feat(mcp): add tools

packages/mcp/server.ts

···
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
 import { getLogger } from "@logtape/logtape";
 import { z } from "zod";
-import type { Consumer } from "@cistern/consumer";
+import type { Consumer, DecryptedMemo } from "@cistern/consumer";
 
 export function createServer(consumer: Consumer) {
   const logger = getLogger("cistern-mcp");
···
     version: "1.0.0",
   });
 
+  let iterator:
+    | AsyncGenerator<DecryptedMemo, void, "stop" | undefined>
+    | undefined;
+
   server.registerTool(
-    "add",
+    "next_memo",
+    {
+      title: "Next memo",
+      description: "Retrieve the next outstanding memo",
+      outputSchema: { tid: z.string(), text: z.string() },
+    },
+    async () => {
+      if (!iterator) {
+        logger.trace("creating iterator");
+        iterator ??= consumer.listMemos();
+      }
+
+      const res = await iterator.next();
+
+      if (res.done) {
+        logger.trace("iterator done; cleaning up");
+        iterator = undefined;
+      }
+
+      return {
+        content: [{
+          type: "text",
+          text: res.value?.text ?? "no memos remaining",
+        }],
+        structuredContent: {
+          tid: res.value?.tid ?? "",
+          text: res.value?.text ?? "no memos remaining",
+        },
+      };
+    },
+  );
+
+  server.registerTool(
+    "delete_memo",
     {
-      title: "Addition Tool",
-      description: "Add two numbers",
-      inputSchema: { a: z.number(), b: z.number() },
-      outputSchema: { result: z.number() },
+      title: "Delete memo",
+      description:
+        "Delete a memo by record key, after it has been handled as instructed by the user",
+      inputSchema: { key: z.string() },
+      outputSchema: { success: z.boolean() },
     },
-    ({ a, b }) => {
-      logger.trace("Addition Tool called", { a, b });
+    async ({ key }) => {
+      try {
+        await consumer.deleteMemo(key);
 
-      const output = { result: a + b };
+        return {
+          content: [{ type: "text", text: "delete successful" }],
+          structuredContent: { success: true },
+        };
+      } catch (error) {
+        logger.error("failed to delete memo: {error}", { error });
 
-      return Promise.resolve({
-        content: [{ type: "text", text: JSON.stringify(output) }],
-        structuredContent: output,
-      });
+        return {
+          content: [{ type: "text", text: "delete unsuccessful" }],
+          structuredContent: { success: false },
+        };
+      }
     },
   );