Use a builder instead of a raw function

This pattern will, in the future, allow the registration of events
handlers and context objects.

examples/dummy.rs

@@ -1,6 +1,7 @@
 use env_logger::{Builder, Env};
+use opensmtpd::SmtpIn;
 
 fn main() {
     Builder::from_env(Env::default().default_filter_or("debug")).init();
-    opensmtpd::run();
+    SmtpIn::new().run();
 }

src/entry.rs

@@ -1,8 +1,6 @@
 use crate::errors::Error;
-use nom::{
-    alt, alt_complete, call, complete, cond, do_parse, error_position, map_res, named, tag,
-    take_until, take_while,
-};
+use nom::{alt, alt_complete, call, complete, cond, do_parse, error_position, map_res, named, tag,
+          take_until, take_while};
 
 #[derive(Debug, PartialEq)]
 pub enum Kind {

src/lib.rs

@@ -9,25 +9,27 @@ use std::io;
 use std::sync::mpsc;
 use std::thread;
 
-/// Read a line from the standard input.
-/// Since EOF should not append, it is considered as an error.
-fn read() -> Result<String, Error> {
+pub struct SmtpIn {
+    sessions: HashMap<u64, (mpsc::Sender<Entry>, thread::JoinHandle<()>)>,
+}
+
+impl SmtpIn {
+    /// Read a line from the standard input.
+    /// Since EOF should not append, it is considered as an error.
+    fn read() -> Result<String, Error> {
         let mut input = String::new();
         let nb = io::stdin().read_line(&mut input)?;
         match nb {
             0 => Err(Error::new("end of file")),
             _ => Ok(input),
         }
-}
+    }
 
-/// Dispatch the entry into its session's thread. If such thread does not
-/// already exists, creates it.
-fn dispatch(
-    sessions: &mut HashMap<u64, (mpsc::Sender<Entry>, thread::JoinHandle<()>)>,
-    input: &str,
-) -> Result<(), Error> {
+    /// Dispatch the entry into its session's thread. If such thread does not
+    /// already exists, creates it.
+    fn dispatch(&mut self, input: &str) -> Result<(), Error> {
         let entry = Entry::from_str(input)?;
-    let channel = match sessions.get(&entry.session_id) {
+        let channel = match self.sessions.get(&entry.session_id) {
             Some((r, _)) => r,
             None => {
                 let (tx, rx) = mpsc::channel();
@@ -41,46 +43,50 @@ fn dispatch(
                         debug!("thread {}: {:?}", thread::current().name().unwrap(), e);
                     }
                 })?;
-            sessions.insert(entry.session_id, (tx, handle));
-            let (r, _) = sessions.get(&entry.session_id).unwrap();
+                self.sessions.insert(entry.session_id, (tx, handle));
+                let (r, _) = self.sessions.get(&entry.session_id).unwrap();
                 r
             }
         };
         channel.send(entry)?;
         Ok(())
-}
+    }
 
-/// Allow each child thread to exit gracefully. First, the session table is
-/// drained so all the references to the senders are dropped, which will
-/// cause the receivers threads to exit. Then, we uses the join handlers in
-/// order to wait for the actual exit.
-fn graceful_exit_children(
-    sessions: &mut HashMap<u64, (mpsc::Sender<Entry>, thread::JoinHandle<()>)>,
-) {
+    /// Allow each child thread to exit gracefully. First, the session table is
+    /// drained so all the references to the senders are dropped, which will
+    /// cause the receivers threads to exit. Then, we uses the join handlers in
+    /// order to wait for the actual exit.
+    fn graceful_exit_children(&mut self) {
         let mut handles = Vec::new();
-    for (_, (_, h)) in sessions.drain() {
+        for (_, (_, h)) in self.sessions.drain() {
             handles.push(h);
         }
         for h in handles {
             let _ = h.join();
         }
-}
+    }
 
-/// Run the infinite loop that will read and process input from stdin.
-pub fn run() {
-    let mut sessions = HashMap::new();
+    pub fn new() -> Self {
+        SmtpIn {
+            sessions: HashMap::new(),
+        }
+    }
+
+    /// Run the infinite loop that will read and process input from stdin.
+    pub fn run(&mut self) {
         loop {
-        let line = match read() {
+            let line = match SmtpIn::read() {
                 Ok(l) => l,
                 Err(e) => {
-                graceful_exit_children(&mut sessions);
+                    self.graceful_exit_children();
                     error!("{}", e);
                     std::process::exit(1);
                 }
             };
-        match dispatch(&mut sessions, &line) {
+            match self.dispatch(&line) {
                 Ok(_) => {}
                 Err(e) => warn!("{}", e),
             }
         }
+    }
 }