import { json } from '@sveltejs/kit';
import { spawn } from 'child_process';
import type { RequestEvent } from '@sveltejs/kit';

export async function POST({ request }: RequestEvent) {
	try {
		const { messages, config } = await request.json();

		const lastMsg = messages?.[messages.length - 1]?.content || '';
		const modelFlag = config?.model ? ['-m', config.model] : [];
		const providerFlag = config?.provider ? ['--provider', config.provider] : [];
		const tempFlag = config?.temperature ? ['--temperature', String(config.temperature)] : [];
		const maxTokensFlag = config?.maxTokens ? ['--max-tokens', String(config.maxTokens)] : [];

		const hermes = spawn('hermes', [
			'chat',
			'-q', lastMsg,
			...modelFlag,
			...providerFlag,
			...tempFlag,
			...maxTokensFlag,
			'-Q',
			'--source', 'hermes-chat-v2'
		], {
			timeout: 120000,
			env: { ...process.env }
		});

		const stream = new ReadableStream({
			async start(controller) {
				const decoder = new TextDecoder();
				let buffer = '';

				const processChunk = (chunk: Buffer) => {
					buffer += decoder.decode(chunk, { stream: true });

					while (buffer.includes('\n')) {
						const idx = buffer.indexOf('\n');
						const line = buffer.slice(0, idx);
						buffer = buffer.slice(idx + 1);

						if (line.trim()) {
							const payload = JSON.stringify({
								choices: [{ delta: { content: line + '\n' } }]
							});
							controller.enqueue(new TextEncoder().encode(`data: ${payload}\n\n`));
						}
					}
				};

				hermes.stdout?.on('data', processChunk);

				hermes.stderr?.on('data', (data: Buffer) => {
					const text = decoder.decode(data, { stream: true });
					if (text.trim()) {
						const payload = JSON.stringify({
							choices: [{ delta: { content: `*${text.trim()}* ` } }]
						});
						controller.enqueue(new TextEncoder().encode(`data: ${payload}\n\n`));
					}
				});

				hermes.on('close', () => {
					if (buffer.trim()) {
						const payload = JSON.stringify({
							choices: [{ delta: { content: buffer } }]
						});
						controller.enqueue(new TextEncoder().encode(`data: ${payload}\n\n`));
					}
					controller.enqueue(new TextEncoder().encode('data: [DONE]\n\n'));
					controller.close();
				});

				hermes.on('error', (err) => {
					controller.enqueue(
						new TextEncoder().encode(
							`data: ${JSON.stringify({ error: err.message })}\n\n`
						)
					);
					controller.enqueue(new TextEncoder().encode('data: [DONE]\n\n'));
					controller.close();
				});
			}
		});

		return new Response(stream, {
			headers: {
				'Content-Type': 'text/event-stream',
				'Cache-Control': 'no-cache',
				Connection: 'keep-alive'
			}
		});
	} catch (err) {
		return json(
			{ error: err instanceof Error ? err.message : 'Internal server error' },
			{ status: 500 }
		);
	}
}