterceptorConstantValue() =>
      const DummyInterceptorConstantValue._();

  const DummyInterceptorConstantValue._();

  @override
  bool get isDummy => true;

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitDummyInterceptor(this, arg);
  }

  @override
  DartType getType(CommonElements types) => types.dynamicType;

  @override
  ConstantValueKind get kind => ConstantValueKind.dummyInterceptor;

  @override
  String toDartText(DartTypes? dartTypes) => 'dummy_interceptor()';

  @override
  String toStructuredText(DartTypes? dartTypes) => 'DummyInterceptorConstant()';
}

/// A constant used to represent the sentinel for uninitialized late fields and
/// variables.
class LateSentinelConstantValue extends ConstantValue {
  factory LateSentinelConstantValue() => const LateSentinelConstantValue._();

  const LateSentinelConstantValue._();

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitLateSentinel(this, arg);
  }

  @override
  DartType getType(CommonElements types) => types.dartTypes.neverType();

  @override
  ConstantValueKind get kind => ConstantValueKind.lateSentinel;

  @override
  String toDartText(DartTypes? dartTypes) => 'late_sentinel()';

  @override
  String toStructuredText(DartTypes? dartTypes) => 'LateSentinelConstant()';
}

// A constant with an empty type used in [HInstruction]s of an expression
// in an unreachable context.
class UnreachableConstantValue extends ConstantValue {
  factory UnreachableConstantValue() => const UnreachableConstantValue._();

  const UnreachableConstantValue._();

  @override
  bool get isDummy => true;

  @override
  List<ConstantValue> getDependencies() => const [];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitUnreachable(this, arg);
  }

  @override
  DartType getType(CommonElements types) => types.dynamicType;

  @override
  ConstantValueKind get kind => ConstantValueKind.unreachable;

  @override
  String toDartText(DartTypes? dartTypes) => 'unreachable()';

  @override
  String toStructuredText(DartTypes? dartTypes) => 'UnreachableConstant()';
}

class ConstructedConstantValue extends ObjectConstantValue {
  // TODO(johnniwinther): Make [fields] private to avoid misuse of the map
  // ordering and mutability.
  final Map<FieldEntity, ConstantValue> fields;
  @override
  final int hashCode;

  ConstructedConstantValue(super.type, this.fields)
    : hashCode = Hashing.unorderedMapHash(fields, Hashing.objectHash(type));

  @override
  bool operator ==(var other) {
    if (identical(this, other)) return true;
    if (other is! ConstructedConstantValue) return false;
    if (hashCode != other.hashCode) return false;
    if (type != other.type) return false;
    if (fields.length != other.fields.length) return false;
    for (FieldEntity field in fields.keys) {
      if (fields[field] != other.fields[field]) return false;
    }
    return true;
  }

  @override
  List<ConstantValue> getDependencies() => fields.values.toList();

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitConstructed(this, arg);
  }

  @override
  ConstantValueKind get kind => ConstantValueKind.constructed;

  Iterable<FieldEntity> get _fieldsSortedByName {
    return fields.keys.toList()..sort((a, b) => a.name!.compareTo(b.name!));
  }

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write(type.element.name);
    _unparseTypeArguments(dartTypes, sb);
    sb.write('(');
    int i = 0;
    for (FieldEntity field in _fieldsSortedByName) {
      ConstantValue value = fields[field]!;
      if (i > 0) sb.write(',');
      sb.write(field.name);
      sb.write('=');
      sb.write(value.toDartText(dartTypes));
      i++;
    }
    sb.write(')');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('ConstructedConstant(');
    sb.write(type);
    sb.write('(');
    int i = 0;
    for (FieldEntity field in _fieldsSortedByName) {
      ConstantValue value = fields[field]!;
      if (i > 0) sb.write(',');
      sb.write(field.name);
      sb.write('=');
      sb.write(value.toStructuredText(dartTypes));
      i++;
    }
    sb.write('))');
    return sb.toString();
  }
}

class RecordConstantValue extends ConstantValue {
  final RecordShape shape;
  final List<ConstantValue> values;
  @override
  final int hashCode;

  RecordConstantValue(this.shape, this.values)
    : assert(shape.fieldCount == values.length),
      hashCode = Hashing.objectHash(shape, Hashing.listHash(values));

  @override
  bool operator ==(Object other) {
    return other is RecordConstantValue &&
        hashCode == other.hashCode &&
        shape == other.shape &&
        _listsEqual(values, other.values);
  }

  @override
  DartType getType(CommonElements types) {
    return types.dartTypes.recordType(
      shape,
      values.map((value) => value.getType(types)).toList(),
    );
  }

  @override
  List<ConstantValue> getDependencies() => values;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) {
    return visitor.visitRecord(this, arg);
  }

  @override
  ConstantValueKind get kind => ConstantValueKind.record;

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('(');
    for (int i = 0; i < values.length; i++) {
      if (i > 0) sb.write(',');
      if (i >= shape.positionalFieldCount) {
        sb.write(shape.fieldNames[i - shape.positionalFieldCount]);
        sb.write(': ');
      }
      sb.write(values[i].toDartText(dartTypes));
    }
    sb.write(')');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('RecordConstant(');
    sb.write(shape);
    sb.write('(');
    for (int i = 0; i < values.length; i++) {
      if (i > 0) sb.write(',');
      if (i >= shape.positionalFieldCount) {
        sb.write(shape.fieldNames[i - shape.positionalFieldCount]);
        sb.write(': ');
      }
      sb.write(values[i].toStructuredText(dartTypes));
    }
    sb.write('))');
    return sb.toString();
  }
}

class InstantiationConstantValue extends ConstantValue {
  final List<DartType> typeArguments;
  final FunctionConstantValue function;

  InstantiationConstantValue(this.typeArguments, this.function);

  @override
  bool operator ==(other) {
    if (identical(this, other)) return true;
    return other is InstantiationConstantValue &&
        function == other.function &&
        equalElements(typeArguments, other.typeArguments);
  }

  @override
  int get hashCode {
    return Hashing.objectHash(function, Hashing.listHash(typeArguments));
  }

  @override
  List<ConstantValue> getDependencies() => [function];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitInstantiation(this, arg);

  @override
  DartType getType(CommonElements types) {
    FunctionType type = function.getType(types);
    return types.dartTypes.instantiate(type, typeArguments);
  }

  @override
  ConstantValueKind get kind => ConstantValueKind.instantiation;

  @override
  String toDartText(DartTypes? dartTypes) =>
      '<${typeArguments.join(', ')}>(${function.toDartText(dartTypes)})';

  @override
  String toStructuredText(DartTypes? dartTypes) {
    return 'InstantiationConstant($typeArguments,'
        '${function.toStructuredText(dartTypes)})';
  }
}

/// A JavaScript Object Literal used as a constant.
class JavaScriptObjectConstantValue extends ConstantValue {
  final List<ConstantValue> keys;
  final List<ConstantValue> values;
  @override
  late final int hashCode = Hashing.listHash(values, Hashing.listHash(keys, 9));

  JavaScriptObjectConstantValue(this.keys, this.values) {
    assert(keys.length == values.length);
  }

  @override
  bool operator ==(var other) {
    return identical(this, other) ||
        other is JavaScriptObjectConstantValue && _equals(this, other);
  }

  static bool _equals(
    JavaScriptObjectConstantValue a,
    JavaScriptObjectConstantValue b,
  ) {
    if (a.hashCode != b.hashCode) return false;
    if (a.length != b.length) return false;
    if (!_listsEqual(a.keys, b.keys)) return false;
    if (!_listsEqual(a.values, b.values)) return false;
    return true;
  }

  @override
  List<ConstantValue> getDependencies() => [...keys, ...values];

  int get length => keys.length;

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitJavaScriptObject(this, arg);

  @override
  DartType getType(CommonElements types) {
    return types.dynamicType; // TODO: Lookup JavaScriptObject.
  }

  @override
  ConstantValueKind get kind => ConstantValueKind.javaScriptObject;

  @override
  String toDartText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('{');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(',');
      sb.write(keys[i].toDartText(dartTypes));
      sb.write(':');
      sb.write(values[i].toDartText(dartTypes));
    }
    sb.write('}');
    return sb.toString();
  }

  @override
  String toStructuredText(DartTypes? dartTypes) {
    StringBuffer sb = StringBuffer();
    sb.write('JavaScriptObject(');
    sb.write('{');
    for (int i = 0; i < length; i++) {
      if (i > 0) sb.write(', ');
      sb.write(keys[i].toStructuredText(dartTypes));
      sb.write(': ');
      sb.write(values[i].toStructuredText(dartTypes));
    }
    sb.write('})');
    return sb.toString();
  }
}

/// A reference to a constant in another output unit.
///
/// Used for referring to deferred constants that appear as initializers of
/// final (non-const) global fields.
///
// TODO(sigmund): this should eventually not be a constant value. In particular,
// [DeferredConstantValue] is introduced by the constant evaluator when it first
// sees constants used in the program. [DeferredGlobalConstantValue] are
// introduced later by the SSA builder and should be represented
// with a dedicated JEntity instead. We currently model them as a regular
// constant to take advantage of the machinery we already have in place to
// generate deferred constants in the emitter.
class DeferredGlobalConstantValue extends ConstantValue {
  DeferredGlobalConstantValue(this.referenced, this.unit);

  final ConstantValue referenced;
  final OutputUnit unit;

  bool get isReference => true;

  @override
  bool operator ==(other) {
    return other is DeferredGlobalConstantValue &&
        referenced == other.referenced &&
        unit == other.unit;
  }

  @override
  int get hashCode => (referenced.hashCode * 17 + unit.hashCode) & 0x3fffffff;

  @override
  List<ConstantValue> getDependencies() => [referenced];

  @override
  R accept<R, A>(ConstantValueVisitor<R, A> visitor, A arg) =>
      visitor.visitDeferredGlobal(this, arg);

  @override
  DartType getType(CommonElements types) => referenced.getType(types);

  @override
  ConstantValueKind get kind => ConstantValueKind.deferredGlobal;

  @override
  String toDartText(DartTypes? dartTypes) =>
      'deferred_global(${referenced.toDartText(dartTypes)})';

  @override
  String toStructuredText(DartTypes? dartTypes) {
    return 'DeferredGlobalConstant(${referenced.toStructuredText(dartTypes)})';
  }
}