RealmCollectionImpl.swift

////////////////////////////////////////////////////////////////////////////
//
// Copyright 2021 Realm Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////

import Foundation
import Realm

// RealmCollectionImpl implements all of the RealmCollection protocol except for
// description and single-element subscript. description actually varies between
// the collection wrappers, and Sequence infers its associated types from subscript,
// so moving that here requires defining those explicitly in each collection.
//
// The functions don't need to be documented here because Xcode/DocC inherit
// the documentation from the RealmCollection protocol definition, and jazzy
// excludes this file entirely.
@usableFromInline
internal protocol RealmCollectionImpl: RealmCollection where Index == Int, SubSequence == Slice<Self>, Iterator == RLMIterator<Element> {
    var collection: RLMCollection { get }
    init(collection: RLMCollection)
}
extension RealmCollectionImpl {
    public var realm: Realm? { collection.realm.map(Realm.init) }
    public var isInvalidated: Bool { collection.isInvalidated }
    public var count: Int { Int(collection.count) }

    public subscript(bounds: Range<Self.Index>) -> SubSequence {
        return SubSequence(base: self, bounds: bounds)
    }
    public var first: Element? {
        return collection.firstObject!().map(staticBridgeCast)
    }
    public var last: Element? {
        return collection.lastObject!().map(staticBridgeCast)
    }
    public func objects(at indexes: IndexSet) -> [Element] {
        guard let r = collection.objects!(at: indexes) else {
            throwRealmException("Indexes for collection are out of bounds.")
        }
        return r.map(staticBridgeCast)
    }

    public func index(of object: Element) -> Int? {
        if let indexOf = collection.index(of:) {
            return notFoundToNil(index: indexOf(staticBridgeCast(fromSwift: object) as AnyObject))
        }
        fatalError("Collection does not support index(of:)")
    }
    public func index(matching predicate: NSPredicate) -> Int? {
        if let indexMatching = collection.indexOfObject(with:) {
            return notFoundToNil(index: indexMatching(predicate))
        }
        fatalError("Collection does not support index(matching:)")
    }

    public func filter(_ predicate: NSPredicate) -> Results<Element> {
        return Results<Element>(collection.objects(with: predicate))
    }

    public func sorted<S: Sequence>(by sortDescriptors: S) -> Results<Element>
        where S.Iterator.Element == SortDescriptor {
            return Results<Element>(collection.sortedResults(using: sortDescriptors.map { $0.rlmSortDescriptorValue }))
    }

    public func distinct<S: Sequence>(by keyPaths: S) -> Results<Element>
        where S.Iterator.Element == String {
            return Results<Element>(collection.distinctResults(usingKeyPaths: Array(keyPaths)))
    }

    public func min<T: _HasPersistedType>(ofProperty property: String) -> T? where T.PersistedType: MinMaxType {
        return collection.min(ofProperty: property).map(staticBridgeCast)
    }
    public func max<T: _HasPersistedType>(ofProperty property: String) -> T? where T.PersistedType: MinMaxType {
        return collection.max(ofProperty: property).map(staticBridgeCast)
    }
    public func sum<T: _HasPersistedType>(ofProperty property: String) -> T where T.PersistedType: AddableType {
        return staticBridgeCast(fromObjectiveC: collection.sum(ofProperty: property))
    }
    public func average<T: _HasPersistedType>(ofProperty property: String) -> T? where T.PersistedType: AddableType {
        return collection.average(ofProperty: property).map(staticBridgeCast)
    }

    public func value(forKey key: String) -> Any? {
        return collection.value(forKey: key)
    }
    public func value(forKeyPath keyPath: String) -> Any? {
        return collection.value(forKeyPath: keyPath)
    }
    public func setValue(_ value: Any?, forKey key: String) {
        return collection.setValue(value, forKey: key)
    }

    public func observe(keyPaths: [String]?,
                        on queue: DispatchQueue?,
                        _ block: @escaping (RealmCollectionChange<Self>) -> Void) -> NotificationToken {
        // We want to pass the same object instance to the change callback each time.
        // If the callback is being called on the source thread the instance should
        // be `self`, but if it's on a different thread it needs to be a new Swift
        // wrapper for the obj-c type, which we'll construct the first time the
        // callback is called.
        var col: Self?
        func wrapped(collection: RLMCollection?, change: RLMCollectionChange?, error: Error?) {
            if col == nil, let collection = collection {
                col = self.collection === collection ? self : Self(collection: collection)
            }
            block(.init(value: col, change: change, error: error))
        }
        return collection.addNotificationBlock(wrapped, keyPaths: keyPaths, queue: queue)
    }

#if compiler(<6)
    @available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
    @_unsafeInheritExecutor
    public func observe<A: Actor>(
        keyPaths: [String]?, on actor: A,
        _ block: @Sendable @escaping (isolated A, RealmCollectionChange<Self>) -> Void
    ) async -> NotificationToken {
        await with(self, on: actor) { actor, collection in
            collection.observe(keyPaths: keyPaths, on: nil) { change in
                actor.invokeIsolated(block, change)
            }
        }
    }
#else
    @available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
    public func observe<A: Actor>(
        keyPaths: [String]?, on actor: A,
        _isolation: isolated (any Actor)? = #isolation,
        _ block: @Sendable @escaping (isolated A, RealmCollectionChange<Self>) -> Void
    ) async -> NotificationToken {
        await with(self, on: actor) { actor, collection in
            collection.observe(keyPaths: keyPaths, on: nil) { change in
                actor.invokeIsolated(block, change)
            }
        }
    }
#endif

    public var isFrozen: Bool {
        return collection.isFrozen
    }
    public func freeze() -> Self {
        return Self(collection: collection.freeze())
    }
    public func thaw() -> Self? {
        return Self(collection: collection.thaw())
    }

    public func sectioned<Key: _Persistable>(sortDescriptors: [SortDescriptor],
                                             _ keyBlock: @escaping ((Element) -> Key)) -> SectionedResults<Key, Element> {
        if sortDescriptors.isEmpty {
            throwRealmException("There must be at least one SortDescriptor when using SectionedResults.")
        }
        let sectionedResults = collection.sectionedResults(using: sortDescriptors.map(ObjectiveCSupport.convert)) { value in
            return keyBlock(Element._rlmFromObjc(value)!)._rlmObjcValue as? RLMValue
        }

        return SectionedResults(rlmSectionedResult: sectionedResults)
    }
}

// A helper protocol which lets us check for Optional in where clauses
public protocol OptionalProtocol {
    associatedtype Wrapped
    func _rlmInferWrappedType() -> Wrapped
}

extension Optional: OptionalProtocol {
    public func _rlmInferWrappedType() -> Wrapped { return self! }
}

// `with(object, on: actor) { object, actor in ... }` hands the object over
// to the given actor and then invokes the callback within the actor.
#if compiler(<6)
@available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
@_unsafeInheritExecutor
internal func with<A: Actor, Value: ThreadConfined>(
    _ value: Value, on actor: A,
    _ block: @Sendable @escaping (isolated A, Value) async throws -> NotificationToken
) async rethrows -> NotificationToken {
    if value.realm == nil {
        fatalError("Change notifications are only supported for managed objects")
    }

    let tsr = ThreadSafeReference(to: value)
    let config = Unchecked(wrappedValue: value.realm!.rlmRealm.configurationSharingSchema())
    return try await actor.invoke { actor in
        if Task.isCancelled {
            return nil
        }
        let scheduler = RLMScheduler.actor(actor, invoke: actor.invoke, verify: actor.verifier())
        let realm = Realm(try! RLMRealm(configuration: config.wrappedValue, confinedTo: scheduler))
        guard let value = tsr.resolve(in: realm) else {
            return nil
        }
        // This is safe but 5.10's sendability checking can't prove it
        // nonisolated(unsafe) can't be applied to a let in guard so we need
        // a second variable
        nonisolated(unsafe) let v = value
        return try await block(actor, v)
    } ?? NotificationToken()
}
#else
@available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
internal func with<A: Actor, Value: ThreadConfined>(
    _ value: Value,
    on actor: A,
    _isolation: isolated (any Actor)? = #isolation,
    _ block: @Sendable @escaping (isolated A, Value) async throws -> NotificationToken?
) async rethrows -> NotificationToken {
    if value.realm == nil {
        fatalError("Change notifications are only supported for managed objects")
    }

    let tsr = ThreadSafeReference(to: value)
    nonisolated(unsafe) let config = value.realm!.rlmRealm.configurationSharingSchema()
    return try await actor.invoke { actor in
        if Task.isCancelled {
            return nil
        }
        let scheduler = RLMScheduler.actor(actor, invoke: actor.invoke, verify: actor.verifier())
        let realm = Realm(try! RLMRealm(configuration: config, confinedTo: scheduler))
        guard let value = tsr.resolve(in: realm) else {
            return nil
        }
        return try await block(actor, value)
    } ?? NotificationToken()
}
#endif