Better command line parsing, version, usage

Also tests for same

src/main.rs

@@ -1,19 +1,132 @@
-// TODO: An actual proper UI.
+// TODO: An actual proper command line parsing
+use indoc::indoc;
+
+const VERSION: &str = env!("CARGO_PKG_VERSION");
+
+fn usage() {
+    println!(indoc! {"
+usage: fwd [--version] (<server> | browse <url>)
+
+To connect a client to a server that has an `fwd` installed in its path, run
+`fwd <server>` on the client, where <server> is the name of the server to
+connect to.
+
+On a server that already has a client connected to it you can use `fwd browse
+<url>` to open `<url>` in the default browser of the client.
+    "});
+}
+
+#[derive(Debug)]
+enum Args {
+    Help,
+    Version,
+    Server,
+    Client(String),
+    Browse(String),
+    Error,
+}
+
+fn parse_args(args: Vec<String>) -> Args {
+    // Look for help; allow it to come anywhere because sometimes you just
+    // want to jam it on the end of an existing command line.
+    for arg in &args {
+        if arg == "--help" || arg == "-?" || arg == "-h" {
+            return Args::Help;
+        }
+    }
+
+    // No help, parse for reals.
+    if args.len() >= 2 && args[1] == "--version" {
+        Args::Version
+    } else if args.len() == 2 && &args[1] == "--server" {
+        Args::Server
+    } else if args.len() == 3 && args[1] == "browse" {
+        Args::Browse(args[2].to_string())
+    } else {
+        if args.len() != 2 {
+            Args::Error
+        } else {
+            Args::Client(args[1].to_string())
+        }
+    }
+}
 
 #[tokio::main]
 async fn main() {
-    let args: Vec<String> = std::env::args().collect();
-
-    if args.len() == 2 && &args[1] == "--server" {
-        fwd::run_server().await;
-    } else if args.len() == 3 && args[1] == "browse" {
-        fwd::browse_url(&args[2]).await;
-    } else {
-        if args.len() < 2 {
-            eprintln!("Usage: fwd <server>");
+    match parse_args(std::env::args().collect()) {
+        Args::Help => {
+            usage();
+        }
+        Args::Version => {
+            println!("fwd {VERSION}");
+        }
+        Args::Server => {
+            fwd::run_server().await;
+        }
+        Args::Browse(url) => {
+            fwd::browse_url(&url).await;
+        }
+        Args::Client(server) => {
+            fwd::run_client(&server).await;
+        }
+        Args::Error => {
+            usage();
             std::process::exit(1);
         }
+    };
+}
 
-        fwd::run_client(&args[1]).await;
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use assert_matches::assert_matches;
+
+    // Goldarn it.
+    fn args(x: &[&str]) -> Vec<String> {
+        let mut vec: Vec<String> =
+            x.into_iter().map(|a| a.to_string()).collect();
+        vec.insert(0, "fwd".to_string());
+        vec
+    }
+
+    macro_rules! assert_arg_parse {
+        ( $x:expr, $p:pat ) => {
+            assert_matches!(parse_args(args($x)), $p)
+        };
+    }
+
+    #[test]
+    fn help() {
+        assert_arg_parse!(&["--help"], Args::Help);
+        assert_arg_parse!(&["browse", "--help"], Args::Help);
+        assert_arg_parse!(&["foo.com", "--help"], Args::Help);
+        assert_arg_parse!(&["--help", "foo.com"], Args::Help);
+        assert_arg_parse!(&["browse", "-?"], Args::Help);
+        assert_arg_parse!(&["foo.com", "-h"], Args::Help);
+    }
+
+    #[test]
+    fn errors() {
+        assert_arg_parse!(&[], Args::Error);
+        assert_arg_parse!(&["browse", "google.com", "what"], Args::Error);
+        assert_arg_parse!(&["a", "b"], Args::Error);
+        assert_arg_parse!(&["--server", "something"], Args::Error);
+    }
+
+    #[test]
+    fn client() {
+        assert_arg_parse!(&["foo.com"], Args::Client(_));
+        assert_arg_parse!(&["a"], Args::Client(_));
+        assert_arg_parse!(&["browse"], Args::Client(_));
+    }
+
+    #[test]
+    fn server() {
+        assert_arg_parse!(&["--server"], Args::Server);
+    }
+
+    #[test]
+    fn browse() {
+        assert_arg_parse!(&["browse", "google.com"], Args::Browse(_));
     }
 }