Update status page to use statuspage.io, retinize assets

@StatusPage have kindly donated an account to Clojars. This commit adds
a link to their hosted status page, and their logo to the footer.

It also adds helper functions to generate img tags which support srcset
so that we can server retina images to capable devices.

src/clojars/web/common.clj

@@ -2,7 +2,10 @@
   (:require [hiccup.core :refer [html]]
             [hiccup.page :refer [include-css include-js]]
             [hiccup.element :refer [link-to unordered-list image]]
-            [clojars.web.safe-hiccup :refer [html5 raw form-to]]))
+            [clojars.web.safe-hiccup :refer [html5 raw form-to]]
+            [clojars.web.helpers :as helpers]
+            [clojure.string :refer [join]]
+            [clojure.java.io :as io]))
 
 (defn when-ie [& contents]
   (str
@@ -13,6 +16,7 @@
 (def footer
   [:footer.row
    (link-to "https://github.com/clojars/clojars-web/wiki/About" "about")
+   (link-to "http://status.clojars.org" "status")
    (link-to "/projects" "projects")
    (link-to "https://github.com/clojars/clojars-web/wiki/Contributing" "contribute")
    (link-to "https://groups.google.com/forum/?fromgroups#!topicsearchin/clojars-maintainers/group:clojars-maintainers$20AND$20subject:ann" "news")
@@ -42,12 +46,19 @@
           "https://dnsimple.link/resolving-clojars"
           [:span "resolving with" [:br]]
           [:span
-           (image "https://cdn.dnsimple.com/assets/resolving-with-us/logo-light.png" "DNSimple")])]]]]]
+           (image "https://cdn.dnsimple.com/assets/resolving-with-us/logo-light.png" "DNSimple")])]]
+      [:tr
+       [:td.sponsor]
+       [:td.sponsor
+        (link-to {:target "_blank"}
+                 "https://www.statuspage.io"
+                 (helpers/retinized-image "/images/statuspage-io-logo.png" "StatusPage.io"))]
+       [:td.sponsor]]]]]
    [:div.row.sponsors
     "remixed by"
     (link-to {:target "_blank"}
              "http://www.bendyworks.com/"
-             (image "/images/bendyworks_logo_white.png" "Bendyworks Inc."))]])
+             (image "/images/bendyworks-logo.svg" "Bendyworks Inc."))]])
 
 (defn google-analytics-js []
   [:script "(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){

src/clojars/web/helpers.clj

@@ -0,0 +1,40 @@
+(ns clojars.web.helpers
+  (:require [clojure.java.io :as io]
+            [clojure.string :as str]))
+
+(defn public-resource-exists?
+  "Takes a path and checks whether the resource exists under the public directory
+  at that path."
+  [path]
+  (some-> (str "public" path)
+          (io/resource)
+          (io/file)
+          (.exists)))
+
+(defn srcset-part
+  "Creates a srcset part, e.g.
+  \"images/[email protected] 2x\"
+  Returns nil if the file referenced does not exist"
+  [base extension scale]
+  (let [retina-path (str base "@" scale extension)]
+    (when (and retina-path (public-resource-exists? retina-path))
+      (str retina-path " " scale))))
+
+(defn retinized-image
+  "Creates an img tag with support for 2x and 3x retina images.
+  Will check if the retina images exist before adding them to srcset.
+  Throws if the src image does not exist."
+  [src alt]
+  (assert (= (first src) \/) (format "src %s must start with a /" src))
+  (assert (public-resource-exists? src)
+          (format "File %s does not exist" (str "public" src)))
+
+  (let [last-period (.lastIndexOf src ".")
+        base (.substring src 0 last-period)
+        extension (.substring src last-period (count src))]
+    [:img {:src    src
+           :alt    alt
+           ;; If 1x is not provided in srcset, then browsers will default to src as the 1x image
+           :srcset (->> (filter identity [(srcset-part base extension "2x")
+                                          (srcset-part base extension "3x")])
+                        (str/join ", "))}]))

test/clojars/test/unit/web/helpers.clj

@@ -0,0 +1,33 @@
+(ns clojars.test.unit.web.helpers
+  (require [clojure.test :refer :all]
+           [clojars.web.helpers :as helpers]))
+
+(deftest resource-exists?
+  (is (helpers/public-resource-exists? "/test-resource"))
+  (is (not (helpers/public-resource-exists? "/nonexistent-resource"))))
+
+(deftest srcset-part
+  (is (= "/[email protected] 2x"
+         (helpers/srcset-part "/img1" ".png" "2x")))
+  (is (= "/[email protected] 3x"
+         (helpers/srcset-part "/img1" ".png" "3x")))
+  (is (nil? (helpers/srcset-part "/img2" ".png" "2x"))))
+
+(deftest retinized-imaged
+  (is (= [:img
+          {:alt    "Image 1"
+           :src    "/img1.png"
+           :srcset "/[email protected] 2x, /[email protected] 3x"}]
+         (helpers/retinized-image "/img1.png" "Image 1")))
+  (is (= [:img
+          {:alt    "Image 2"
+           :src    "/img2.png"
+           :srcset "/[email protected] 3x"}]
+         (helpers/retinized-image "/img2.png" "Image 2")))
+  (is (= [:img
+          {:alt    "Image 3"
+           :src    "/img3.jpeg"
+           :srcset ""}]
+         (helpers/retinized-image "/img3.jpeg" "Image 3")))
+  (is (thrown? AssertionError (helpers/retinized-image "/img-not-exist.png" "Nope")))
+  (is (thrown? AssertionError (helpers/retinized-image "img1.png" "Image 1"))))