From 86bfdf80e4b60dd3792c3e9a59b16cdf6153be4c Mon Sep 17 00:00:00 2001
From: Nicholas Kariniemi <nicholas.kariniemi@gmail.com>
Date: Sat, 4 Oct 2014 23:20:55 +0300
Subject: [PATCH] Simplify MongoDB code by just storing whole state

- Every time it receives a state, it blows away the existing one and
  puts in the new one.
- There's a non-zero probability of losing the entire state if the
  server fails after blowing away the previous state and before
  inserting the new.
---
 src/clj/grub/core.clj                   |  4 +-
 src/clj/grub/db.clj                     | 58 ++++++-------------------
 src/cljx/grub/state.cljx                |  6 +--
 src/test/grub/test/integration/core.clj |  4 +-
 4 files changed, 21 insertions(+), 51 deletions(-)

diff --git a/src/clj/grub/core.clj b/src/clj/grub/core.clj
index fedd41c..f6a9665 100644
--- a/src/clj/grub/core.clj
+++ b/src/clj/grub/core.clj
@@ -73,14 +73,14 @@
   (reset! index-page prod-index-page)
   (let [to-db (chan)]
     (db/connect-production-database to-db mongo-url)
-    (state/init-server to-db (db/get-current-grubs) (db/get-current-recipes))
+    (state/init-server to-db (db/get-current-state))
     (println "Starting production server on localhost:" port)
     (start-server port)))
 
 (defn start-development-server [{:keys [port]}]
   (let [to-db (chan)]
     (db/connect-development-database to-db)
-    (state/init-server to-db (db/get-current-grubs) (db/get-current-recipes))
+    (state/init-server to-db (db/get-current-state))
     (println "Starting development server on localhost:" port)
     (start-server port)))
 
diff --git a/src/clj/grub/db.clj b/src/clj/grub/db.clj
index 90cdac5..30765d5 100644
--- a/src/clj/grub/db.clj
+++ b/src/clj/grub/db.clj
@@ -1,5 +1,6 @@
 (ns grub.db
   (:require [grub.util :as util]
+            [grub.sync :as sync]
             [monger.core :as m]
             [monger.collection :as mc]
             [monger.operators :as mo]
@@ -7,54 +8,22 @@
 
 (def conn (atom nil))
 (def db (atom nil))
-(def grub-collection "grubs")
-(def recipe-collection "recipes")
+(def collection "grub-lists")
 (def production-db "grub")
 (def development-db "grub-dev")
 
-(defn clear-grubs [] 
-  (mc/drop @db grub-collection))
-
-(defn clear-recipes [] 
-  (mc/drop @db recipe-collection))
-
 (defn clear-all []
-  (clear-grubs)
-  (clear-recipes))
+  (mc/drop @db collection))
 
-(defn update-db! [{:keys [grubs recipes]}]
-  (let [deleted-grubs (:deleted grubs)
-        updated-grubs (->> (:updated grubs)
-                           (seq)
-                           (map (fn [[k v]] 
-                                  (-> v
-                                      (dissoc :id)
-                                      (assoc :_id k)))))
-        deleted-recipes (:deleted recipes)
-        updated-recipes (->> (:updated recipes)
-                             (seq)
-                             (map (fn [[k v]] 
-                                    (-> v
-                                        (dissoc :id)
-                                        (assoc :_id k)))))]
-    (doseq [g deleted-grubs] 
-      (mc/remove-by-id @db grub-collection g))
-    (doseq [g updated-grubs] 
-      (mc/update-by-id @db grub-collection (:_id g) g {:upsert true}))
-    (doseq [r deleted-recipes]
-      (mc/remove-by-id @db recipe-collection r))
-    (doseq [r updated-recipes]
-      (mc/update-by-id @db recipe-collection (:_id r) r {:upsert true}))))
+(defn update-db! [state]
+  (mc/drop @db collection)
+  (mc/insert @db collection state))
 
-(defn get-current-grubs []
-  (->> (mc/find-maps @db grub-collection)
-       (sort-by :_id)
-       (map #(clojure.set/rename-keys % {:_id :id}))))
-
-(defn get-current-recipes []
-  (->> (mc/find-maps @db recipe-collection)
-       (sort-by :_id)
-       (map #(clojure.set/rename-keys % {:_id :id}))))
+(defn get-current-state []
+  (let [state (first (mc/find-maps @db collection))]
+    (if state
+      (dissoc state :_id)
+      sync/empty-state)))
 
 (defn connect! [db-name mongo-url]
   (if mongo-url
@@ -65,8 +34,9 @@
 
 (defn connect-and-handle-events [to-db db-name & [mongo-url]]
   (a/go-loop []
-             (if-let [diff (<! to-db)]
-               (do (update-db! diff)
+             (if-let [state (<! to-db)]
+               (do (println "DB got new state")
+                   (update-db! state)
                    (recur))
                (println "Database disconnected")))
   (let [_conn (connect! db-name mongo-url)]
diff --git a/src/cljx/grub/state.cljx b/src/cljx/grub/state.cljx
index 671f875..f3a8f8b 100644
--- a/src/cljx/grub/state.cljx
+++ b/src/cljx/grub/state.cljx
@@ -65,7 +65,6 @@
 (def states (atom []))
 (def empty-state sync/empty-state)
 
-;; TODO: Remove watch, close up channels properly
 #+clj
 (defn sync-new-client! [>client <client]
   (let [client-id (java.util.UUID/randomUUID)
@@ -85,8 +84,9 @@
                       (a/close! state-change-events)))))
     (make-server-agent client-events >client states)))
 
-(defn init-server [to-db grubs recipes]
-  (reset! states (sync/initial-state grubs recipes))
+#+clj
+(defn init-server [to-db initial-state]
+  (reset! states (sync/new-state initial-state))
   (add-watch states :to-db (fn [_ _ old-states new-states] 
                              (a/put! to-db (sync/get-current-state new-states)))))
 
diff --git a/src/test/grub/test/integration/core.clj b/src/test/grub/test/integration/core.clj
index cc12d05..3916f34 100644
--- a/src/test/grub/test/integration/core.clj
+++ b/src/test/grub/test/integration/core.clj
@@ -35,7 +35,7 @@
     (doseq [grub grubs]
       (test/is (taxi/find-element driver {:value grub})
                "Previously added grubs should be loaded on refresh")))
-  (db/clear-grubs))
+  (db/clear-all))
 
 (defn test-added-grubs-sync [url driver1 driver2]
   (taxi/to driver1 url)
@@ -75,7 +75,7 @@
 (defn start-db-and-websocket-server! []
   (let [to-db (chan)]
     (db/connect-and-handle-events to-db "grub-integration-test")
-    (state/init-server to-db (db/get-current-grubs) (db/get-current-recipes))))
+    (state/init-server to-db (db/get-current-state))))
 
 (defn run []
   (println "Starting integration test")