add system-check to filestore boot process

src/clj/app/file_utils.clj

@@ -1,10 +1,12 @@
 (ns app.file-utils
   (:require
-   [clojure.string :as str]
-   [clojure.java.io :as io])
-  (:import [java.io File]
-           [java.nio.file Path Paths]
-           [java.nio.file Files]))
+   [clojure.java.io :as io]
+   [clojure.java.shell :refer [sh]]
+   [clojure.string :as str])
+  (:import
+   [java.io File]
+   [java.nio.file Path Paths]
+   [java.nio.file Files]))
 
 (defn-  file
   ^File [& args]
@@ -138,6 +140,24 @@
 (defn delete-if-exists [f]
   (Files/deleteIfExists (to-path f)))
 
+(defn exists?
+  "Checks for the existence of file/directory.  File can be a path or a File object."
+  [file] (.exists (io/file file)))
+
+(defn writeable?
+  "Checks if the file is writeable.  File can be a path or a File object."
+  [file]
+  (.canWrite (io/file file)))
+
+(defn program-exists?
+  "Checks if the program exists in the PATH."
+  [program]
+  (let [cmd "which"]
+    (try
+      (= 0 (:exit (sh cmd program)))
+      (catch Exception e ;in the unlikely event where which is unavailable
+        (throw (ex-info (format "Unable to determine whether '%s' exists. Notifications may not work." program) {}))))))
+
 (comment
   (= true (validate-base-path "/" "/foo/bar"))
   (= true (validate-base-path "/foo/bar" "/foo/bar"))

src/clj/app/filestore.clj

@@ -1,12 +1,26 @@
 (ns app.filestore
   (:require
+   [app.file-utils :as fs]
    [app.filestore.image :as im]
    [blocks.core :as block]
    [blocks.store.file :as blocks.store.file]
    [com.stuartsierra.component :as component]
    [multiformats.hash :as mhash]))
 
+(defn system-check! [store-path]
+  (when-not (fs/exists? store-path)
+    (throw (ex-info "Filestore path does not exist" {:store-path store-path})))
+  (when-not (fs/writeable? store-path)
+    (throw (ex-info "Filestore path is not writeable" {:store-path store-path})))
+  (when-not (fs/program-exists? "convert")
+    (throw (ex-info "ImageMagick convert program not found in PATH" {})))
+  (when-not (fs/program-exists? "mogrify")
+    (throw (ex-info "ImageMagick mogrify program not found in PATH" {})))
+  (when-not (fs/program-exists? "identify")
+    (throw (ex-info "ImageMagick identify program not found in PATH" {}))))
+
 (defn start! [{:keys [store-path]}]
+  (system-check! store-path)
   (-> store-path
       (blocks.store.file/file-block-store)
       (component/start)))