4: Create decompiler

src/main/java/com/bartek/esa/decompiler/decompiler/Decompiler.java

@@ -1,11 +1,50 @@
 package com.bartek.esa.decompiler.decompiler;
 
+import com.bartek.esa.error.EsaException;
+import com.bartek.esa.file.provider.FileProvider;
+import io.vavr.control.Try;
+
 import javax.inject.Inject;
+import java.io.File;
 
 public class Decompiler {
+    private final FileProvider fileProvider;
 
     @Inject
-    public Decompiler() {
+    public Decompiler(FileProvider fileProvider) {
 
+        this.fileProvider = fileProvider;
+    }
+
+    public File decompile(File inputApk) {
+        File target = provideTargetDirectory();
+        Process process = decompile(inputApk, target);
+        waitForProcess(process);
+        checkExitValue(process);
+        return target;
+    }
+
+    private void checkExitValue(Process process) {
+        if(process.exitValue() != 0) {
+            throw new EsaException("'apktool' process has finished with non-zero code. Interrupting...");
+        }
+    }
+
+    private void waitForProcess(Process process) {
+        Try.run(process::waitFor).getOrElseThrow(EsaException::new);
+    }
+
+    private Process decompile(File inputApk, File target) {
+        return Try.of(() -> Runtime.getRuntime().exec(provideCommandArray(inputApk, target)))
+                    .getOrElseThrow(EsaException::new);
+    }
+
+    private String[] provideCommandArray(File inputApk, File target) {
+        return new String[]{"apktool", "d", inputApk.getAbsolutePath(), "-o", target.getAbsolutePath()};
+    }
+
+    private File provideTargetDirectory() {
+        File tmp = fileProvider.createTemporaryDirectory();
+        return new File(tmp, "apktool_out");
     }
 }

src/main/java/com/bartek/esa/decompiler/di/DecompilerModule.java

@@ -1,6 +1,7 @@
 package com.bartek.esa.decompiler.di;
 
 import com.bartek.esa.decompiler.decompiler.Decompiler;
+import com.bartek.esa.file.provider.FileProvider;
 import dagger.Module;
 import dagger.Provides;
 
@@ -8,7 +9,7 @@ import dagger.Provides;
 public class DecompilerModule {
 
     @Provides
-    public Decompiler decompiler() {
+    public Decompiler decompiler(FileProvider fileProvider) {
-        return new Decompiler();
+        return new Decompiler(fileProvider);
     }
 }

src/main/java/com/bartek/esa/file/provider/FileProvider.java

@@ -18,6 +18,12 @@ public class FileProvider {
 
     }
 
+    public File createTemporaryDirectory() {
+        return Try.of(() -> Files.createTempDirectory(null))
+                .getOrElseThrow(EsaException::new)
+                .toFile();
+    }
+
     public String readFile(File file) {
         StringBuilder content = new StringBuilder();
         Try.run(() -> Files.lines(file.toPath())