Moved argument parsing into module

* Port was redefined as i16 as that is the valid range for ports
* argument parsing is cleaned up and moved into args module
* correctly prefer arguments over config if present

src/args.rs

@@ -0,0 +1,56 @@
+use std::str::FromStr;
+
+use clap::ArgMatches;
+
+use config::model::Config;
+
+fn get_config_for_string(arg_value: Option<&str>, config_value: Option<String>, default_value: &str) -> String {
+    String::from(match arg_value {
+        Some(v) => v,
+        None => match c.server.host {
+            Some(host) => host,
+            None => default_host,
+        }
+    })
+}
+
+fn get_config_for_number<T: FromStr>(arg_value: Option<&str>, config_value: Option<T>, default_value: T) -> T {
+    match arg_value {
+        Some(v) => v.parse::<T>().unwrap_or(default_value),
+        None => match config_value {
+            Some(v) => v,
+            None => default_value
+        }
+    }
+}
+
+fn get_number<T: FromStr>(arg_value: Option<&str>, default_value: T) -> T {
+    match arg_value {
+        Some(value) => port.parse::<T>().unwrap_or(default_port),
+        None => default_port
+    }
+}
+
+pub fn get_host(args: &ArgMatches, config: &Option<Config>, default_host: &str) -> String {
+    let arg_value = args.value_of("host");
+    match config {
+        Some(c) => get_config_for_string(arg_value, c.server.host, default_host),
+        None => String::from(arg_value.unwrap_or(default_host))
+    }.clone()
+}
+
+pub fn get_port(args: &ArgMatches, config: &Option<Config>, default_port: i16) -> i16 {
+    let arg_value = args.value_of("port");
+    match config {
+        Some(c) => get_config_for_number(arg_value, c.server.port, default_port),
+        None => get_number(arg_value, default_port)
+    }
+}
+
+pub fn get_workers(args: &ArgMatches, config: &Option<Config>, default_workers: usize) -> usize {
+    let arg_value = args.value_of("workers");
+    match config {
+        Some(c) => get_config_for_number(arg_value, c.server.workers, default_workers),
+        None => get_number(args_value, default_workers)
+    }
+}

src/config/model.rs

@@ -1,7 +1,7 @@
 #[derive(Debug, PartialEq, Serialize, Deserialize)]
 pub struct ServerConfig {
     pub host: Option<String>,
-    pub port: Option<i32>,
+    pub port: Option<i16>,
     pub workers: Option<usize>,
 }
 

src/main.rs

@@ -15,12 +15,14 @@ extern crate serde_yaml;
 
 use clap::{App, Arg};
 
-mod server;
+mod args;
 mod config;
+mod server;
+
 
 const VERSION: &'static str = env!("CARGO_PKG_VERSION");
 const DEFAULT_HOST: &'static str = "localhost";
-const DEFAULT_PORT: i32 = 8080;
+const DEFAULT_PORT: i16 = 8080;
 
 lazy_static! {
         static ref DEFAULT_PORT_STR: String = String::from(DEFAULT_PORT.to_string());
@@ -83,28 +85,9 @@ fn main() {
         }
     };
 
-    let host = String::from(match &config {
-        Some(c) => match &c.server.host {
-            Some(host) => host,
-            None => DEFAULT_HOST,
-        }
-        None => args.value_of("host").unwrap_or(DEFAULT_HOST)
-    }.clone());
-    let port = match &config {
-        Some(c) => c.server.port.unwrap_or(DEFAULT_PORT),
-        None => args
-            .value_of("port")
-            .unwrap()
-            .parse::<i32>()
-            .unwrap_or(DEFAULT_PORT)
-    };
-    let workers = match &config {
-        Some(c) => c.server.workers.unwrap_or(*DEFAULT_WORKERS),
-        None => match args.value_of("workers") {
-            Some(count) => count.parse::<usize>().unwrap_or(*DEFAULT_WORKERS),
-            None => num_cpus::get(),
-        }
-    };
+    let host = args::get_host(&args, &config, DEFAULT_HOST);
+    let port = args::get_port(&args, &config, DEFAULT_PORT);
+    let workers = args::get_workers(&args, &config, *DEFAULT_WORKERS);
 
     info!(
         "Starting server on {}:{} with workers={} and config {}",