tsk-76: Improve getting path of Song or CoverArt (#81)

Closes #76

Reviewed-on: #81
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

src/util/mod.rs

@@ -0,0 +1,19 @@
+pub fn concatenate_path(
+    directory: &str,
+    filename: &str,
+    last_index: usize,
+) -> Result<String, std::io::Error> {
+    if let Some(character) = directory.chars().nth(last_index) {
+        let buffer: String = if character != '/' {
+            format!("{directory}/")
+        } else {
+            String::from(directory)
+        };
+
+        Ok(format!("{buffer}{filename}"))
+    } else {
+        Err(std::io::Error::other(
+            crate::constants::error::LAST_CHARACTER_IN_DIRECTORY,
+        ))
+    }
+}