qbert.clj

(ns alandipert.minihttpd
  (:use [clojure.contrib.duck-streams :only (reader writer read-lines spit to-byte-array)]
        [clojure.contrib.str-utils :only (re-split str-join)])
  (:import (java.net ServerSocket Socket InetAddress URLDecoder)
           (java.io File)))

(def codes {200 "HTTP/1.0 200 OK" 
            404 "HTTP/1.0 404 Not Found"})

(def mimes {"css"  "Content-type: text/css" 
            "html" "Content-type: text/html" 
            "jpg"  "Content-type: image/jpeg" 
            "png"  "Content-type: image/png" 
            "gif"  "Content-type: image/gif" 
            "clj"  "Content-type: text/plain" 
            "txt"  "Content-type: text/plain"})

(def error {404 "The file was not found."
            500 "There was a server error."})

(def doc-root "/Users/alan/Sites")

(defn build-headers [& headers]
  "Build a header string and end it with two spaces"
  (str (str-join "\r\n" headers) "\r\n\r\n"))

(defn get-ext [abspath]
  "Try to get a file's extension for use mapping to a MIME type"
  (last (re-split #"\." abspath)))

(defn send-resource [sock file]
  "Open the socket's output stream and send headers and content"
  (with-open [os (.getOutputStream sock)]
    (let [path (.getAbsolutePath file)
          headers (build-headers (codes 200) (mimes (get-ext path) "txt"))]
      (.write os (to-byte-array headers) 0 (count headers))
      (.write os (to-byte-array file) 0 (.length file)))))

(defn send-error [sock code msg]
  "Open the socket's output stream and send header and error message"
  (with-open [wrt (writer (.getOutputStream sock))]
    (spit wrt (str (build-headers (codes code) (mimes "txt")) msg))))

(defn handle-request [sock]
  "Send the file if it exists, or a 404"
  (with-open [rdr (reader (.getInputStream sock))]
    (let [uri (second (re-split #"\s+" (first (line-seq rdr))))
          file (File. (str doc-root (URLDecoder/decode uri)))]
      (if (.exists file)
        (send-resource sock file)
        (send-error sock 404 "File not found")))))

(defmulti http-listen class)

(defmethod http-listen ServerSocket [socket]
  "Bind to a socket and keep listening"
  (let [client-socket (.accept socket)]
    (handle-request client-socket))
  (recur socket))

(defmethod http-listen Integer [port]
  "Takes a port number to listen on; defers to the listen loop function"
  (http-listen (ServerSocket. port)))

(http-listen 8081)