feat: deno task db:restore (denoland#535)

Prerequisite for denoland#514.

.gitignore

@@ -4,3 +4,4 @@ cov/
 cov.lcov
 .idea
 _fresh/
+backup.json

README.md

@@ -119,7 +119,9 @@ Use the following commands to work with your local Deno KV database:
 
 - `deno task db:seed` - Populate the database with data from the
   [Hacker News API](https://github.com/HackerNews/API).
-- `deno task db:dump` - Print all database values.
+- `deno task db:dump > backup.json` - Write all database entries to
+  `backup.json`.
+- `deno task db:restore backup.json` - Restore the database from `backup.json`.
 - `deno task db:reset` - Reset the database. This is not recoverable.
 
 ## Customize and Extend

deno.json

@@ -3,6 +3,7 @@
   "tasks": {
     "init:stripe": "deno run --allow-read --allow-env --allow-net tasks/init_stripe.ts",
     "db:dump": "deno run --allow-read --allow-env --unstable tasks/db_dump.ts",
+    "db:restore": "deno run --allow-read --allow-env --unstable tasks/db_restore.ts",
     "db:seed": "deno run --allow-read --allow-env --allow-net --unstable tasks/db_seed.ts",
     "db:migrate": "deno run --allow-read --allow-env --allow-net --unstable tasks/db_migrate.ts",
     "db:reset": "deno run --allow-read --allow-env --unstable tasks/db_reset.ts",
@@ -49,14 +50,6 @@
         "fresh",
         "recommended"
       ]
-    },
-    "exclude": [
-      "_fresh"
-    ]
-  },
-  "fmt": {
-    "exclude": [
-      "_fresh"
-    ]
+    }
   }
 }

tasks/db_dump.ts

@@ -1,4 +1,13 @@
 // Copyright 2023 the Deno authors. All rights reserved. MIT license.
+/**
+ * This script prints all entries in the KV database formatted as JSON. This
+ * can be used to create a backup file.
+ *
+ * @example
+ * ```bash
+ * deno task db:dump > backup.json
+ * ```
+ */
 import { kv } from "@/utils/db.ts";
 
 // https://github.com/GoogleChromeLabs/jsbi/issues/30#issuecomment-521460510
@@ -8,7 +17,7 @@ function replacer(_key: unknown, value: unknown) {
 
 const iter = kv.list({ prefix: [] });
 const items = [];
-for await (const res of iter) items.push({ [res.key.toString()]: res.value });
-console.log(`${JSON.stringify(items, replacer, 2)}`);
+for await (const { key, value } of iter) items.push({ key, value });
+console.log(JSON.stringify(items, replacer, 2));
 
 kv.close();

tasks/db_restore.ts

@@ -0,0 +1,41 @@
+// Copyright 2023 the Deno authors. All rights reserved. MIT license.
+/**
+ * This script is used to restore a KV database by a file generated by the dump
+ * script.
+ *
+ * @example
+ * ```
+ * deno task db:restore backup.json
+ * ```
+ */
+import { kv } from "@/utils/db.ts";
+
+interface StoredKvU64 {
+  value: string;
+}
+
+function isStoredKvU64(value: unknown): value is StoredKvU64 {
+  return (value as StoredKvU64).value !== undefined &&
+    typeof (value as StoredKvU64).value === "string";
+}
+
+function reviver(_key: unknown, value: unknown) {
+  return isStoredKvU64(value) ? new Deno.KvU64(BigInt(value.value)) : value;
+}
+
+if (!confirm("WARNING: The database will be restored. Continue?")) Deno.exit();
+
+const [filePath] = Deno.args;
+if (filePath === undefined) throw new Error("File path must be defined");
+
+const rawEntries = Deno.readTextFileSync(filePath);
+const entries = JSON.parse(rawEntries, reviver) as Omit<
+  Deno.KvEntry<unknown>,
+  "versionstamp"
+>[];
+
+const promises = [];
+for (const { key, value } of entries) promises.push(kv.set(key, value));
+await Promise.all(promises);
+
+kv.close();