find lastfm artist recommendations based on top artists listened by an user

gistfile1.clj

(ns lastfm
  (:require [clojure.string :as str]
            [clojure.java.io :as io]
            [clj-http.client :as client]
            [clojure.zip :as zip]
            [clojure.xml :as xml])
  (:use [clojure.data.zip.xml]))

(defn- parse-str [s]
  (zip/xml-zip (xml/parse (org.xml.sax.InputSource.
                           (java.io.StringReader. s)))))

(defn- build-get-data [attrs]
  (let [remove-spaces #(str/replace % #" " "+")]
    (str/join "&"
              (map (fn [[k v]]
                     (str (remove-spaces k) "=" (remove-spaces v)))
                   attrs))))

(def api-addr "http://ws.audioscrobbler.com/2.0/")
(def api-key "133e0a02d0ffc0a34e19c8252a49aba0")

(defn user->top-artists [user]
  (let [get-data (build-get-data {"method" "user.gettopartists",
                                  "user" user,
                                  "api_key" api-key})
        xml-data (parse-str (:body (client/get (str api-addr "?" get-data))))]
    (xml-> xml-data (tag= :topartists) (tag= :artist) (tag= :name) text)))

(defn artist->similar-artists [artist]
  (let [get-data (build-get-data {"method"  "artist.getsimilar",
                                  "artist" artist,
                                  "api_key" api-key})]
    (xml-> (parse-str (:body (client/get (str api-addr "?" get-data))))
           (tag= :similarartists) (tag= :artist) (tag= :name) text)))

(defn recommend [user]
  (let [top-artists (set (user->top-artists user))
        similars (apply concat (pmap artist->similar-artists top-artists))]
    (sort #(compare (last %1) (last %2))
          (reduce (fn [d artist]
                    (when (nil? (top-artists artist))
                      (conj d [artist (inc (get d artist 0))])))
                  {} similars))))

;;; USAGE:
;;; (recommend user-id)