import express from 'express';
import multer from 'multer';
import cors from 'cors';
import * as tf from '@tensorflow/tfjs';
import '@tensorflow/tfjs-backend-wasm';
import '@tensorflow/tfjs-backend-cpu';
import { createCanvas, loadImage } from 'canvas';
import { createRequire } from 'module';

// Pro importy CommonJS balíčků
const require = createRequire(import.meta.url);



// Import Upscaler using dynamic import
let Upscaler;

const app = express();
const PORT = process.env.PORT || 7860;

// Middleware
app.use(cors());
app.use(express.json({ limit: '50mb' }));
app.use(express.urlencoded({ extended: true, limit: '50mb' }));

// Serve static files from public directory
app.use(express.static('public'));

// Configure multer for file uploads
const upload = multer({
  storage: multer.memoryStorage(),
  limits: {
    fileSize: 10 * 1024 * 1024, // 10MB limit
  },
  fileFilter: (req, file, cb) => {
    if (file.mimetype.startsWith('image/')) {
      cb(null, true);
    } else {
      cb(new Error('Only image files are allowed'), false);
    }
  }
});

// Global upscaler instance
let upscalerInstance = null;

// Get model for scale and type
async function getModelForScaleAndType(scale, modelType) {
  switch (modelType) {
    case 'esrgan-slim':
      const { x2: slimX2, x3: slimX3, x4: slimX4 } = await import('@upscalerjs/esrgan-slim');
      if (scale === 2) return slimX2;
      if (scale === 3) return slimX3;
      return slimX4;

    case 'esrgan-medium':
      const { x2: mediumX2, x3: mediumX3, x4: mediumX4 } = await import('@upscalerjs/esrgan-medium');
      if (scale === 2) return mediumX2;
      if (scale === 3) return mediumX3;
      return mediumX4;

    case 'esrgan-thick':
      const { x2: thickX2, x3: thickX3, x4: thickX4 } = await import('@upscalerjs/esrgan-thick');
      if (scale === 2) return thickX2;
      if (scale === 3) return thickX3;
      return thickX4;

    default:
      const { x2: defaultX2, x3: defaultX3, x4: defaultX4 } = await import('@upscalerjs/esrgan-slim');
      if (scale === 2) return defaultX2;
      if (scale === 3) return defaultX3;
      return defaultX4;
  }
}

// Initialize upscaler with specific model
async function initializeUpscaler(scale = 2, modelType = 'esrgan-slim') {
  try {
    console.log(`Initializing upscaler with scale ${scale}x and model ${modelType}...`);

    if (!Upscaler) {
      const upscalerModule = await import('upscaler');
      Upscaler = upscalerModule.default;
    }

    const model = await getModelForScaleAndType(scale, modelType);
    upscalerInstance = new Upscaler({ model });

    console.log('Upscaler initialized successfully');
    return upscalerInstance;
  } catch (error) {
    console.error('Failed to initialize upscaler:', error);
    throw error;
  }
}

// Convert buffer to base64 data URL
function bufferToDataURL(buffer, mimeType = 'image/png') {
  const base64 = buffer.toString('base64');
  return `data:${mimeType};base64,${base64}`;
}

// Health check endpoint
app.get('/', (req, res) => {
  res.json({
    status: 'ok',
    message: 'AI Image Upscaler API',
    backend: tf.getBackend(),
    version: '1.0.0',
    endpoints: {
      upscale: 'POST /upscale',
      health: 'GET /'
    }
  });
});

// Main upscale endpoint
app.post('/upscale', upload.single('image'), async (req, res) => {
  try {
    if (!req.file) {
      return res.status(400).json({ error: 'No image file provided' });
    }

    const { scale = 2, modelType = 'esrgan-slim', patchSize = 128, padding = 8 } = req.body;
    
    // Validate parameters
    const validScales = [2, 3, 4];
    const validModels = ['esrgan-slim', 'esrgan-medium', 'esrgan-thick'];
    
    if (!validScales.includes(parseInt(scale))) {
      return res.status(400).json({ error: 'Invalid scale. Must be 2, 3, or 4' });
    }
    
    if (!validModels.includes(modelType)) {
      return res.status(400).json({ error: 'Invalid model type' });
    }

    console.log(`Processing image with scale ${scale}x, model ${modelType}`);
    
    // Initialize upscaler if needed
    if (!upscalerInstance) {
      await initializeUpscaler(parseInt(scale), modelType);
    }

    // Convert image buffer to data URL
    const inputDataURL = bufferToDataURL(req.file.buffer, req.file.mimetype);
    
    // Perform upscaling
    console.log('Starting upscaling...');
    const startTime = Date.now();
    
    const result = await upscalerInstance.upscale(inputDataURL, {
      output: 'base64',
      patchSize: parseInt(patchSize),
      padding: parseInt(padding),
      awaitNextFrame: true
    });
    
    const processingTime = Date.now() - startTime;
    console.log(`Upscaling completed in ${processingTime}ms`);

    // Return the upscaled image
    res.json({
      success: true,
      result: result,
      metadata: {
        scale: parseInt(scale),
        modelType: modelType,
        patchSize: parseInt(patchSize),
        padding: parseInt(padding),
        processingTime: processingTime,
        backend: tf.getBackend()
      }
    });

  } catch (error) {
    console.error('Upscaling error:', error);
    res.status(500).json({
      error: 'Failed to upscale image',
      message: error.message,
      backend: tf.getBackend()
    });
  }
});

// Error handling middleware
app.use((error, req, res, next) => {
  if (error instanceof multer.MulterError) {
    if (error.code === 'LIMIT_FILE_SIZE') {
      return res.status(400).json({ error: 'File too large. Maximum size is 10MB' });
    }
  }
  
  console.error('Unhandled error:', error);
  res.status(500).json({ error: 'Internal server error' });
});

// Initialize TensorFlow.js
async function initializeTensorFlow() {
  try {
    console.log('Initializing TensorFlow.js...');
    
    // Try WASM backend first
    try {
      await tf.setBackend('wasm');
      await tf.ready();
      console.log('TensorFlow.js initialized with WASM backend');
      console.log('Current backend:', tf.getBackend());
      return true;
    } catch (wasmError) {
      console.warn('WASM backend failed, trying CPU backend:', wasmError.message);
      
      // Fallback to CPU backend
      try {
        await tf.setBackend('cpu');
        await tf.ready();
        console.log('TensorFlow.js initialized with CPU backend');
        console.log('Current backend:', tf.getBackend());
        return true;
      } catch (cpuError) {
        console.error('Both WASM and CPU backends failed:', cpuError.message);
        return false;
      }
    }
  } catch (error) {
    console.error('Failed to initialize TensorFlow.js:', error);
    return false;
  }
}

// Start server
async function startServer() {
  try {
    // Initialize TensorFlow.js
    const tfInitialized = await initializeTensorFlow();
    if (!tfInitialized) {
      console.error('Failed to initialize TensorFlow.js. Exiting...');
      process.exit(1);
    }

    // Start the server
    app.listen(PORT, '0.0.0.0', () => {
      console.log(`🚀 Upscaler API server running on port ${PORT}`);
      console.log(`📊 TensorFlow.js backend: ${tf.getBackend()}`);
      console.log(`🔗 Health check: http://localhost:${PORT}/`);
    });
  } catch (error) {
    console.error('Failed to start server:', error);
    process.exit(1);
  }
}

// Handle graceful shutdown
process.on('SIGTERM', () => {
  console.log('Received SIGTERM, shutting down gracefully...');
  if (upscalerInstance) {
    try {
      upscalerInstance.dispose();
    } catch (error) {
      console.warn('Error disposing upscaler:', error);
    }
  }
  process.exit(0);
});

// Start the server
startServer();