style/src/routes/api/convert/+server.ts

import { json } from '@sveltejs/kit';
import type { RequestHandler } from './$types';
import { getStyleById, getIntensityConfig } from '$lib/styles';
import { convertText } from '$lib/llm';
import type { ConversionRequest, ConversionResponse } from '$lib/types';

export const POST: RequestHandler = async ({ request }) => {
	let body: ConversionRequest;
	try {
		body = await request.json();
	} catch {
		return json({ error: 'Invalid JSON body' }, { status: 400 });
	}

	const { text, styleId, intensity } = body;

	// Validate text
	if (!text || typeof text !== 'string' || text.trim().length === 0) {
		return json({ error: 'Text is required and must be non-empty' }, { status: 400 });
	}

	// Validate styleId
	if (!styleId || typeof styleId !== 'string') {
		return json({ error: 'styleId is required' }, { status: 400 });
	}

	const style = getStyleById(styleId);
	if (!style) {
		return json({ error: `Unknown style: ${styleId}` }, { status: 400 });
	}

	// Validate intensity
	if (typeof intensity !== 'number' || !Number.isInteger(intensity) || intensity < 1 || intensity > 5) {
		return json({ error: 'Intensity must be an integer between 1 and 5' }, { status: 400 });
	}

	const intensityConfig = getIntensityConfig(intensity);
	if (!intensityConfig) {
		return json({ error: 'Invalid intensity level' }, { status: 400 });
	}

	try {
		const result = convertText(text, style.promptModifier, intensityConfig.instruction);

		// Await the promise
		const { converted, systemPrompt, userMessage } = await result;

		const response: ConversionResponse = {
			original: text,
			converted,
			styleId,
			intensity,
			systemPrompt,
			userMessage
		};

		return json(response);
	} catch (err) {
		const message = err instanceof Error ? err.message : 'LLM call failed';
		return json({ error: `Failed to convert text: ${message}` }, { status: 502 });
	}
};