servers/src/everything/resources/dynamic.ts

import {McpServer, ResourceTemplate} from "@modelcontextprotocol/sdk/server/mcp.js";

/**
 * Register dynamic resources with the MCP server.
 *
 * - Text and blob resources, dynamically generated from the URI {index} variable
 * - Any finite integer is acceptable for the index variable
 * - List resources method will not return these resources
 * - These are only accessible via template URIs
 * - Both blob and text resources:
 *   - have content that is dynamically generated, including a timestamp
 *   - have different template URIs
 *     - Blob: "test://dynamic/resource/blob/{index}"
 *     - Text: "test://dynamic/resource/text/{index}"
 *
 * @param server
 */
export const addDynamicResources = (server: McpServer) => {
    const uriBase: string = "test://dynamic/resource";
    const textUri: string = `${uriBase}/text/{index}`
    const blobUri: string = `${uriBase}/blob/{index}`

    // Format a GMT timestamp like "7:30AM GMT on November 3"
    const formatGmtTimestamp = () => {
        const d = new Date();
        const h24 = d.getUTCHours();
        const minutes = d.getUTCMinutes();
        const ampm = h24 >= 12 ? "PM" : "AM";
        let h12 = h24 % 12;
        if (h12 === 0) h12 = 12;
        const mm = String(minutes).padStart(2, "0");
        const months = [
            "January", "February", "March", "April", "May", "June",
            "July", "August", "September", "October", "November", "December"
        ];
        const monthName = months[d.getUTCMonth()];
        const day = d.getUTCDate();
        return `${h12}:${mm}${ampm} GMT on ${monthName} ${day}`;
    };

    const parseIndex = (uri: URL, variables: Record<string, unknown>) => {
        const uriError = `Unknown resource: ${uri}`;
        if (uri.toString() !== textUri && uri.toString() !== blobUri) {
            throw new Error(uriError);
        }
        const idxStr = String((variables as any).index ?? "");
        const idx = Number(idxStr);
        if (Number.isFinite(idx) && Number.isInteger(idx)) {
            return idx;
        } else {
            throw new Error(uriError);
        }
    };

    // Text resource registration
    server.registerResource(
        "Dynamic Text Resource",
        new ResourceTemplate(textUri, { list: undefined }),
        {
            mimeType: "text/plain",
            description: "Plaintext dynamic resource fabricated from the {index} variable, which must be an integer.",
        },
        async (uri, variables) => {
            const index = parseIndex(uri, variables);
            return {
                contents: [
                    {
                        uri: uri.toString(),
                        mimeType: "text/plain",
                        text: `Resource ${index}: This is a plaintext resource created at ${formatGmtTimestamp()}`,
                    },
                ],
            };
        }
    );

    // Blob resource registration
    server.registerResource(
        "Dynamic Blob Resource",
        new ResourceTemplate(blobUri, { list: undefined }),
        {
            mimeType: "application/octet-stream",
            description: "Binary (base64) dynamic resource fabricated from the {index} variable, which must be an integer.",
        },
        async (uri, variables) => {
            const index = parseIndex(uri, variables);
            const buffer = Buffer.from(`Resource ${index}: This is a base64 blob created at ${formatGmtTimestamp()}`);
            return {
                contents: [
                    {
                        uri: uri.toString(),
                        mimeType: "application/octet-stream",
                        blob: buffer.toString("base64"),
                    },
                ],
            };
        }
    );
};