const express = require('express');
const router = express.Router();
const UserSelection = require('../models/UserSelection');
const Recipe = require('../models/Recipe');
const jwt = require('jsonwebtoken');

// Middleware to authenticate JWT token
function authenticateToken(req, res, next) {
  const authHeader = req.headers['authorization'];
  const token = authHeader && authHeader.split(' ')[1];
  
  if (!token) {
    return res.status(401).json({ error: 'Access token required' });
  }
  
  jwt.verify(token, process.env.JWT_SECRET, (err, decoded) => {
    if (err) {
      return res.status(403).json({ error: 'Invalid or expired token' });
    }
    req.userId = decoded.userId;
    next();
  });
}

// Helper function to aggregate ingredients
async function aggregateIngredients(selectedRecipes) {
  const aggregated = {};
  
  for (const selection of selectedRecipes) {
    const recipe = await Recipe.findById(selection.recipeId);
    if (!recipe) continue;
    
    for (const ingredient of recipe.ingredients) {
      const key = `${ingredient.name}_${ingredient.unit}`;
      
      if (!aggregated[key]) {
        aggregated[key] = {
          name: ingredient.name,
          totalAmount: 0,
          unit: ingredient.unit,
          recipes: []
        };
      }
      
      const totalAmount = ingredient.amount * selection.quantity;
      aggregated[key].totalAmount += totalAmount;
      aggregated[key].recipes.push({
        recipeId: recipe._id,
        recipeTitle: recipe.title,
        amount: ingredient.amount,
        quantity: selection.quantity
      });
    }
  }
  
  return Object.values(aggregated);
}

// Get user's selections
router.get('/', authenticateToken, async (req, res) => {
  try {
    let userSelection = await UserSelection.findOne({ userId: req.userId })
      .populate('selectedRecipes.recipeId', 'title description imageUrl category');
    
    if (!userSelection) {
      userSelection = new UserSelection({
        userId: req.userId,
        selectedRecipes: [],
        aggregatedIngredients: []
      });
      await userSelection.save();
    }
    
    res.json(userSelection);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Add recipe to user's selection
router.post('/add', authenticateToken, async (req, res) => {
  try {
    const { recipeId, quantity = 1 } = req.body;
    
    // Verify recipe exists
    const recipe = await Recipe.findById(recipeId);
    if (!recipe) {
      return res.status(404).json({ error: 'Recipe not found' });
    }
    
    let userSelection = await UserSelection.findOne({ userId: req.userId });
    
    if (!userSelection) {
      userSelection = new UserSelection({
        userId: req.userId,
        selectedRecipes: [],
        aggregatedIngredients: []
      });
    }
    
    // Check if recipe is already selected
    const existingIndex = userSelection.selectedRecipes.findIndex(
      item => item.recipeId.toString() === recipeId
    );
    
    if (existingIndex >= 0) {
      // Update quantity if recipe already exists
      userSelection.selectedRecipes[existingIndex].quantity += quantity;
    } else {
      // Add new recipe selection
      userSelection.selectedRecipes.push({
        recipeId,
        quantity,
        addedAt: new Date()
      });
    }
    
    // Recalculate aggregated ingredients
    userSelection.aggregatedIngredients = await aggregateIngredients(userSelection.selectedRecipes);
    
    await userSelection.save();
    
    // Populate recipe details for response
    await userSelection.populate('selectedRecipes.recipeId', 'title description imageUrl category');
    
    res.json(userSelection);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Update recipe quantity in selection
router.put('/update', authenticateToken, async (req, res) => {
  try {
    const { recipeId, quantity } = req.body;
    
    if (quantity < 0) {
      return res.status(400).json({ error: 'Quantity must be positive' });
    }
    
    const userSelection = await UserSelection.findOne({ userId: req.userId });
    if (!userSelection) {
      return res.status(404).json({ error: 'No selections found' });
    }
    
    const recipeIndex = userSelection.selectedRecipes.findIndex(
      item => item.recipeId.toString() === recipeId
    );
    
    if (recipeIndex === -1) {
      return res.status(404).json({ error: 'Recipe not found in selections' });
    }
    
    if (quantity === 0) {
      // Remove recipe if quantity is 0
      userSelection.selectedRecipes.splice(recipeIndex, 1);
    } else {
      // Update quantity
      userSelection.selectedRecipes[recipeIndex].quantity = quantity;
    }
    
    // Recalculate aggregated ingredients
    userSelection.aggregatedIngredients = await aggregateIngredients(userSelection.selectedRecipes);
    
    await userSelection.save();
    await userSelection.populate('selectedRecipes.recipeId', 'title description imageUrl category');
    
    res.json(userSelection);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Remove recipe from selection
router.delete('/remove/:recipeId', authenticateToken, async (req, res) => {
  try {
    const { recipeId } = req.params;
    
    const userSelection = await UserSelection.findOne({ userId: req.userId });
    if (!userSelection) {
      return res.status(404).json({ error: 'No selections found' });
    }
    
    userSelection.selectedRecipes = userSelection.selectedRecipes.filter(
      item => item.recipeId.toString() !== recipeId
    );
    
    // Recalculate aggregated ingredients
    userSelection.aggregatedIngredients = await aggregateIngredients(userSelection.selectedRecipes);
    
    await userSelection.save();
    await userSelection.populate('selectedRecipes.recipeId', 'title description imageUrl category');
    
    res.json(userSelection);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

// Clear all selections
router.delete('/clear', authenticateToken, async (req, res) => {
  try {
    const userSelection = await UserSelection.findOne({ userId: req.userId });
    if (!userSelection) {
      return res.status(404).json({ error: 'No selections found' });
    }
    
    userSelection.selectedRecipes = [];
    userSelection.aggregatedIngredients = [];
    
    await userSelection.save();
    
    res.json(userSelection);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
});

module.exports = router;