A Gradle task to compute checksums

ChecksumTask.kt

import org.gradle.api.DefaultTask
import org.gradle.api.file.DirectoryProperty
import org.gradle.api.file.RegularFileProperty
import org.gradle.api.provider.Property
import org.gradle.api.tasks.*
import java.security.MessageDigest

@CacheableTask
abstract class Checksum : DefaultTask() {

    @get:Input
    abstract val algorithm: Property<String>

    @get:InputFile
    @get:PathSensitive(PathSensitivity.NONE)
    abstract val file: RegularFileProperty

    @get:Input
    @get:Optional
    abstract val expectedChecksum: Property<String>

    @get:Internal // represented by `checksumFile`
    abstract val checksumDirectory: DirectoryProperty

    @get:Internal // represented by `checksumFile`
    abstract val checksumFileName: Property<String>

    @get:OutputFile
    abstract val checksumFile: RegularFileProperty

    init {
        with(project) {
            checksumDirectory.convention(layout.dir(provider { temporaryDir }))
            checksumFileName.convention(file.asFile.zip(algorithm) { file, algo ->
                "${file.name}.${algo.replace("-", "").toLowerCase()}"
            })
            checksumFile.convention(checksumDirectory.zip(checksumFileName) { dir, file -> dir.file(file) })
        }
    }

    @TaskAction
    fun compute() = with(MessageDigest.getInstance(algorithm.get())) {
        val file = file.asFile.get()
        val checksum = file.inputStream().use {
            val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
            var bytes = it.read(buffer)
            while (bytes >= 0) {
                update(buffer, 0, bytes)
                bytes = it.read(buffer)
            }

            digest().joinToString(separator = "", transform = "%02x"::format)
        }

        checksumFile.asFile.get().writeText(checksum)

        expectedChecksum.orNull?.let { expected ->
            check(expected == checksum) {
                """
                        Verification of '$file' has failed, '$algorithm' checksum does not match:
                        Expected: $expected
                        Actual: $checksum
                    """.trimIndent()
            }
        }
    }

}