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| 1 | /** |
| 2 | * An MCP server over plain HTTP: `POST /mcp` takes one JSON-RPC 2.0 |
| 3 | * message and answers with JSON (streamable HTTP without the stream — |
| 4 | * nothing here needs to push). The tools are the actions, called with the |
| 5 | * same identity the page gets, so an agent speaking MCP through the forge |
| 6 | * is the person whose grant it carries, and a bare one is anonymous. |
| 7 | */ |
| 8 | |
| 9 | import type { Database } from "bun:sqlite"; |
| 10 | import { addNote, deleteNote, listNotes, type Result } from "./actions.ts"; |
| 11 | import { title } from "./env.ts"; |
| 12 | import { fields } from "./http.ts"; |
| 13 | import type { Who } from "./who.ts"; |
| 14 | |
| 15 | interface Tool { |
| 16 | readonly name: string; |
| 17 | readonly description: string; |
| 18 | readonly inputSchema: Record<string, unknown>; |
| 19 | readonly run: ( |
| 20 | db: Database, |
| 21 | who: Who, |
| 22 | args: Record<string, unknown>, |
| 23 | ) => Result<unknown>; |
| 24 | } |
| 25 | |
| 26 | export const tools: readonly Tool[] = [ |
| 27 | { |
| 28 | name: "list_notes", |
| 29 | description: "The notes, newest first.", |
| 30 | inputSchema: { |
| 31 | type: "object", |
| 32 | properties: { |
| 33 | limit: { |
| 34 | type: "integer", |
| 35 | minimum: 1, |
| 36 | maximum: 500, |
| 37 | description: "At most this many (100).", |
| 38 | }, |
| 39 | }, |
| 40 | }, |
| 41 | run: (db, who, args) => |
| 42 | listNotes(db, who, { limit: Number(args.limit ?? 100) }), |
| 43 | }, |
| 44 | { |
| 45 | name: "add_note", |
| 46 | description: |
| 47 | "Add a note as the signed-in person. Anonymous callers cannot.", |
| 48 | inputSchema: { |
| 49 | type: "object", |
| 50 | properties: { body: { type: "string", maxLength: 500 } }, |
| 51 | required: ["body"], |
| 52 | }, |
| 53 | run: (db, who, args) => addNote(db, who, { body: String(args.body ?? "") }), |
| 54 | }, |
| 55 | { |
| 56 | name: "delete_note", |
| 57 | description: "Remove a note by id. Only its author or an admin can.", |
| 58 | inputSchema: { |
| 59 | type: "object", |
| 60 | properties: { id: { type: "integer" } }, |
| 61 | required: ["id"], |
| 62 | }, |
| 63 | run: (db, who, args) => deleteNote(db, who, { id: Number(args.id) }), |
| 64 | }, |
| 65 | ]; |
| 66 | |
| 67 | /** One JSON-RPC message in, an HTTP status and a body out (a notification gets 202 and no body). */ |
| 68 | export function rpc( |
| 69 | db: Database, |
| 70 | who: Who, |
| 71 | message: unknown, |
| 72 | ): { status: number; body?: unknown } { |
| 73 | const m = fields(message); |
| 74 | const id = m.id ?? null; |
| 75 | const reply = (result: unknown) => ({ |
| 76 | status: 200, |
| 77 | body: { jsonrpc: "2.0", id, result }, |
| 78 | }); |
| 79 | const refuse = (code: number, text: string) => ({ |
| 80 | status: 200, |
| 81 | body: { jsonrpc: "2.0", id, error: { code, message: text } }, |
| 82 | }); |
| 83 | if (m.jsonrpc !== "2.0" || typeof m.method !== "string") |
| 84 | return refuse(-32600, "not a JSON-RPC 2.0 request"); |
| 85 | if (m.id === undefined) return { status: 202 }; |
| 86 | const params = fields(m.params); |
| 87 | switch (m.method) { |
| 88 | case "initialize": |
| 89 | return reply({ |
| 90 | protocolVersion: "2025-06-18", |
| 91 | capabilities: { tools: {} }, |
| 92 | serverInfo: { name: title, version: "1" }, |
| 93 | }); |
| 94 | case "ping": |
| 95 | return reply({}); |
| 96 | case "tools/list": |
| 97 | return reply({ |
| 98 | tools: tools.map(({ name, description, inputSchema }) => ({ |
| 99 | name, |
| 100 | description, |
| 101 | inputSchema, |
| 102 | })), |
| 103 | }); |
| 104 | case "tools/call": { |
| 105 | const tool = tools.find((t) => t.name === params.name); |
| 106 | if (tool === undefined) |
| 107 | return refuse(-32602, `no tool named ${String(params.name)}`); |
| 108 | const result = tool.run(db, who, fields(params.arguments)); |
| 109 | return reply( |
| 110 | result.ok |
| 111 | ? { content: [{ type: "text", text: JSON.stringify(result.value) }] } |
| 112 | : { |
| 113 | content: [ |
| 114 | { type: "text", text: `${result.error}: ${result.message}` }, |
| 115 | ], |
| 116 | isError: true, |
| 117 | }, |
| 118 | ); |
| 119 | } |
| 120 | default: |
| 121 | return refuse(-32601, `no method ${m.method}`); |
| 122 | } |
| 123 | } |