HexConversion.kt

import org.junit.Test
import org.junit.runner.RunWith
import org.junit.runners.Parameterized
import kotlin.test.assertEquals
import kotlin.test.assertFailsWith


// Returning Result types would be preferable to throwing exceptions however this is currently not
// supported https://github.com/Kotlin/KEEP/blob/master/proposals/stdlib/result.md#limitations

fun bin(ch: Char): Int = when (ch) {
    in '0'..'9' -> ch - '0'
    in 'A'..'F' -> ch - 'A' + 10
    in 'a'..'f' -> ch - 'a' + 10
    else -> throw(IllegalArgumentException("'$ch' is not a valid hex character"))
}

fun hex(bytes: ByteArray): String {
    return bytes.joinToString("") { "%02x".format(it.toInt() and 0XFF) }
}

fun xeh(hexStr: String): ByteArray {
    // Remove whitespace and optional 0x prefix
    val digits = hexStr.replace("\\s".toRegex(), "").replace("^0x".toRegex(), "")

    if (digits.length % 2 != 0) {
        throw IllegalArgumentException("Hex values must have an even number of nibbles")
    }

    return digits.chunked(2).map { ((bin(it[0]) shl 4) + bin(it[1])).toByte() }.toByteArray()
}

@RunWith(value = Parameterized::class)
class XehConversionTest(private val hexStr: String) {
    @Test
    fun `test xeh conversion`() {
        assertEquals(
            byteArrayOf(
                0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b,
                0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
                0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
            ).toList(),
            xeh(hexStr).toList()
        )
    }

    companion object {
        @JvmStatic
        @Parameterized.Parameters(name = "{index}: xeh({0})")
        fun data(): List<String> {
            return arrayListOf(
                "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
                "0x000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
                "0001 0203 0405 0607 0809 0a0b 0c0d 0e0f 1011 1213 1415 1617 1819 1a1b 1c1d 1e1f"
            ).toList()
        }
    }
}


@RunWith(value = Parameterized::class)
class XehInvalidConversionTest(private val hexStr: String) {
    @Test
    fun `test xeh conversion throws`() {
        assertFailsWith(IllegalArgumentException::class) {
            xeh(hexStr)
        }
    }

    companion object {
        @JvmStatic
        @Parameterized.Parameters()
        fun data(): List<String> {
            return arrayListOf(
                "Not a hex string",
                "0x00120" // Odd number of digits
            ).toList()
        }
    }
}

class HexConversionTest {

    @Test
    fun `hex conversion`() {
        val bytes = byteArrayOf(
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b,
            0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
            0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
        )
        assertEquals(
            "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
            hex(bytes)
        )
    }

    @Test
    fun `test hex-xeh roundtrip`() {
        val bytes = byteArrayOf(
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b,
            0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
            0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
        )
        assertEquals(xeh(hex(bytes)).toList(), bytes.toList())
    }
}