PostgreSQLDataConvertible.swift

/// Capable of being converted to/from `PostgreSQLData`
public protocol PostgreSQLDataConvertible {
    /// This type's preferred data type.
    static var postgreSQLDataType: PostgreSQLDataType { get }

    /// This type's preferred array type.
    static var postgreSQLDataArrayType: PostgreSQLDataType { get }

    /// Creates a `Self` from the supplied `PostgreSQLData`
    static func convertFromPostgreSQLData(_ data: PostgreSQLData) throws -> Self

    /// Converts `Self` to a `PostgreSQLData`
    func convertToPostgreSQLData() throws -> PostgreSQLData
}

extension PostgreSQLData {
    /// Gets a `String` from the supplied path or throws a decoding error.
    public func decode<T>(_ type: T.Type) throws -> T where T: PostgreSQLDataConvertible {
        return try T.convertFromPostgreSQLData(self)
    }
}

extension PostgreSQLData: PostgreSQLDataConvertible {
    /// See `PostgreSQLDataCustomConvertible.postgreSQLDataType`
    public static var postgreSQLDataType: PostgreSQLDataType { return .void }

    /// See `PostgreSQLDataCustomConvertible.postgreSQLDataArrayType`
    public static var postgreSQLDataArrayType: PostgreSQLDataType { return .void }

    /// See `PostgreSQLDataCustomConvertible.convertFromPostgreSQLData(_:)`
    public static func convertFromPostgreSQLData(_ data: PostgreSQLData) throws -> PostgreSQLData {
        return data
    }

    /// See `PostgreSQLDataCustomConvertible.convertToPostgreSQLData()`
    public func convertToPostgreSQLData() throws -> PostgreSQLData {
        return self
    }
}

extension RawRepresentable where RawValue: PostgreSQLDataConvertible {
    /// See `PostgreSQLDataCustomConvertible.postgreSQLDataType`
    public static var postgreSQLDataType: PostgreSQLDataType {
        return RawValue.postgreSQLDataType
    }

    /// See `PostgreSQLDataCustomConvertible.postgreSQLDataArrayType`
    public static var postgreSQLDataArrayType: PostgreSQLDataType {
        return RawValue.postgreSQLDataArrayType
    }

    /// See `PostgreSQLDataCustomConvertible.convertFromPostgreSQLData(_:)`
    public static func convertFromPostgreSQLData(_ data: PostgreSQLData) throws -> Self {
        let aRawValue = try RawValue.convertFromPostgreSQLData(data)
        guard let enumValue = Self(rawValue: aRawValue) else {
            throw PostgreSQLError(identifier: "invalidRawValue", reason: "Unable to decode RawRepresentable from the database value.", source: .capture())
        }
        return enumValue
    }

    /// See `PostgreSQLDataCustomConvertible.convertToPostgreSQLData()`
    public func convertToPostgreSQLData() throws -> PostgreSQLData {
        return try self.rawValue.convertToPostgreSQLData()
    }
}