import Adwaita
import CMath

struct ViewModel {
    private var numberBuffer: String = ""
    private var number1: Double? = nil
    private var number2: Double? = nil
    private var op: Operator? = nil
    @State
    private(set) var display: String = ""

    mutating func clear() {
        numberBuffer = ""
        number1 = nil
        number2 = nil
        op = nil
        display = ""
    }

    mutating func addComma() {
        guard !numberBuffer.isEmpty else { return }

        numberBuffer.append(",")
        display = numberBuffer
    }

    mutating func addNumber(_ number: UInt8) {
        if numberBuffer.isEmpty { display = "" } // Reset display after new number is added to cleared buffer

        numberBuffer.append(String(number))
        display = numberBuffer
    }

    mutating func operation(_ op: Operator) {
        guard !numberBuffer.isEmpty && number1 == nil else { return }

        self.op = op
        if number1 == nil { number1 = Double(numberBuffer) }
        else { number2 = Double(numberBuffer) }
        numberBuffer = ""

        if op == .sqrt {
            display = String(sqrt(number1!))
            number1 = nil
            self.op = nil
        }
    }

    mutating func calculate() {
        number2 = Double(numberBuffer)
        numberBuffer = ""

        var result: Double = 0.0

        switch op {
        case .add:
            result = add_nums(number1!, number2!)
        case .sub:
            result = sub_nums(number1!, number2!)
        case .mul:
            result = mul_nums(number1!, number2!)
        case .div:
            result = div_nums(number1!, number2!)
        case .pow:
            result = pow(number1!, number2!)
        case .sqrt, .none:
            // do nothing
            print("Attempting to apply Square Root to nothing!")
        }

        display = String(result)
    }
}