//
// Copyright 2021 New Vector Ltd
//
// 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

/// A property wrapped used to inject from the dependency container on the instance, to instance properties.
///
/// ```
/// @Inject var someClass: SomeClass
/// ```
@propertyWrapper struct Inject<Value> {
    static subscript<T: Injectable>(_enclosingInstance instance: T,
                                    wrapped wrappedKeyPath: ReferenceWritableKeyPath<T, Value>,
                                    storage storageKeyPath: ReferenceWritableKeyPath<T, Self>) -> Value {
        get {
            // Resolve dependencies from enclosing instance's `dependencies` property
            let v: Value = instance.dependencies.resolve()
            return v
        }
        set {
            fatalError("Only subscript get is supported for injection")
        }
    }
    
    @available(*, unavailable, message: "This property wrapper can only be applied to classes")
    var wrappedValue: Value {
        get { fatalError("wrappedValue get not used") }
        set { fatalError("wrappedValue set not used. \(newValue)") }
    }
}