//
//  UInt128.swift
//
//  Copyright (C) 2014-2021 Marcin Krzyżanowski <marcin@krzyzanowskim.com>
//  This software is provided 'as-is', without any express or implied warranty.
//
//  In no event will the authors be held liable for any damages arising from the use of this software.
//
//  Permission is granted to anyone to use this software for any purpose,including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
//
//  - The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation is required.
//  - Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
//  - This notice may not be removed or altered from any source or binary distribution.
//

import Foundation

struct UInt128: Equatable, ExpressibleByIntegerLiteral {
  let i: (a: UInt64, b: UInt64)

  typealias IntegerLiteralType = UInt64

  init(integerLiteral value: IntegerLiteralType) {
    self = UInt128(value)
  }

  init(_ raw: Array<UInt8>) {
    self = raw.prefix(MemoryLayout<UInt128>.stride).withUnsafeBytes({ (rawBufferPointer) -> UInt128 in
      let arr = rawBufferPointer.bindMemory(to: UInt64.self)
      return UInt128((arr[0].bigEndian, arr[1].bigEndian))
    })
  }

  init(_ raw: ArraySlice<UInt8>) {
    self.init(Array(raw))
  }

  init(_ i: (a: UInt64, b: UInt64)) {
    self.i = i
  }

  init(a: UInt64, b: UInt64) {
    self.init((a, b))
  }

  init(_ b: UInt64) {
    self.init((0, b))
  }

  // Bytes
  var bytes: Array<UInt8> {
    var at = self.i.a.bigEndian
    var bt = self.i.b.bigEndian

    let ar = Data(bytes: &at, count: MemoryLayout.size(ofValue: at))
    let br = Data(bytes: &bt, count: MemoryLayout.size(ofValue: bt))

    var result = Data()
    result.append(ar)
    result.append(br)
    return result.bytes
  }

  static func ^ (n1: UInt128, n2: UInt128) -> UInt128 {
    UInt128((n1.i.a ^ n2.i.a, n1.i.b ^ n2.i.b))
  }

  static func & (n1: UInt128, n2: UInt128) -> UInt128 {
    UInt128((n1.i.a & n2.i.a, n1.i.b & n2.i.b))
  }

  static func >> (value: UInt128, by: Int) -> UInt128 {
    var result = value
    for _ in 0..<by {
      let a = result.i.a >> 1
      let b = result.i.b >> 1 + ((result.i.a & 1) << 63)
      result = UInt128((a, b))
    }
    return result
  }

  // Equatable.
  static func == (lhs: UInt128, rhs: UInt128) -> Bool {
    lhs.i == rhs.i
  }

  static func != (lhs: UInt128, rhs: UInt128) -> Bool {
    !(lhs == rhs)
  }
}