import tailwindcss from '@tailwindcss/vite';
import react from '@vitejs/plugin-react';
import fs from 'fs/promises';
import { existsSync } from 'fs';
import path from 'path';
import { defineConfig, Plugin } from 'vite';

const SAVES_DIR = path.resolve(__dirname, 'saves');

const ensureSavesDir = async () => {
  await fs.mkdir(SAVES_DIR, { recursive: true });
};

const sanitizeSaveName = (name: string) => {
  const cleaned = name
    .replace(/\.json$/i, '')
    .replace(/[<>:"/\\|?*\x00-\x1F]/g, '_')
    .trim();
  return `${cleaned || `save-${Date.now()}`}.json`;
};

const readJsonBody = async (req: any) => {
  const chunks: Buffer[] = [];
  for await (const chunk of req) {
    chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
  }
  const raw = Buffer.concat(chunks).toString('utf-8');
  return raw ? JSON.parse(raw) : {};
};

const sendJson = (res: any, statusCode: number, payload: unknown) => {
  res.statusCode = statusCode;
  res.setHeader('Content-Type', 'application/json; charset=utf-8');
  res.end(JSON.stringify(payload));
};

const localSavesPlugin = (): Plugin => ({
  name: 'local-saves-api',
  configureServer(server) {
    server.middlewares.use(async (req, res, next) => {
      if (!req.url?.startsWith('/api/saves')) {
        next();
        return;
      }

      try {
        await ensureSavesDir();
        const url = new URL(req.url, 'http://localhost');
        const fileNameFromPath = decodeURIComponent(url.pathname.replace(/^\/api\/saves\/?/, ''));

        if (req.method === 'GET' && url.pathname === '/api/saves') {
          const entries = await fs.readdir(SAVES_DIR);
          const files = await Promise.all(
            entries
              .filter((entry) => entry.toLowerCase().endsWith('.json'))
              .map(async (entry) => {
                const filePath = path.join(SAVES_DIR, entry);
                const stat = await fs.stat(filePath);
                let lineCount: number | null = null;
                let title = entry.replace(/\.json$/i, '');
                try {
                  const parsed = JSON.parse(await fs.readFile(filePath, 'utf-8'));
                  lineCount = Array.isArray(parsed?.lines) ? parsed.lines.length : null;
                  title = typeof parsed?.title === 'string' && parsed.title.trim() ? parsed.title : title;
                } catch {
                  lineCount = null;
                }

                return {
                  name: entry,
                  title,
                  savedAt: stat.mtime.toISOString(),
                  size: stat.size,
                  lineCount,
                };
              })
          );

          files.sort((a, b) => new Date(b.savedAt).getTime() - new Date(a.savedAt).getTime());
          sendJson(res, 200, { files });
          return;
        }

        if (req.method === 'GET' && fileNameFromPath) {
          const fileName = sanitizeSaveName(fileNameFromPath);
          const filePath = path.join(SAVES_DIR, fileName);
          if (!existsSync(filePath)) {
            sendJson(res, 404, { error: 'Save file not found' });
            return;
          }

          const content = await fs.readFile(filePath, 'utf-8');
          sendJson(res, 200, JSON.parse(content));
          return;
        }

        if (req.method === 'POST' && url.pathname === '/api/saves') {
          const body = await readJsonBody(req);
          const fileName = sanitizeSaveName(String(body.name || 'current'));
          const document = body.document;
          if (!document || typeof document !== 'object') {
            sendJson(res, 400, { error: 'Missing document payload' });
            return;
          }

          const filePath = path.join(SAVES_DIR, fileName);
          await fs.writeFile(filePath, JSON.stringify(document, null, 2), 'utf-8');
          const stat = await fs.stat(filePath);
          sendJson(res, 200, {
            file: {
              name: fileName,
              savedAt: stat.mtime.toISOString(),
              size: stat.size,
              lineCount: Array.isArray(document.lines) ? document.lines.length : null,
            },
          });
          return;
        }

        if (req.method === 'DELETE' && fileNameFromPath) {
          const fileName = sanitizeSaveName(fileNameFromPath);
          const filePath = path.join(SAVES_DIR, fileName);
          if (!existsSync(filePath)) {
            sendJson(res, 404, { error: 'Save file not found' });
            return;
          }
          await fs.unlink(filePath);
          sendJson(res, 200, { ok: true });
          return;
        }

        sendJson(res, 405, { error: 'Unsupported saves API request' });
      } catch (error) {
        console.error(error);
        sendJson(res, 500, { error: 'Local saves API failed' });
      }
    });
  },
});

export default defineConfig(() => {
  return {
    plugins: [react(), tailwindcss(), localSavesPlugin()],
    resolve: {
      alias: {
        '@': path.resolve(__dirname, '.'),
      },
    },
    server: {
      // HMR is disabled in AI Studio via DISABLE_HMR env var.
      // Do not modify—file watching is disabled to prevent flickering during agent edits.
      hmr: process.env.DISABLE_HMR !== 'true',
      // Disable file watching when DISABLE_HMR is true to save CPU during agent edits.
      watch: process.env.DISABLE_HMR === 'true' ? null : {},
    },
  };
});