/**
 * Server-Sent Events (SSE) endpoint for real-time extraction progress
 * 
 * This endpoint streams extraction progress updates to the frontend
 * using the SSE protocol. Each event contains status updates, method attempts,
 * retry information, and final results.
 */

import { json, type RequestHandler } from '@sveltejs/kit';
import { extractTextAndThumbnail, type ProgressEvent } from '$lib/server/extraction';
import { extractRecipe } from '$lib/server/parser';

export const POST: RequestHandler = async ({ request }) => {
	const { url } = await request.json();

	if (!url) {
		return json({ error: 'URL is required' }, { status: 400 });
	}

	// Create a ReadableStream for SSE
	const stream = new ReadableStream({
		async start(controller) {
			const encoder = new TextEncoder();

			// Helper to send SSE message
			const sendEvent = (event: ProgressEvent) => {
				const data = JSON.stringify(event);
				const message = `event: progress\ndata: ${data}\n\n`;
				controller.enqueue(encoder.encode(message));
			};

			try {
				// Extract with progress callback
				const extracted = await extractTextAndThumbnail(url, sendEvent);

				// Parse recipe from extracted text
				sendEvent({
					type: 'status',
					message: 'Parsing recipe...',
					timestamp: new Date().toISOString()
				});

				const recipe = await extractRecipe(extracted.bodyText);

				// Send final result
				const completeEvent: ProgressEvent = {
					type: 'complete',
					message: 'Extraction and parsing completed',
					data: {
						recipe,
						thumbnail: extracted.thumbnail
					},
					timestamp: new Date().toISOString()
				};

				const completeMessage = `event: complete\ndata: ${JSON.stringify(completeEvent)}\n\n`;
				controller.enqueue(encoder.encode(completeMessage));

				controller.close();
			} catch (error) {
				// Send error event
				const errorEvent: ProgressEvent = {
					type: 'error',
					message: error instanceof Error ? error.message : 'Unknown error occurred',
					timestamp: new Date().toISOString()
				};

				const errorMessage = `event: error\ndata: ${JSON.stringify(errorEvent)}\n\n`;
				controller.enqueue(encoder.encode(errorMessage));

				controller.close();
			}
		}
	});

	// Return SSE response
	return new Response(stream, {
		headers: {
			'Content-Type': 'text/event-stream',
			'Cache-Control': 'no-cache',
			Connection: 'keep-alive'
		}
	});
};