Fix SplitFileReader logic for parts

nod/src/io/split.rs

@@ -28,21 +28,19 @@ fn split_path_1(input: &Path, index: u32) -> PathBuf {
     let input_str = input.to_str().unwrap_or("[INVALID]");
     let mut out = input_str.to_string();
     out.push('.');
-    out.push(char::from_digit(index, 10).unwrap());
+    out.push_str(&index.to_string());
     PathBuf::from(out)
 }
 
 // .part1.iso, .part2.iso, etc.
 fn split_path_2(input: &Path, index: u32) -> PathBuf {
     let extension = input.extension().and_then(|s| s.to_str()).unwrap_or("iso");
-    let input_without_ext = input.with_extension("");
-    let input_str = input_without_ext.to_str().unwrap_or("[INVALID]");
-    let mut out = input_str.to_string();
-    out.push_str(".part");
-    out.push(char::from_digit(index, 10).unwrap());
-    out.push('.');
-    out.push_str(extension);
-    PathBuf::from(out)
+    let stem = input.file_stem().and_then(|s| s.to_str()).unwrap_or("[INVALID]");
+    let base_stem = stem
+        .rsplit_once(".part")
+        .filter(|(_, suffix)| !suffix.is_empty() && suffix.chars().all(|c| c.is_ascii_digit()))
+        .map_or(stem, |(base, _)| base);
+    input.with_file_name(format!("{base_stem}.part{index}.{extension}"))
 }
 
 // .wbf1, .wbf2, etc.
@@ -51,7 +49,7 @@ fn split_path_3(input: &Path, index: u32) -> PathBuf {
     let mut chars = input_str.chars();
     chars.next_back();
     let mut out = chars.as_str().to_string();
-    out.push(char::from_digit(index, 10).unwrap());
+    out.push_str(&index.to_string());
     PathBuf::from(out)
 }
 
@@ -72,17 +70,23 @@ impl SplitFileReader {
         }
         for path_fn in [split_path_1, split_path_2, split_path_3] {
             let mut index = 1;
+            let mut found_split = false;
             loop {
                 let path = path_fn(path, index);
+                if path == files[0].inner {
+                    index += 1;
+                    continue;
+                }
                 if let Ok(metadata) = path.metadata() {
                     files.push(Split { inner: path, begin, size: metadata.len() });
                     begin += metadata.len();
                     index += 1;
+                    found_split = true;
                 } else {
                     break;
                 }
             }
-            if index > 1 {
+            if found_split {
                 break;
             }
         }
@@ -140,3 +144,70 @@ impl DiscStream for SplitFileReader {
 
     fn stream_len(&mut self) -> io::Result<u64> { Ok(self.len()) }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::{
+        fs,
+        time::{SystemTime, UNIX_EPOCH},
+    };
+
+    use super::*;
+
+    struct TestDir(PathBuf);
+
+    impl TestDir {
+        fn new() -> Self {
+            let mut path = std::env::temp_dir();
+            let nanos = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_nanos();
+            path.push(format!("nod-split-test-{}-{nanos}", std::process::id()));
+            fs::create_dir(&path).unwrap();
+            Self(path)
+        }
+
+        fn path(&self) -> &Path { &self.0 }
+    }
+
+    impl Drop for TestDir {
+        fn drop(&mut self) {
+            let _ = fs::remove_dir_all(&self.0);
+        }
+    }
+
+    #[test]
+    fn part_zero_input_builds_next_part_paths() {
+        let input = Path::new("/tmp/game.part0.iso");
+
+        assert_eq!(split_path_2(input, 1), PathBuf::from("/tmp/game.part1.iso"));
+        assert_eq!(split_path_2(input, 10), PathBuf::from("/tmp/game.part10.iso"));
+    }
+
+    #[test]
+    fn reads_part_zero_sequence_across_multiple_parts() {
+        let dir = TestDir::new();
+        for index in 0..=10 {
+            let path = dir.path().join(format!("game.part{index}.iso"));
+            fs::write(path, [index as u8]).unwrap();
+        }
+
+        let input = dir.path().join("game.part0.iso");
+        let mut reader = SplitFileReader::new(&input).unwrap();
+        let mut buf = [0; 11];
+        reader.read_exact_at(&mut buf, 0).unwrap();
+
+        assert_eq!(reader.len(), 11);
+        assert_eq!(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    }
+
+    #[test]
+    fn numbered_input_is_not_added_twice() {
+        let dir = TestDir::new();
+        let input = dir.path().join("game.part1.iso");
+        fs::write(&input, [1]).unwrap();
+
+        let reader = SplitFileReader::new(&input).unwrap();
+
+        assert_eq!(reader.len(), 1);
+        assert_eq!(reader.files.len(), 1);
+    }
+}