add resource and FileSystemResource

libraries/io/src/main/kotlin/de/itkl/io/implementation/FileSystemResource.kt

@@ -0,0 +1,19 @@
+package de.itkl.io.implementation
+
+import de.itkl.io.interfaces.Resource
+import io.ktor.http.*
+import java.io.File
+import java.io.InputStream
+
+class FileSystemResource(private val file: File) : Resource() {
+    override val filename: String
+        get() = file.name
+    override val contentType: ContentType
+        get() = ContentType.fromFilePath(file.path).first()
+    override val length: Long
+        get() = file.length()
+
+    override fun doRead(): InputStream {
+        return file.inputStream()
+    }
+}

libraries/io/src/main/kotlin/de/itkl/io/interfaces/Resource.kt

@@ -1,11 +1,24 @@
 package de.itkl.io.interfaces
 
 import io.ktor.http.*
+import org.koin.core.component.KoinComponent
+import org.koin.core.component.get
+import org.koin.core.qualifier.named
 import java.io.InputStream
 import java.io.InputStreamReader
 
-interface Resource {
-    val filename: String
-    val contentType: ContentType
-    fun read(): InputStream
+abstract class Resource : KoinComponent {
+    abstract val filename: String
+    abstract val contentType: ContentType
+    abstract val length: Long?
+
+    protected abstract fun doRead(): InputStream
+    fun read(): InputStream {
+        return length?.let { length ->
+            get<ResourceReadDecorator>().decorate(
+                length = length,
+                read()
+            )
+        } ?: read()
+    }
 }

libraries/io/src/main/kotlin/de/itkl/io/interfaces/ResourceReadDecorator.kt

@@ -0,0 +1,15 @@
+package de.itkl.io.interfaces
+
+import java.io.InputStream
+
+interface ResourceReadDecorator {
+    fun decorate(
+        length: Long,
+        inputStream: InputStream): InputStream
+}
+
+class NoopResourceReadDecorator : ResourceReadDecorator {
+    override fun decorate(length: Long, inputStream: InputStream): InputStream {
+        return inputStream
+    }
+}

libraries/io/src/main/kotlin/de/itkl/io/ioModule.kt

@@ -1 +1,9 @@
 package de.itkl.io
+
+import de.itkl.io.interfaces.NoopResourceReadDecorator
+import de.itkl.io.interfaces.ResourceReadDecorator
+import org.koin.dsl.module
+
+val ioModule = module {
+    single<ResourceReadDecorator> { NoopResourceReadDecorator() }
+}