import { NextResponse } from 'next/server';
import fs from 'fs';
import path from 'path';
import { requireAuth } from '../../../../lib/jwt';
import type { Locale } from '../../../../lib/i18n';

type LocaleFields = { title: string; teaser: string; description: string };
const SUPPORTED_LOCALES: Locale[] = ['en', 'fi', 'sv'];

function loadApiKey() {
  if (process.env.OPENAI_API_KEY) return process.env.OPENAI_API_KEY;
  const keyPath = path.join(process.cwd(), 'creds', 'openai.key');
  try {
    return fs.readFileSync(keyPath, 'utf8').trim();
  } catch {
    return null;
  }
}

export async function POST(req: Request) {
  try {
    await requireAuth(req);
  } catch (err) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
  }

  const apiKey = loadApiKey();
  if (!apiKey) {
    return NextResponse.json({ error: 'Missing OpenAI API key' }, { status: 500 });
  }

  let body: any;
  try {
    body = await req.json();
  } catch {
    return NextResponse.json({ error: 'Invalid request' }, { status: 400 });
  }

  const incoming = body?.translations as Record<Locale, LocaleFields> | undefined;
  const currentLocale = (body?.currentLocale as Locale) ?? 'en';
  if (!incoming) {
    return NextResponse.json({ error: 'Missing translations' }, { status: 400 });
  }

  const payload = SUPPORTED_LOCALES.reduce(
    (acc, loc) => ({
      ...acc,
      [loc]: {
        title: incoming[loc]?.title || '',
        teaser: incoming[loc]?.teaser || '',
        description: incoming[loc]?.description || '',
      },
    }),
    {} as Record<Locale, LocaleFields>,
  );

  const messages = [
    {
      role: 'system',
      content:
        'You are translating holiday rental listing copy between Finnish, Swedish, and English. Fill in missing locales, keep existing text unchanged, preserve meaning and tone, and respond with JSON only.',
    },
    {
      role: 'user',
      content: JSON.stringify(
        {
          sourceLocale: currentLocale,
          targetLocales: SUPPORTED_LOCALES.filter((l) => l !== currentLocale),
          locales: payload,
        },
        null,
        2,
      ),
    },
    {
      role: 'system',
      content:
        'Return JSON with top-level "locales" containing keys en, fi, sv. Each locale has title, teaser, description. Do not include explanations.',
    },
  ];

  let content = '';
  try {
    const res = await fetch('https://api.openai.com/v1/chat/completions', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${apiKey}`,
      },
      body: JSON.stringify({
        model: 'gpt-4o-mini',
        temperature: 0.2,
        messages,
      }),
    });

    if (!res.ok) {
      const errText = await res.text();
      return NextResponse.json({ error: 'AI request failed', detail: errText }, { status: 500 });
    }

    const data = await res.json();
    content = data?.choices?.[0]?.message?.content ?? '';
  } catch (err) {
    return NextResponse.json({ error: 'AI request failed' }, { status: 500 });
  }

  const jsonText = content.match(/\{[\s\S]*\}/)?.[0] ?? content;
  try {
    const parsed = JSON.parse(jsonText);
    const locales = parsed?.locales || parsed;
    if (!locales) throw new Error('missing locales');
    const result = SUPPORTED_LOCALES.reduce(
      (acc, loc) => ({
        ...acc,
        [loc]: {
          title: locales[loc]?.title ?? '',
          teaser: locales[loc]?.teaser ?? '',
          description: locales[loc]?.description ?? '',
        },
      }),
      {} as Record<Locale, LocaleFields>,
    );
    return NextResponse.json({ translations: result });
  } catch (err) {
    return NextResponse.json({ error: 'Could not parse AI response' }, { status: 500 });
  }
}