import { env } from '$env/dynamic/private';
import type { LLMConfig } from './types';

const DEFAULT_CONFIG: LLMConfig = {
	baseUrl: 'http://localhost:11434/v1',
	apiKey: 'ollama',
	model: 'llama3'
};

function getConfig(): LLMConfig {
	return {
		baseUrl: env.OPENAI_BASE_URL || DEFAULT_CONFIG.baseUrl,
		apiKey: env.OPENAI_API_KEY || DEFAULT_CONFIG.apiKey,
		model: env.OPENAI_MODEL || DEFAULT_CONFIG.model
	};
}

export interface ConvertResult {
	converted: string;
	systemPrompt: string;
	userMessage: string;
}

export function buildSystemPrompt(styleModifier: string, intensityInstruction: string): string {
	const intensityFilled = intensityInstruction.replace('{style}', styleModifier);
	return `You are an expert English style converter.
${intensityFilled}.
${styleModifier}
Preserve the core meaning but fully transform the voice and tone.
Output ONLY the converted text — no explanations, no labels, no quotes.`;
}

export function buildUserMessage(text: string): string {
	return text;
}

export async function convertText(
	text: string,
	styleModifier: string,
	intensityInstruction: string,
overrides?: Partial<LLMConfig>
): Promise<ConvertResult> {
	const merged: LLMConfig = { ...DEFAULT_CONFIG, ...getConfig(), ...overrides };

	const systemPrompt = buildSystemPrompt(styleModifier, intensityInstruction);
	const userMessage = buildUserMessage(text);

	const response = await fetch(`${merged.baseUrl}/chat/completions`, {
		method: 'POST',
		headers: {
			'Content-Type': 'application/json',
			Authorization: `Bearer ${merged.apiKey}`
		},
		body: JSON.stringify({
			model: merged.model,
			messages: [
				{ role: 'system', content: systemPrompt },
				{ role: 'user', content: userMessage }
			],
			temperature: 0.8
		})
	});

	if (!response.ok) {
		const errorText = await response.text().catch(() => 'Unknown error');
		throw new Error(`LLM request failed (${response.status}): ${errorText}`);
	}

	const data = await response.json();
	const converted = data.choices?.[0]?.message?.content?.trim();

	if (!converted) {
		throw new Error('LLM returned empty response');
	}

	return { converted, systemPrompt, userMessage };
}