Add Metadata core with MongoDB for persistence

With the new process dependency, process handling has been added to
ensure that the ExpressJS server and MongoDB client connections get
closed up properly.

As noted in the Metadata file above the Branch interface, the schema is
definitely not finalized. Eventually metadata will be needed at the repo
level anyways, so reorganizing the document schema is high on the
priority list.

1 files changed, 54 insertions, 0 deletions

diff --git a/src/metadata.ts b/src/metadata.ts
new file mode 100644
index 0000000..1eb7f1a
--- /dev/null
+++ b/src/metadata.ts
@@ -0,0 +1,54 @@
+import { Db } from "mongodb";
+
+/** //FIXME fix document schema
+ * Rather than using branches as the core, this should be adopted into the following document model:
+ * repo:
+ *  - org
+ *  - name
+ *  - token
+ *  - branches: {
+ *      [branchname]: {
+ *        head
+ *      }
+ *    }
+ */
+export interface Branch {
+  org: string;
+  repo: string;
+  name: string;
+  head: string;
+}
+
+class Metadata {
+  database: Db;
+
+  constructor(client: Db) {
+    this.database = client;
+  }
+
+  async getHeadCommit(
+    org: string,
+    repo: string,
+    branch: string
+  ): Promise<string> {
+    const result = await this.database
+      .collection<Branch>("branch")
+      .findOne({ org, repo, name: branch });
+
+    if (result !== null) {
+      return result.head;
+    } else {
+      throw Error("Branch not found");
+    }
+  }
+
+  async updateBranch(branch: Branch): Promise<boolean> {
+    const { head, ...matcher } = branch;
+    const { result } = await this.database
+      .collection<Branch>("branch")
+      .replaceOne(matcher, branch, { upsert: true });
+    return result.ok === 1;
+  }
+}
+
+export default Metadata;