import Foundation

enum DeviceInfoError: Error {
    case missingData
}

extension Data {
    
    mutating func decodeUInt16() throws -> UInt16 {
        guard count >= 2 else {
            throw DeviceInfoError.missingData
        }
        let low = removeFirst()
        let high = removeFirst()
        return UInt16(high: high, low: low)
    }
    
    mutating func decodeTwoByteInteger() throws -> Int {
        try decodeUInt16().integer
    }
    
    mutating func decodeFourByteInteger() throws -> Int {
        guard count >= 4 else {
            throw DeviceInfoError.missingData
        }
        let byte0 = removeFirst()
        let byte1 = removeFirst()
        let byte2 = removeFirst()
        let byte3 = removeFirst()
        return (Int(byte3) << 24) | (Int(byte2) << 16) | (Int(byte1) << 8) | Int(byte0)
    }
    
    mutating func decodeSensor() throws -> TemperatureSensor? {
        guard count >= 11 else {
            throw DeviceInfoError.missingData
        }
        let address = Array(self[startIndex..<startIndex+8])
        removeFirst(8)
        let temperatureByte = removeFirst()
        let time = try decodeUInt16()
        return .init(address: address, valueByte: temperatureByte, secondsAgo: time)
    }
}