Implement engine revert mechanism.

The mechanism rolls back all applied actions in case of errors, leaving
the project in the state in which it was found (with the exception of
some apparent permission bit shifting).

Cargo.toml

@@ -2,7 +2,7 @@
 authors = ["Mustafa <mustafa.moiz125@gmail.com>"]
 edition = "2018"
 name = "renom"
-version = "0.1.3"
+version = "0.1.4"
 description = "A simple program to rename Unreal Engine 4 projects."
 keywords = ["gamedev", "ue4", "unreal_engine", "rename"]
 categories = [

src/director.rs

@@ -79,28 +79,43 @@ impl Director {
 
         Log::header("Application");
         let mut engine = Engine::new();
-        ok_or_quit!(engine.execute(changeset, &backup_dir));
+        match engine.execute(changeset, &backup_dir) {
+            Ok(_) => {
+                Log::header("Cleanup");
+                match project_type {
+                    ProjectType::Blueprint => {
+                        Log::basic("Nothing to clean up for Blueprint project.");
+                    }
+                    ProjectType::Code => {
+                        Log::basic("Though not strictly necessary, it is a good idea to clean up outdated Saved, Intermediate, and Binaries folders.\nShall we go ahead and do so for you?");
+                        Log::prompt("[Y]es/[N]o");
+                        if Director::request_cleanup() {
+                            ok_or_quit!(Director::cleanup(
+                                &project_root.with_file_name(&final_name)
+                            ));
+                        } else {
+                            Log::basic("Cleanup skipped.");
+                        }
+                    }
+                }
 
-        Log::header("Cleanup");
-        match project_type {
-            ProjectType::Blueprint => {
-                Log::basic("Nothing to clean up for Blueprint project.");
+                Log::header("Success");
+                Log::basic("Project successfully renamed.");
             }
-            ProjectType::Code => {
-                Log::basic("Though not strictly necessary, it is a good idea to clean up outdated Saved, Intermediate, and Binaries folders.\nShall we go ahead and do so for you?");
+            Err(err) => {
+                Log::error(err);
+                Log::header("Recovery");
+                Log::basic("Looks like things did not work out as planned. Would you like to revert the changes made so far?");
                 Log::prompt("[Y]es/[N]o");
-                if Director::request_cleanup() {
-                    ok_or_quit!(Director::cleanup(&project_root.with_file_name(&final_name)));
+                if Director::request_recover() {
+                    ok_or_quit!(engine.revert());
                 } else {
-                    Log::basic("Cleanup skipped.");
+                    Log::basic("Recovery skipped.");
                 }
             }
         }
 
-        Log::header("Success");
-        Log::basic("Project successfully renamed.");
         Log::newline();
-
         Log::prompt("Press Enter to exit.");
         let _ = stdin().read(&mut [0u8]);
     }
@@ -200,6 +215,13 @@ impl Director {
         Ok(files)
     }
 
+    /// Request recover desired from the user.
+    fn request_recover() -> bool {
+        let mut buffer = String::new();
+        stdin().read_line(&mut buffer).unwrap();
+        matches!(buffer.trim(), "y" | "Y" | "yes" | "Yes")
+    }
+
     /// Request cleanup desired from the user.
     fn request_cleanup() -> bool {
         let mut buffer = String::new();

src/engine.rs

@@ -32,7 +32,7 @@ impl Engine {
         backup_dir: impl AsRef<Path>,
     ) -> Result<(), String> {
         for change in changeset {
-            Log::basic(format!("{}", change));
+            Log::basic(format!("Apply: {}", change));
             self.execute_single(change, backup_dir.as_ref())?;
         }
         Ok(())
@@ -54,6 +54,16 @@ impl Engine {
             Err(err) => Err(err.to_string()),
         }
     }
+
+    /// Revert entire history of actions.
+    /// Upon error, it will halt execution and return the error.
+    pub fn revert(&mut self) -> Result<(), String> {
+        while let Some((change, revert)) = self.history.pop() {
+            Log::basic(format!("Revert: {}", change));
+            revert().map_err(|err| err.to_string())?;
+        }
+        Ok(())
+    }
 }
 
 fn rename_file(params: &RenameFile) -> io::Result<Revert> {