/**
 * Event Stream API
 * GET /api/transparency/events - Get recent events or SSE stream
 * POST /api/transparency/events - Emit a custom event
 *
 * Provides real-time event streaming for transparency.
 */

import type { NextApiRequest, NextApiResponse } from 'next';
import { getEventStream, TransparencyEventType, EventPriority } from '../../../lib/transparency';

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  const eventStream = getEventStream();

  if (req.method === 'GET') {
    const { stream, types, limit = '50', start, end } = req.query;

    // Server-Sent Events mode
    if (stream === 'true') {
      res.setHeader('Content-Type', 'text/event-stream');
      res.setHeader('Cache-Control', 'no-cache');
      res.setHeader('Connection', 'keep-alive');

      const connectionId = `sse_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;

      // Send initial connection event
      res.write(`event: connected\ndata: ${JSON.stringify({ connectionId })}\n\n`);

      // Register SSE callback
      eventStream.registerSSE(connectionId, (event) => {
        try {
          res.write(eventStream.formatSSE(event));
        } catch {
          // Connection closed
          eventStream.unregisterSSE(connectionId);
        }
      });

      // Handle client disconnect
      req.on('close', () => {
        eventStream.unregisterSSE(connectionId);
      });

      // Keep connection alive
      const keepAlive = setInterval(() => {
        try {
          res.write(': keepalive\n\n');
        } catch {
          clearInterval(keepAlive);
          eventStream.unregisterSSE(connectionId);
        }
      }, 30000);

      return;
    }

    // Regular GET - return recent events
    try {
      const typeList = types ? (types as string).split(',') as TransparencyEventType[] : undefined;

      let events;
      if (start && end) {
        events = eventStream.getByTimeRange(
          start as string,
          end as string,
          {
            types: typeList,
            limit: parseInt(limit as string, 10)
          }
        );
      } else {
        events = eventStream.getRecent(parseInt(limit as string, 10), typeList);
      }

      return res.status(200).json({
        success: true,
        data: {
          events,
          count: events.length,
          availableTypes: eventStream.getAvailableEventTypes()
        }
      });
    } catch (error) {
      console.error('[API] Events error:', error);
      return res.status(500).json({
        success: false,
        error: 'Failed to fetch events'
      });
    }
  }

  if (req.method === 'POST') {
    try {
      const { type, source, data, priority, metadata } = req.body;

      if (!type || !source || !data) {
        return res.status(400).json({
          success: false,
          error: 'Missing required fields: type, source, data'
        });
      }

      const event = eventStream.emit(
        type as TransparencyEventType,
        source,
        data,
        {
          priority: priority as EventPriority,
          metadata
        }
      );

      return res.status(201).json({
        success: true,
        data: event
      });
    } catch (error) {
      console.error('[API] Event emit error:', error);
      return res.status(500).json({
        success: false,
        error: 'Failed to emit event'
      });
    }
  }

  return res.status(405).json({ error: 'Method not allowed' });
}