pkgs/objective_c/lib/src/internal.dart

// Copyright (c) 2024, 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 'dart:ffi';
import 'dart:isolate';

import 'package:ffi/ffi.dart';

import 'c_bindings_generated.dart' as c;
import 'ns_string.dart';
import 'objective_c_bindings_generated.dart' as objc;
import 'runtime_bindings_generated.dart' as r;

typedef ObjectPtr = Pointer<r.ObjCObjectImpl>;
typedef BlockPtr = Pointer<c.ObjCBlockImpl>;
typedef VoidPtr = Pointer<Void>;

final class UseAfterReleaseError extends StateError {
  UseAfterReleaseError() : super('Use after release error');
}

final class DoubleReleaseError extends StateError {
  DoubleReleaseError() : super('Double release error');
}

final class UnimplementedOptionalMethodException implements Exception {
  final String clazz;
  final String method;
  UnimplementedOptionalMethodException(this.clazz, this.method);

  @override
  String toString() =>
      '$runtimeType: Instance of $clazz does not implement $method';
}

final class FailedToLoadClassException implements Exception {
  final String clazz;
  FailedToLoadClassException(this.clazz);

  @override
  String toString() => '$runtimeType: Failed to load Objective-C class: $clazz';
}

final class FailedToLoadProtocolException implements Exception {
  final String protocol;
  FailedToLoadProtocolException(this.protocol);

  @override
  String toString() =>
      '$runtimeType: Failed to load Objective-C protocol: $protocol';
}

/// Failed to load a method of a protocol.
///
/// This means that a method that was seen in the protocol declaration at
/// compile time was missing from the protocol at runtime. This is usually
/// caused by a version mismatch between the compile time header and the runtime
/// framework (eg, running an app on an older iOS device).
///
/// To fix this, check whether the method exists at runtime, using
/// `ObjCProtocolMethod.isAvailable`, and implement fallback logic if it's
/// missing.
final class FailedToLoadProtocolMethodException implements Exception {
  final String protocol;
  final String method;
  FailedToLoadProtocolMethodException(this.protocol, this.method);

  @override
  String toString() =>
      '$runtimeType: Failed to load Objective-C protocol method: '
      '$protocol.$method';
}

final class ObjCRuntimeError extends Error {
  final String message;
  ObjCRuntimeError(this.message);

  @override
  String toString() => '$runtimeType: $message';
}

/// Wrapper [Exception] around an Objective-C `NSError`.
///
/// In Dart, an "exception" is an ordinary runtime failure that can be caught
/// and handled, while an "error" is a program failure that the programmer
/// should have avoided (and catching [Error]s is bad practice).
///
/// Objective-C inverts this nomenclature. Ordinary runtime failures are
/// signaled using `NSError`, so these are analogous to Dart's [Exception]s,
/// though they're returned by reference rather than thrown. On the other hand,
/// `NSException` is intended to be used in an `@throw` statement, and not
/// intended to be caught (in fact Objective-C doesn't intend throwing and
/// catching to be part of an ordinary control flow at all).
final class NSErrorException implements Exception {
  final objc.NSError error;
  NSErrorException(this.error);

  static void checkErrorPointer(ObjectPtr pointer) {
    if (pointer.address != 0) {
      throw NSErrorException(
        objc.NSError.fromPointer(pointer, retain: true, release: true),
      );
    }
  }

  @override
  String toString() => 'NSError: ${error.localizedDescription.toDartString()}';
}

extension GetProtocolName on Pointer<r.ObjCProtocolImpl> {
  /// Returns the name of the protocol.
  String get name => r.getProtocolName(this).cast<Utf8>().toDartString();
}

/// Only for use by ffigen bindings.
Pointer<r.ObjCSelector> registerName(String name) {
  _ensureDartAPI();
  final cstr = name.toNativeUtf8();
  final sel = r.registerName(cstr.cast());
  calloc.free(cstr);
  return sel;
}

/// Only for use by FFIgen bindings.
ObjectPtr getClass(String name) {
  _ensureDartAPI();
  final cstr = name.toNativeUtf8();
  final clazz = r.getClass(cstr.cast());
  calloc.free(cstr);
  if (clazz == nullptr) {
    throw FailedToLoadClassException(name);
  }
  return clazz;
}

/// Only for use by ffigen bindings.
Pointer<r.ObjCProtocolImpl> getProtocol(String name) {
  _ensureDartAPI();
  final cstr = name.toNativeUtf8();
  final clazz = r.getProtocol(cstr.cast());
  calloc.free(cstr);
  if (clazz == nullptr) {
    throw FailedToLoadProtocolException(name);
  }
  return clazz;
}

/// Only for use by FFIgen bindings.
Pointer<Char>? getProtocolMethodSignature(
  Pointer<r.ObjCProtocolImpl> protocol,
  Pointer<r.ObjCSelector> sel, {
  required bool isRequired,
  required bool isInstanceMethod,
}) {
  _ensureDartAPI();
  final sig = r
      .getMethodDescription(protocol, sel, isRequired, isInstanceMethod)
      .types;
  return sig == nullptr ? null : sig;
}

/// Only for use by FFIgen bindings.
final msgSendPointer = Native.addressOf<NativeFunction<Void Function()>>(
  r.msgSend,
);

/// Only for use by FFIgen bindings.
final msgSendFpretPointer = Native.addressOf<NativeFunction<Void Function()>>(
  r.msgSendFpret,
);

/// Only for use by FFIgen bindings.
final msgSendStretPointer = Native.addressOf<NativeFunction<Void Function()>>(
  r.msgSendStret,
);

/// Only for use by FFIgen bindings.
final useMsgSendVariants =
    Abi.current() == Abi.iosX64 || Abi.current() == Abi.macosX64;

/// Only for use by ffigen bindings.
bool respondsToSelector(ObjectPtr obj, Pointer<r.ObjCSelector> sel) =>
    _objcMsgSendRespondsToSelector(obj, _selRespondsToSelector, sel);
final _selRespondsToSelector = registerName('respondsToSelector:');
final _objcMsgSendRespondsToSelector = msgSendPointer
    .cast<
      NativeFunction<
        Bool Function(
          ObjectPtr,
          Pointer<r.ObjCSelector>,
          Pointer<r.ObjCSelector> aSelector,
        )
      >
    >()
    .asFunction<
      bool Function(ObjectPtr, Pointer<r.ObjCSelector>, Pointer<r.ObjCSelector>)
    >();

// _FinalizablePointer exists because we can't access `this` in the initializers
// of _ObjCReference's constructor, and we have to have an owner to attach the
// Dart_FinalizableHandle to. Ideally _ObjCReference would be the owner.
@pragma('vm:deeply-immutable')
final class _FinalizablePointer<T extends NativeType> implements Finalizable {
  final Pointer<T> ptr;
  _FinalizablePointer(this.ptr);
}

bool _dartAPIInitialized = false;
void _ensureDartAPI() {
  if (!_dartAPIInitialized) {
    final result = c.initializeApi(NativeApi.initializeApiDLData);
    assert(result == 0);
    _dartAPIInitialized = true;
  }
}

c.Dart_FinalizableHandle _newFinalizableHandle(
  _FinalizablePointer finalizable,
) {
  _ensureDartAPI();
  return c.newFinalizableHandle(finalizable, finalizable.ptr.cast());
}

Pointer<Bool> _newFinalizableBool(Object owner) {
  _ensureDartAPI();
  return c.newFinalizableBool(owner);
}

@pragma('vm:deeply-immutable')
abstract final class _ObjCReference<T extends NativeType>
    implements Finalizable {
  final _FinalizablePointer<T> _finalizable;
  final c.Dart_FinalizableHandle? _ptrFinalizableHandle;
  final Pointer<Bool> _isReleased;

  _ObjCReference(
    this._finalizable, {
    required bool retain,
    required bool release,
  }) : _ptrFinalizableHandle = release
           ? _newFinalizableHandle(_finalizable)
           : null,
       _isReleased = _newFinalizableBool(_finalizable) {
    assert(_isValid(_finalizable.ptr));
    if (retain) {
      _retain(_finalizable.ptr);
    }
  }

  bool get isReleased => _isReleased.value;

  void _release(void Function(ObjectPtr) releaser) {
    if (isReleased) {
      throw DoubleReleaseError();
    }
    assert(_isValid(_finalizable.ptr));
    if (_ptrFinalizableHandle != null) {
      c.deleteFinalizableHandle(_ptrFinalizableHandle, _finalizable);
      releaser(_finalizable.ptr.cast());
    }
    _isReleased.value = true;
  }

  void release() => _release(r.objectRelease);

  Pointer<T> autorelease() {
    _release(r.objectAutorelease);
    return _finalizable.ptr;
  }

  @override
  bool operator ==(Object other) =>
      other is _ObjCReference && _finalizable.ptr == other._finalizable.ptr;

  @override
  int get hashCode => _finalizable.ptr.hashCode;

  Pointer<T> get pointer {
    if (isReleased) {
      throw UseAfterReleaseError();
    }
    assert(_isValid(_finalizable.ptr));
    return _finalizable.ptr;
  }

  Pointer<T> retainAndReturnPointer() {
    final ptr = pointer;
    _retain(ptr);
    return ptr;
  }

  Pointer<T> retainAndAutorelease() {
    final ptr = pointer;
    _retain(ptr);
    r.objectAutorelease(ptr.cast());
    return ptr;
  }

  void _retain(Pointer<T> ptr);
  bool _isValid(Pointer<T> ptr);
}

// Wrapper around ObjCObjectRef/ObjCBlockRef. This is needed because
// deeply-immutable classes must be final, but the FFIgen bindings need to
// extend ObjCObject/ObjCBlockBase.
class _ObjCRefHolder<T extends NativeType, Ref extends _ObjCReference<T>> {
  final Ref ref;

  _ObjCRefHolder(this.ref);

  @override
  bool operator ==(Object other) => other is _ObjCRefHolder && ref == other.ref;

  @override
  int get hashCode => ref.hashCode;
}

@pragma('vm:deeply-immutable')
final class ObjCObjectRef extends _ObjCReference<r.ObjCObjectImpl> {
  ObjCObjectRef(ObjectPtr ptr, {required super.retain, required super.release})
    : super(_FinalizablePointer(ptr));

  @override
  void _retain(ObjectPtr ptr) => r.objectRetain(ptr);

  @override
  bool _isValid(ObjectPtr ptr) => _isValidObject(ptr);
}

/// Base class for all Objective-C objects.
class ObjCObject extends _ObjCRefHolder<r.ObjCObjectImpl, ObjCObjectRef> {
  ObjCObject(ObjectPtr ptr, {required bool retain, required bool release})
    : super(ObjCObjectRef(ptr, retain: retain, release: release));
}

// Returns whether the object is valid and live. The pointer must point to
// readable memory, or be null. May (rarely) return false positives.
bool _isValidObject(ObjectPtr ptr) {
  if (ptr == nullptr) return false;
  return _isValidClass(r.getObjectClass(ptr));
}

final _allClasses = <ObjectPtr>{};

bool _isValidClass(ObjectPtr clazz, {bool forceReloadClasses = false}) {
  if (!forceReloadClasses && _allClasses.contains(clazz)) return true;

  // If the class is missing from the list, it either means we haven't created
  // the set yet, or more classes have been loaded since we created the set, or
  // the class is actually invalid. To rule out the first two cases, rebulid the
  // set then try again. This is expensive, but only happens if asserts are
  // enabled, and only happens more than O(1) times if there are actually
  // invalid objects in use, which shouldn't happen in correct code.
  final countPtr = calloc<UnsignedInt>();
  final classList = r.copyClassList(countPtr);
  final count = countPtr.value;
  calloc.free(countPtr);
  _allClasses.clear();
  for (var i = 0; i < count; ++i) {
    _allClasses.add(classList[i]);
  }
  calloc.free(classList);

  return _allClasses.contains(clazz);
}

/// Base class for all Objective-C protocols.
// This exists so that interface_lists_test.dart can tell the difference between
// a protocol and an interface.
typedef ObjCProtocol = ObjCObject;

@pragma('vm:deeply-immutable')
final class ObjCBlockRef extends _ObjCReference<c.ObjCBlockImpl> {
  ObjCBlockRef(BlockPtr ptr, {required super.retain, required super.release})
    : super(_FinalizablePointer(ptr));

  @override
  void _retain(BlockPtr ptr) => r.blockRetain(ptr.cast());

  @override
  bool _isValid(BlockPtr ptr) => c.isValidBlock(ptr);
}

/// Only for use by FFIgen bindings.
class ObjCBlockBase extends _ObjCRefHolder<c.ObjCBlockImpl, ObjCBlockRef> {
  ObjCBlockBase(BlockPtr ptr, {required bool retain, required bool release})
    : super(ObjCBlockRef(ptr, retain: retain, release: release));
}

Pointer<c.ObjCBlockDesc> _newBlockDesc(
  Pointer<NativeFunction<Void Function(BlockPtr)>> disposeHelper,
) {
  final desc = calloc.allocate<c.ObjCBlockDesc>(sizeOf<c.ObjCBlockDesc>());
  desc.ref.reserved = 0;
  desc.ref.size = sizeOf<c.ObjCBlockImpl>();
  desc.ref.copy_helper = nullptr;
  desc.ref.dispose_helper = disposeHelper.cast();
  desc.ref.signature = nullptr;
  return desc;
}

final _pointerBlockDesc = _newBlockDesc(nullptr);
final _closureBlockDesc = _newBlockDesc(
  Native.addressOf<NativeFunction<Void Function(BlockPtr)>>(
    c.disposeObjCBlockWithClosure,
  ),
);

BlockPtr _newBlock(
  VoidPtr invoke,
  VoidPtr target,
  Pointer<c.ObjCBlockDesc> descriptor,
  int disposePort,
  int flags,
) {
  final b = calloc.allocate<c.ObjCBlockImpl>(sizeOf<c.ObjCBlockImpl>());
  b.ref.isa = Native.addressOf<Array<VoidPtr>>(r.NSConcreteGlobalBlock).cast();
  b.ref.flags = flags;
  b.ref.reserved = 0;
  b.ref.invoke = invoke;
  b.ref.target = target;
  b.ref.dispose_port = disposePort;
  b.ref.descriptor = descriptor;
  assert(c.isValidBlock(b));
  final copy = r.blockRetain(b.cast()).cast<c.ObjCBlockImpl>();
  calloc.free(b);
  assert(
    copy.ref.isa ==
        Native.addressOf<Array<VoidPtr>>(r.NSConcreteMallocBlock).cast(),
  );
  assert(c.isValidBlock(copy));
  return copy;
}

const int _blockHasCopyDispose = 1 << 25;

/// Only for use by FFIgen bindings.
BlockPtr newClosureBlock(VoidPtr invoke, Function fn, bool keepIsolateAlive) =>
    _newBlock(
      invoke,
      _registerBlockClosure(fn, keepIsolateAlive),
      _closureBlockDesc,
      _blockClosureDisposer.sendPort.nativePort,
      _blockHasCopyDispose,
    );

/// Only for use by FFIgen bindings.
BlockPtr newPointerBlock(VoidPtr invoke, VoidPtr target) =>
    _newBlock(invoke, target, _pointerBlockDesc, 0, 0);

typedef _RegEntry = ({Function closure, RawReceivePort? keepAlivePort});

final _blockClosureRegistry = <int, _RegEntry>{};

int _blockClosureRegistryLastId = 0;

final _blockClosureDisposer = () {
  _ensureDartAPI();
  return RawReceivePort((dynamic msg) {
    final id = msg as int;
    assert(_blockClosureRegistry.containsKey(id));
    final entry = _blockClosureRegistry.remove(id)!;
    entry.keepAlivePort?.close();
  }, 'ObjCBlockClosureDisposer')..keepIsolateAlive = false;
}();

VoidPtr _registerBlockClosure(Function closure, bool keepIsolateAlive) {
  ++_blockClosureRegistryLastId;
  assert(!_blockClosureRegistry.containsKey(_blockClosureRegistryLastId));
  _blockClosureRegistry[_blockClosureRegistryLastId] = (
    closure: closure,
    keepAlivePort: keepIsolateAlive ? RawReceivePort() : null,
  );
  return VoidPtr.fromAddress(_blockClosureRegistryLastId);
}

/// Only for use by FFIgen bindings.
Function getBlockClosure(BlockPtr block) {
  var id = block.ref.target.address;
  assert(_blockClosureRegistry.containsKey(id));
  return _blockClosureRegistry[id]!.closure;
}

/// Only for use by FFIgen bindings.
final Pointer<c.DOBJC_Context> objCContext = c.fillContext(
  calloc<c.DOBJC_Context>(),
);

// Not exported by ../objective_c.dart, because they're only for testing.
bool blockHasRegisteredClosure(BlockPtr block) =>
    _blockClosureRegistry.containsKey(block.ref.target.address);
bool isValidBlock(BlockPtr block) => c.isValidBlock(block);
bool isValidClass(ObjectPtr clazz, {bool forceReloadClasses = false}) =>
    _isValidClass(clazz, forceReloadClasses: forceReloadClasses);
bool isValidObject(ObjectPtr object) => _isValidObject(object);