import { createRouter, type ServerConfig } from '@surf-lab/mcprouter';
import { createOpenAI } from '@ai-sdk/openai';
import {
  createBoundedModel,
  createRoutingModel,
  createModelRanker,
} from '@surf-lab/mcprouter/ai-sdk';

function env(name: string): string {
  const value = process.env[name];
  if (!value) throw new Error(`Missing ${name}`);
  return value;
}

const connection = {
  baseURL: env('MODEL_BASE_URL'),
  apiKey: env('MODEL_API_KEY'),
};

function connectModel(modelId: string) {
  const model = createBoundedModel({
    fetch: globalThis.fetch,
    createModel: fetch => createOpenAI({ ...connection, fetch }).chat(modelId),
  });
  return {
    routing: createRoutingModel({ model }),
    ranking: createModelRanker({ model }),
  };
}

const models = {
  general: connectModel(env('GENERAL_MODEL_ID')),
  database: connectModel(env('DATABASE_MODEL_ID')),
  billing: connectModel(env('BILLING_MODEL_ID')),
};

const mcpServers: ServerConfig[] = [
  { serverId: 'database-server', transport: 'http',
    url: env('DATABASE_MCP_URL'),
    headers: { Authorization: `Bearer ${env('DATABASE_MCP_TOKEN')}` } },
  { serverId: 'billing-server', transport: 'http',
    url: env('BILLING_MCP_URL'),
    headers: { Authorization: `Bearer ${env('BILLING_MCP_TOKEN')}` } },
];

function createAppRouter() {
  return createRouter({
    models,
    model: 'general',
    policy: {
      modelBindings: {
        servers: { 'database-server': 'database', 'billing-server': 'general' },
        tools: [{ serverId: 'billing-server',
          toolName: 'get_customer_balance', model: 'billing' }],
      },
      modelAccess: { allowedModels: ['general', 'database', 'billing'] },
      eligibility: (tool, context) => context.role === 'reader' &&
        'serverId' in tool &&
        (tool.serverId === 'database-server' && tool.name === 'list_tables' ||
         tool.serverId === 'billing-server' && tool.name === 'get_customer_balance'),
      authorize: (call, context) => {
        const target = `${call.origin.serverId}/${call.descriptor.upstreamName}`;
        if (context.role !== 'reader') return { decision: 'deny' };
        if (target === 'database-server/list_tables') return { decision: 'allow' };
        if (target === 'billing-server/get_customer_balance' &&
            typeof context.customerId === 'string' && context.customerId &&
            call.arguments.customerId === context.customerId) return { decision: 'allow' };
        return { decision: 'deny' };
      },
      revision: () => 1,
    },
  });
}