//===--- Bit.swift - A 1-bit type that can be used as an Index ------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
//  Used to index SequenceOfOne<T>
//
//===----------------------------------------------------------------------===//
public enum Bit : Int, RandomAccessIndexType, Reflectable {
  case Zero = 0, One = 1

  public func successor() -> Bit {
    _precondition(self == .Zero, "Can't increment past one")
    return .One
  }

  public func predecessor() -> Bit {
    _precondition(self == .One, "Can't decrement past zero")
    return .Zero
  }

  public func distanceTo(other: Bit) -> Int {
    return toRaw().distanceTo(other.toRaw())
  }

  public func advancedBy(distance: Int) -> Bit {
    return toRaw().advancedBy(distance) > 0 ? One : Zero
  }

  public
  func getMirror() -> MirrorType {
    return _BitMirror(self)
  }
}

struct _BitMirror: MirrorType {
  let _value: Bit
  
  init(_ v: Bit) {
    self._value = v
  }
  
  var value: Any { return _value }

  var valueType: Any.Type { return (_value as Any).dynamicType }

  var objectIdentifier: ObjectIdentifier? { return .None }

  var count: Int { return 0 }

  subscript(i: Int) -> (String, MirrorType) {
    _preconditionFailure("MirrorType access out of bounds")
  }

  var summary: String { 
    switch _value {
      case .Zero: return ".Zero"
      case .One:  return ".One"
    }
  }

  var quickLookObject: QuickLookObject? { return .None }

  var disposition: MirrorDisposition { return .Enum }
}

public func == (lhs: Bit, rhs: Bit) -> Bool {
  return lhs.toRaw() == rhs.toRaw()
}

public func < (lhs: Bit, rhs: Bit) -> Bool {
  return lhs.toRaw() < rhs.toRaw()
}

extension Bit : IntegerArithmeticType {
  static func _withOverflow(v: (Int, overflow: Bool)) -> (Bit, overflow: Bool) {
    return (Bit.fromRaw(v.0)!, v.overflow)
  }
  
  public static func addWithOverflow(
    lhs: Bit, _ rhs: Bit
  ) -> (Bit, overflow: Bool) {
    return _withOverflow(Int.addWithOverflow(lhs.toRaw(), rhs.toRaw()))
  }

  public static func subtractWithOverflow(
    lhs: Bit, _ rhs: Bit
  ) -> (Bit, overflow: Bool) {
    return _withOverflow(Int.subtractWithOverflow(lhs.toRaw(), rhs.toRaw()))
  }

  public static func multiplyWithOverflow(
    lhs: Bit, _ rhs: Bit
  ) -> (Bit, overflow: Bool) {
    return _withOverflow(Int.multiplyWithOverflow(lhs.toRaw(), rhs.toRaw()))
  }

  public static func divideWithOverflow(
    lhs: Bit, _ rhs: Bit
  ) -> (Bit, overflow: Bool) {
    return _withOverflow(Int.divideWithOverflow(lhs.toRaw(), rhs.toRaw()))
  }

  public static func remainderWithOverflow(
    lhs: Bit, _ rhs: Bit
  ) -> (Bit, overflow: Bool) {
    return _withOverflow(Int.remainderWithOverflow(lhs.toRaw(), rhs.toRaw()))
  }

  public func toIntMax() -> IntMax {
    return IntMax(toRaw())
  }
}