diff --git a/src/main/lombok/org/warp/filesponge/BaseMirrorFileSource.java b/src/main/lombok/org/warp/filesponge/BaseMirrorFileSource.java
new file mode 100644
index 0000000..232bb3f
--- /dev/null
+++ b/src/main/lombok/org/warp/filesponge/BaseMirrorFileSource.java
@@ -0,0 +1,31 @@
+/*
+ *     FileSponge
+ *     Copyright (C) 2020 Andrea Cavalli
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.warp.filesponge;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import org.warp.filesponge.api.FileSource;
+import org.warp.filesponge.api.MirrorURI;
+
+@AllArgsConstructor(access = AccessLevel.PRIVATE)
+public abstract class BaseMirrorFileSource implements FileSource {
+
+	private final MirrorURI mirrorURI;
+
+}
diff --git a/src/main/lombok/org/warp/filesponge/api/FileAccessor.java b/src/main/lombok/org/warp/filesponge/api/FileAccessor.java
index 1669878..f38f0ab 100644
--- a/src/main/lombok/org/warp/filesponge/api/FileAccessor.java
+++ b/src/main/lombok/org/warp/filesponge/api/FileAccessor.java
@@ -19,9 +19,13 @@
 package org.warp.filesponge.api;
 
 import java.util.Optional;
+import org.jetbrains.annotations.NotNull;
 
 public interface FileAccessor {
-	void delete(FileURI fileURI);
-	Optional<FileContent> getContent(FileURI fileURI, boolean offlineOnly);
-	FileStatus getStatus(FileURI fileURI);
+
+	void delete(@NotNull FileURI fileURI);
+
+	Optional<FileContent> getContent(@NotNull FileURI fileURI, boolean offlineOnly);
+
+	@NotNull FileStatus getStatus(@NotNull FileURI fileURI);
 }
diff --git a/src/main/lombok/org/warp/filesponge/api/FileActor.java b/src/main/lombok/org/warp/filesponge/api/FileActor.java
new file mode 100644
index 0000000..c92b1ee
--- /dev/null
+++ b/src/main/lombok/org/warp/filesponge/api/FileActor.java
@@ -0,0 +1,21 @@
+/*
+ *     FileSponge
+ *     Copyright (C) 2020 Andrea Cavalli
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.warp.filesponge.api;
+
+public interface FileActor {}
diff --git a/src/main/lombok/org/warp/filesponge/api/FileExtension.java b/src/main/lombok/org/warp/filesponge/api/FileExtension.java
new file mode 100644
index 0000000..ad6cebd
--- /dev/null
+++ b/src/main/lombok/org/warp/filesponge/api/FileExtension.java
@@ -0,0 +1,21 @@
+/*
+ *     FileSponge
+ *     Copyright (C) 2020 Andrea Cavalli
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.warp.filesponge.api;
+
+public interface FileExtension {}
diff --git a/src/main/lombok/org/warp/filesponge/api/FileSource.java b/src/main/lombok/org/warp/filesponge/api/FileSource.java
new file mode 100644
index 0000000..79142ac
--- /dev/null
+++ b/src/main/lombok/org/warp/filesponge/api/FileSource.java
@@ -0,0 +1,35 @@
+/*
+ *     FileSponge
+ *     Copyright (C) 2020 Andrea Cavalli
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.warp.filesponge.api;
+
+import java.nio.ByteBuffer;
+import org.jetbrains.annotations.NotNull;
+
+public interface FileSource {
+
+	void onAvailable();
+
+	void onUnavailable();
+
+	boolean onNewFile(@NotNull FileURI fileURI, @NotNull FileExtension fileExtension);
+
+	void onFile(@NotNull FileURI fileURI, @NotNull FileSourceAvailability fileAvailability, long totalSize);
+
+	void onFilePiece(@NotNull FileURI fileURI, long offset, long size, @NotNull ByteBuffer piece);
+}
diff --git a/src/main/lombok/org/warp/filesponge/App.java b/src/main/lombok/org/warp/filesponge/api/FileSourceAvailability.java
similarity index 83%
rename from src/main/lombok/org/warp/filesponge/App.java
rename to src/main/lombok/org/warp/filesponge/api/FileSourceAvailability.java
index b95796f..310eb73 100644
--- a/src/main/lombok/org/warp/filesponge/App.java
+++ b/src/main/lombok/org/warp/filesponge/api/FileSourceAvailability.java
@@ -16,14 +16,11 @@
  *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package org.warp.filesponge;
+package org.warp.filesponge.api;
 
-/**
- * FileSponge
- */
-public class App {
-
-	public static void main(String[] args) {
-		System.out.println("FileSponge");
-	}
+public enum FileSourceAvailability {
+	DOWNLOADABLE,
+	DOWNLOADING,
+	DOWNLOADED,
+	FAILED
 }
diff --git a/src/main/lombok/org/warp/filesponge/api/MirrorURI.java b/src/main/lombok/org/warp/filesponge/api/MirrorURI.java
new file mode 100644
index 0000000..e21db57
--- /dev/null
+++ b/src/main/lombok/org/warp/filesponge/api/MirrorURI.java
@@ -0,0 +1,21 @@
+/*
+ *     FileSponge
+ *     Copyright (C) 2020 Andrea Cavalli
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.warp.filesponge.api;
+
+public interface MirrorURI {}