feat(cli): Add clap

Cargo.toml

@@ -6,4 +6,5 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-
+anyhow = "1.0.66"
+clap = { version = "4.4.6" }

src/cli.rs

@@ -0,0 +1,14 @@
+use crate::cliapp::make_app;
+use anyhow::Result;
+
+pub fn execute() -> Result<()> {
+    let app = make_app();
+    let matches = app.get_matches();
+
+    if let Some(_matches) = matches.subcommand_matches("run") {
+        println!("Hello world");
+        Ok(())
+    } else {
+        unreachable!();
+    }
+}

src/cliapp.rs

@@ -0,0 +1,30 @@
+//! This module implements the definition of the command line app.
+
+use clap::builder::ValueParser;
+use clap::{Arg, Command, ValueHint};
+
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+pub const ABOUT: &str = "The Sentry uptime checker service.";
+
+pub fn make_app() -> Command {
+    Command::new("relay")
+        .disable_help_subcommand(true)
+        .subcommand_required(true)
+        .propagate_version(true)
+        .version(VERSION)
+        .about(ABOUT)
+        .arg(
+            Arg::new("config")
+                .long("config")
+                .short('c')
+                .global(true)
+                .value_hint(ValueHint::DirPath)
+                .value_parser(ValueParser::path_buf())
+                .help("The path to the config file."),
+        )
+        .subcommand(
+            Command::new("run")
+                .about("Run the service")
+                .after_help("This runs the uptime-checker in the foreground until it's shut down."),
+        )
+}

src/main.rs

@@ -1,11 +1,16 @@
-fn main() {
-    println!("Hello, world!");
-}
+mod cli;
+mod cliapp;
+
+use std::process;
 
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn test_addition() {
-        assert_eq!(1 + 1, 2);
-    }
+pub fn main() {
+    let exit_code = match cli::execute() {
+        Ok(()) => 0,
+        Err(_err) => {
+            // TODO(epurkhiser): capture error? Here's what relay did
+            // relay_log::ensure_error(&err);
+            1
+        }
+    };
+    process::exit(exit_code);
 }