package com.example

import org.junit.Test
import java.net.URI
import java.net.URL
import java.nio.file.FileSystem
import java.nio.file.FileSystemNotFoundException
import java.nio.file.FileSystems
import java.nio.file.Files
import java.nio.file.Paths

class FooBar {
    @Test
    fun `test walk`() {
        fun dump(fs: FileSystem, uri: URI) = Files.walk(fs.provider().getPath(uri)).forEach(::println)

        // Filesystem walking...
        run {
            val cwd = Paths.get("")
            val uri = cwd.toUri()
            val fs = cwd.fileSystem

            println(uri.path)
            dump(fs, uri)
        }

        // You might imagine the URI above could be used in the logic below but for some reason the path
        // component of the URI passed to FileSystems.getFileSystem(uri) must be "/" if the scheme is "file"
        // but not if it's "jar". So it seems you can't easily write a scheme agnostic solution :(

        // Jar walking...
        run {
            val pkg = URL("jar:file:/usr/lib/jvm/java-8-oracle/jre/lib/rt.jar!/java/lang")
            val uri = pkg.toURI()
            val fs = try {
                FileSystems.getFileSystem(uri)
            } catch (e: FileSystemNotFoundException) {
                FileSystems.newFileSystem(uri, mapOf<String, Any>())
            }

            println(uri.path)
            dump(fs, uri)
        }

        // Note that there's no easy way to get a URL for a package rather than a class.
        println(this.javaClass.getResource("/java/lang/String.class"))
        // The above is fine but the following all return null:
        println(this.javaClass.getResource("/java/lang/"))
        println(this.javaClass.getResource("/java/lang"))
        println(this.javaClass.getResource("java/lang/"))
        println(this.javaClass.getResource("java/lang"))
        println(this.javaClass.classLoader.getResource("/java/lang/"))
        println(this.javaClass.classLoader.getResource("/java/lang"))
        println(this.javaClass.classLoader.getResource("java/lang/"))
        println(this.javaClass.classLoader.getResource("java/lang"))
    }
}