feat: add patch to loki

Author: jkoenig134

package-lock.json

@@ -29,6 +29,7 @@
     "dependencies": {
         "@js-soft/docdb-access-abstractions": "1.1.0",
         "@types/lokijs": "1.5.14",
+        "fast-json-patch": "^3.1.1",
         "lokijs": "1.5.12"
     },
     "publishConfig": {

packages/loki/package.json

@@ -5,6 +5,7 @@ import {
     DatabaseType,
     IDatabaseCollection
 } from "@js-soft/docdb-access-abstractions";
+import jsonpatch from "fast-json-patch";
 
 export class LokiJsCollection implements IDatabaseCollection {
     public readonly name: string;
@@ -43,6 +44,30 @@ export class LokiJsCollection implements IDatabaseCollection {
         return data;
     }
 
+    public async patch(oldDocument: any, data: any): Promise<any> {
+        if (typeof data.toJSON === "function") {
+            data = data.toJSON();
+        }
+
+        if (!("id" in oldDocument)) {
+            throw new Error("Patching is not supported for documents with an 'id' field. Use 'update' instead.");
+        }
+
+        data.$loki = oldDocument.$loki;
+        data.meta = oldDocument.meta;
+
+        const patch = jsonpatch.compare(oldDocument, data);
+        const updated = this.collection
+            .chain()
+            .find({ id: oldDocument.id }, true)
+            .update((doc) => jsonpatch.applyPatch(doc, patch))
+            .data();
+
+        if (updated.length < 1) throw new Error("Document not found for patching");
+
+        return updated[0];
+    }
+
     public async delete(query: any): Promise<boolean> {
         if (typeof query === "string") {
             query = { id: query };

packages/loki/src/LokiJsCollection.ts

@@ -224,4 +224,40 @@ describe("DatabaseCollection", () => {
 
         await expect(db.create({ id: "uniqueValue" })).rejects.toThrow("Duplicate key for property id: uniqueValue");
     });
+
+    describe("patch vs update", () => {
+        test("update is not working properly", async () => {
+            const db = await getRandomCollection();
+
+            const entry = { id: "test", name: "test" };
+            const createdEntry = await db.create(entry);
+
+            // this will completely replaced
+            await db.update(createdEntry, { id: "test", name: "updated" });
+
+            // this will replace the above
+            await db.update(createdEntry, { id: "test", name: "test", anotherField: "newField" });
+
+            const queriedEntry = await db.findOne({ id: "test" });
+            expect(queriedEntry.name).toBe("test");
+            expect(queriedEntry.anotherField).toBe("newField");
+        });
+
+        test("patch is better", async () => {
+            const db = await getRandomCollection();
+
+            const entry = { id: "test", name: "test" };
+            const createdEntry = await db.create(entry);
+
+            // this changes name
+            await db.patch(createdEntry, { id: "test", name: "updated" });
+
+            // this only adds another field
+            await db.patch(createdEntry, { id: "test", name: "test", anotherField: "newField" });
+
+            const queriedEntry = await db.findOne({ id: "test" });
+            expect(queriedEntry.name).toBe("updated");
+            expect(queriedEntry.anotherField).toBe("newField");
+        });
+    });
 });