//
//  Copyright (c) 2023 Touch Instinct
//
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//  of this software and associated documentation files (the Software), to deal
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//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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//  THE SOFTWARE.
//

import TISwiftUtils

public extension MigratingBackingStore where Store: CodableKeyValueStorage,
                                             StoreContent: Codable {

    init<Value: Codable>(key: StorageKey<Value>,
                         storageContainer: Store,
                         decoder: CodableKeyValueDecoder = JSONKeyValueDecoder(),
                         encoder: CodableKeyValueEncoder = JSONKeyValueEncoder())
    where StoreContent == Value? {

        let getClosure: GetClosure = { container in
            Self.getValue(from: container, forKey: key, decoder: decoder, encoder: encoder)
        }

        let setClosure: SetClosure = { container, value in
            try? container.setOrRemove(codableObject: value, forKey: key, encoder: encoder).get()
        }

        self.init(store: storageContainer, getClosure: getClosure, setClosure: setClosure)
    }

    init<Value: Codable>(wrappedValue: Value,
                         key: StorageKey<Value>,
                         storageContainer: Store,
                         decoder: CodableKeyValueDecoder = JSONKeyValueDecoder(),
                         encoder: CodableKeyValueEncoder = JSONKeyValueEncoder())
    where StoreContent == Value? {

        let getClosure: GetClosure = { container in
            Self.getValue(from: container, forKey: key, wrappedValue: wrappedValue, decoder: decoder, encoder: encoder)
        }

        let setClosure: SetClosure = { container, value in
            try? container.setOrRemove(codableObject: value, forKey: key, encoder: encoder).get()
        }

        self.init(store: storageContainer, getClosure: getClosure, setClosure: setClosure)
    }

    static func getValue<Value: Codable>(from container: Store,
                                         forKey key: StorageKey<Value>,
                                         wrappedValue: Value? = nil,
                                         decoder: CodableKeyValueDecoder,
                                         encoder: CodableKeyValueEncoder) -> StoreContent where StoreContent == Value? {

        // Storage container can't handle migration when source storage has value and target doesn't.
        // This happens because of Decodable restrictions for Value in method `codableObject(forKey:decoder)`
        // and absence of encoder.
        try? container.codableObject(forKey: key, decoder: decoder)
            .flatMap {
                let _ = container.set(encodableObject: $0, forKey: key, encoder: encoder)

                return .success($0)
            }
            .flatMapError {
                guard let wrappedValue else {
                    return .failure($0)
                }

                return container.set(encodableObject: wrappedValue, forKey: key, encoder: encoder)
                    .flatMap { _ in .success(wrappedValue) }
            }
            .get()
    }
}