/**
 * API Server
 *
 * HTTP server for the OpenAI-compatible API gateway.
 */

import * as http from 'node:http';
import type { IApiConfig } from '../interfaces/config.ts';
import type { IHealthResponse } from '../interfaces/api.ts';
import { logger } from '../logger.ts';
import { API_SERVER } from '../constants.ts';
import { ApiRouter } from './router.ts';
import { ContainerManager } from '../containers/container-manager.ts';
import { ModelRegistry } from '../models/registry.ts';
import { ModelLoader } from '../models/loader.ts';
import { GpuDetector } from '../hardware/gpu-detector.ts';

/**
 * API Server for ModelGrid
 */
export class ApiServer {
  private server?: http.Server;
  private config: IApiConfig;
  private router: ApiRouter;
  private containerManager: ContainerManager;
  private modelRegistry: ModelRegistry;
  private modelLoader: ModelLoader;
  private gpuDetector: GpuDetector;
  private startTime: number = 0;

  constructor(
    config: IApiConfig,
    containerManager: ContainerManager,
    modelRegistry: ModelRegistry,
  ) {
    this.config = config;
    this.containerManager = containerManager;
    this.modelRegistry = modelRegistry;
    this.gpuDetector = new GpuDetector();
    this.modelLoader = new ModelLoader(modelRegistry, containerManager, true);
    this.router = new ApiRouter(
      containerManager,
      modelRegistry,
      this.modelLoader,
      config.apiKeys,
    );
  }

  /**
   * Start the API server
   */
  public async start(): Promise<void> {
    if (this.server) {
      logger.warn('API server is already running');
      return;
    }

    this.startTime = Date.now();

    this.server = http.createServer(async (req, res) => {
      await this.handleRequest(req, res);
    });

    return new Promise((resolve, reject) => {
      this.server!.listen(this.config.port, this.config.host, () => {
        logger.success(`API server started on ${this.config.host}:${this.config.port}`);
        logger.info('OpenAI-compatible API available at:');
        logger.info(`  POST /v1/chat/completions`);
        logger.info(`  GET  /v1/models`);
        logger.info(`  POST /v1/embeddings`);
        resolve();
      });

      this.server!.on('error', (error) => {
        logger.error(`API server error: ${error.message}`);
        reject(error);
      });
    });
  }

  /**
   * Stop the API server
   */
  public async stop(): Promise<void> {
    if (!this.server) {
      return;
    }

    return new Promise((resolve) => {
      this.server!.close(() => {
        logger.log('API server stopped');
        this.server = undefined;
        resolve();
      });
    });
  }

  /**
   * Handle incoming HTTP request
   */
  private async handleRequest(
    req: http.IncomingMessage,
    res: http.ServerResponse,
  ): Promise<void> {
    const startTime = Date.now();

    // Set CORS headers if enabled
    if (this.config.cors) {
      this.setCorsHeaders(req, res);
    }

    // Handle preflight requests
    if (req.method === 'OPTIONS') {
      res.writeHead(204);
      res.end();
      return;
    }

    // Parse URL
    const url = new URL(req.url || '/', `http://${req.headers.host || 'localhost'}`);
    const path = url.pathname;

    // Health check endpoint (no auth required)
    if (path === '/health' || path === '/healthz') {
      await this.handleHealthCheck(res);
      return;
    }

    // Metrics endpoint (no auth required)
    if (path === '/metrics') {
      await this.handleMetrics(res);
      return;
    }

    // Route request
    try {
      await this.router.route(req, res, path);
    } catch (error) {
      logger.error(`Request error: ${error instanceof Error ? error.message : String(error)}`);
      this.sendError(res, 500, 'Internal server error', 'internal_error');
    }

    // Log request
    const duration = Date.now() - startTime;
    logger.dim(`${req.method} ${path} - ${res.statusCode} (${duration}ms)`);
  }

  /**
   * Set CORS headers
   */
  private setCorsHeaders(
    req: http.IncomingMessage,
    res: http.ServerResponse,
  ): void {
    const origin = req.headers.origin || '*';
    const allowedOrigins = this.config.corsOrigins || ['*'];

    if (allowedOrigins.includes('*') || allowedOrigins.includes(origin)) {
      res.setHeader('Access-Control-Allow-Origin', origin);
    }

    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
    res.setHeader('Access-Control-Max-Age', '86400');
  }

  /**
   * Handle health check
   */
  private async handleHealthCheck(res: http.ServerResponse): Promise<void> {
    try {
      const statuses = await this.containerManager.getAllStatus();
      const gpus = await this.gpuDetector.detectGpus();
      const models = await this.containerManager.getAllAvailableModels();

      let status: 'ok' | 'degraded' | 'error' = 'ok';
      const containerHealth: Record<string, 'healthy' | 'unhealthy'> = {};
      const gpuStatus: Record<string, 'available' | 'in_use' | 'error'> = {};

      // Check container health
      for (const [id, containerStatus] of statuses) {
        if (containerStatus.running && containerStatus.health === 'healthy') {
          containerHealth[id] = 'healthy';
        } else {
          containerHealth[id] = 'unhealthy';
          status = 'degraded';
        }
      }

      // Check GPU status
      for (const gpu of gpus) {
        gpuStatus[gpu.id] = 'available';
      }

      const response: IHealthResponse = {
        status,
        version: '1.0.0', // TODO: Get from config
        uptime: Math.floor((Date.now() - this.startTime) / 1000),
        containers: statuses.size,
        models: models.size,
        gpus: gpus.length,
        details: {
          containers: containerHealth,
          gpus: gpuStatus,
        },
      };

      res.writeHead(status === 'ok' ? 200 : 503, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify(response, null, 2));
    } catch (error) {
      res.writeHead(500, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({
        status: 'error',
        error: error instanceof Error ? error.message : String(error),
      }));
    }
  }

  /**
   * Handle metrics endpoint (Prometheus format)
   */
  private async handleMetrics(res: http.ServerResponse): Promise<void> {
    try {
      const metrics: string[] = [];
      const timestamp = Date.now();

      // Server uptime
      const uptime = Math.floor((timestamp - this.startTime) / 1000);
      metrics.push(`# HELP modelgrid_uptime_seconds Server uptime in seconds`);
      metrics.push(`# TYPE modelgrid_uptime_seconds gauge`);
      metrics.push(`modelgrid_uptime_seconds ${uptime}`);

      // Container count
      const statuses = await this.containerManager.getAllStatus();
      metrics.push(`# HELP modelgrid_containers_total Total number of containers`);
      metrics.push(`# TYPE modelgrid_containers_total gauge`);
      metrics.push(`modelgrid_containers_total ${statuses.size}`);

      // Running containers
      const running = Array.from(statuses.values()).filter((s) => s.running).length;
      metrics.push(`# HELP modelgrid_containers_running Number of running containers`);
      metrics.push(`# TYPE modelgrid_containers_running gauge`);
      metrics.push(`modelgrid_containers_running ${running}`);

      // Available models
      const models = await this.containerManager.getAllAvailableModels();
      metrics.push(`# HELP modelgrid_models_available Number of available models`);
      metrics.push(`# TYPE modelgrid_models_available gauge`);
      metrics.push(`modelgrid_models_available ${models.size}`);

      // GPU count
      const gpus = await this.gpuDetector.detectGpus();
      metrics.push(`# HELP modelgrid_gpus_total Total number of GPUs`);
      metrics.push(`# TYPE modelgrid_gpus_total gauge`);
      metrics.push(`modelgrid_gpus_total ${gpus.length}`);

      res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });
      res.end(metrics.join('\n') + '\n');
    } catch (error) {
      res.writeHead(500, { 'Content-Type': 'text/plain' });
      res.end(`# Error: ${error instanceof Error ? error.message : String(error)}\n`);
    }
  }

  /**
   * Send error response
   */
  private sendError(
    res: http.ServerResponse,
    statusCode: number,
    message: string,
    type: string,
  ): void {
    res.writeHead(statusCode, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({
      error: {
        message,
        type,
        code: null,
      },
    }));
  }

  /**
   * Get server info
   */
  public getInfo(): {
    running: boolean;
    host: string;
    port: number;
    uptime: number;
  } {
    return {
      running: !!this.server,
      host: this.config.host,
      port: this.config.port,
      uptime: this.startTime ? Math.floor((Date.now() - this.startTime) / 1000) : 0,
    };
  }
}