/**
 * ==============================================================================
 * EATHVISION FRONTEND LOGIC
 * Description: Handles DOM manipulation, file uploads, and async API requests.
 * ==============================================================================
 */

document.addEventListener('DOMContentLoaded', () => {

    // --- DOM Elements ---
    const elements = {
        fileInput: document.getElementById('fileInput'),
        dropZone: document.getElementById('dropZone'),
        imagePreview: document.getElementById('imagePreview'),
        uploadUI: document.getElementById('uploadUI'),
        portionSlider: document.getElementById('portionSlider'),
        portionLabel: document.getElementById('portionLabel'),
        analyzeBtn: document.getElementById('analyzeBtn'),
        modelSelector: document.getElementById('modelSelector'),

        // State Containers
        states: {
            welcome: document.getElementById('welcomeState'),
            loading: document.getElementById('loadingState'),
            results: document.getElementById('resultsState')
        },

        // Result Fields
        res: {
            badge: document.getElementById('badgeModel'),
            name: document.getElementById('resDishName'),
            confText: document.getElementById('resConfText'),
            confBar: document.getElementById('resConfBar'),
            portion: document.getElementById('resPortion'),
            kcal: document.getElementById('resKcal'),
            prot: document.getElementById('resProt'),
            fat: document.getElementById('resFat'),
            carb: document.getElementById('resCarb'),
            ingList: document.getElementById('ingredientsList'),
            noIngMsg: document.getElementById('noIngredientsMsg')
        }
    };

    // --- Event Listeners ---

    // 1. Update portion slider label dynamically
    elements.portionSlider.addEventListener('input', (e) => {
        elements.portionLabel.innerText = `${e.target.value} g`;
    });

    // 2. Handle File Selection & Image Preview
    elements.fileInput.addEventListener('change', handleFileSelect);

    // 3. Drag and Drop Visual Feedback
    elements.dropZone.addEventListener('dragover', (e) => {
        e.preventDefault();
        elements.dropZone.classList.add('drag-active');
    });

    elements.dropZone.addEventListener('dragleave', () => {
        elements.dropZone.classList.remove('drag-active');
    });

    elements.dropZone.addEventListener('drop', (e) => {
        e.preventDefault();
        elements.dropZone.classList.remove('drag-active');
        if (e.dataTransfer.files.length > 0) {
            elements.fileInput.files = e.dataTransfer.files;
            handleFileSelect();
        }
    });

    // 4. API Request Execution
    elements.analyzeBtn.addEventListener('click', executeAnalysis);


    // --- Core Functions ---

    function handleFileSelect() {
        const file = elements.fileInput.files[0];
        if (file) {
            const reader = new FileReader();
            reader.onload = function (e) {
                elements.imagePreview.src = e.target.result;
                elements.imagePreview.classList.remove('hidden');
                elements.uploadUI.classList.add('hidden');
                // Make preview slightly transparent so the drop zone remains visible
                elements.imagePreview.classList.add('opacity-90');
            }
            reader.readAsDataURL(file);
        }
    }

    async function executeAnalysis() {
        if (elements.fileInput.files.length === 0) {
            alert("⚠️ Please select an image first.");
            return;
        }

        const file = elements.fileInput.files[0];
        const formData = new FormData();
        formData.append('file', file);
        formData.append('model_type', elements.modelSelector.value);
        formData.append('portion_g', elements.portionSlider.value);

        // Transition UI to Loading
        toggleState('loading');
        elements.analyzeBtn.disabled = true;

        try {
            // Call the local FastAPI backend
            const response = await fetch('/api/predict', {
                method: 'POST',
                body: formData
            });

            const data = await response.json();

            if (!response.ok) throw new Error(data.detail || "Server Error");

            // Populate AI Data
            elements.res.badge.innerText = data.ai_prediction.model_used.toUpperCase();
            elements.res.name.innerText = data.ai_prediction.dish_name;
            elements.res.confText.innerText = `${data.ai_prediction.confidence}%`;

            // Delay width application for smooth CSS transition
            setTimeout(() => {
                elements.res.confBar.style.width = `${data.ai_prediction.confidence}%`;
            }, 100);

            // Populate Nutrition Data
            elements.res.portion.innerText = data.nutrition_insights.portion_g;
            if (data.nutrition_insights.status === "success") {
                const b = data.nutrition_insights.base_data;
                elements.res.kcal.innerText = b.energy_kcal;
                elements.res.prot.innerText = b.protein_g;
                elements.res.fat.innerText = b.fat_g;
                elements.res.carb.innerText = b.carbs_g;
            } else {
                elements.res.kcal.innerText = "--";
                elements.res.prot.innerText = "--";
                elements.res.fat.innerText = "--";
                elements.res.carb.innerText = "--";
            }

            // Populate Ingredients Data
            elements.res.ingList.innerHTML = ''; // Clear previous
            if (data.ingredients && data.ingredients.length > 0) {
                elements.res.noIngMsg.classList.add('hidden');
                data.ingredients.forEach(ing => {
                    const li = document.createElement('li');
                    li.innerText = ing;
                    // Capitalize first letter
                    li.style.textTransform = "capitalize";
                    elements.res.ingList.appendChild(li);
                });
            } else {
                elements.res.noIngMsg.classList.remove('hidden');
            }

            // Show Results
            toggleState('results');

        } catch (error) {
            console.error("API Error:", error);
            alert("❌ Analysis failed: " + error.message);
            toggleState('welcome');
        } finally {
            elements.analyzeBtn.disabled = false;
        }
    }

    /**
     * Helper to toggle main view states
     * @param {string} targetState - 'welcome', 'loading', or 'results'
     */
    function toggleState(targetState) {
        elements.states.welcome.classList.add('hidden');
        elements.states.loading.classList.add('hidden');
        elements.states.results.classList.add('hidden');

        elements.states[targetState].classList.remove('hidden');

        // Reset progress bar if not in results view
        if (targetState !== 'results') {
            elements.res.confBar.style.width = '0%';
        }
    }
});