implemented main entry point

hostnames_allocator/sample.in

@@ -0,0 +1,11 @@
+A gateway
+A gateway
+A gateway
+A proxy
+A proxy
+D gateway2
+D gateway5
+A proxy
+A gateway
+A gateway
+A gateway

hostnames_allocator/src/main.rs

@@ -1,3 +1,24 @@
+use std::io::{self, BufRead};
+
+use lazy_static::lazy_static;
+use regex::Regex;
+
+use hostnames_allocator::hostnames_allocator::HostnamesAllocator;
+
+lazy_static! {
+    static ref COMMAND_REGEX: Regex = Regex::new(r"^([AD])\s+(\w+)$").unwrap();
+}
+
 fn main() {
-    println!("Hello, world!");
+    let mut hostnames_allocator = HostnamesAllocator::new();
+    let stdin = io::stdin();
+    for line_result in stdin.lock().lines() {
+        let line = line_result.unwrap();
+        let (_, [command, argument]) = COMMAND_REGEX.captures(&line).unwrap().extract();
+        match command {
+            "A" => println!("{}", hostnames_allocator.allocate(argument)),
+            "D" => hostnames_allocator.free(argument),
+            _ => panic!(),
+        }
+    }
 }