fix: draw multi-sequence fasta support not available currently

Author: Ebedthan

src/cgr.rs

@@ -91,11 +91,16 @@ impl DnaToChaos for fasta::Record {
 pub fn draw<R: io::Read>(source: R, destination: Option<PathBuf>) -> anyhow::Result<()> {
     let mut reader = fasta::Reader::new(BufReader::new(source));
 
-    for result in reader.records() {
+    for (count, result) in reader.records().enumerate() {
         let record = result?;
-        let chaos = record.record_to_chaos();
-        chaos.draw(destination.clone())?;
+        if count == 0 {
+            let chaos = record.record_to_chaos();
+            chaos.draw(destination.clone())?;
+        } else {
+            anyhow::bail!("Cannot draw from multi-sequence fasta");
+        }
     }
+
     Ok(())
 }
 

src/cli.rs

@@ -78,7 +78,7 @@ pub struct DrawArgs {
     /// Input sequence file in FASTA format
     pub file: PathBuf,
 
-    /// Output file
+    /// Output file name (.png), defaults to sequence ID
     #[arg(short, value_parser = validate_image_output)]
     pub output: Option<PathBuf>,
 }
@@ -131,7 +131,7 @@ fn validate_image_output(s: &str) -> Result<PathBuf, String> {
             ));
         }
     } else {
-        return Err("Output file must have an extension".to_string());
+        return Err("Output file must have png extension (.png)".to_string());
     }
 
     Ok(mp)