TempTrack-iOS/TempTrack/Bluetooth/BluetoothRequest.swift

import Foundation

enum BluetoothRequest {
    /**
     * Request the number of bytes already recorded
     *
     * Request:
     * - No additional bytes expected
     *
     * Response:
     * - `BluetoothResponseType.success`
     * - the number of recorded bytes as a `Uint16` (2 bytes)
     * - the number of seconds until the next measurement as a `Uint16` (2 bytes)
     * - the number of seconds between measurements as a `Uint16` (2 bytes)
     * - the number of measurements as a `Uint16` (2 bytes)
     * - the maximum number of bytes to request as a `Uint16` (2 bytes)
     * - the number of seconds since power on as a `Uint32` (4 bytes)
     */
    case getInfo

    /**
     * Request recording data
     *
     * Request:
     * - Bytes 1-2: Memory offset (`UInt16`)
     * - Bytes 3-4: Number of bytes (`UInt16`)
     *
     * Response:
     * - `BluetoothResponseType.success`, plus the requested bytes
     * - `BluetoothResponseType.responseTooLarge` if too many bytes are requested
     */
    case getRecordingData(offset: Int, count: Int)
    
    /**
     * Request deletion of recordings
     *
     * Request:
     * - Bytes 1-2: Number of bytes to clear (uint16_t)
     *
     * Response:
     * - `BluetoothResponseType.success`
     * - `BluetoothResponseType.invalidNumberOfBytesToDelete`, if the number of bytes does not match.
     *   This may happen when a new temperature recording is performed in between calls
     */
    case clearRecordingBuffer(byteCount: Int)
    
    var serialized: Data {
        let firstByte = Data([byte])
        switch self {
        case .getInfo:
            return firstByte
        case .getRecordingData(let offset, let count):
            return firstByte + count.twoByteData + offset.twoByteData
        case .clearRecordingBuffer(let byteCount):
            return firstByte + byteCount.twoByteData
        }
    }
    
    var byte: UInt8 {
        switch self {
        case .getInfo: return 0
        case .getRecordingData: return 1
        case .clearRecordingBuffer: return 2
        }
    }
}

private extension Int {
    
    var twoByteData: Data {
        let value = UInt16(clamping: self)
        return Data([value.low, value.high])
    }
}

private extension UInt16 {
    
    var low: UInt8 {
        UInt8(self & 0xFF)
    }
    
    var high: UInt8 {
        UInt8((self >> 8) & 0xFF)
    }
}