feat: skip update if target file already exists with correct checksum

QaidVoid · QaidVoid · commit 4653f6f11487 · 2026-03-22T10:03:19.000+05:45
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -5,8 +5,10 @@ edition = "2024"
 
 [dependencies]
 clap = { version = "4.6.0", features = ["derive"] }
+hex = "0.4.3"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.149"
+sha1 = "0.10.6"
 thiserror = "2.0.18"
 ureq = "3.3.0"
 zsync-rs = { git = "https://github.com/QaidVoid/zsync-rs.git", version = "0.1.0" }
diff --git a/src/main.rs b/src/main.rs
@@ -65,7 +65,8 @@ fn run(cli: Cli) -> Result<(), Error> {
                 let new_path = updater.perform_update()?;
                 println!("Updated AppImage: {}", new_path.display());
             } else {
-                println!("No update available.");
+                let output_path = updater.output_path()?;
+                println!("Already up to date: {}", output_path.display());
             }
         }
         Commands::Check { path } => {
diff --git a/src/updater.rs b/src/updater.rs
@@ -73,15 +73,35 @@ impl Updater {
         Ok(self.output_dir.join(filename))
     }
 
+    fn verify_existing_file(&self, path: &Path, expected_sha1: &str) -> Result<bool> {
+        use sha1::{Digest, Sha1};
+
+        let mut file = fs::File::open(path)?;
+        let mut hasher = Sha1::new();
+        std::io::copy(&mut file, &mut hasher)?;
+        let hash = hasher.finalize();
+        let actual_sha1 = hex::encode(hash);
+
+        Ok(actual_sha1.eq_ignore_ascii_case(expected_sha1))
+    }
+
     pub fn check_for_update(&self) -> Result<bool> {
         let (control, _zsync_url) = self.fetch_control_file()?;
-
         let output_path = self.resolve_output_path(&control)?;
-        if output_path.exists() && !self.overwrite {
-            return Err(Error::AppImage(format!(
-                "Output file already exists: {}",
-                output_path.display()
-            )));
+
+        if output_path.exists() {
+            if let Some(ref expected_sha1) = control.sha1
+                && self.verify_existing_file(&output_path, expected_sha1)?
+            {
+                return Ok(false);
+            }
+
+            if !self.overwrite {
+                return Err(Error::AppImage(format!(
+                    "Output file already exists: {}",
+                    output_path.display()
+                )));
+            }
         }
 
         Ok(true)
@@ -91,11 +111,19 @@ impl Updater {
         let (control, zsync_url) = self.fetch_control_file()?;
         let output_path = self.resolve_output_path(&control)?;
 
-        if output_path.exists() && !self.overwrite {
-            return Err(Error::AppImage(format!(
-                "Output file already exists: {}",
-                output_path.display()
-            )));
+        if output_path.exists() {
+            if let Some(ref expected_sha1) = control.sha1
+                && self.verify_existing_file(&output_path, expected_sha1)?
+            {
+                return Ok(output_path);
+            }
+
+            if !self.overwrite {
+                return Err(Error::AppImage(format!(
+                    "Output file already exists: {}",
+                    output_path.display()
+                )));
+            }
         }
 
         let original_perms = fs::metadata(self.appimage.path())
@@ -130,6 +158,11 @@ impl Updater {
         Ok(output_path)
     }
 
+    pub fn output_path(&self) -> Result<PathBuf> {
+        let (control, _zsync_url) = self.fetch_control_file()?;
+        self.resolve_output_path(&control)
+    }
+
     pub fn progress(&self) -> Option<(u64, u64)> {
         None
     }

Original file line number	Diff line number	Diff line change
`@@ -65,7 +65,8 @@ fn run(cli: Cli) -> Result<(), Error> {`
`65`	`65`	`let new_path = updater.perform_update()?;`
`66`	`66`	`println!("Updated AppImage: {}", new_path.display());`
`67`	`67`	`} else {`
`68`		`- println!("No update available.");`
	`68`	`+ let output_path = updater.output_path()?;`
	`69`	`+ println!("Already up to date: {}", output_path.display());`
`69`	`70`	`}`
`70`	`71`	`}`
`71`	`72`	`Commands::Check { path } => {`