/**
 * tRPC HTTP Adapter
 *
 * Handles tRPC requests over HTTP using node:http.
 * Routes /trpc/* requests to the tRPC router.
 */

import type { IncomingMessage, ServerResponse } from 'node:http';
import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import { appRouter, createContext } from '../trpc/index.js';
import type { EventBus } from '../events/index.js';
import type { AgentManager } from '../agent/types.js';
import type { TaskRepository } from '../db/repositories/task-repository.js';
import type { MessageRepository } from '../db/repositories/message-repository.js';
import type { InitiativeRepository } from '../db/repositories/initiative-repository.js';
import type { PhaseRepository } from '../db/repositories/phase-repository.js';
import type { PlanRepository } from '../db/repositories/plan-repository.js';
import type { DispatchManager, PhaseDispatchManager } from '../dispatch/types.js';
import type { CoordinationManager } from '../coordination/types.js';

/**
 * Options for creating the tRPC request handler.
 */
export interface TrpcAdapterOptions {
  /** Event bus for inter-module communication */
  eventBus: EventBus;
  /** When the server started */
  serverStartedAt: Date;
  /** Number of managed processes */
  processCount: number;
  /** Agent manager for agent lifecycle operations (optional until full wiring) */
  agentManager?: AgentManager;
  /** Task repository for task CRUD operations */
  taskRepository?: TaskRepository;
  /** Message repository for agent-user communication */
  messageRepository?: MessageRepository;
  /** Initiative repository for initiative CRUD operations */
  initiativeRepository?: InitiativeRepository;
  /** Phase repository for phase CRUD operations */
  phaseRepository?: PhaseRepository;
  /** Plan repository for plan CRUD operations */
  planRepository?: PlanRepository;
  /** Dispatch manager for task queue operations */
  dispatchManager?: DispatchManager;
  /** Coordination manager for merge queue operations */
  coordinationManager?: CoordinationManager;
  /** Phase dispatch manager for phase queue operations */
  phaseDispatchManager?: PhaseDispatchManager;
}

/**
 * Creates a tRPC request handler for node:http.
 *
 * Converts IncomingMessage/ServerResponse to fetch Request/Response
 * and delegates to the tRPC fetch adapter.
 *
 * @param options - Adapter options with context values
 * @returns Request handler function
 */
export function createTrpcHandler(options: TrpcAdapterOptions) {
  return async (req: IncomingMessage, res: ServerResponse): Promise<void> => {
    // Build full URL from request
    const protocol = 'http';
    const host = req.headers.host ?? 'localhost';
    const url = new URL(req.url ?? '/', `${protocol}://${host}`);

    // Read request body if present
    let body: string | undefined;
    if (req.method !== 'GET' && req.method !== 'HEAD') {
      body = await new Promise<string>((resolve) => {
        let data = '';
        req.on('data', (chunk: Buffer) => {
          data += chunk.toString();
        });
        req.on('end', () => {
          resolve(data);
        });
      });
    }

    // Convert headers to fetch Headers
    const headers = new Headers();
    for (const [key, value] of Object.entries(req.headers)) {
      if (value) {
        if (Array.isArray(value)) {
          value.forEach((v) => headers.append(key, v));
        } else {
          headers.set(key, value);
        }
      }
    }

    // Create fetch Request
    const fetchRequest = new Request(url.toString(), {
      method: req.method,
      headers,
      body: body ?? undefined,
    });

    // Handle with tRPC fetch adapter
    const fetchResponse = await fetchRequestHandler({
      endpoint: '/trpc',
      req: fetchRequest,
      router: appRouter,
      createContext: () =>
        createContext({
          eventBus: options.eventBus,
          serverStartedAt: options.serverStartedAt,
          processCount: options.processCount,
          agentManager: options.agentManager,
          taskRepository: options.taskRepository,
          messageRepository: options.messageRepository,
          initiativeRepository: options.initiativeRepository,
          phaseRepository: options.phaseRepository,
          planRepository: options.planRepository,
          dispatchManager: options.dispatchManager,
          coordinationManager: options.coordinationManager,
          phaseDispatchManager: options.phaseDispatchManager,
        }),
    });

    // Send response
    res.statusCode = fetchResponse.status;

    // Set response headers BEFORE streaming body
    fetchResponse.headers.forEach((value, key) => {
      res.setHeader(key, value);
    });

    // Stream body if it's a ReadableStream (SSE subscriptions), otherwise buffer
    if (fetchResponse.body) {
      const reader = fetchResponse.body.getReader();
      const pump = async () => {
        while (true) {
          const { done, value } = await reader.read();
          if (done) {
            res.end();
            return;
          }
          res.write(value);
        }
      };
      pump().catch(() => res.end());
    } else {
      const responseBody = await fetchResponse.text();
      res.end(responseBody);
    }
  };
}