Implement live collection preview system with contextual template selection

Replace isolated template previews with live collection reconstruction:
- Frontend now reconstructs collection container with all template variants
- Users click directly on rendered templates in proper CSS context
- Perfect preservation of grid/flex layouts and responsive behavior
- Simplified API: preview endpoint returns container_html + templates for frontend reconstruction
- Enhanced UX: WYSIWYG template selection shows exactly what will be added
- Removed redundant templates endpoint in favor of unified preview approach

Backend changes:
- Add GET /api/collections/{id}/preview endpoint
- Remove GET /api/collections/{id}/templates endpoint
- Return container HTML + templates for frontend reconstruction

Frontend changes:
- Replace isolated template modal with live collection preview
- Add generateLivePreview() method for container reconstruction
- Update CollectionManager to use preview API
- Add interactive CSS styling for template selection

This provides true contextual template selection where CSS inheritance,
grid layouts, and responsive design work perfectly in preview mode.

internal/api/handlers.go

@@ -405,8 +405,8 @@ func (h *ContentHandler) GetCollectionItems(w http.ResponseWriter, r *http.Reque
 	json.NewEncoder(w).Encode(items)
 }
 
-// GetCollectionTemplates handles GET /api/collections/{id}/templates
+// GetCollectionPreview handles GET /api/collections/{id}/preview
-func (h *ContentHandler) GetCollectionTemplates(w http.ResponseWriter, r *http.Request) {
+func (h *ContentHandler) GetCollectionPreview(w http.ResponseWriter, r *http.Request) {
 	collectionID := chi.URLParam(r, "id")
 	siteID := r.URL.Query().Get("site_id")
 
@@ -415,14 +415,24 @@ func (h *ContentHandler) GetCollectionTemplates(w http.ResponseWriter, r *http.R
 		return
 	}
 
+	// Get collection container
+	collection, err := h.repository.GetCollection(context.Background(), siteID, collectionID)
+	if err != nil {
+		http.Error(w, fmt.Sprintf("Collection not found: %v", err), http.StatusNotFound)
+		return
+	}
+
+	// Get all templates for this collection
 	templates, err := h.repository.GetCollectionTemplates(context.Background(), siteID, collectionID)
 	if err != nil {
-		http.Error(w, fmt.Sprintf("Database error: %v", err), http.StatusInternalServerError)
+		http.Error(w, fmt.Sprintf("Templates not found: %v", err), http.StatusInternalServerError)
 		return
 	}
 
 	response := map[string]interface{}{
-		"templates": templates,
+		"collection_id":  collectionID,
+		"container_html": collection.ContainerHTML,
+		"templates":      templates,
 	}
 
 	w.Header().Set("Content-Type", "application/json")
@@ -525,10 +535,10 @@ func (h *ContentHandler) RegisterRoutes(r chi.Router) {
 		// COLLECTION MANAGEMENT - Groups of related content
 		// =============================================================================
 		r.Route("/collections", func(r chi.Router) {
-			r.Get("/", h.GetAllCollections)                    // GET /api/collections?site_id=X
+			r.Get("/", h.GetAllCollections)                // GET /api/collections?site_id=X
-			r.Get("/{id}", h.GetCollection)                    // GET /api/collections/{id}?site_id=X
+			r.Get("/{id}", h.GetCollection)                // GET /api/collections/{id}?site_id=X
-			r.Get("/{id}/items", h.GetCollectionItems)         // GET /api/collections/{id}/items?site_id=X
+			r.Get("/{id}/items", h.GetCollectionItems)     // GET /api/collections/{id}/items?site_id=X
-			r.Get("/{id}/templates", h.GetCollectionTemplates) // GET /api/collections/{id}/templates?site_id=X
+			r.Get("/{id}/preview", h.GetCollectionPreview) // GET /api/collections/{id}/preview?site_id=X
 
 			// Protected routes
 			r.Group(func(r chi.Router) {

lib/src/core/api-client.js

@@ -243,25 +243,25 @@ export class ApiClient {
     }
 
     /**
-     * Get available templates for a collection
+     * Get collection preview data (container + templates for frontend reconstruction)
      * @param {string} collectionId - Collection ID
-     * @returns {Promise<Array>} Array of collection templates
+     * @returns {Promise<Object>} Object with collection_id, container_html, and templates
      */
-    async getCollectionTemplates(collectionId) {
+    async getCollectionPreview(collectionId) {
         try {
             const collectionsUrl = this.getCollectionsUrl();
-            const response = await fetch(`${collectionsUrl}/${collectionId}/templates?site_id=${this.siteId}`);
+            const response = await fetch(`${collectionsUrl}/${collectionId}/preview?site_id=${this.siteId}`);
             
             if (response.ok) {
                 const result = await response.json();
-                return result.templates || [];
+                return result;
             } else {
-                console.warn(`⚠️ Failed to fetch collection templates (${response.status}): ${collectionId}`);
+                console.warn(`⚠️ Failed to fetch collection preview (${response.status}): ${collectionId}`);
-                return [];
+                return null;
             }
         } catch (error) {
-            console.error('Failed to fetch collection templates:', collectionId, error);
+            console.error('Failed to fetch collection preview:', collectionId, error);
-            return [];
+            return null;
         }
     }
 

lib/src/styles/insertr.css

@@ -1098,3 +1098,147 @@ body:not(.insertr-edit-mode) .insertr-editing-hover::after {
         font-size: 14px;
     }
 }
+
+/* =================================================================
+   LIVE COLLECTION PREVIEW MODAL
+   ================================================================= */
+
+.insertr-collection-preview-modal {
+    background: var(--insertr-bg-primary);
+    color: var(--insertr-text-primary);
+    border-radius: var(--insertr-border-radius);
+    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
+    max-width: 90vw;
+    max-height: 90vh;
+    width: auto;
+    overflow: hidden;
+    position: relative;
+    z-index: var(--insertr-z-modal);
+    display: flex;
+    flex-direction: column;
+}
+
+.insertr-preview-header {
+    padding: var(--insertr-spacing-lg);
+    border-bottom: 1px solid var(--insertr-border-color);
+    text-align: center;
+}
+
+.insertr-preview-header h3 {
+    margin: 0 0 var(--insertr-spacing-xs) 0;
+    font-size: 1.2rem;
+    color: var(--insertr-text-primary);
+}
+
+.insertr-preview-header p {
+    margin: 0;
+    color: var(--insertr-text-secondary);
+    font-size: 0.9rem;
+}
+
+.insertr-preview-container {
+    padding: var(--insertr-spacing-lg);
+    overflow-y: auto;
+    flex: 1;
+}
+
+.insertr-preview-actions {
+    padding: var(--insertr-spacing-md) var(--insertr-spacing-lg);
+    border-top: 1px solid var(--insertr-border-color);
+    display: flex;
+    justify-content: center;
+    gap: var(--insertr-spacing-md);
+}
+
+/* Preview item selection styling */
+.insertr-preview-item {
+    cursor: pointer;
+    transition: all 0.2s ease;
+    position: relative;
+    border-radius: var(--insertr-border-radius);
+    overflow: hidden;
+}
+
+.insertr-preview-item:hover {
+    transform: scale(1.02);
+    box-shadow: 0 4px 20px rgba(59, 130, 246, 0.25);
+    z-index: 1;
+}
+
+.insertr-preview-item::after {
+    content: 'Click to select';
+    position: absolute;
+    top: var(--insertr-spacing-xs);
+    right: var(--insertr-spacing-xs);
+    background: rgba(59, 130, 246, 0.95);
+    color: white;
+    padding: var(--insertr-spacing-xs) var(--insertr-spacing-sm);
+    border-radius: var(--insertr-border-radius);
+    font-size: 0.75rem;
+    font-weight: 500;
+    opacity: 0;
+    transition: opacity 0.2s ease;
+    pointer-events: none;
+    white-space: nowrap;
+}
+
+.insertr-preview-item:hover::after {
+    opacity: 1;
+}
+
+/* Enhanced hover effect for better visual feedback */
+.insertr-preview-item:hover {
+    outline: 2px solid var(--insertr-primary-color);
+    outline-offset: 2px;
+}
+
+/* Button styling for preview modal */
+.insertr-template-btn {
+    background: var(--insertr-bg-secondary);
+    color: var(--insertr-text-primary);
+    border: 1px solid var(--insertr-border-color);
+    border-radius: var(--insertr-border-radius);
+    padding: var(--insertr-spacing-sm) var(--insertr-spacing-md);
+    font-size: 0.9rem;
+    cursor: pointer;
+    transition: all 0.2s ease;
+    min-width: 80px;
+}
+
+.insertr-template-btn:hover {
+    background: var(--insertr-bg-hover);
+    border-color: var(--insertr-primary-color);
+}
+
+.insertr-template-btn-cancel {
+    background: var(--insertr-bg-secondary);
+    color: var(--insertr-text-primary);
+}
+
+.insertr-template-btn-cancel:hover {
+    background: var(--insertr-danger-color);
+    color: white;
+    border-color: var(--insertr-danger-color);
+}
+
+/* Mobile responsiveness for preview modal */
+@media (max-width: 768px) {
+    .insertr-collection-preview-modal {
+        max-width: 95vw;
+        max-height: 95vh;
+        margin: var(--insertr-spacing-sm);
+    }
+    
+    .insertr-preview-container {
+        padding: var(--insertr-spacing-md);
+    }
+    
+    .insertr-preview-item:hover {
+        transform: scale(1.01);
+    }
+    
+    .insertr-preview-item::after {
+        font-size: 0.7rem;
+        padding: 2px 6px;
+    }
+}

lib/src/ui/collection-manager.js

@@ -28,7 +28,7 @@ export class CollectionManager {
         this.template = null;
         this.items = [];
         this.isActive = false;
-        this.cachedTemplates = null; // Cache for available templates
+        this.cachedPreview = null; // Cache for collection preview data
         
         // UI elements
         this.addButton = null;
@@ -412,16 +412,16 @@ export class CollectionManager {
         }
 
         try {
-            // 1. Get available templates for this collection
+            // 1. Get collection preview data
-            const templates = await this.getAvailableTemplates();
+            const previewData = await this.getCollectionPreview();
-            if (!templates || templates.length === 0) {
+            if (!previewData || !previewData.templates || previewData.templates.length === 0) {
                 console.error('❌ No templates available for collection:', this.collectionId);
                 alert('No templates available for this collection. Please refresh the page.');
                 return;
             }
 
-            // 2. Select template (auto-select if only one, otherwise present options)
+            // 2. Select template (auto-select if only one, otherwise show live preview)
-            const selectedTemplate = await this.selectTemplate(templates);
+            const selectedTemplate = await this.selectTemplate(previewData);
             if (!selectedTemplate) {
                 console.log('Template selection cancelled by user');
                 return;
@@ -465,46 +465,48 @@ export class CollectionManager {
     }
 
     /**
-     * Get available templates for this collection
+     * Get collection preview data (container + templates)
-     * @returns {Promise<Array>} Array of template objects
+     * @returns {Promise<Object>} Object with collection_id, container_html, and templates
      */
-    async getAvailableTemplates() {
+    async getCollectionPreview() {
         try {
-            if (!this.cachedTemplates) {
+            if (!this.cachedPreview) {
-                console.log('🔍 Fetching templates for collection:', this.collectionId);
+                console.log('🔍 Fetching preview for collection:', this.collectionId);
-                this.cachedTemplates = await this.apiClient.getCollectionTemplates(this.collectionId);
+                this.cachedPreview = await this.apiClient.getCollectionPreview(this.collectionId);
-                console.log('📋 Templates fetched:', this.cachedTemplates);
+                console.log('📋 Preview fetched:', this.cachedPreview);
             }
-            return this.cachedTemplates;
+            return this.cachedPreview;
         } catch (error) {
-            console.error('❌ Failed to fetch templates for collection:', this.collectionId, error);
+            console.error('❌ Failed to fetch preview for collection:', this.collectionId, error);
-            return [];
+            return null;
         }
     }
 
     /**
      * Select a template for creating new items
-     * @param {Array} templates - Available templates
+     * @param {Object} previewData - Preview data with container_html and templates
      * @returns {Promise<Object|null>} Selected template or null if cancelled
      */
-    async selectTemplate(templates) {
+    async selectTemplate(previewData) {
+        const templates = previewData.templates;
+        
         // Auto-select if only one template
         if (templates.length === 1) {
             console.log('🎯 Auto-selecting single template:', templates[0].name);
             return templates[0];
         }
 
-        // Present selection UI for multiple templates
+        // Present live collection preview for multiple templates
-        console.log('🎨 Multiple templates available, showing selection UI');
+        console.log('🎨 Multiple templates available, showing live preview');
-        return this.showTemplateSelectionModal(templates);
+        return this.showLiveCollectionPreview(previewData);
     }
 
     /**
-     * Show template selection modal
+     * Show live collection preview for template selection
-     * @param {Array} templates - Available templates
+     * @param {Object} previewData - Preview data with container_html and templates
      * @returns {Promise<Object|null>} Selected template or null if cancelled
      */
-    async showTemplateSelectionModal(templates) {
+    async showLiveCollectionPreview(previewData) {
         return new Promise((resolve) => {
             // Create modal overlay
             const overlay = document.createElement('div');
@@ -512,73 +514,38 @@ export class CollectionManager {
 
             // Create modal content
             const modal = document.createElement('div');
-            modal.className = 'insertr-template-selector';
+            modal.className = 'insertr-collection-preview-modal';
+
+            // Generate live preview by reconstructing collection with all templates
+            const previewHTML = this.generateLivePreview(previewData.container_html, previewData.templates);
 
-            // Create modal HTML using CSS classes
             modal.innerHTML = `
-                <h3>Choose Template</h3>
+                <div class="insertr-preview-header">
-                <div class="insertr-template-options">
+                    <h3>Choose Template</h3>
-                    ${templates.map(template => `
+                    <p>Click on the item you want to add</p>
-                        <div class="insertr-template-option ${template.is_default ? 'insertr-template-default' : ''}" 
-                             data-template-id="${template.template_id}">
-                            <div class="insertr-template-name">
-                                ${template.name}${template.is_default ? ' (default)' : ''}
-                            </div>
-                            <div class="insertr-template-preview-container">
-                                ${this.createStyledTemplatePreview(template.html_template)}
-                            </div>
-                        </div>
-                    `).join('')}
                 </div>
-                <div class="insertr-template-actions">
+                <div class="insertr-preview-container">
+                    ${previewHTML}
+                </div>
+                <div class="insertr-preview-actions">
                     <button class="insertr-template-btn insertr-template-btn-cancel">Cancel</button>
-                    <button class="insertr-template-btn insertr-template-btn-select" disabled>Add Item</button>
                 </div>
             `;
 
-            let selectedTemplate = null;
+            // Handle template selection by clicking on preview items
-            let userHasInteracted = false;
+            modal.addEventListener('click', (e) => {
+                const previewItem = e.target.closest('.insertr-preview-item');
+                if (previewItem) {
+                    const templateId = parseInt(previewItem.dataset.templateId);
+                    const selectedTemplate = previewData.templates.find(t => t.template_id === templateId);
                     
-            // Add event listeners for template selection
+                    if (selectedTemplate) {
-            modal.querySelectorAll('.insertr-template-option').forEach(option => {
+                        console.log('🎯 Template selected from preview:', selectedTemplate.name);
-                option.addEventListener('click', (e) => {
+                        document.body.removeChild(overlay);
-                    // Mark that user has interacted
+                        resolve(selectedTemplate);
-                    userHasInteracted = true;
+                    }
-                    
-                    // Remove previous selection from all options
-                    modal.querySelectorAll('.insertr-template-option').forEach(opt => {
-                        opt.classList.remove('insertr-template-selected');
-                    });
-                    
-                    // Add selection class to clicked option
-                    option.classList.add('insertr-template-selected');
-                    
-                    // Find selected template
-                    const templateId = parseInt(option.dataset.templateId);
-                    selectedTemplate = templates.find(t => t.template_id === templateId);
-                    
-                    // Enable select button
-                    const selectBtn = modal.querySelector('.insertr-template-btn-select');
-                    selectBtn.disabled = false;
-                    
-                    console.log('🎯 Template selected by user:', selectedTemplate.name);
-                });
-            });
-
-            // Auto-select default template only if user hasn't interacted
-            const defaultTemplate = templates.find(t => t.is_default);
-            if (defaultTemplate) {
-                // Set initial selection without triggering click event
-                selectedTemplate = defaultTemplate;
-                const defaultOption = modal.querySelector(`[data-template-id="${defaultTemplate.template_id}"]`);
-                if (defaultOption) {
-                    // Apply visual selection without click event
-                    defaultOption.classList.add('insertr-template-selected');
-                    const selectBtn = modal.querySelector('.insertr-template-btn-select');
-                    selectBtn.disabled = false;
-                    console.log('🎯 Default template pre-selected:', defaultTemplate.name);
                 }
-            }
+            });
 
             // Cancel button handler
             modal.querySelector('.insertr-template-btn-cancel').addEventListener('click', () => {
@@ -586,13 +553,6 @@ export class CollectionManager {
                 resolve(null);
             });
 
-            // Select button handler
-            modal.querySelector('.insertr-template-btn-select').addEventListener('click', () => {
-                console.log('✅ Adding item with template:', selectedTemplate ? selectedTemplate.name : 'none');
-                document.body.removeChild(overlay);
-                resolve(selectedTemplate);
-            });
-
             // Close on overlay click
             overlay.addEventListener('click', (e) => {
                 if (e.target === overlay) {
@@ -983,4 +943,57 @@ export class CollectionManager {
         
         console.log('🧹 CollectionManager destroyed');
     }
+
+    /**
+     * Generate live collection preview by reconstructing container with all template variants
+     * @param {string} containerHTML - Collection container HTML
+     * @param {Array} templates - Array of template objects
+     * @returns {string} HTML string with reconstructed collection
+     */
+    generateLivePreview(containerHTML, templates) {
+        try {
+            // Parse the container HTML
+            const tempContainer = document.createElement('div');
+            tempContainer.innerHTML = containerHTML;
+            const collectionContainer = tempContainer.querySelector('.insertr-add');
+            
+            if (!collectionContainer) {
+                console.error('❌ No .insertr-add container found in collection HTML');
+                return '<div>Preview generation failed</div>';
+            }
+            
+            // Clear existing children
+            collectionContainer.innerHTML = '';
+            
+            // Add one instance of each template with preview classes
+            templates.forEach(template => {
+                // Parse template HTML
+                const templateContainer = document.createElement('div');
+                templateContainer.innerHTML = template.html_template;
+                const templateElement = templateContainer.firstElementChild;
+                
+                if (templateElement) {
+                    // Clone the template element
+                    const previewElement = templateElement.cloneNode(true);
+                    
+                    // Add preview classes and data attributes for selection
+                    previewElement.classList.add('insertr-preview-item');
+                    previewElement.setAttribute('data-template-id', template.template_id);
+                    previewElement.setAttribute('data-template-name', template.name);
+                    
+                    // Add the preview element to the collection container
+                    collectionContainer.appendChild(previewElement);
+                    
+                    console.log(`✅ Added template ${template.template_id} (${template.name}) to preview`);
+                }
+            });
+            
+            // Return the complete collection HTML
+            return tempContainer.innerHTML;
+            
+        } catch (error) {
+            console.error('❌ Failed to generate live preview:', error);
+            return '<div>Preview generation failed</div>';
+        }
+    }
 }