From 16e92fa5811f90bca5afae042b7caeb223dd8906 Mon Sep 17 00:00:00 2001
From: Toni Dahl <988779+K1ll3rF0x@users.noreply.github.com>
Date: Wed, 10 Mar 2021 23:42:09 +0200
Subject: [PATCH] Guess and add correct "Content-Type" headers for responses.
 (#750) [skip ci]

* A correct MIME type of a served file is guessed by file extension.
* For example, SVG images are now displayed correctly in a web browser.
---
 examples/file-server.clj | 116 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 115 insertions(+), 1 deletion(-)

diff --git a/examples/file-server.clj b/examples/file-server.clj
index 65284357..d8fa3f72 100755
--- a/examples/file-server.clj
+++ b/examples/file-server.clj
@@ -37,6 +37,119 @@
 
 (assert (fs/directory? dir) (str "The given dir `" dir "` is not a directory."))
 
+;; A simple mime type utility from https://github.com/ring-clojure/ring/blob/master/ring-core/src/ring/util/mime_type.clj
+(def ^{:doc "A map of file extensions to mime-types."}
+  default-mime-types
+  {"7z"       "application/x-7z-compressed"
+   "aac"      "audio/aac"
+   "ai"       "application/postscript"
+   "appcache" "text/cache-manifest"
+   "asc"      "text/plain"
+   "atom"     "application/atom+xml"
+   "avi"      "video/x-msvideo"
+   "bin"      "application/octet-stream"
+   "bmp"      "image/bmp"
+   "bz2"      "application/x-bzip"
+   "class"    "application/octet-stream"
+   "cer"      "application/pkix-cert"
+   "crl"      "application/pkix-crl"
+   "crt"      "application/x-x509-ca-cert"
+   "css"      "text/css"
+   "csv"      "text/csv"
+   "deb"      "application/x-deb"
+   "dart"     "application/dart"
+   "dll"      "application/octet-stream"
+   "dmg"      "application/octet-stream"
+   "dms"      "application/octet-stream"
+   "doc"      "application/msword"
+   "dvi"      "application/x-dvi"
+   "edn"      "application/edn"
+   "eot"      "application/vnd.ms-fontobject"
+   "eps"      "application/postscript"
+   "etx"      "text/x-setext"
+   "exe"      "application/octet-stream"
+   "flv"      "video/x-flv"
+   "flac"     "audio/flac"
+   "gif"      "image/gif"
+   "gz"       "application/gzip"
+   "htm"      "text/html"
+   "html"     "text/html"
+   "ico"      "image/x-icon"
+   "iso"      "application/x-iso9660-image"
+   "jar"      "application/java-archive"
+   "jpe"      "image/jpeg"
+   "jpeg"     "image/jpeg"
+   "jpg"      "image/jpeg"
+   "js"       "text/javascript"
+   "json"     "application/json"
+   "lha"      "application/octet-stream"
+   "lzh"      "application/octet-stream"
+   "mov"      "video/quicktime"
+   "m3u8"     "application/x-mpegurl"
+   "m4v"      "video/mp4"
+   "mjs"      "text/javascript"
+   "mp3"      "audio/mpeg"
+   "mp4"      "video/mp4"
+   "mpd"      "application/dash+xml"
+   "mpe"      "video/mpeg"
+   "mpeg"     "video/mpeg"
+   "mpg"      "video/mpeg"
+   "oga"      "audio/ogg"
+   "ogg"      "audio/ogg"
+   "ogv"      "video/ogg"
+   "pbm"      "image/x-portable-bitmap"
+   "pdf"      "application/pdf"
+   "pgm"      "image/x-portable-graymap"
+   "png"      "image/png"
+   "pnm"      "image/x-portable-anymap"
+   "ppm"      "image/x-portable-pixmap"
+   "ppt"      "application/vnd.ms-powerpoint"
+   "ps"       "application/postscript"
+   "qt"       "video/quicktime"
+   "rar"      "application/x-rar-compressed"
+   "ras"      "image/x-cmu-raster"
+   "rb"       "text/plain"
+   "rd"       "text/plain"
+   "rss"      "application/rss+xml"
+   "rtf"      "application/rtf"
+   "sgm"      "text/sgml"
+   "sgml"     "text/sgml"
+   "svg"      "image/svg+xml"
+   "swf"      "application/x-shockwave-flash"
+   "tar"      "application/x-tar"
+   "tif"      "image/tiff"
+   "tiff"     "image/tiff"
+   "ts"       "video/mp2t"
+   "ttf"      "font/ttf"
+   "txt"      "text/plain"
+   "webm"     "video/webm"
+   "wmv"      "video/x-ms-wmv"
+   "woff"     "font/woff"
+   "woff2"    "font/woff2"
+   "xbm"      "image/x-xbitmap"
+   "xls"      "application/vnd.ms-excel"
+   "xml"      "text/xml"
+   "xpm"      "image/x-xpixmap"
+   "xwd"      "image/x-xwindowdump"
+   "zip"      "application/zip"})
+
+;; https://github.com/ring-clojure/ring/blob/master/ring-core/src/ring/util/mime_type.clj
+(defn- filename-ext
+  "Returns the file extension of a filename or filepath."
+  [filename]
+  (if-let [ext (second (re-find #"\.([^./\\]+)$" filename))]
+    (str/lower-case ext)))
+
+;; https://github.com/ring-clojure/ring/blob/master/ring-core/src/ring/util/mime_type.clj
+(defn ext-mime-type
+  "Get the mimetype from the filename extension. Takes an optional map of
+  extensions to mimetypes that overrides values in the default-mime-types map."
+  ([filename]
+   (ext-mime-type filename {}))
+  ([filename mime-types]
+   (let [mime-types (merge default-mime-types mime-types)]
+     (mime-types (filename-ext filename)))))
+
 (defn index [f]
   (let [files (map #(str (.relativize dir %))
                    (fs/list-dir f))]
@@ -56,7 +169,8 @@
                str)}))
 
 (defn body [path]
-  {:body (fs/file path)})
+  {:headers {"Content-Type" (ext-mime-type (fs/file-name path))}
+   :body (fs/file path)})
 
 (server/run-server
  (fn [{:keys [:uri]}]