Ponyboy47/Trailblazer

/// A struct for manipulating the uid, gid, and sticky bits of a file mode (mode_t in C)
public struct FileBits: OptionSet, ExpressibleByIntegerLiteral, Hashable {
    public typealias IntegerLiteralType = OSUInt

    public private(set) var rawValue: IntegerLiteralType

    /// Whether or not the uid bit is set
    public var uid: Bool {
        return contains(.uid)
    }

    /// Whether or not the gid bit is set
    public var gid: Bool {
        return contains(.gid)
    }

    /// Whether or not the sticky bit is set
    public var sticky: Bool {
        return contains(.sticky)
    }

    /// A FileBits struct with all the bits turned on
    public static let all: FileBits = 0o7
    /// A FileBits struct with only the uid bit turned on
    public static let uid: FileBits = 0o4
    /// A FileBits struct with only the gid bit turned on
    public static let gid: FileBits = 0o2
    /// A FileBits struct with only the sticky bit turned on
    public static let sticky: FileBits = 0o1
    /// A FileBits struct with none of the bits turned on
    public static let none: FileBits = 0

    /// Whether or not all of the bits are off
    public var hasNone: Bool { return !(uid || gid || sticky) }

    public init(rawValue: IntegerLiteralType = 0) {
        self.rawValue = rawValue
    }

    public init(_ bits: FileBits...) {
        self.init(rawValue: bits.reduce(0) { $0 | $1.rawValue })
    }

    public init(uid: Bool = false, gid: Bool = false, sticky: Bool = false) {
        self.init(rawValue: (uid ? 4 : 0) | (gid ? 2 : 0) | (sticky ? 1 : 0))
    }

    public init(integerLiteral value: IntegerLiteralType) {
        self.init(rawValue: value)
    }

    /// Returns the inverse FileBits with all bits flipped
    public static prefix func ~ (lhs: FileBits) -> FileBits {
        // NOTing flips too many bits and may cause rawValues of equivalent
        // FileBitss to no longer be equivalent
        return FileBits(rawValue: ~lhs.rawValue & FileBits.all.rawValue)
    }

    /// Returns a FileBits with the bits contained in either mode
    public static func | (lhs: FileBits, rhs: FileBits) -> FileBits {
        return FileBits(rawValue: lhs.rawValue | rhs.rawValue)
    }

    /// Returns a FileBits with the bits contained in either mode
    public static func | (lhs: FileBits, rhs: IntegerLiteralType) -> FileBits {
        return FileBits(rawValue: lhs.rawValue | rhs)
    }

    /// Sets the FileBits with the bits contained in either mode
    public static func |= (lhs: inout FileBits, rhs: FileBits) {
        lhs.rawValue = lhs.rawValue | rhs.rawValue
    }

    /// Sets the FileBits with the bits contained in either mode
    public static func |= (lhs: inout FileBits, rhs: IntegerLiteralType) {
        lhs.rawValue = lhs.rawValue | rhs
    }

    /// Returns a FileBits with only the bits contained in both modes
    public static func & (lhs: FileBits, rhs: FileBits) -> FileBits {
        return FileBits(rawValue: lhs.rawValue & rhs.rawValue)
    }

    /// Returns a FileBits with only the bits contained in both modes
    public static func & (lhs: FileBits, rhs: IntegerLiteralType) -> FileBits {
        return FileBits(rawValue: lhs.rawValue & rhs)
    }

    /// Sets the FileBits with only the bits contained in both modes
    public static func &= (lhs: inout FileBits, rhs: FileBits) {
        lhs.rawValue = lhs.rawValue & rhs.rawValue
    }

    /// Sets the FileBits with only the bits contained in both modes
    public static func &= (lhs: inout FileBits, rhs: IntegerLiteralType) {
        lhs.rawValue = lhs.rawValue & rhs
    }
}

extension FileBits: CustomStringConvertible {
    public var description: String {
        var bits: [String] = []

        if contains(.uid) {
            bits.append("uid")
        }
        if contains(.gid) {
            bits.append("gid")
        }
        if contains(.sticky) {
            bits.append("sticky")
        }

        if bits.isEmpty {
            bits.append("none")
        }

        return "\(type(of: self))(\(bits.joined(separator: ", ")))"
    }
}