Persist items to the database

The database that was chosen here is SQLite, because it's dead simple to
setup and more than enough for this project.

Please note that I took some liberty with the assignment. I chose to use
a numeric field for the `id` column of an item. This leverages automatic
creation and incrementation of the id by SQLite itself.

.gitignore

@@ -11,3 +11,4 @@ pom.xml.asc
 /.lsp
 /.nrepl-port
 /.prepl-port
+*.db

README.md

@@ -20,6 +20,7 @@ default, the server listens on port 3000.
 * `reitit`: for handling routes
 * `jetty`: web server
 * `muuntaja`: JSON handling
+* `next.jdbc`: database interface (SQLite)
 
 ## Documentation links
 
@@ -29,3 +30,5 @@ The following links proved more than useful when working on this assignment:
 * <https://github.com/metosin/reitit/blob/master/doc/ring/content_negotiation.md>
 * <https://ostash.dev/posts/2021-08-22-data-validation-in-clojure/>
 * <https://clojurecivitas.github.io/malli/elements_of_malli.html>
+* <https://github.com/metosin/reitit/blob/master/doc/coercion/malli_coercion.md>
+* <https://cljdoc.org/d/com.github.seancorfield/next.jdbc/1.3.1086/doc/getting-started>

project.clj

@@ -8,7 +8,9 @@
                  [ring/ring-jetty-adapter "1.15.3"]
                  [metosin/reitit "0.10.0"]
                  [metosin/reitit-malli "0.10.0"]
-                 [metosin/muuntaja "0.6.11"]]
+                 [metosin/muuntaja "0.6.11"]
+                 [com.github.seancorfield/next.jdbc "1.3.1086"]
+                 [org.xerial/sqlite-jdbc "3.51.1.0"]]
   :main ^:skip-aot yohoho.core
   :target-path "target/%s"
   :profiles {:uberjar {:aot :all

src/yohoho/core.clj

@@ -4,7 +4,10 @@
             [reitit.ring.middleware.muuntaja :as muuntaja]
             [muuntaja.core :as m]
             [reitit.coercion.malli :as malli]
-            [reitit.ring.coercion :as coercion])
+            [reitit.ring.coercion :as coercion]
+            [next.jdbc :as jdbc]
+            [next.jdbc.sql :as sql]
+            [next.jdbc.result-set :as rs])
   (:gen-class))
 
 
@@ -23,6 +26,38 @@
    [:email Email]])
 
 
+;; Database stuff -------------------------------------------------
+(def db {:dbtype "sqlite" :dbname "yohoho.db"})
+
+(defn init-db!
+  "Create database structure if needed"
+  []
+  (jdbc/execute!
+   db
+   ["CREATE TABLE IF NOT EXISTS items (
+       id INTEGER PRIMARY KEY,
+       name TEXT NOT NULL,
+       email TEXT NOT NULL)"]))
+
+(defn db-store-item!
+  "Store a new item in database and returns it ID"
+  [name email]
+  (let [db-result (sql/insert! db :items {:name name, :email email})]
+    ;; SQLite returns the generated ID of the new item like this:
+    ;; {:last_insert_rowid() 42}
+    (get db-result (keyword "last_insert_rowid()"))))
+
+(defn db-get-item
+  "Retrieve an item given its ID"
+  [id]
+  (sql/get-by-id db :items id
+                 {:builder-fn rs/as-unqualified-lower-maps}))
+
+(defn db-get-all-items
+  "Retrieve every item from the database"
+  []
+  (sql/query db ["select * from items"] {:builder-fn rs/as-unqualified-lower-maps}))
+
 ;; Handlers -------------------------------------------------------
 (defn ahoy-handler
   [_]
@@ -32,19 +67,18 @@
 (defn get-items-handler
   [_]
   {:status 200
-   :body {:id 1
-          :name "Jack Sparrow"
-          :email "jack.sparrow@triangle.bm"}})
+   :body {:items (db-get-all-items)}})
 
-(defn post-items-handler
+(defn create-item-handler
   [request]
   (let [item (:body-params request)
-        id 1
         name (:name item)
-        email (:email item)]
+        email (:email item)
+        id (db-store-item! name email)]
+
     {:status 201
      :headers {"Location" (str "/item/" id)}
-     :body {:id id, :name name, :email email}}))
+     :body (db-get-item id)}))
 
 
 ;; Custom middleware ----------------------------------------------
@@ -68,7 +102,7 @@
    (ring/router
     [["/ahoy"  {:get ahoy-handler}]
      ["/items" {:get get-items-handler
-                :post {:handler post-items-handler
+                :post {:handler create-item-handler
                        :parameters {:body Item}}}]]
     ;; Middlewares:
     ;; - wrap-content-type-json: ensure POST routes are sent JSON payload
@@ -92,5 +126,8 @@
   "HolidayPirates take-home assignement.
    Goal: build a (very) small REST API that exposes to endpoints."
   [& args]
+  (println "Initializing SQLite database...")
+  (init-db!)
+  (println "Starting server...")
   (http-server/run-jetty app {:port 3000 :join? false})
   (println "Ahoy! Yo-ho-ho API running on port 3000"))