1 files changed, 40 insertions, 0 deletions
diff --git a/app/scripts/lib/migrator/index.js b/app/scripts/lib/migrator/index.js
new file mode 100644
index 000000000..ab5a757b3
--- /dev/null
+++ b/app/scripts/lib/migrator/index.js
@@ -0,0 +1,40 @@
+const asyncQ = require('async-q')
+
+class Migrator {
+
+  constructor (opts = {}) {
+    let migrations = opts.migrations || []
+    this.migrations = migrations.sort((a, b) => a.version - b.version)
+    let lastMigration = this.migrations.slice(-1)[0]
+    // use specified defaultVersion or highest migration version
+    this.defaultVersion = opts.defaultVersion || (lastMigration && lastMigration.version) || 0
+  }
+
+  // run all pending migrations on meta in place
+  migrateData (versionedData = this.generateInitialState()) {
+    let remaining = this.migrations.filter(migrationIsPending)
+    
+    return (
+      asyncQ.eachSeries(remaining, (migration) => migration.migrate(versionedData))
+      .then(() => versionedData)
+    )
+
+    // migration is "pending" if hit has a higher
+    // version number than currentVersion
+    function migrationIsPending(migration) {
+      return migration.version > versionedData.meta.version
+    }
+  }
+
+  generateInitialState (initState) {
+    return {
+      meta: {
+        version: this.defaultVersion,
+      },
+      data: initState,
+    }
+  }
+
+}
+
+module.exports = Migrator