//
//  Updateable.swift
//  Cryptor
//
// 	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 protocol for calculations that can be updated with incremental data buffers.
///
public protocol Updatable {
	
    /// Status of the calculation.
    var status: Status { get }
	
	///
    /// Low-level update routine.
    /// Updates the calculation with the contents of a data buffer.
	///
    /// - Parameters:
 	///		- buffer: 		Pointer to the data buffer
    /// 	- byteCount: 	Length of the buffer in bytes
	///
    /// - Returns: `Self` if no error for optional chaining, nil otherwise
	///
    func update(from buffer: UnsafeRawPointer, byteCount: size_t) -> Self?
}

///
/// Factors out common update code from Digest, HMAC and Cryptor.
///
extension Updatable {
    ///
    /// Updates the current calculation with data contained in an `NSData` object.
    ///
    /// - Parameter data: The `NSData` object
    ///
	/// - Returns: Optional `Self` or nil
	///
	public func update(data: NSData) -> Self? {
		
        _ = update(from: data.bytes, byteCount: size_t(data.length))
        return self.status == .success ? self : nil
    }
	
	///
	/// Updates the current calculation with data contained in an `Data` object.
	///
	/// - Parameters data: The `Data` object
	///
	/// - Returns: Optional `Self` or nil
	///
	public func update(data: Data) -> Self? {
		
		#if swift(>=5.0)
			_ = data.withUnsafeBytes() {
				
				_ = update(from: $0.baseAddress!, byteCount: size_t(data.count))
			}
		#else
			_ = data.withUnsafeBytes() { (buffer: UnsafePointer<UInt8>) in

				_ = update(from: buffer, byteCount: size_t(data.count))
			}
		#endif
		return self.status == .success ? self : nil
	}
	
    ///
    /// Updates the current calculation with data contained in a byte array.
    ///
    /// - Parameter byteArray: The byte array
    ///
	/// - Returns: Optional `Self` or nil
	///
	public func update(byteArray: [UInt8]) -> Self? {
		
        _ = update(from: byteArray, byteCount: size_t(byteArray.count))
		return self.status == .success ? self : nil
    }
	
    ///
    /// Updates the current calculation with data contained in a String.
    /// The corresponding data will be generated using UTF8 encoding.
    ///
    /// - Parameter string: The string of data
    ///
	/// - Returns: Optional `Self` or nil
	///
	public func update(string: String) -> Self? {
		
        _ = update(from: string, byteCount: size_t(string.utf8.count))
		return self.status == .success ? self : nil
    }
}