sundog-calculator/dog-food-calculator-widget.js

/**
 * Dog Calorie Calculator Widget
 * Embeddable JavaScript widget for calculating dog's daily calorie requirements
 * by Canine Nutrition and Wellness - https://caninenutritionandwellness.com
 * 
 * Basic Usage: 
 * <script src="https://yourdomain.com/dog-calculator-widget.js"></script>
 * <div id="dog-calorie-calculator"></div>
 * 
 * Advanced Usage with theme option:
 * <script src="https://yourdomain.com/dog-calculator-widget.js"></script>
 * <div id="dog-calorie-calculator" data-theme="dark"></div>
 * 
 * Or with JavaScript:
 * new DogCalorieCalculatorWidget(container, { theme: 'light' }); // 'light', 'dark', 'system'
 */

(function() {
    'use strict';

    // Widget styles - Using Shadow DOM for better isolation where supported
    const widgetStyles = `
        .dog-calc-widget {
            max-width: 600px;
            margin: 0 auto;
            padding: 24px;
            font-family: 'Montserrat', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
            line-height: 1.5;
            color: #6f3f6d;
            box-sizing: border-box;
        }

        .dog-calc-widget *,
        .dog-calc-widget *::before,
        .dog-calc-widget *::after {
            box-sizing: border-box;
        }

        .dog-calc-section {
            background: #fdfcfe;
            border: 1px solid #e8e3ed;
            border-radius: 8px 8px 0 0;
            padding: 24px;
            margin-bottom: 0;
            box-shadow: 0 3px 6px rgba(0, 0, 0, 0.08);
        }

        .dog-calc-section-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 24px;
            flex-wrap: wrap;
            gap: 16px;
        }

        .dog-calc-section h2 {
            margin: 0;
            color: #6f3f6d;
            font-size: 1.5rem;
            font-weight: 600;
        }

        /* Unit Switch */
        .dog-calc-unit-switch {
            display: flex;
            align-items: center;
            gap: 12px;
        }

        .dog-calc-unit-label {
            font-size: 0.9rem;
            font-weight: 500;
            color: #635870;
            transition: color 0.2s ease;
        }

        .dog-calc-unit-label.active {
            color: #6f3f6d;
            font-weight: 600;
        }

        .dog-calc-switch {
            position: relative;
            display: inline-block;
            width: 48px;
            height: 24px;
        }

        .dog-calc-switch input {
            opacity: 0;
            width: 0;
            height: 0;
        }

        .dog-calc-slider {
            position: absolute;
            cursor: pointer;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background-color: #e8e3ed;
            transition: 0.3s;
            border-radius: 24px;
        }

        .dog-calc-slider:before {
            position: absolute;
            content: "";
            height: 18px;
            width: 18px;
            left: 3px;
            bottom: 3px;
            background-color: white;
            transition: 0.3s;
            border-radius: 50%;
            box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
        }

        .dog-calc-switch input:checked + .dog-calc-slider {
            background-color: #f19a5f;
        }

        .dog-calc-switch input:checked + .dog-calc-slider:before {
            transform: translateX(24px);
        }

        .dog-calc-form-group {
            margin-bottom: 20px;
        }

        .dog-calc-form-group label {
            display: block;
            margin-bottom: 8px;
            font-weight: 500;
            color: #6f3f6d;
            font-size: 1rem;
        }

        .dog-calc-form-group select,
        .dog-calc-form-group input[type="number"],
        .dog-calc-form-group input[type="text"] {
            width: 100%;
            padding: 12px 16px;
            border: 1px solid #e8e3ed;
            border-radius: 6px;
            font-size: 1rem;
            font-family: inherit;
            background-color: #ffffff;
            color: #6f3f6d;
            transition: all 0.2s ease;
            -webkit-appearance: none;
            -moz-appearance: none;
            appearance: none;
            background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%236f3f6d' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
            background-repeat: no-repeat;
            background-position: right 12px center;
            background-size: 20px;
            padding-right: 40px;
        }

        .dog-calc-form-group select option {
            background-color: #ffffff;
            color: #6f3f6d;
        }

        .dog-calc-form-group input[type="number"],
        .dog-calc-form-group input[type="text"] {
            background-image: none;
            padding-right: 16px;
        }

        .dog-calc-form-group select:focus,
        .dog-calc-form-group input[type="number"]:focus,
        .dog-calc-form-group input[type="text"]:focus {
            outline: none;
            border-color: #f19a5f;
            background-color: #ffffff;
            box-shadow: 0 0 0 3px rgba(241, 154, 95, 0.1);
        }

        .dog-calc-form-group input[readonly] {
            background-color: #f8f5fa;
            cursor: not-allowed;
            color: #635870;
        }

        .dog-calc-results {
            background: linear-gradient(135deg, rgba(241, 154, 95, 0.08) 0%, rgba(241, 154, 95, 0.04) 100%);
            border: 1px solid rgba(241, 154, 95, 0.2);
            border-radius: 6px;
            padding: 20px;
            margin-top: 24px;
        }

        .dog-calc-result-item {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 12px;
        }

        .dog-calc-result-item:last-child {
            margin-bottom: 0;
        }

        .dog-calc-result-label {
            font-weight: 500;
            color: #6f3f6d;
            font-size: 0.95rem;
        }

        .dog-calc-result-value {
            font-weight: 600;
            color: #6f3f6d;
            font-size: 1.1rem;
            padding: 4px 12px;
            background: rgba(241, 154, 95, 0.15);
            border-radius: 4px;
        }

        .dog-calc-collapsible {
            background: #ffffff;
            border: 1px solid #e8e3ed;
            border-top: none;
            margin-bottom: 0;
            overflow: hidden;
            box-shadow: 0 3px 6px rgba(0, 0, 0, 0.08);
        }

        .dog-calc-collapsible-header {
            background: #f8f5fa;
            padding: 20px 24px;
            border-bottom: 1px solid #e8e3ed;
        }

        .dog-calc-collapsible-header h3 {
            margin: 0;
            font-size: 1.25rem;
            color: #6f3f6d;
            font-weight: 600;
        }

        .dog-calc-collapsible-content {
            display: block;
        }

        .dog-calc-collapsible-inner {
            padding: 24px;
        }

        /* Action Buttons */
        .dog-calc-action-buttons {
            display: flex;
            justify-content: center;
            gap: 16px;
            padding: 20px;
            background: #f8f5fa;
            border-left: 1px solid #e8e3ed;
            border-right: 1px solid #e8e3ed;
            margin-top: -1px;
        }

        .dog-calc-btn {
            padding: 8px 16px;
            border: 1px solid #e8e3ed;
            border-radius: 6px;
            font-size: 0.9rem;
            font-weight: 500;
            font-family: inherit;
            cursor: pointer;
            transition: all 0.2s ease;
            display: inline-flex;
            align-items: center;
            gap: 6px;
            background: white;
            color: #6f3f6d;
        }

        .dog-calc-btn:hover {
            transform: translateY(-1px);
            box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
        }

        .dog-calc-btn-share:hover {
            border-color: #9f5999;
            color: #9f5999;
        }

        .dog-calc-btn-embed:hover {
            border-color: #7fa464;
            color: #7fa464;
        }

        .dog-calc-input-group {
            display: flex;
            gap: 16px;
            align-items: flex-end;
        }

        .dog-calc-input-group .dog-calc-form-group {
            flex: 1;
            margin-bottom: 0;
        }

        .dog-calc-unit-select {
            min-width: 120px;
        }

        .dog-calc-error {
            color: #e87159;
            font-size: 0.875rem;
            margin-top: 6px;
            font-weight: 500;
        }

        .dog-calc-hidden {
            display: none !important;
        }

        .dog-calc-footer {
            text-align: center;
            padding: 20px;
            background: #fdfcfe;
            border: 1px solid #e8e3ed;
            border-radius: 0 0 8px 8px;
            border-top: none;
            margin-top: -1px;
        }

        .dog-calc-footer a {
            color: #9f5999;
            text-decoration: none;
            font-size: 0.9rem;
            font-weight: 500;
            transition: color 0.2s ease;
        }

        .dog-calc-footer a:hover {
            color: #f19a5f;
            text-decoration: underline;
        }

        @media (max-width: 576px) {
            .dog-calc-widget {
                padding: 16px;
            }

            .dog-calc-section,
            .dog-calc-collapsible-inner {
                padding: 20px;
            }

            .dog-calc-section h2,
            .dog-calc-collapsible-header h3 {
                font-size: 1.3rem;
            }

            .dog-calc-input-group {
                flex-direction: column;
                gap: 20px;
            }

            .dog-calc-input-group .dog-calc-form-group {
                margin-bottom: 20px;
            }

            .dog-calc-result-item {
                flex-direction: column;
                align-items: flex-start;
                gap: 8px;
            }

            .dog-calc-result-value {
                align-self: stretch;
                text-align: center;
            }

            .dog-calc-collapsible-header {
                padding: 16px 20px;
            }

            .dog-calc-section-header {
                flex-direction: column;
                align-items: stretch;
                gap: 12px;
            }

            .dog-calc-section h2 {
                text-align: center;
            }

            .dog-calc-unit-switch {
                justify-content: center;
            }

            .dog-calc-action-buttons {
                flex-direction: column;
                padding: 16px;
            }

            .dog-calc-btn {
                width: 100%;
                justify-content: center;
            }
        }

        /* Dark theme - manual override */
        .dog-calc-widget.dog-calc-theme-dark {
            color: #f5f3f7;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-section,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-collapsible {
            background: #24202d;
            border-color: #433c4f;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-collapsible-header {
            background: #312b3b;
            border-color: #433c4f;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-collapsible-header:hover {
            background: #3a3446;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-section h2,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-collapsible-header h3,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group label,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-result-label {
            color: #f5f3f7;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group select,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group input[type="number"],
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group input[type="text"] {
            background-color: #312b3b;
            border-color: #433c4f;
            color: #f5f3f7;
            background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23f5f3f7' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group select option {
            background-color: #312b3b;
            color: #f5f3f7;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group select:focus,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group input[type="number"]:focus,
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group input[type="text"]:focus {
            background-color: #312b3b;
            border-color: #f19a5f;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-form-group input[readonly] {
            background-color: #433c4f;
            color: #b8b0c2;
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-results {
            background: linear-gradient(135deg, rgba(241, 154, 95, 0.15) 0%, rgba(241, 154, 95, 0.08) 100%);
            border-color: rgba(241, 154, 95, 0.3);
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-result-value {
            color: #f5f3f7;
            background: rgba(241, 154, 95, 0.2);
        }
            
        .dog-calc-widget.dog-calc-theme-dark .dog-calc-footer {
            background: #24202d;
            border-color: #433c4f;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-unit-label {
            color: #b8b0c2;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-unit-label.active {
            color: #f5f3f7;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-slider {
            background-color: #433c4f;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-action-buttons {
            background: #312b3b;
            border-color: #433c4f;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-btn {
            background: #433c4f;
            border-color: #433c4f;
            color: #f5f3f7;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-btn:hover {
            background: #524a5f;
            border-color: #524a5f;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-btn-share:hover {
            border-color: #9f5999;
            color: #f19a5f;
        }

        .dog-calc-widget.dog-calc-theme-dark .dog-calc-btn-embed:hover {
            border-color: #7fa464;
            color: #7fa464;
        }

        /* System theme - follows user's OS preference */
        @media (prefers-color-scheme: dark) {
            .dog-calc-widget.dog-calc-theme-system {
                color: #f5f3f7;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-section,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-collapsible {
                background: #24202d;
                border-color: #433c4f;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-collapsible-header {
                background: #312b3b;
                border-color: #433c4f;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-collapsible-header:hover {
                background: #3a3446;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-section h2,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-collapsible-header h3,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group label,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-result-label {
                color: #f5f3f7;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-unit-label {
                color: #b8b0c2;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-unit-label.active {
                color: #f5f3f7;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-slider {
                background-color: #433c4f;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group select,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group input[type="number"],
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group input[type="text"] {
                background-color: #312b3b;
                border-color: #433c4f;
                color: #f5f3f7;
                background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23f5f3f7' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group select option {
                background-color: #312b3b;
                color: #f5f3f7;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group select:focus,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group input[type="number"]:focus,
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group input[type="text"]:focus {
                background-color: #312b3b;
                border-color: #f19a5f;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-form-group input[readonly] {
                background-color: #433c4f;
                color: #b8b0c2;
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-results {
                background: linear-gradient(135deg, rgba(241, 154, 95, 0.15) 0%, rgba(241, 154, 95, 0.08) 100%);
                border-color: rgba(241, 154, 95, 0.3);
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-result-value {
                color: #f5f3f7;
                background: rgba(241, 154, 95, 0.2);
            }
            
            .dog-calc-widget.dog-calc-theme-system .dog-calc-footer {
                background: #24202d;
                border-color: #433c4f;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-action-buttons {
                background: #312b3b;
                border-color: #433c4f;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-btn {
                background: #433c4f;
                border-color: #433c4f;
                color: #f5f3f7;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-btn:hover {
                background: #524a5f;
                border-color: #524a5f;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-btn-share:hover {
                border-color: #9f5999;
                color: #f19a5f;
            }

            .dog-calc-widget.dog-calc-theme-system .dog-calc-btn-embed:hover {
                border-color: #7fa464;
                color: #7fa464;
            }
        }
    `;

    // Widget HTML template
    const widgetTemplate = `
        <div class="dog-calc-widget">
            <div class="dog-calc-section">
                <div class="dog-calc-section-header">
                    <h2>Dog's Characteristics</h2>
                    <div class="dog-calc-unit-switch">
                        <span class="dog-calc-unit-label active" id="metricLabel">Metric</span>
                        <label class="dog-calc-switch">
                            <input type="checkbox" id="unitToggle">
                            <span class="dog-calc-slider"></span>
                        </label>
                        <span class="dog-calc-unit-label" id="imperialLabel">Imperial</span>
                    </div>
                </div>
                
                <div class="dog-calc-form-group">
                    <label for="dogType">Dog Type / Activity Level:</label>
                    <select id="dogType" aria-describedby="dogTypeHelp">
                        <option value="">Select dog type...</option>
                        <option value="3.0">Puppy (0-4 months)</option>
                        <option value="2.0">Puppy (4 months - adult)</option>
                        <option value="1.2">Adult - inactive/obese</option>
                        <option value="1.6">Adult (neutered/spayed) - average activity</option>
                        <option value="1.8">Adult (intact) - average activity</option>
                        <option value="1.0">Adult - weight loss</option>
                        <option value="1.7">Adult - weight gain</option>
                        <option value="2.0">Working dog - light work</option>
                        <option value="3.0">Working dog - moderate work</option>
                        <option value="5.0">Working dog - heavy work</option>
                        <option value="1.1">Senior dog</option>
                    </select>
                </div>

                <div class="dog-calc-form-group">
                    <label for="weight" id="weightLabel">Dog's Weight (kg):</label>
                    <input type="number" id="weight" min="0.1" step="0.1" placeholder="Enter weight in kg" aria-describedby="weightHelp">
                    <div id="weightError" class="dog-calc-error dog-calc-hidden">Please enter a valid weight (minimum 0.1 kg)</div>
                </div>

                <div class="dog-calc-results" id="calorieResults" style="display: none;">
                    <div class="dog-calc-result-item">
                        <span class="dog-calc-result-label">Resting Energy Requirement (RER):</span>
                        <span class="dog-calc-result-value" id="rerValue">- cal/day</span>
                    </div>
                    <div class="dog-calc-result-item">
                        <span class="dog-calc-result-label">Maintenance Energy Requirement (MER):</span>
                        <span class="dog-calc-result-value" id="merValue">- cal/day</span>
                    </div>
                </div>
            </div>

            <div class="dog-calc-collapsible active" id="foodCalculator">
                <div class="dog-calc-collapsible-header">
                    <h3>How much should I feed?</h3>
                </div>
                <div class="dog-calc-collapsible-content">
                    <div class="dog-calc-collapsible-inner">
                        <div class="dog-calc-form-group">
                            <label for="foodEnergy" id="foodEnergyLabel">Food Energy Content (kcal/100g):</label>
                            <input type="number" id="foodEnergy" min="1" step="1" placeholder="Enter kcal per 100g" aria-describedby="foodEnergyHelp">
                            <div id="foodEnergyError" class="dog-calc-error dog-calc-hidden">Please enter a valid energy content (minimum 1 kcal/100g)</div>
                        </div>

                        <div class="dog-calc-results" id="dailyFoodResults" style="display: none;">
                            <div class="dog-calc-result-item">
                                <span class="dog-calc-result-label">Daily Food Amount:</span>
                                <span class="dog-calc-result-value" id="dailyFoodValue">- g/day</span>
                            </div>
                        </div>

                        <div class="dog-calc-form-group" style="margin-top: 20px;">
                            <label for="days">Number of Days:</label>
                            <input type="number" id="days" min="1" step="1" value="1" placeholder="Enter number of days" aria-describedby="daysHelp">
                            <div id="daysError" class="dog-calc-error dog-calc-hidden">Please enter a valid number of days (minimum 1)</div>
                        </div>

                        <div class="dog-calc-input-group">
                            <div class="dog-calc-form-group">
                                <label for="totalFoodDisplay">Total Food Amount:</label>
                                <input type="text" id="totalFoodDisplay" readonly>
                            </div>
                            <div class="dog-calc-form-group">
                                <label for="unit">Unit:</label>
                                <select id="unit" class="dog-calc-unit-select" aria-describedby="unitHelp">
                                    <option value="g">grams (g)</option>
                                    <option value="kg">kilograms (kg)</option>
                                    <option value="oz">ounces (oz)</option>
                                    <option value="lb">pounds (lb)</option>
                                </select>
                            </div>
                        </div>
                    </div>
                </div>
            </div>

            <div class="dog-calc-action-buttons">
                <button class="dog-calc-btn dog-calc-btn-share" onclick="alert('Share functionality not available in widget mode')">
                    Share
                </button>
                <button class="dog-calc-btn dog-calc-btn-embed" onclick="alert('Embed functionality not available in widget mode')">
                    Embed
                </button>
            </div>

            <div class="dog-calc-footer">
                <a href="https://caninenutritionandwellness.com" target="_blank" rel="noopener noreferrer">
                    by caninenutritionandwellness.com
                </a>
            </div>
        </div>
    `;

    // Calculator class
    class DogCalorieCalculatorWidget {
        constructor(container, options = {}) {
            this.container = container;
            this.currentMER = 0;
            this.isImperial = false;
            this.theme = options.theme || 'system'; // 'light', 'dark', 'system'
            this.init();
        }

        init() {
            this.injectStyles();
            this.injectHTML();
            this.applyTheme();
            this.bindEvents();
            this.updateUnitLabels();
        }

        injectStyles() {
            if (!document.getElementById('dog-calc-widget-styles')) {
                const style = document.createElement('style');
                style.id = 'dog-calc-widget-styles';
                style.textContent = widgetStyles;
                document.head.appendChild(style);
            }
        }

        injectHTML() {
            this.container.innerHTML = widgetTemplate;
        }

        applyTheme() {
            const widget = this.container.querySelector('.dog-calc-widget');
            if (!widget) return;

            // Remove existing theme classes
            widget.classList.remove('dog-calc-theme-light', 'dog-calc-theme-dark', 'dog-calc-theme-system');
            
            // Apply new theme class
            widget.classList.add(`dog-calc-theme-${this.theme}`);
        }

        bindEvents() {
            const weightInput = this.container.querySelector('#weight');
            const dogTypeSelect = this.container.querySelector('#dogType');
            const foodEnergyInput = this.container.querySelector('#foodEnergy');
            const daysInput = this.container.querySelector('#days');
            const unitSelect = this.container.querySelector('#unit');
            const unitToggle = this.container.querySelector('#unitToggle');

            if (weightInput) {
                weightInput.addEventListener('input', () => this.updateCalorieCalculations());
                weightInput.addEventListener('blur', () => this.validateWeight());
            }
            
            if (dogTypeSelect) dogTypeSelect.addEventListener('change', () => this.updateCalorieCalculations());
            
            if (foodEnergyInput) {
                foodEnergyInput.addEventListener('input', () => this.updateFoodCalculations());
                foodEnergyInput.addEventListener('blur', () => this.validateFoodEnergy());
            }
            
            if (daysInput) {
                daysInput.addEventListener('input', () => this.updateFoodCalculations());
                daysInput.addEventListener('blur', () => this.validateDays());
            }
            
            if (unitSelect) unitSelect.addEventListener('change', () => this.updateFoodCalculations());
            
            if (unitToggle) unitToggle.addEventListener('change', () => this.toggleUnits());
        }

        toggleUnits() {
            const toggle = this.container.querySelector('#unitToggle');
            this.isImperial = toggle.checked;
            
            this.updateUnitLabels();
            this.convertExistingValues();
            this.updateCalorieCalculations();
        }

        updateUnitLabels() {
            const metricLabel = this.container.querySelector('#metricLabel');
            const imperialLabel = this.container.querySelector('#imperialLabel');
            const weightLabel = this.container.querySelector('#weightLabel');
            const foodEnergyLabel = this.container.querySelector('#foodEnergyLabel');
            const weightInput = this.container.querySelector('#weight');
            const foodEnergyInput = this.container.querySelector('#foodEnergy');
            const unitSelect = this.container.querySelector('#unit');

            if (metricLabel && imperialLabel) {
                metricLabel.classList.toggle('active', !this.isImperial);
                imperialLabel.classList.toggle('active', this.isImperial);
            }

            if (this.isImperial) {
                if (weightLabel) weightLabel.textContent = "Dog's Weight (lbs):";
                if (weightInput) {
                    weightInput.placeholder = "Enter weight in lbs";
                    weightInput.min = "0.2";
                    weightInput.step = "0.1";
                }
                if (foodEnergyLabel) foodEnergyLabel.textContent = "Food Energy Content (kcal/oz):";
                if (foodEnergyInput) {
                    foodEnergyInput.placeholder = "Enter kcal per oz";
                    foodEnergyInput.min = "0.03";
                    foodEnergyInput.step = "0.01";
                }
                if (unitSelect) {
                    unitSelect.innerHTML = `
                        <option value="oz">ounces (oz)</option>
                        <option value="lb">pounds (lb)</option>
                        <option value="g">grams (g)</option>
                        <option value="kg">kilograms (kg)</option>
                    `;
                }
            } else {
                if (weightLabel) weightLabel.textContent = "Dog's Weight (kg):";
                if (weightInput) {
                    weightInput.placeholder = "Enter weight in kg";
                    weightInput.min = "0.1";
                    weightInput.step = "0.1";
                }
                if (foodEnergyLabel) foodEnergyLabel.textContent = "Food Energy Content (kcal/100g):";
                if (foodEnergyInput) {
                    foodEnergyInput.placeholder = "Enter kcal per 100g";
                    foodEnergyInput.min = "1";
                    foodEnergyInput.step = "1";
                }
                if (unitSelect) {
                    unitSelect.innerHTML = `
                        <option value="g">grams (g)</option>
                        <option value="kg">kilograms (kg)</option>
                        <option value="oz">ounces (oz)</option>
                        <option value="lb">pounds (lb)</option>
                    `;
                }
            }
        }

        convertExistingValues() {
            const weightInput = this.container.querySelector('#weight');
            const foodEnergyInput = this.container.querySelector('#foodEnergy');

            if (weightInput && weightInput.value) {
                const currentWeight = parseFloat(weightInput.value);
                if (!isNaN(currentWeight)) {
                    if (this.isImperial) {
                        weightInput.value = this.formatNumber(currentWeight * 2.20462, 1);
                    } else {
                        weightInput.value = this.formatNumber(currentWeight / 2.20462, 1);
                    }
                }
            }

            if (foodEnergyInput && foodEnergyInput.value) {
                const currentEnergy = parseFloat(foodEnergyInput.value);
                if (!isNaN(currentEnergy)) {
                    if (this.isImperial) {
                        foodEnergyInput.value = this.formatNumber(currentEnergy / 3.52739, 2);
                    } else {
                        foodEnergyInput.value = this.formatNumber(currentEnergy * 3.52739, 0);
                    }
                }
            }
        }

        getWeightInKg() {
            const weightInput = this.container.querySelector('#weight');
            if (!weightInput || !weightInput.value) return null;
            
            const weight = parseFloat(weightInput.value);
            if (isNaN(weight)) return null;
            
            return this.isImperial ? weight / 2.20462 : weight;
        }

        getFoodEnergyPer100g() {
            const foodEnergyInput = this.container.querySelector('#foodEnergy');
            if (!foodEnergyInput || !foodEnergyInput.value) return null;
            
            const energy = parseFloat(foodEnergyInput.value);
            if (isNaN(energy)) return null;
            
            return this.isImperial ? energy * 3.52739 : energy;
        }

        calculateRER(weightKg) {
            return 70 * Math.pow(weightKg, 0.75);
        }

        calculateMER(rer, factor) {
            return rer * factor;
        }

        validateInput(value, min = 0, isInteger = false) {
            const num = parseFloat(value);
            if (isNaN(num) || num < min) return false;
            if (isInteger && !Number.isInteger(num)) return false;
            return true;
        }

        showError(elementId, show = true) {
            const errorElement = this.container.querySelector('#' + elementId);
            if (errorElement) {
                if (show) {
                    errorElement.classList.remove('dog-calc-hidden');
                } else {
                    errorElement.classList.add('dog-calc-hidden');
                }
            }
        }

        convertUnits(grams, unit) {
            switch (unit) {
                case 'kg': return grams / 1000;
                case 'oz': return grams / 28.3495;
                case 'lb': return grams / 453.592;
                default: return grams;
            }
        }

        formatNumber(num, decimals = 0) {
            return num.toFixed(decimals).replace(/\.?0+$/, '');
        }

        validateWeight() {
            const weight = this.container.querySelector('#weight')?.value;
            if (weight && !this.validateInput(weight, 0.1)) {
                this.showError('weightError', true);
            } else {
                this.showError('weightError', false);
            }
        }

        validateFoodEnergy() {
            const energy = this.container.querySelector('#foodEnergy')?.value;
            if (energy && !this.validateInput(energy, 1)) {
                this.showError('foodEnergyError', true);
            } else {
                this.showError('foodEnergyError', false);
            }
        }

        validateDays() {
            const days = this.container.querySelector('#days')?.value;
            if (days && !this.validateInput(days, 1, true)) {
                this.showError('daysError', true);
            } else {
                this.showError('daysError', false);
            }
        }

        updateCalorieCalculations() {
            const dogTypeSelect = this.container.querySelector('#dogType');
            const calorieResults = this.container.querySelector('#calorieResults');
            const rerValue = this.container.querySelector('#rerValue');
            const merValue = this.container.querySelector('#merValue');

            if (!dogTypeSelect || !calorieResults || !rerValue || !merValue) {
                return;
            }

            const weightKg = this.getWeightInKg();
            const dogTypeFactor = dogTypeSelect.value;
            
            this.showError('weightError', false);
            
            if (!weightKg || weightKg < 0.1) {
                const weightInput = this.container.querySelector('#weight');
                if (weightInput && weightInput.value) this.showError('weightError', true);
                calorieResults.style.display = 'none';
                return;
            }

            if (!dogTypeFactor) {
                calorieResults.style.display = 'none';
                return;
            }

            const factor = parseFloat(dogTypeFactor);
            
            const rer = this.calculateRER(weightKg);
            const mer = this.calculateMER(rer, factor);
            
            this.currentMER = mer;
            
            rerValue.textContent = this.formatNumber(rer, 0) + ' cal/day';
            merValue.textContent = this.formatNumber(mer, 0) + ' cal/day';
            calorieResults.style.display = 'block';
            
            this.updateFoodCalculations();
        }

        updateFoodCalculations() {
            if (this.currentMER === 0) return;
            
            const daysInput = this.container.querySelector('#days');
            const unitSelect = this.container.querySelector('#unit');
            const dailyFoodResults = this.container.querySelector('#dailyFoodResults');
            const dailyFoodValue = this.container.querySelector('#dailyFoodValue');
            const totalFoodDisplay = this.container.querySelector('#totalFoodDisplay');

            if (!daysInput || !unitSelect || !dailyFoodResults || !dailyFoodValue || !totalFoodDisplay) {
                return;
            }

            const energyPer100g = this.getFoodEnergyPer100g();
            const days = daysInput.value;
            const unit = unitSelect.value;
            
            this.showError('foodEnergyError', false);
            this.showError('daysError', false);
            
            if (!energyPer100g || energyPer100g < 1) {
                const foodEnergyInput = this.container.querySelector('#foodEnergy');
                if (foodEnergyInput && foodEnergyInput.value) this.showError('foodEnergyError', true);
                dailyFoodResults.style.display = 'none';
                totalFoodDisplay.value = '';
                return;
            }

            if (!days || !this.validateInput(days, 1, true)) {
                if (days) this.showError('daysError', true);
                totalFoodDisplay.value = '';
                return;
            }

            const numDays = parseInt(days);
            
            const dailyFoodGrams = (this.currentMER / energyPer100g) * 100;
            const totalFoodGrams = dailyFoodGrams * numDays;
            
            dailyFoodValue.textContent = this.formatNumber(dailyFoodGrams, 1) + ' g/day';
            dailyFoodResults.style.display = 'block';
            
            const convertedAmount = this.convertUnits(totalFoodGrams, unit);
            const unitLabel = unit === 'g' ? 'g' : unit === 'kg' ? 'kg' : unit === 'oz' ? 'oz' : 'lb';
            const decimals = unit === 'g' ? 0 : unit === 'kg' ? 2 : 1;
            
            totalFoodDisplay.value = this.formatNumber(convertedAmount, decimals) + ' ' + unitLabel;
        }
    }

    // Auto-initialize widget
    function initDogCalorieCalculator() {
        const containers = document.querySelectorAll('#dog-calorie-calculator, .dog-calorie-calculator');
        containers.forEach(container => {
            if (!container.dataset.initialized) {
                const theme = container.dataset.theme || 'system';
                new DogCalorieCalculatorWidget(container, { theme });
                container.dataset.initialized = 'true';
            }
        });
    }

    // Initialize when DOM is ready
    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', initDogCalorieCalculator);
    } else {
        initDogCalorieCalculator();
    }

    // Expose for manual initialization
    window.DogCalorieCalculatorWidget = DogCalorieCalculatorWidget;

})();