use all fonts available on fonts.google.com in Kotlin JVM applications

AutoFont.kt

import org.apache.commons.io.FileUtils
import java.awt.Font
import java.awt.GraphicsEnvironment
import java.io.File
import java.io.FileNotFoundException
import java.net.URL

private const val FONTS_REPOSITORY = "https://github.com/google/fonts/raw/master"
private val LICENSES = arrayOf("apache", "ofl", "ufl")
private val SANITIZE_EXPR = Regex("\\W+")

enum class Emphasis {
    Regular,
    Bold,
    Italic,
    Light,
    Medium,
    Thin,
    Black
}

fun installFont(name: String, vararg emphasis: Emphasis) {
    print("Downloading Font..")
    val file = downloadFont(_fontName = name, emphasis = *emphasis)
    print("Installing Font..")
    GraphicsEnvironment
        .getLocalGraphicsEnvironment()
        .registerFont(Font.createFont(Font.TRUETYPE_FONT, file))
    print("Done!")
}

fun downloadFont(directory: File = createTempDir(), _fontName: String, vararg emphasis: Emphasis): File {
    assert(directory.isDirectory) { "$directory is not a directory" }

    val fontName = _fontName.replace(SANITIZE_EXPR, "")

    val fileName = constructFilename(fontName, *emphasis)

    val targetFile = File(directory, fileName)
    if (targetFile.isFile) {
        println("$targetFile already exists, skipping download")
        return targetFile
    }

    for (license in LICENSES) {
        try {
            val url = URL("$FONTS_REPOSITORY/$license/${fontName.toLowerCase()}/$fileName")
            FileUtils.copyURLToFile(url, targetFile)
            return targetFile
        } catch (_: FileNotFoundException) {
            // Ignore
        }
    }

    throw FileNotFoundException()
}

private fun constructFilename(sanitizedName: String, vararg emphasis: Emphasis): String {
    val emphasisStr = if (emphasis.isEmpty()) {
        "Regular"
    } else {
        emphasis
            .distinct()
            .map(Emphasis::name)
            .joinToString(separator = "")
    }

    return "$sanitizedName-$emphasisStr.ttf"
}

installFont("Roboto", Emphasis.BOLD)