import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js';
import type { Middleware, EditContext } from './types.js';
import { verificationMiddleware } from './verification.js';
/**
* Middleware pipeline registry.
*
* Middlewares are executed in order for onInput (first to last),
* and in reverse order for onOutput (last to first) - like an onion.
*/
class MiddlewarePipeline {
private middlewares: Middleware[] = [];
register( middleware: Middleware ): void {
this.middlewares.push( middleware );
console.error( `[middleware] Registered: ${ middleware.name }` );
}
/**
* Run all onInput transforms in order.
*/
async processInput( context: EditContext ): Promise<EditContext> {
let current = context;
for ( const mw of this.middlewares ) {
if ( mw.onInput ) {
current = await mw.onInput( current );
}
}
return current;
}
/**
* Run all onOutput transforms in reverse order.
*/
async processOutput( context: EditContext, result: CallToolResult ): Promise<CallToolResult> {
let current = result;
for ( let i = this.middlewares.length - 1; i >= 0; i-- ) {
const mw = this.middlewares[i];
if ( mw.onOutput ) {
current = await mw.onOutput( context, current );
}
}
return current;
}
/**
* Convenience method to wrap a tool handler with middleware.
*/
async wrapHandler<T extends CallToolResult>(
context: EditContext,
handler: ( ctx: EditContext ) => Promise<T>
): Promise<CallToolResult> {
const transformedContext = await this.processInput( context );
const result = await handler( transformedContext );
return await this.processOutput( transformedContext, result );
}
}
// Global pipeline instance
export const pipeline = new MiddlewarePipeline();
// Register default middlewares
pipeline.register( verificationMiddleware );
export type { Middleware, EditContext };
