//
//  Coding.swift
//  TuskerPreferences
//
//  Created by Shadowfacts on 4/13/24.
//

import Foundation

private protocol PreferenceProtocol {
    associatedtype Key: PreferenceKey
    var storedValue: Key.Value? { get }
    init()
}

extension Preference: PreferenceProtocol {
}

struct PreferenceCoding<Wrapped: Codable>: Codable {
    let wrapped: Wrapped
    
    init(wrapped: Wrapped) {
        self.wrapped = wrapped
    }
    
    init(from decoder: any Decoder) throws {
        self.wrapped = try Wrapped(from: PreferenceDecoder(wrapped: decoder))
    }
    
    func encode(to encoder: any Encoder) throws {
        try wrapped.encode(to: PreferenceEncoder(wrapped: encoder))
    }
}

private struct PreferenceDecoder: Decoder {
    let wrapped: any Decoder
    
    var codingPath: [any CodingKey] {
        wrapped.codingPath
    }
    
    var userInfo: [CodingUserInfoKey : Any] {
        wrapped.userInfo
    }
    
    func container<Key>(keyedBy type: Key.Type) throws -> KeyedDecodingContainer<Key> where Key : CodingKey {
        KeyedDecodingContainer(PreferenceDecodingContainer(wrapped: try wrapped.container(keyedBy: type)))
    }
    
    func unkeyedContainer() throws -> any UnkeyedDecodingContainer {
        throw Error.onlyKeyedContainerSupported
    }
    
    func singleValueContainer() throws -> any SingleValueDecodingContainer {
        throw Error.onlyKeyedContainerSupported
    }
    
    enum Error: Swift.Error {
        case onlyKeyedContainerSupported
    }
}

private struct PreferenceDecodingContainer<Key: CodingKey>: KeyedDecodingContainerProtocol {
    let wrapped: KeyedDecodingContainer<Key>
    
    var codingPath: [any CodingKey] {
        wrapped.codingPath
    }
    
    var allKeys: [Key] {
        wrapped.allKeys
    }
    
    func contains(_ key: Key) -> Bool {
        wrapped.contains(key)
    }
    
    func decodeNil(forKey key: Key) throws -> Bool {
        try wrapped.decodeNil(forKey: key)
    }
    
    func decode(_ type: Bool.Type, forKey key: Key) throws -> Bool {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: String.Type, forKey key: Key) throws -> String {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Double.Type, forKey key: Key) throws -> Double {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Float.Type, forKey key: Key) throws -> Float {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Int.Type, forKey key: Key) throws -> Int {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Int8.Type, forKey key: Key) throws -> Int8 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Int16.Type, forKey key: Key) throws -> Int16 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Int32.Type, forKey key: Key) throws -> Int32 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: Int64.Type, forKey key: Key) throws -> Int64 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: UInt.Type, forKey key: Key) throws -> UInt {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: UInt8.Type, forKey key: Key) throws -> UInt8 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: UInt16.Type, forKey key: Key) throws -> UInt16 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: UInt32.Type, forKey key: Key) throws -> UInt32 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode(_ type: UInt64.Type, forKey key: Key) throws -> UInt64 {
        try wrapped.decode(type, forKey: key)
    }
    
    func decode<T>(_ type: T.Type, forKey key: Key) throws -> T where T : Decodable {
        if let type = type as? any PreferenceProtocol.Type,
           !contains(key) {
            func makePreference<P: PreferenceProtocol>(_: P.Type) -> T {
                P() as! T
            }
            return _openExistential(type, do: makePreference)
        }
        return try wrapped.decode(type, forKey: key)
    }
    
    func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer<NestedKey> where NestedKey : CodingKey {
        try wrapped.nestedContainer(keyedBy: type, forKey: key)
    }
    
    func nestedUnkeyedContainer(forKey key: Key) throws -> any UnkeyedDecodingContainer {
        try wrapped.nestedUnkeyedContainer(forKey: key)
    }
    
    func superDecoder() throws -> any Decoder {
        try wrapped.superDecoder()
    }
    
    func superDecoder(forKey key: Key) throws -> any Decoder {
        try wrapped.superDecoder(forKey: key)
    }
}

private struct PreferenceEncoder: Encoder {
    let wrapped: any Encoder
    
    var codingPath: [any CodingKey] {
        wrapped.codingPath
    }
    
    var userInfo: [CodingUserInfoKey : Any] {
        wrapped.userInfo
    }
    
    func container<Key>(keyedBy type: Key.Type) -> KeyedEncodingContainer<Key> where Key : CodingKey {
        KeyedEncodingContainer(PreferenceEncodingContainer(wrapped: wrapped.container(keyedBy: type)))
    }
    
    func unkeyedContainer() -> any UnkeyedEncodingContainer {
        fatalError("Only keyed containers supported")
    }
    
    func singleValueContainer() -> any SingleValueEncodingContainer {
        fatalError("Only keyed containers supported")
    }
}

private struct PreferenceEncodingContainer<Key: CodingKey>: KeyedEncodingContainerProtocol {
    var wrapped: KeyedEncodingContainer<Key>
    
    var codingPath: [any CodingKey] {
        wrapped.codingPath
    }
    
    mutating func encodeNil(forKey key: Key) throws {
        try wrapped.encodeNil(forKey: key)
    }
    
    mutating func encode(_ value: Bool, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: String, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Double, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Float, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Int, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Int8, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Int16, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Int32, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: Int64, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: UInt, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: UInt8, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: UInt16, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: UInt32, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode(_ value: UInt64, forKey key: Key) throws {
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func encode<T>(_ value: T, forKey key: Key) throws where T : Encodable {
        if let value = value as? any PreferenceProtocol,
           value.storedValue == nil {
            return
        }
        try wrapped.encode(value, forKey: key)
    }
    
    mutating func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type, forKey key: Key) -> KeyedEncodingContainer<NestedKey> where NestedKey : CodingKey {
        wrapped.nestedContainer(keyedBy: keyType, forKey: key)
    }
    
    mutating func nestedUnkeyedContainer(forKey key: Key) -> any UnkeyedEncodingContainer {
        wrapped.nestedUnkeyedContainer(forKey: key)
    }
    
    mutating func superEncoder() -> any Encoder {
        wrapped.superEncoder()
    }
    
    mutating func superEncoder(forKey key: Key) -> any Encoder {
        wrapped.superEncoder(forKey: key)
    }
    
    
}