♻️ Make the namespacing independent of the branding.

backend/src/app/util/migrations.clj

@@ -0,0 +1,86 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) 2019 Andrey Antukh <niwi@niwi.nz>
+
+(ns app.util.migrations
+  (:require
+   [clojure.tools.logging :as log]
+   [clojure.java.io :as io]
+   [clojure.spec.alpha :as s]
+   [cuerdas.core :as str]
+   [next.jdbc :as jdbc]))
+
+(s/def ::name string?)
+(s/def ::step (s/keys :req-un [::name ::desc ::fn]))
+(s/def ::steps (s/every ::step :kind vector?))
+(s/def ::migrations
+  (s/keys :req-un [::name ::steps]))
+
+;; --- Implementation
+
+(defn- registered?
+  "Check if concrete migration is already registred."
+  [pool modname stepname]
+  (let [sql  "select * from migrations where module=? and step=?"
+        rows (jdbc/execute! pool [sql modname stepname])]
+    (pos? (count rows))))
+
+(defn- register!
+  "Register a concrete migration into local migrations database."
+  [pool modname stepname]
+  (let [sql "insert into migrations (module, step) values (?, ?)"]
+    (jdbc/execute! pool [sql modname stepname])
+    nil))
+
+(defn- impl-migrate-single
+  [pool modname {:keys [name] :as migration}]
+  (letfn [(execute []
+            (register! pool modname name)
+            ((:fn migration) pool))]
+    (when-not (registered? pool modname (:name migration))
+      (log/info (str/format "applying migration %s/%s" modname name))
+      (register! pool modname name)
+      ((:fn migration) pool))))
+
+(defn- impl-migrate
+  [conn migrations {:keys [fake] :or {fake false}}]
+  (s/assert ::migrations migrations)
+  (let [mname (:name migrations)
+        steps (:steps migrations)]
+    (jdbc/with-transaction [conn conn]
+      (run! #(impl-migrate-single conn mname %) steps))))
+
+(defprotocol IMigrationContext
+  (-migrate [_ migration options]))
+
+;; --- Public Api
+(defn setup!
+  "Initialize the database if it is not initialized."
+  [conn]
+  (let [sql (str "create table if not exists migrations ("
+                 " module text,"
+                 " step text,"
+                 " created_at timestamp DEFAULT current_timestamp,"
+                 " unique(module, step)"
+                 ");")]
+    (jdbc/execute! conn [sql])
+    nil))
+
+(defn migrate!
+  "Main entry point for apply a migration."
+  ([conn migrations]
+   (impl-migrate conn migrations nil))
+  ([conn migrations options]
+   (impl-migrate conn migrations options)))
+
+(defn resource
+  "Helper for setup migration functions
+  just using a simple path to sql file
+  located in the class path."
+  [path]
+  (fn [pool]
+    (let [sql (slurp (io/resource path))]
+      (jdbc/execute! pool [sql])
+      true)))