Fix extension detection by using the extension function

src/main.rs

@@ -1,6 +1,8 @@
 use std::fs::File;
 use std::io::{Read, Write};
 use std::process::exit;
+use std::path::PathBuf;
+use std::ffi::OsStr;
 
 use clap::{crate_authors, crate_description, crate_name, crate_version, Command, Arg};
 
@@ -30,34 +32,42 @@ fn main() {
              .short('i')
              .help("Input markdown files")
              .required(true)
-             .value_parser(clap::value_parser!(std::path::PathBuf))
+             .value_parser(clap::value_parser!(PathBuf))
             )
         .arg(Arg::new("OUTPUT")
              .long("output")
              .short('o')
              .help("Output tex or pdf file")
              .required(true)
-             .value_parser(clap::value_parser!(std::path::PathBuf))
+             .value_parser(clap::value_parser!(PathBuf))
             )
         .get_matches();
 
-    let input_path = matches.get_one::<std::path::PathBuf>("INPUT").unwrap();
+    let input_path = matches.get_one::<PathBuf>("INPUT").unwrap();
     let mut content = String::new();
     let mut input = unwrap!(File::open(input_path), "couldn't open input file");
     unwrap!(input.read_to_string(&mut content), "couldn't read file content");
 
-    let output_path = matches.get_one::<std::path::PathBuf>("OUTPUT").unwrap();
+    let output_path = matches.get_one::<PathBuf>("OUTPUT").unwrap();
+    let output_path_ext = output_path.extension().and_then(OsStr::to_str);
     let mut output = unwrap!(File::create(output_path), "couldn't open output file");
 
-    if output_path.ends_with(".tex") {
+    match output_path_ext {
+        Some("tex") => {
             let tex = markdown_to_latex(content);
             unwrap!(output.write(tex.as_bytes()), "couldn't write output file");
-    } else if output_path.ends_with(".pdf") {
+        },
+        Some("pdf") => {
             let data = unwrap!(markdown_to_pdf(content), "error while compiling latex, this is most likely a bug");
-        unwrap!(output.write(&data), "coudln't write output file");
+            unwrap!(output.write(&data), "couldn't write output file");
-    } else {
+        },
+        Some(ext) => {
+            eprintln!("unknown file format ({}) for output: {}", ext, output_path.display());
+            exit(1);
+        },
+        None => {
             eprintln!("unknown file format for output: {}", output_path.display());
             exit(1);
+        },
     }
-
 }