update app.py

app.py

@@ -53,10 +53,15 @@ with open("sentinel_datasets.json") as f:
 with open("band_options.json") as f:
     band_options = json.load(f)
     
+# Function to load available bands for the selected dataset and allow user to create custom formula
+def get_available_bands_for_custom_formula(dataset):
+    # Fetch available bands for the selected dataset
+    return band_data.get(dataset, {}).get('bands', [])
+
 # Display the title and dataset selection
 st.title("Sentinel Dataset")
 
-# Select dataset category and subcategory (case-insensitive selection)
+# Select dataset category and subcategory
 main_selection = st.selectbox("Select Sentinel Dataset Category", list(data.keys()))
 
 if main_selection:
@@ -66,19 +71,13 @@ if main_selection:
 # Earth Engine Index Calculator Section
 st.header("Earth Engine Index Calculator")
 
-# Choose Index or Custom Formula (case-insensitive)
+# Choose Index or Custom Formula
 index_choice = st.selectbox("Select an Index or Enter Custom Formula", ['NDVI', 'NDWI', 'Average NO₂', 'Custom Formula'])
 
 # Initialize custom_formula variable
 custom_formula = ""
 
-# Get the available bands for the selected dataset category and subcategory
-if main_selection and sub_selection:
-    available_bands = band_options.get(main_selection, {}).get(sub_selection, [])
-else:
-    available_bands = []
-
-# Display corresponding formula based on the index selected (case-insensitive)
+# Display corresponding formula based on the index selected
 if index_choice.lower() == 'ndvi':
     st.write("Formula for NDVI: NDVI = (B8 - B4) / (B8 + B4)")
 elif index_choice.lower() == 'ndwi':
@@ -86,19 +85,25 @@ elif index_choice.lower() == 'ndwi':
 elif index_choice.lower() == 'average no₂':
     st.write("Formula for Average NO₂: Average NO₂ = Mean(NO2 band)")
 elif index_choice.lower() == 'custom formula':
-    # Allow the user to select up to 3 bands
-    band_selection = st.multiselect("Select up to 3 bands for custom calculation", available_bands, max_selections=3)
-    
-    # Show the selected bands in the custom formula input
-    if len(band_selection) > 0:
-        st.write("You selected the following bands:")
-        st.write(band_selection)
+    # Dynamically fetch available bands for the selected dataset
+    available_bands = get_available_bands_for_custom_formula(sub_selection)
     
-    # Allow the user to enter a custom formula with the selected bands
-    if band_selection:
-        custom_formula = st.text_input("Enter Custom Formula (e.g., 'B5 - B4 / B5 + B4')")
+    if available_bands:
+        # Allow users to select bands for the custom formula
+        st.write(f"Available bands for {sub_selection}:")
+        selected_bands = st.multiselect("Select Bands", available_bands)
+
+        # Show instructions for the custom formula
+        st.write("Example formula: (B8 - B4) / (B8 + B4)")
+
+        # Let the user input a custom formula using selected bands
+        custom_formula = st.text_area("Enter Custom Formula", value="")
+        
+        # Display the formula that the user entered
         st.write(f"Custom Formula: {custom_formula}")  # Display the custom formula after the user inputs it
-
+    else:
+        st.warning(f"No available bands found for the selected dataset ({sub_selection}). Please ensure the dataset contains bands.")
+        
 # Function to check if the polygon geometry is valid and convert it to the correct format
 def convert_to_ee_geometry(geometry):
     # Ensure the polygon geometry is in the right format