Initial implementations

.gitignore

@@ -39,4 +39,7 @@ bin/
 .vscode/
 
 ### Mac OS ###
-.DS_Store
+.DS_Store
+
+### Custom ###
+_tmp/

.idea/gradle.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="GradleMigrationSettings" migrationVersion="1" />
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>

.idea/misc.xml

@@ -4,7 +4,7 @@
   <component name="FrameworkDetectionExcludesConfiguration">
     <file type="web" url="file://$PROJECT_DIR$" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="corretto-19" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" project-jdk-name="corretto-19" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>

build.gradle.kts

@@ -18,5 +18,5 @@ tasks.test {
 }
 
 kotlin {
-    jvmToolchain(8)
+    jvmToolchain(11)
 }

src/main/kotlin/filesystem/FSCreator.kt

@@ -1,9 +1,13 @@
 package filesystem
 
+import java.nio.file.FileAlreadyExistsException
+import java.nio.file.FileSystemException
 import java.nio.file.Files
 import java.nio.file.Path
 
 class FSCreator {
+    // Create entry, leaving existing folders' contents, but overwriting existing files.
+    @Throws(FileSystemException::class)
     fun create(entryToCreate: FSEntry, destination: String) {
         val queue = ArrayDeque<Pair<FSEntry, Path>>()
         queue.add(entryToCreate to Path.of(destination))
@@ -17,8 +21,9 @@ class FSCreator {
                     is FSFolder -> Files.createDirectory(path)
                 }
             } catch (_: FileAlreadyExistsException) {} // Allow files/folders to already exist.
-            if (entry is FSFolder) {
-                queue.addAll(entry.entries.map { it to path })
+            when (entry) {
+                is FSFile -> Files.write(path, entry.content.toByteArray())
+                is FSFolder -> queue.addAll(entry.entries.map { it to path })
             }
         }
     }

src/test/kotlin/filesystem/FSCreatorTest.kt

@@ -0,0 +1,103 @@
+package filesystem
+
+import org.junit.jupiter.api.*
+import java.nio.file.FileSystemException
+import java.nio.file.Files
+import java.nio.file.Path
+import java.util.concurrent.TimeUnit
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class FSCreatorTest {
+    private val creator = FSCreator()
+
+    @BeforeEach
+    fun `before each`() {
+        assertDoesNotThrow("should create _tmp directory") {
+            Files.createDirectory(Path.of("_tmp"))
+        }
+    }
+
+    @AfterEach
+    fun `after each`() {
+        assertDoesNotThrow("should delete _tmp directory") {
+            deleteRecursive(Path.of("_tmp"))
+        }
+    }
+
+    @Test
+    fun `create entries`() {
+        val readme = FSFile("README", "Hello World!")
+        val gomod = FSFile("go.mod", "module example.com/hello-world\n\ngo1.21.5")
+        val maingo = FSFile("main.go", "package main\n\nimport \"example.com/hello-world/utils\"\n\n" +
+            "func main() {\n\tprintln(\"Hello World!\")\n}")
+        val helloworldgo = FSFile("hello-world.go", "package utils\n\nfunc PrintHelloWorld() {\n" +
+            "\tprintln(\"Hello World!\")\n}")
+        assertDoesNotThrow("should create entries") {
+            creator.create(FSFolder("folder", listOf(
+                readme,
+                gomod,
+                maingo,
+                FSFolder("utils", listOf(
+                    helloworldgo
+                ))
+            )), "_tmp")
+        }
+        // If objects don't exist, these functions will throw anyway, so don't explicitly check for existence.
+        // Similarly, don't explicitly check if an object is a directory.
+        assertEquals(readme.content, Files.readString(Path.of("_tmp/folder", readme.name)))
+        assertEquals(gomod.content, Files.readString(Path.of("_tmp/folder", gomod.name)))
+        assertEquals(maingo.content, Files.readString(Path.of("_tmp/folder", maingo.name)))
+        assertEquals(helloworldgo.content, Files.readString(Path.of("_tmp/folder/utils", helloworldgo.name)))
+    }
+
+    @Test
+    fun `create existing entries`() {
+        assertDoesNotThrow("creation one") {
+            creator.create(FSFolder("folder", listOf(
+                FSFolder("sub-folder", listOf(
+                    FSFile("hi", "hi")
+                )),
+                FSFolder("another-folder", listOf()),
+                FSFile("1.txt", "One!"),
+                FSFile("2.txt", "Two!")
+            )), "_tmp")
+        }
+        assertDoesNotThrow("creation two") {
+            creator.create(FSFolder("folder", listOf(
+                FSFolder("another-folder", listOf(
+                    FSFolder("secrets", listOf(
+                        FSFile("secret", "P4ssW0rd")
+                    ))
+                )),
+                FSFile("1.txt", "One is a good number"),
+                FSFile("3.txt", "Three!")
+            )), "_tmp")
+        }
+        assertEquals("hi", Files.readString(Path.of("_tmp/folder/sub-folder/hi")))
+        assertEquals("P4ssW0rd", Files.readString(Path.of("_tmp/folder/another-folder/secrets/secret")))
+        assertEquals("One is a good number", Files.readString(Path.of("_tmp/folder/1.txt")))
+        assertEquals("Two!", Files.readString(Path.of("_tmp/folder/2.txt")))
+        assertEquals("Three!", Files.readString(Path.of("_tmp/folder/3.txt")))
+    }
+
+    @Test
+    @Timeout(500, unit = TimeUnit.MILLISECONDS) // in case implementation starts trying to handle recursion
+    fun `create throws on recursive folder`() {
+        val files = mutableListOf<FSEntry>()
+        val folder = FSFolder("folder", files)
+        files.add(folder)
+        assertThrows<FileSystemException> {
+            creator.create(folder, "_tmp")
+        }
+    }
+}
+
+fun deleteRecursive(path: Path) {
+    if (Files.isDirectory(path)) {
+        for (child in Files.list(path)) {
+            deleteRecursive(child)
+        }
+    }
+    Files.delete(path)
+}