/*
 * This file was generated by the Gradle 'init' task.
 *
 * The settings file is used to specify which projects to include in your build.
 *
 * Detailed information about configuring a multi-project build in Gradle can be found
 * in the user manual at https://docs.gradle.org/7.3.3/userguide/multi_project_builds.html
 */
rootProject.name = "multiformats"
include("lib")

package multiformats
import java.io.File
import java.math.BigInteger
import java.util.Base64
import kotlin.ExperimentalUnsignedTypes
import kotlin.math.min
import kotlin.random.Random
import kotlin.test.*
import kotlin.test.Test
import kotlin.ubyteArrayOf
val decoder = Base64.getDecoder()
@kotlin.ExperimentalUnsignedTypes
class UnsignedVarIntTest {
    @Test
    fun exampleValuesFromSpec() {
        val testVectors: List<Pair<BigInteger, ByteArray>> =
                File("../../../spec/multiformats/unsigned-varint-examples.csv")
                        .readLines()
                        .map { it.split(',') }
                        .map { Pair(it.component1().trim(), it.component2().trim()) }
                        .map { (int, bytes) -> Pair(int.toBigInteger(), decoder.decode(bytes)) }
        testVectors.forEach { (int, bytes) ->
            assertContentEquals(bytes, UnsignedVarInt(int).bytes)
            assertEquals(int, UnsignedVarInt(bytes).int)
        }
    }
    @Test
    fun randomValues() {
        for (i in 1..1000) {
            val cieling = min(Long.MAX_VALUE, UnsignedVarInt.PRACTICAL_MAX.toLong())
            val random = Random.nextLong(cieling)
            assertEquals(
                    random,
                    UnsignedVarInt(UnsignedVarInt(random.toBigInteger()).bytes).int.toLong()
            )
        }
    }
    @Test
    fun throwsErrors() {
        // Negatives are not valid
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt.digits(-1.toBigInteger())
        }
        assertFailsWith(IllegalArgumentException::class) { UnsignedVarInt(-1.toBigInteger()) }
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt.encode(-1.toBigInteger())
        }
        // PRACTICAL_MAX is tipping point
        UnsignedVarInt(UnsignedVarInt.PRACTICAL_MAX)
        UnsignedVarInt(UnsignedVarInt(UnsignedVarInt.PRACTICAL_MAX).bytes)
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt(UnsignedVarInt.PRACTICAL_MAX + 1.toBigInteger())
        }
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt.digits(UnsignedVarInt.PRACTICAL_MAX + 1.toBigInteger())
        }
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt.encode(UnsignedVarInt.PRACTICAL_MAX + 1.toBigInteger())
        }
        // Empty nor several nulls are valid
        assertFailsWith(IllegalArgumentException::class) { UnsignedVarInt(byteArrayOf()) }
        for (i in 2..UnsignedVarInt.PRACTICAL_MAX_BYTES) {
            assertFailsWith(IllegalArgumentException::class) { UnsignedVarInt(ByteArray(i) { 0 }) }
        }
        // Last should be less than 128
        for (i in 2..UnsignedVarInt.PRACTICAL_MAX_BYTES) {
            assertFailsWith(IllegalArgumentException::class) {
                UnsignedVarInt(ByteArray(i) { 128.toUByte().toByte() })
            }
        }
        // PRACTICAL_MAX_BYTES is tipping point
        UnsignedVarInt(
                (UByteArray(UnsignedVarInt.PRACTICAL_MAX_BYTES - 1) { 255.toUByte() } +
                                ubyteArrayOf(127.toUByte()))
                        .toByteArray()
        )
        assertFailsWith(IllegalArgumentException::class) {
            UnsignedVarInt(
                    (UByteArray(UnsignedVarInt.PRACTICAL_MAX_BYTES) { 255.toUByte() } +
                                    ubyteArrayOf(127.toUByte()))
                            .toByteArray()
            )
        }
    }
}

package multiformats
import java.math.BigInteger
data class UnsignedVarInt(val int: BigInteger) {
    companion object {
        const val PRACTICAL_MAX_BYTES: Int = 9
        val PRACTICAL_MAX: BigInteger =
                128.toBigInteger().pow(PRACTICAL_MAX_BYTES) - 1.toBigInteger()
        @JvmStatic
        fun digits(int: BigInteger): Int {
            require(int >= BigInteger.ZERO)
            require(int <= PRACTICAL_MAX)
            var exp: Int = 0
            while (128.toBigInteger().pow(exp) - 1.toBigInteger() < int) exp += 1
            return exp
        }
        @JvmStatic
        fun encode(int: BigInteger): ByteArray {
            require(int >= BigInteger.ZERO)
            require(int <= PRACTICAL_MAX)
            val digits = digits(int)
            val bytes =
                    ByteArray(digits) { idx ->
                        (int.divide(128.toBigInteger().pow(idx))
                                        .mod(128.toBigInteger())
                                        .toInt()
                                        .toUByte() +
                                        if (idx == digits - 1) 0.toUByte() else 128.toUByte())
                                .toByte()
                    }
            return bytes
        }
        @JvmStatic
        fun decode(bytes: ByteArray): BigInteger {
            require(bytes.size > 0)
            require(bytes.size <= PRACTICAL_MAX_BYTES)
            require(bytes.dropLast(1).all { it.toUByte() >= 128.toUByte() })
            require(bytes.last().toUByte() < 128.toUByte())
            return bytes
                    .mapIndexed { idx, byte ->
                        128.toBigInteger().pow(idx) *
                                byte.toUByte().mod(128.toUByte()).toInt().toBigInteger()
                    }
                    .reduce { a, b -> a + b }
        }
    }
    constructor(bytes: ByteArray) : this(decode(bytes))
    init {
        require(int >= BigInteger.ZERO)
        require(int <= PRACTICAL_MAX)
    }
    val bytes: ByteArray by lazy { encode(int) }
}

plugins {
    id("org.jetbrains.kotlin.jvm") version "1.6.10"
    `java-library`
    jacoco
}
repositories { mavenCentral() }
dependencies {
    // Align versions of all Kotlin components
    implementation(platform("org.jetbrains.kotlin:kotlin-bom"))
    implementation("org.jetbrains.kotlin:kotlin-stdlib")
    testImplementation("org.jetbrains.kotlin:kotlin-test")
}
// Show STDOUT in test run
tasks.withType<AbstractTestTask> { testLogging { showStandardStreams = true } }
tasks.test { finalizedBy(tasks.jacocoTestReport) }
tasks.jacocoTestReport { dependsOn(tasks.test) }
jacoco { toolVersion = "0.8.7" }