Add reload-observer

src/main/clojure/lazytest/loader.clj

@@ -1,9 +1,11 @@
 (ns lazytest.loader
   "Loading namespaces and managing dependencies."
-  (:use [lazytest.dependency :only (graph depend)]
+  (:use [lazytest.dependency :only (graph depend dependents remove-key)]
 	[lazytest.nsdeps :only (deps-from-ns-decl)]
+	[lazytest.reload :only (reload)]
 	[clojure.contrib.find-namespaces :only (find-clojure-sources-in-dir
 						read-file-ns-decl)]
+	[clojure.set :only (union)]
 	[clojure.java.io :only (file)]))
 
 (defn find-sources
@@ -12,20 +14,47 @@
 	 (every? (fn [d] (instance? java.io.File d)) dirs)]}
   (mapcat find-clojure-sources-in-dir dirs))
 
-(defn namespace-and-deps-for-file [f]
-  (let [decl (read-file-ns-decl f)]
-    (when decl
-      [(second decl)
-       (deps-from-ns-decl decl)])))
-
 (defn newer-sources [dirs timestamp]
   (filter #(> (.lastModified %) timestamp) (find-sources dirs)))
 
-(defn newer-namespaces [dirs timestamp]
-  (remove nil? (map namespace-and-deps-for-file (newer-sources dirs timestamp))))
+(defn newer-namespace-decls [dirs timestamp]
+  (remove nil? (map read-file-ns-decl (newer-sources dirs timestamp))))
+
+(defn add-to-dep-graph [dep-graph namespace-decls]
+  (reduce (fn [g decl]
+	    (let [nn (second decl)
+		  deps (deps-from-ns-decl decl)]
+	      (if (seq deps)
+		(apply depend g nn deps)
+		g)))
+	  dep-graph namespace-decls))
+
+(defn remove-from-dep-graph [dep-graph new-decls]
+  (apply remove-key dep-graph (map second new-decls)))
+
+(defn update-dependency-graph [dep-graph new-decls]
+  (-> dep-graph
+      (remove-from-dep-graph new-decls)
+      (add-to-dep-graph new-decls)))
+
+(defn affected-namespaces [changed-namespaces old-dependency-graph]
+  (apply union (set changed-namespaces) (map #(dependents old-dependency-graph %)
+					     changed-namespaces)))
 
-(defn dep-graph [names-and-deps]
-  (reduce (fn [g [n deps]] (if (seq deps)
-			     (apply depend g n deps)
-			     g))
-	  (graph) names-and-deps))
+(defn reload-observer [dirs initial-timestamp]
+  "Returns a no-arg function which, when called, returns a set of
+  namespaces that need to be reloaded, based on file modification
+  timestamps and the graph of namespace dependencies."
+  {:pre [(integer? initial-timestamp)
+	 (every? (fn [f] (instance? java.io.File f)) dirs)]}
+  (let [timestamp (atom initial-timestamp)
+	dependency-graph (atom (graph))]
+    (fn []
+      (let [then @timestamp
+	    now (System/currentTimeMillis)
+	    new-decls (newer-namespace-decls dirs then)
+	    new-names (map second new-decls)
+	    affected-names (affected-namespaces new-names @dependency-graph)]
+	(reset! timestamp now)
+	(swap! dependency-graph update-dependency-graph new-decls)
+	affected-names))))