/**
 * BOGO Service - Handles Buy One Get One logic
 * 
 * Processes BOGO rules from the API and calculates free items/discounts
 */
const BogoService = {
    /**
     * Check if a product has any BOGO rules
     * @param {Object} product 
     * @returns {boolean}
     */
    hasBogoRules(product) {
        return product.bogo_rules && product.bogo_rules.length > 0;
    },

    /**
     * Get the primary BOGO rule for a product (first one)
     * @param {Object} product 
     * @returns {Object|null}
     */
    getPrimaryBogoRule(product) {
        if (!this.hasBogoRules(product)) return null;
        return product.bogo_rules[0];
    },

    /**
     * Get BOGO label for display
     * @param {Object} product 
     * @returns {string|null}
     */
    getBogoLabel(product) {
        const rule = this.getPrimaryBogoRule(product);
        return rule ? rule.label : null;
    },

    /**
     * Calculate BOGO discount for cart items
     * 
     * @param {Array} cartItems - Array of cart items with product data
     * @param {Array} products - Full products list with BOGO rules
     * @returns {Object} { freeItems: [], discountAmount: number }
     */
    calculateBogoForCart(cartItems, products) {
        const result = {
            freeItems: [],
            discountAmount: 0,
            appliedRules: []
        };

        // Group cart items by product ID
        const itemsByProduct = this.groupCartItemsByProduct(cartItems);

        // Check each product group for BOGO eligibility
        for (const [productId, items] of Object.entries(itemsByProduct)) {
            const product = products.find(p => p.id == productId);
            if (!product || !this.hasBogoRules(product)) continue;

            const rule = this.getPrimaryBogoRule(product);
            const quantity = items.length;

            // Calculate how many free items based on the rule
            const bogoResult = this.applyBogoRule(rule, quantity, product, products);
            
            if (bogoResult.freeItems.length > 0 || bogoResult.discountAmount > 0) {
                result.freeItems.push(...bogoResult.freeItems);
                result.discountAmount += bogoResult.discountAmount;
                result.appliedRules.push({
                    rule,
                    productId: parseInt(productId),
                    productName: product.name,
                    ...bogoResult
                });
            }
        }

        return result;
    },

    /**
     * Group cart items by product ID
     * @param {Array} cartItems 
     * @returns {Object}
     */
    groupCartItemsByProduct(cartItems) {
        return cartItems.reduce((groups, item) => {
            const id = item.id;
            if (!groups[id]) groups[id] = [];
            groups[id].push(item);
            return groups;
        }, {});
    },

    /**
     * Apply a BOGO rule to calculate free items/discount
     * 
     * @param {Object} rule - BOGO rule from API
     * @param {number} quantity - Number of items in cart
     * @param {Object} product - The product
     * @param {Array} products - All products (for Buy X Get Y)
     * @returns {Object}
     */
    applyBogoRule(rule, quantity, product, products) {
        const result = {
            freeItems: [],
            discountAmount: 0,
            freeQuantity: 0
        };

        if (quantity < rule.buy_qty) {
            return result; // Not enough items to trigger BOGO
        }

        // Calculate how many times the rule applies
        let timesApplied = 1;
        if (rule.recursive) {
            timesApplied = Math.floor(quantity / rule.buy_qty);
        }

        const freeQty = timesApplied * rule.get_qty;
        result.freeQuantity = freeQty;

        if (rule.type === 'buy_x_get_x') {
            // Same product is free or discounted
            if (rule.discount_type === 'free_product' || rule.discount_value >= 100) {
                // Fully free - automatically add to cart
                result.discountAmount = freeQty * parseFloat(product.price);
                result.freeItems.push({
                    id: product.id,
                    name: product.name + ' (GRATIS)',
                    price: '0.00',
                    originalPrice: product.price,
                    isFree: true,
                    ruleId: rule.rule_id
                });
            }
            // For percentage and flat discounts, we DON'T automatically add items
            // These are handled manually via addBogoDiscountedItem() in cart.js
            // The user clicks a button to add the discounted item
        } else if (rule.type === 'buy_x_get_y' && rule.get_product_ids) {
            // Different product is free
            for (const freeProductId of rule.get_product_ids) {
                const freeProduct = products.find(p => p.id == freeProductId);
                if (!freeProduct) continue;

                if (rule.discount_type === 'free_product' || rule.discount_value >= 100) {
                    result.discountAmount += freeQty * parseFloat(freeProduct.price);
                    result.freeItems.push({
                        id: freeProduct.id,
                        name: freeProduct.name + ' (GRATIS)',
                        price: '0.00',
                        originalPrice: freeProduct.price,
                        isFree: true,
                        ruleId: rule.rule_id
                    });
                }
            }
        }

        return result;
    },

    /**
     * Get suggested free items for a product (for display before adding to cart)
     * 
     * @param {Object} product 
     * @param {Array} products 
     * @returns {Array}
     */
    getSuggestedFreeItems(product, products) {
        if (!this.hasBogoRules(product)) return [];

        const rule = this.getPrimaryBogoRule(product);
        const suggestions = [];

        if (rule.type === 'buy_x_get_y' && rule.get_product_ids) {
            for (const freeProductId of rule.get_product_ids) {
                const freeProduct = products.find(p => p.id == freeProductId);
                if (freeProduct) {
                    suggestions.push({
                        ...freeProduct,
                        bogoLabel: `Gratis bij ${rule.buy_qty}x ${product.name}`
                    });
                }
            }
        }

        return suggestions;
    }
};