/**
 * companion-stdio.js
 *
 * Exposes the four Void companion tools through the MCP stdio protocol.
 * The `claude` CLI spawns this file as a subprocess and communicates
 * over stdin/stdout using JSON-RPC.
 *
 * Usage (via claude MCP config):
 *   VOID_AGENT_JSON='...' VOID_SPACE_ID='...' node lib/mcp/companion-stdio.js
 *
 * Exported helpers (transport-free — safe to import in tests):
 *   listMcpTools()          → array of {name, description, input_schema}
 *   callMcpTool(name, args, ctx) → raw handler result object
 */

import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
import {
  ListToolsRequestSchema,
  CallToolRequestSchema
} from '@modelcontextprotocol/sdk/types.js';
import { companionRegistry } from '../ai/agent/tools/index.js';
import { buildCtxFromEnv } from './context.js';

// ---------------------------------------------------------------------------
// Transport-free helpers (exported for testing)
// ---------------------------------------------------------------------------

/**
 * Returns the list of MCP tool descriptors (no handler) from the companion registry.
 * @returns {{ name: string, description: string, input_schema: object }[]}
 */
export function listMcpTools() {
  return companionRegistry.listTools().map(({ name, description, input_schema }) => ({
    name,
    description,
    input_schema
  }));
}

/**
 * Calls a tool handler directly (same code path as the MCP server), bypassing transport.
 * @param {string} name
 * @param {object} args
 * @param {object} ctx  – tool context {agent, space_id, view, actor}
 * @returns {Promise<object>} raw handler result
 */
export async function callMcpTool(name, args, ctx) {
  const tool = companionRegistry.getTool(name);
  if (!tool) {
    throw new Error(`Unknown tool: ${name}`);
  }
  return tool.handler(args, ctx);
}

// ---------------------------------------------------------------------------
// MCP server factory (used when running as a script)
// ---------------------------------------------------------------------------

function createServer() {
  const server = new Server(
    { name: 'void-companion', version: '1.0.0' },
    { capabilities: { tools: {} } }
  );

  // tools/list — return all companion tools with their raw JSON schemas
  server.setRequestHandler(ListToolsRequestSchema, () => ({
    tools: listMcpTools().map(({ name, description, input_schema }) => ({
      name,
      description,
      inputSchema: input_schema   // MCP protocol field name is inputSchema
    }))
  }));

  // tools/call — delegate to the registry handler, wrap result as text content
  server.setRequestHandler(CallToolRequestSchema, async (request) => {
    const { name, arguments: args = {} } = request.params;
    const ctx = buildCtxFromEnv();
    try {
      const result = await callMcpTool(name, args, ctx);
      const text = JSON.stringify(result);
      return {
        content: [{ type: 'text', text }],
        structuredContent: result
      };
    } catch (err) {
      return {
        content: [{ type: 'text', text: err.message ?? String(err) }],
        isError: true
      };
    }
  });

  return server;
}

// ---------------------------------------------------------------------------
// Entry point — only connect stdio transport when run as a script
// ---------------------------------------------------------------------------

const isMain =
  typeof process !== 'undefined' &&
  process.argv[1] &&
  import.meta.url === new URL(process.argv[1], 'file://').href;

if (isMain) {
  const server = createServer();
  const transport = new StdioServerTransport();
  await server.connect(transport);
}