/**
 * Passkey REST API Server — Spec Section 3.7, 16.3
 *
 * Proxies browser FIDO2 requests to PasskeyPlatformService (→ amiPro FIDO2 server).
 *
 * Endpoints:
 *   POST /api/passkey/attestation/options   — Get registration challenge
 *   POST /api/passkey/attestation/result    — Submit registration result
 *   POST /api/passkey/assertion/options     — Get authentication challenge
 *   POST /api/passkey/assertion/result      — Submit authentication result
 *   POST /api/passkey/session/validate      — Validate a session
 *   POST /api/passkey/session/delete        — Delete/logout a session
 */

import http from 'node:http';
import type { PasskeyPlatformService } from './platform-service.js';

export class PasskeyAPIServer {
  private server: http.Server | null = null;

  constructor(
    private readonly platformService: PasskeyPlatformService,
    private readonly rpId: string,
    private readonly origin: string,
  ) {}

  start(port: number): void {
    this.server = http.createServer((req, res) => {
      void this.handleRequest(req, res);
    });

    this.server.listen(port, '127.0.0.1', () => {
      console.log(`[passkey-api] Server listening on http://127.0.0.1:${port}`);
    });
  }

  stop(): void {
    this.server?.close();
  }

  private async handleRequest(req: http.IncomingMessage, res: http.ServerResponse): Promise<void> {
    const url = new URL(req.url ?? '/', 'http://localhost');

    // CORS headers
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'POST, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type');

    if (req.method === 'OPTIONS') {
      res.writeHead(200);
      res.end();
      return;
    }

    if (req.method !== 'POST') {
      sendJson(res, 405, { error: 'Method Not Allowed' });
      return;
    }

    try {
      const body = await parseJsonBody(req) as Record<string, unknown>;

      switch (url.pathname) {
        case '/api/passkey/attestation/options':
          await this.handleAttestationOptions(res, body);
          break;
        case '/api/passkey/attestation/result':
          await this.handleAttestationResult(res, body);
          break;
        case '/api/passkey/assertion/options':
          await this.handleAssertionOptions(res, body);
          break;
        case '/api/passkey/assertion/result':
          await this.handleAssertionResult(res, body);
          break;
        case '/api/passkey/session/validate':
          await this.handleSessionValidate(res, body);
          break;
        case '/api/passkey/session/delete':
          await this.handleSessionDelete(res, body);
          break;
        default:
          sendJson(res, 404, { error: 'Not Found' });
      }
    } catch (err) {
      sendJson(res, 400, { error: (err as Error).message });
    }
  }

  // ─── Registration ────────────────────────────────────────────────────

  private async handleAttestationOptions(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const username = body.username as string;
    const displayName = (body.displayName as string) || username;

    if (!username) {
      sendJson(res, 400, { error: 'username is required' });
      return;
    }

    const result = await this.platformService.getAttestationOptions(username, displayName);
    sendJson(res, result.success ? 200 : 400, result.success ? result.options : { error: result.error });
  }

  private async handleAttestationResult(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const result = await this.platformService.submitAttestationResult(body as any);
    sendJson(res, result.success ? 200 : 400, result);
  }

  // ─── Authentication ──────────────────────────────────────────────────

  private async handleAssertionOptions(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const username = body.username as string | undefined;

    const result = await this.platformService.getAssertionOptions(username);
    sendJson(res, result.success ? 200 : 400, result.success ? result.options : { error: result.error });
  }

  private async handleAssertionResult(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const result = await this.platformService.submitAssertionResult(body as any);
    sendJson(res, result.success ? 200 : 400, result);
  }

  // ─── Session ─────────────────────────────────────────────────────────

  private async handleSessionValidate(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const session = body.session as string;
    if (!session) {
      sendJson(res, 400, { error: 'session is required' });
      return;
    }

    const valid = await this.platformService.validateSession(session);
    sendJson(res, 200, { valid });
  }

  private async handleSessionDelete(
    res: http.ServerResponse,
    body: Record<string, unknown>,
  ): Promise<void> {
    const session = body.session as string;
    const username = body.username as string;
    if (!session || !username) {
      sendJson(res, 400, { error: 'session and username are required' });
      return;
    }

    await this.platformService.deleteSession(session, username);
    sendJson(res, 200, { ok: true });
  }
}

function sendJson(res: http.ServerResponse, status: number, body: unknown): void {
  res.writeHead(status, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify(body));
}

function parseJsonBody(req: http.IncomingMessage): Promise<unknown> {
  return new Promise((resolve, reject) => {
    let data = '';
    req.on('data', (chunk: Buffer) => { data += chunk.toString(); });
    req.on('end', () => {
      try {
        resolve(JSON.parse(data));
      } catch {
        reject(new Error('Invalid JSON'));
      }
    });
    req.on('error', reject);
  });
}