Update app.py

app.py

@@ -1222,183 +1222,547 @@ def visualize_reorganization(df_items, df_loc, df_pairs, df_recs, coords, id_to_
     return img
 
 # =============================================================================
-# GRADIO INTERFACE LAYOUT
+# GRADIO INTERFACE
 # =============================================================================
 
-# --- Navigation Handler ---
-def change_page(page_name):
-    """
-    Returns visibility updates (True/False) for the four main containers.
-    The order must match the 'outputs' list in the .click() methods.
-    """
-    is_main = page_name == 'main'
-    is_checkout = page_name == 'checkout'
-    is_add_items = page_name == 'add_items'
-    is_analysis = page_name == 'analysis'
-
-    return gr.update(visible=is_main), gr.update(visible=is_checkout), gr.update(visible=is_add_items), gr.update(visible=is_analysis)
-
-
-# --- Gradio Blocks UI Definition ---
-with gr.Blocks(css=CUSTOM_CSS, title="Makerspace Inventory Management System") as demo:
-
-    # 1. Define Page Containers (Visibility controlled via the .click() method)
-    # The initial page (main menu) is visible=True, all others are visible=False.
-    main_menu_container = gr.Box(elem_id="main-menu-container")
-    checkout_page = gr.Box(visible=False, elem_classes="module-page")
-    add_items_page = gr.Box(visible=False, elem_classes="module-page")
-    analysis_page = gr.Box(visible=False, elem_classes="module-page")
-
-    # The list of outputs used by all navigation buttons
-    page_outputs = [main_menu_container, checkout_page, add_items_page, analysis_page]
-
-    # --- MAIN MENU (Always Visible Initially) ---
-    with main_menu_container:
-        gr.Markdown("# <span id='main-menu-title'>Integrated Makerspace Inventory</span>")
-        gr.Markdown("## <span id='main-menu-subtitle'>Smart inventory management powered by AI</span>")
+with gr.Blocks(title="Makerspace Inventory System", css=CUSTOM_CSS) as demo:
+    
+    # State variables
+    matched_items_state = gr.State(None)
+    proposals_state = gr.State([])
+    
+    # Main menu
+    with gr.Group(visible=True, elem_id="main-menu-container") as main_menu:
+        gr.Markdown("# 🔧 Makerspace Inventory System", elem_id="main-menu-title")
+        gr.Markdown("*Smart inventory management powered by AI*", elem_id="main-menu-subtitle")
+        
         with gr.Row():
-            checkout_btn = gr.Button("🛒 Check Out Items", elem_classes="module-button primary-button")
-            add_items_btn = gr.Button("➕ Add Items to Inventory", elem_classes="module-button primary-button")
-            analysis_btn = gr.Button("📊 Inventory Analysis", elem_classes="module-button primary-button")
-
-    # --- CHECK OUT MODULE ---
-    with checkout_page:
-        back_to_main_btn_c = gr.Button("← Back to Main Menu")
-        gr.Markdown("<div class='section-header'>🛒 Check Out Items</div>")
-
-        # Your existing CHECK OUT UI components go here:
-        with gr.Row(variant="panel", elem_classes="gap"):
-            with gr.Column(min_width=400):
-                gr.Markdown("### 📸 Scan Item(s) with Image or Webcam")
-                image_input = gr.Image(type="filepath", label="Upload Item Image", sources=["upload", "webcam"], elem_classes="image-upload-container")
-                manual_text_input = gr.Textbox(label="Manual Item Entry (Optional)", placeholder="e.g., drill bit, digital multimeter, 1/4 inch wrench", info="Enter comma-separated items if image detection fails.")
-
-            with gr.Column():
-                scan_btn = gr.Button("🔍 Scan & Match Items", variant="primary", elem_classes="primary-button")
-                match_status = gr.Markdown("Ready to scan.", elem_classes="instructions-box")
-                matched_items_state = gr.State(value=[])  # To hold the matched items data
-
-        gr.Markdown("### 📝 Review & Confirm Checkout")
-        checkout_preview = gr.Markdown("No items scanned yet.")
-        user_id_input = gr.Textbox(label="Your ID (Optional)", placeholder="Enter your student/staff ID for tracking.")
-        confirm_checkout_btn = gr.Button("✅ Confirm Checkout", variant="primary", elem_classes="primary-button")
+            checkout_btn = gr.Button("🛒 Check Out Items", size="lg", elem_classes=["module-button"], scale=1)
+            add_items_btn = gr.Button("📦 Add Items", size="lg", elem_classes=["module-button"], scale=1)
+            analysis_btn = gr.Button("📊 Inventory Analysis", size="lg", elem_classes=["module-button"], scale=1)
+    
+    # CHECK OUT MODULE
+    with gr.Group(visible=False, elem_classes=["module-page"]) as checkout_module:
+        gr.Markdown("# 🛒 Check Out Items", elem_classes=["section-header"])
+        
+        with gr.Accordion("📖 How to Use", open=False):
+            gr.Markdown("""
+            **Step 1:** Upload a photo of items or type item names manually (comma-separated)
+            
+            **Step 2:** Review detected items and adjust quantities
+            
+            **Step 3:** Confirm checkout with optional user ID
+            
+            💡 **Tip:** The AI automatically matches items to inventory using smart search!
+            """)
+        
+        with gr.Group(visible=True) as checkout_screen1:
+            gr.Markdown("### 📸 Scan Items", elem_classes=["subsection-header"])
+            
+            with gr.Row():
+                with gr.Column(scale=2):
+                    checkout_image = gr.Image(
+                        type="pil", 
+                        label="Upload Image of Items", 
+                        sources=["upload", "webcam"],
+                        height=400
+                    )
+                    
+                    if EXAMPLE_CHECKOUT_IMAGE:
+                        load_example_checkout_btn = gr.Button("📸 Load Example", size="sm", variant="secondary", scale=0)
+                
+                with gr.Column(scale=1):
+                    gr.Markdown("""
+                    ### Quick Guide
+                    
+                    **Upload:** Click the upload icon to select an image from your device
+                    
+                    **Webcam:** Click the camera icon to take a photo with your webcam
+                    
+                    💡 Make sure items are clearly visible and well-lit
+                    """)
+            
+            checkout_manual = gr.Textbox(
+                label="Or Enter Item Names Manually",
+                placeholder="e.g., drill, safety glasses, Arduino",
+                info="Separate multiple items with commas"
+            )
+            
+            checkout_status = gr.Markdown("")
+            checkout_scan_btn = gr.Button("🔍 Scan & Match Items", variant="primary", size="lg")
+        
+        with gr.Group(visible=False) as checkout_screen2:
+            gr.Markdown("### ✅ Review Items", elem_classes=["subsection-header"])
+            gr.Markdown("*Adjust quantities or remove items before checkout*")
+            
+            checkout_item_controls = []
+            for i in range(10):
+                with gr.Row(visible=False) as item_row:
+                    with gr.Column(scale=3):
+                        item_info = gr.Markdown("")
+                    with gr.Column(scale=1):
+                        item_qty = gr.Number(value=1, minimum=1, label="Qty")
+                    with gr.Column(scale=1):
+                        item_remove = gr.Button("🗑️ Remove", size="sm", variant="stop")
+                
+                checkout_item_controls.append({
+                    'row': item_row,
+                    'info': item_info,
+                    'qty': item_qty,
+                    'remove': item_remove
+                })
+            
+            with gr.Row():
+                checkout_rescan_btn = gr.Button("↩️ Rescan", variant="secondary")
+                checkout_confirm_btn = gr.Button("✅ Proceed to Checkout", variant="primary", size="lg")
+        
+        with gr.Group(visible=False) as checkout_screen3:
+            gr.Markdown("### 🎫 Confirm Checkout", elem_classes=["subsection-header"])
+            
+            checkout_preview = gr.Markdown("")
+            
+            checkout_user_id = gr.Textbox(
+                label="User ID (Optional)",
+                placeholder="Enter your ID or leave blank",
+                info="Leave blank for auto-generated ID"
+            )
+            
+            checkout_processing = gr.Markdown("")
+            
+            with gr.Row():
+                checkout_cancel_btn = gr.Button("❌ Cancel", variant="secondary")
+                checkout_final_btn = gr.Button("✅ Complete Checkout", variant="primary", size="lg")
+        
         checkout_result = gr.Markdown("")
-
-        # Link CHECKOUT button actions to functions
-        scan_btn.click(
-            scan_items_checkout,
-            inputs=[image_input, manual_text_input],
-            outputs=[matched_items_state, match_status]
-        ).then(
-            confirm_checkout_preview,
-            inputs=[matched_items_state],
-            outputs=[checkout_preview]
-        )
-
-        confirm_checkout_btn.click(
-            process_checkout,
-            inputs=[matched_items_state, user_id_input],
-            outputs=[checkout_result]
-        ).then(
-            lambda: (gr.update(value=None), gr.update(value="Ready to scan.", visible=True)),
-            inputs=None,
-            outputs=[image_input, match_status]
-        )
-
-
-    # --- ADD ITEMS MODULE ---
-    with add_items_page:
-        back_to_main_btn_a = gr.Button("← Back to Main Menu")
-        gr.Markdown("<div class='section-header'>➕ Add Items to Inventory</div>")
-
-        # Your existing ADD ITEMS UI components go here:
-        with gr.Tabs():
-            with gr.TabItem("Receipt/Invoice Upload"):
-                gr.Markdown("Upload a PDF or image of a receipt/invoice to automatically add new inventory items.")
-                receipt_file = gr.File(label="Upload Receipt (PDF or Image)")
-                process_receipt_btn = gr.Button("Extract & Propose Updates", variant="primary", elem_classes="primary-button")
-                receipt_updates_table = gr.Dataframe(
-                    headers=["Include", "Item Name", "Quantity", "Match Type"],
-                    datatype=["checkbox", "str", "number", "str"],
-                    row_count=0,
-                    col_count=4,
-                    interactive=True,
-                    label="Proposed Inventory Updates"
+        
+        with gr.Row():
+            checkout_return_btn = gr.Button("🏠 Return to Main Menu", variant="secondary")
+            checkout_another_btn = gr.Button("🛒 Check Out More Items", variant="primary", visible=False)
+    
+    # ADD ITEMS MODULE
+    with gr.Group(visible=False, elem_classes=["module-page"]) as add_items_module:
+        gr.Markdown("# 📦 Add Items to Inventory", elem_classes=["section-header"])
+        
+        with gr.Accordion("📖 How to Use", open=False):
+            gr.Markdown("""
+            **Receipt Upload:**
+            1. Upload receipt image or PDF → AI extracts items
+            2. Review and edit detected items (check/uncheck, edit quantities)
+            3. Click "Apply Updates" to add to inventory
+            
+            **Manual Entry:**
+            - Enter item name and quantity for quick updates
+            - System uses fuzzy matching to find items
+            
+            **View & History:**
+            - Browse inventory with category filters
+            - Track all changes with timestamps
+            """)
+        
+        with gr.Tab("📄 Receipt Upload"):
+            gr.Markdown("### Upload Receipt", elem_classes=["subsection-header"])
+            
+            receipt_file = gr.File(label="Upload Receipt (PDF or Image)", file_types=[".pdf", ".png", ".jpg", ".jpeg"])
+            
+            if EXAMPLE_RECEIPT_PDF:
+                load_example_receipt_btn = gr.Button("📄 Load Example", size="sm", variant="secondary", scale=0)
+            
+            receipt_status = gr.Markdown("")
+            
+            gr.Markdown("### Review Detected Items", elem_classes=["subsection-header"])
+            gr.Markdown("*Check items to include, edit quantities, then apply*")
+            
+            add_items_table = gr.Dataframe(
+                headers=["Include", "Item Name", "Quantity", "Match Confidence"],
+                label="Detected Items",
+                datatype=["bool", "str", "number", "str"],
+                interactive=True,
+                col_count=(4, "fixed")
+            )
+            
+            add_items_status = gr.Markdown("")
+            
+            with gr.Row():
+                add_items_reject_btn = gr.Button("❌ Clear All", variant="secondary")
+                add_items_confirm_btn = gr.Button("✅ Apply Updates", variant="primary", interactive=False)
+        
+        with gr.Tab("✍️ Manual Entry"):
+            gr.Markdown("### Manually Add Items", elem_classes=["subsection-header"])
+            
+            with gr.Row():
+                manual_item = gr.Textbox(
+                    label="Item Name",
+                    placeholder="e.g., Arduino Uno",
+                    info="Fuzzy matching will find similar items"
                 )
-                apply_updates_btn = gr.Button("Apply Selected Updates", variant="primary", elem_classes="primary-button")
-                receipt_summary = gr.Markdown("")
-
-                process_receipt_btn.click(
-                    extract_text_from_receipt,
-                    inputs=[receipt_file],
-                    outputs=[receipt_updates_table, gr.State(value=[])] # Note: The proposals state is not fully used here but kept for completeness
+                manual_qty = gr.Number(
+                    label="Quantity to Add",
+                    value=1,
+                    minimum=1
                 )
-                apply_updates_btn.click(
-                    apply_updates_from_table,
-                    inputs=[receipt_updates_table],
-                    outputs=[receipt_summary, gr.State(value=None)] # Outputting to a dummy State to avoid confusion
+            
+            manual_apply_btn = gr.Button("➕ Add to Inventory", variant="primary")
+            manual_status = gr.Markdown("")
+            manual_inventory_display = gr.Dataframe(label="Updated Inventory", visible=False)
+        
+        with gr.Tab("📊 View & History"):
+            gr.Markdown("### Current Inventory", elem_classes=["subsection-header"])
+            
+            with gr.Row():
+                inventory_category_filter = gr.Dropdown(
+                    choices=["All"] + get_categories(),
+                    value="All",
+                    label="Filter by Category"
                 )
-
-            with gr.TabItem("Manual Single Update"):
-                gr.Markdown("Manually update the quantity of a single item. Use a positive number to add, or a negative number to remove.")
-                manual_item_name = gr.Textbox(label="Item Name", placeholder="e.g., Arduino Uno, 3D Printer Filament (White)")
-                manual_quantity = gr.Number(label="Quantity Change (+ or -)", value=1)
-                manual_update_btn = gr.Button("Apply Manual Update", variant="primary", elem_classes="primary-button")
-                manual_update_summary = gr.Markdown("")
-
-                manual_update_btn.click(
-                    manual_update,
-                    inputs=[manual_item_name, manual_quantity],
-                    outputs=[manual_update_summary, gr.State(value=None)]
+                view_inventory_btn = gr.Button("🔄 Refresh Inventory")
+            
+            inventory_display = gr.Dataframe(label="Current Inventory", visible=False)
+            
+            gr.Markdown("### Update History", elem_classes=["subsection-header"])
+            
+            view_history_btn = gr.Button("📜 View Update Log")
+            history_display = gr.Textbox(label="Update History", lines=10, visible=False)
+        
+        add_items_return_btn = gr.Button("🏠 Return to Main Menu", variant="secondary")
+    
+    # INVENTORY ANALYSIS MODULE
+    with gr.Group(visible=False, elem_classes=["module-page"]) as analysis_module:
+        gr.Markdown("# 📊 Inventory Layout Analysis", elem_classes=["section-header"])
+        
+        with gr.Accordion("📖 Understanding the Analysis", open=True):
+            gr.Markdown("""
+            This module analyzes checkout patterns to optimize item placement and minimize walking distance.
+            
+            ### 📈 Key Metrics:
+            
+            **Support** - Frequency of co-occurrence (e.g., 0.10 = 10% of checkouts)
+            
+            **Lift** - Correlation strength (Lift > 1 = items checked out together more than random)
+            
+            **Confidence** - Conditional probability (e.g., 0.80 = 80% chance of B when checking A)
+            
+            **Distance Saved** - Walking distance reduction in grid units
+            
+            ### 🎯 Goal:
+            Items frequently checked together should be placed closer to reduce travel time!
+            """)
+        
+        with gr.Row():
+            with gr.Column(scale=1):
+                gr.Markdown("### ⚙️ Parameters", elem_classes=["subsection-header"])
+                
+                min_support = gr.Slider(
+                    minimum=0.01,
+                    maximum=0.2,
+                    value=0.02,
+                    step=0.01,
+                    label="Minimum Support",
+                    info="Lower = more patterns (less significant)"
                 )
-
-
-    # --- INVENTORY ANALYSIS MODULE ---
-    with analysis_page:
-        back_to_main_btn_n = gr.Button("← Back to Main Menu")
-        gr.Markdown("<div class='section-header'>📊 Inventory Analysis</div>")
-
-        # Your existing ANALYSIS UI components go here:
-        with gr.Accordion("Analysis Configuration", open=False):
-            min_support_slider = gr.Slider(minimum=0.01, maximum=0.1, step=0.005, value=0.02, label="Min Support for Item Pairs")
-            top_k_pairs_slider = gr.Slider(minimum=10, maximum=100, step=5, value=30, label="Top K Pairs for Relocation")
-            max_moves_slider = gr.Slider(minimum=5, maximum=50, step=5, value=15, label="Max Relocation Moves")
-            min_gain_slider = gr.Slider(minimum=0.01, maximum=1.0, step=0.01, value=0.05, label="Minimum Gain for a Move")
-
-        run_analysis_btn = gr.Button("🚀 Run Inventory Optimization Analysis", variant="primary", elem_classes="primary-button")
-        analysis_status = gr.Markdown("Press 'Run Inventory Optimization Analysis' to start.")
-
-        with gr.Tabs():
-            with gr.TabItem("Frequent Item Pairs (Recommendations)"):
-                item_pairs_df = gr.Dataframe(interactive=False, label="Frequent Item Pairs", height=300)
-
-            with gr.TabItem("Location Relocation Recommendations"):
-                relocation_df = gr.Dataframe(interactive=False, label="Optimized Relocation Moves", height=300)
-
-            with gr.TabItem("Current Inventory"):
-                category_dropdown = gr.Dropdown(choices=["All"] + get_categories(), value="All", label="Filter by Category")
-                inventory_df = gr.Dataframe(view_inventory_table(), interactive=False, label="Current Inventory Status", height=500)
-                category_dropdown.change(view_inventory_table, inputs=category_dropdown, outputs=inventory_df)
-
-            with gr.TabItem("Update History"):
-                update_history_text = gr.Textbox(view_update_history(), label="Inventory Update Log", interactive=False)
-
-        run_analysis_btn.click(
-            run_analysis,
-            inputs=[min_support_slider, top_k_pairs_slider, max_moves_slider, min_gain_slider],
-            outputs=[item_pairs_df, relocation_df, analysis_status, inventory_df]
+                
+                top_k_pairs = gr.Slider(
+                    minimum=5,
+                    maximum=50,
+                    value=25,
+                    step=5,
+                    label="Top K Pairs",
+                    info="Number of frequent pairs to optimize"
+                )
+                
+                max_moves = gr.Slider(
+                    minimum=5,
+                    maximum=30,
+                    value=10,
+                    step=1,
+                    label="Maximum Moves",
+                    info="Limit on relocations"
+                )
+                
+                min_gain = gr.Slider(
+                    minimum=0.0,
+                    maximum=1.0,
+                    value=0.05,
+                    step=0.01,
+                    label="Minimum Distance Gain",
+                    info="Threshold for suggestions"
+                )
+                
+                run_analysis_btn = gr.Button("🔍 Run Analysis", variant="primary", size="lg")
+            
+            with gr.Column(scale=2):
+                gr.Markdown("### 📊 Summary", elem_classes=["subsection-header"])
+                analysis_summary = gr.Textbox(label="", lines=14, show_label=False)
+        
+        gr.Markdown("### 🗺️ Visual Layout Comparison", elem_classes=["subsection-header"])
+        analysis_viz = gr.Image(label="", type="numpy", show_label=False)
+        
+        with gr.Row():
+            with gr.Column():
+                gr.Markdown("### 🔗 Frequent Pairs", elem_classes=["subsection-header"])
+                pairs_table = gr.Dataframe(label="", show_label=False)
+            
+            with gr.Column():
+                gr.Markdown("### 📍 Recommendations", elem_classes=["subsection-header"])
+                recs_table = gr.Dataframe(label="", show_label=False)
+        
+        analysis_return_btn = gr.Button("🏠 Return to Main Menu", variant="secondary")
+    
+    # EVENT HANDLERS - Navigation
+    def show_checkout():
+        return (gr.update(visible=False), gr.update(visible=True), 
+                gr.update(visible=False), gr.update(visible=False))
+    
+    def show_add_items():
+        return (gr.update(visible=False), gr.update(visible=False),
+                gr.update(visible=True), gr.update(visible=False))
+    
+    def show_analysis():
+        return (gr.update(visible=False), gr.update(visible=False),
+                gr.update(visible=False), gr.update(visible=True))
+    
+    def return_to_menu():
+        return (gr.update(visible=True), gr.update(visible=False),
+                gr.update(visible=False), gr.update(visible=False))
+    
+    checkout_btn.click(fn=show_checkout, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    add_items_btn.click(fn=show_add_items, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    analysis_btn.click(fn=show_analysis, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    
+    checkout_return_btn.click(fn=return_to_menu, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    add_items_return_btn.click(fn=return_to_menu, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    analysis_return_btn.click(fn=return_to_menu, outputs=[main_menu, checkout_module, add_items_module, analysis_module])
+    
+    # EVENT HANDLERS - Checkout
+    def update_checkout_screen2(matched_items):
+        updates = []
+        
+        if not matched_items:
+            for i in range(10):
+                updates.extend([gr.update(visible=False), gr.update(value=""), gr.update(value=1)])
+            return updates
+        
+        for i in range(10):
+            if i < len(matched_items):
+                item_data = matched_items[i]
+                updates.extend([
+                    gr.update(visible=True),
+                    gr.update(value=create_checkout_item_display(item_data, i)),
+                    gr.update(value=item_data['quantity'], maximum=item_data['item']['Quantity']),
+                ])
+            else:
+                updates.extend([gr.update(visible=False), gr.update(value=""), gr.update(value=1)])
+        
+        return updates
+    
+    def remove_checkout_item(matched_items, item_idx):
+        if matched_items and 0 <= item_idx < len(matched_items):
+            matched_items.pop(item_idx)
+        return matched_items
+    
+    def set_checkout_quantity(matched_items, item_idx, new_qty):
+        if matched_items and 0 <= item_idx < len(matched_items):
+            max_qty = matched_items[item_idx]['item']['Quantity']
+            matched_items[item_idx]['quantity'] = max(1, min(int(new_qty), max_qty))
+        return matched_items
+    
+    def reset_checkout():
+        return (
+            gr.update(visible=True), gr.update(visible=False), gr.update(visible=False),
+            None, "", None, "", "", gr.update(visible=False)
+        )
+    
+    def show_checkout_complete_options():
+        return gr.update(visible=False), gr.update(visible=True)
+    
+    checkout_scan_btn.click(
+        fn=lambda: (gr.update(value="⏳ Scanning...", interactive=False), "🔍 **Processing...** AI is analyzing your image..."),
+        outputs=[checkout_scan_btn, checkout_status]
+    ).then(
+        fn=scan_items_checkout,
+        inputs=[checkout_image, checkout_manual],
+        outputs=[matched_items_state, checkout_status]
+    ).then(
+        fn=lambda: gr.update(value="🔍 Scan & Match Items", interactive=True),
+        outputs=[checkout_scan_btn]
+    ).then(
+        fn=lambda items: (
+            gr.update(visible=False) if items else gr.update(),
+            gr.update(visible=True) if items else gr.update(),
+            gr.update(visible=False)
+        ),
+        inputs=[matched_items_state],
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3]
+    ).then(
+        fn=update_checkout_screen2,
+        inputs=[matched_items_state],
+        outputs=[checkout_item_controls[i][key] for i in range(10) for key in ['row', 'info', 'qty']]
+    )
+    
+    for i in range(10):
+        checkout_item_controls[i]['qty'].change(
+            fn=lambda items, new_qty, idx=i: set_checkout_quantity(items, idx, new_qty),
+            inputs=[matched_items_state, checkout_item_controls[i]['qty']],
+            outputs=[matched_items_state]
         )
         
+        checkout_item_controls[i]['remove'].click(
+            fn=lambda items, idx=i: remove_checkout_item(items, idx),
+            inputs=[matched_items_state],
+            outputs=[matched_items_state]
+        ).then(
+            fn=update_checkout_screen2,
+            inputs=[matched_items_state],
+            outputs=[checkout_item_controls[j][key] for j in range(10) for key in ['row', 'info', 'qty']]
+        )
+    
+    checkout_confirm_btn.click(
+        fn=confirm_checkout_preview,
+        inputs=[matched_items_state],
+        outputs=[checkout_preview]
+    ).then(
+        fn=lambda: (gr.update(visible=False), gr.update(visible=False), gr.update(visible=True)),
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3]
+    )
+    
+    checkout_rescan_btn.click(
+        fn=reset_checkout,
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3, matched_items_state,
+                checkout_status, checkout_image, checkout_manual, checkout_result, checkout_another_btn]
+    )
+    
+    checkout_cancel_btn.click(
+        fn=reset_checkout,
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3, matched_items_state,
+                checkout_status, checkout_image, checkout_manual, checkout_result, checkout_another_btn]
+    )
+    
+    checkout_final_btn.click(
+        fn=lambda: (gr.update(value="⏳ Processing...", interactive=False), "⏳ **Processing checkout...** Updating inventory..."),
+        outputs=[checkout_final_btn, checkout_processing]
+    ).then(
+        fn=process_checkout,
+        inputs=[matched_items_state, checkout_user_id],
+        outputs=[checkout_result]
+    ).then(
+        fn=lambda: (gr.update(value="✅ Complete Checkout", interactive=True), ""),
+        outputs=[checkout_final_btn, checkout_processing]
+    ).then(
+        fn=lambda: (gr.update(visible=False), gr.update(visible=False), gr.update(visible=False)),
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3]
+    ).then(
+        fn=show_checkout_complete_options,
+        outputs=[checkout_return_btn, checkout_another_btn]
+    )
+    
+    checkout_another_btn.click(
+        fn=reset_checkout,
+        outputs=[checkout_screen1, checkout_screen2, checkout_screen3, matched_items_state,
+                checkout_status, checkout_image, checkout_manual, checkout_result, checkout_another_btn]
+    ).then(
+        fn=lambda: (gr.update(visible=True), gr.update(visible=False)),
+        outputs=[checkout_return_btn, checkout_another_btn]
+    )
+    
+    # EVENT HANDLERS - Add Items
+    receipt_file.change(
+        fn=lambda: "📄 **Processing receipt...** Extracting text with OCR...",
+        outputs=[receipt_status]
+    ).then(
+        fn=extract_text_from_receipt,
+        inputs=[receipt_file],
+        outputs=[add_items_table, proposals_state]
+    ).then(
+        fn=lambda proposals: (gr.update(interactive=len(proposals) > 0), "✅ Items detected! Review and edit the table below."),
+        inputs=[proposals_state],
+        outputs=[add_items_confirm_btn, receipt_status]
+    )
+    
+    add_items_confirm_btn.click(
+        fn=lambda: (gr.update(value="⏳ Applying...", interactive=False), "⏳ **Updating inventory...**"),
+        outputs=[add_items_confirm_btn, add_items_status]
+    ).then(
+        fn=apply_updates_from_table,
+        inputs=[add_items_table],
+        outputs=[add_items_status, inventory_display]
+    ).then(
+        fn=lambda: (gr.update(value="✅ Apply Updates", interactive=False), gr.update(visible=True)),
+        outputs=[add_items_confirm_btn, inventory_display]
+    )
+    
+    add_items_reject_btn.click(
+        fn=lambda: ([["No items", "", "", ""]], "❌ Cleared all items.", []),
+        outputs=[add_items_table, add_items_status, proposals_state]
+    ).then(
+        fn=lambda: gr.update(interactive=False),
+        outputs=[add_items_confirm_btn]
+    )
+    
+    manual_apply_btn.click(
+        fn=lambda: gr.update(value="⏳ Adding...", interactive=False),
+        outputs=[manual_apply_btn]
+    ).then(
+        fn=manual_update,
+        inputs=[manual_item, manual_qty],
+        outputs=[manual_status, manual_inventory_display]
+    ).then(
+        fn=lambda: (gr.update(value="➕ Add to Inventory", interactive=True), gr.update(visible=True)),
+        outputs=[manual_apply_btn, manual_inventory_display]
+    )
+    
+    view_inventory_btn.click(
+        fn=view_inventory_table,
+        inputs=[inventory_category_filter],
+        outputs=[inventory_display]
+    ).then(
+        fn=lambda: gr.update(visible=True),
+        outputs=[inventory_display]
+    )
+    
+    inventory_category_filter.change(
+        fn=view_inventory_table,
+        inputs=[inventory_category_filter],
+        outputs=[inventory_display]
+    )
+    
+    view_history_btn.click(
+        fn=view_update_history,
+        outputs=[history_display]
+    ).then(
+        fn=lambda: gr.update(visible=True),
+        outputs=[history_display]
+    )
+    
+    # EVENT HANDLERS - Analysis
+    run_analysis_btn.click(
+        fn=run_analysis,
+        inputs=[min_support, top_k_pairs, max_moves, min_gain],
+        outputs=[pairs_table, recs_table, analysis_summary, analysis_viz]
+    )
+    
+    # EXAMPLE INPUTS
+    if EXAMPLE_CHECKOUT_IMAGE:
+        def load_checkout_example():
+            try:
+                return Image.open(EXAMPLE_CHECKOUT_IMAGE)
+            except:
+                return None
+        
+        load_example_checkout_btn.click(
+            fn=load_checkout_example,
+            outputs=[checkout_image]
+        )
+    
+    if EXAMPLE_RECEIPT_PDF:
+        def load_receipt_example():
+            try:
+                return EXAMPLE_RECEIPT_PDF
+            except:
+                return None
+        
+        load_example_receipt_btn.click(
+            fn=load_receipt_example,
+            outputs=[receipt_file]
+        )
 
-    # 3. Add the click events for general navigation (The fix for "No API Found")
-    checkout_btn.click(lambda: change_page('checkout'), outputs=page_outputs)
-    add_items_btn.click(lambda: change_page('add_items'), outputs=page_outputs)
-    analysis_btn.click(lambda: change_page('analysis'), outputs=page_outputs)
-
-    # Back button logic
-    for btn in [back_to_main_btn_c, back_to_main_btn_a, back_to_main_btn_n]:
-        btn.click(lambda: change_page('main'), outputs=page_outputs)
-
-
-# Launch the Gradio App
-demo.launch()
+if __name__ == "__main__":
+    demo.launch()