import os                                                                       # Imports the 'os' module, which provides a way of using operating system dependent functionality
import joblib                                                                   # Imports the 'joblib' library, used for efficient serialization and deserialization of Python objects
from flask import Flask, request, jsonify                                       # Imports specific classes from the 'flask' framework
import pandas as pd                                                             # Imports the 'pandas' library, providing data structures and data analysis tools
import logging                                                                  # Imports the 'logging' module, used for logging events that occur during the execution of the program

# Initialize flask app with a name
sales_prediction = Flask(__name__)                                              # Creates an instance of the Flask class

# Configure logging
logging.basicConfig(level=logging.DEBUG)                                        # Configures the logging system to record all events at DEBUG level and above

# Load the trained model pipeline
try:                                                                            # Tries to load the model from a file
    model = joblib.load("SuperKart_best_Model.joblib")                          # # Attempts to load the pre-trained machine learning model pipeline                                      
    logging.info("Model loaded successfully.")                                  # Logs an informational message indicating that the model was loaded without errors
except Exception as e:                                                          # If an error occurs during the loading process
    logging.error(f"Error loading model: {e}")                                  # Logs an error message containing the specific error that occurred
    raise                                                                       # Raises the exception to propagate it to the caller

# Define an endpoint for making predictions
@sales_prediction.get('/')                                                      # Decorator that registers the home() function to handle GET requests                                                                                                                                
def home():                                                                     # Function that handles GET requests to the root URL ('/') of the API
    """
    This function handles GET requests to the root URL ('/') of the API.
    It returns a simple welcome message.
    """
    return "Welcome to the SuperKart Sales Prediction App!"                     

# Define an endpoint for single property prediction (POST request)
@sales_prediction.post('/v1/predict')                                           # Decorator that registers the predict_sales() function to handle POST requests to the '/v1/predict' endpoint
def predict_sales():                                                            # Function that handles POST requests to the '/v1/predict' endpoint
    """
    This function handles POST requests to the '/v1/predict' endpoint.
    It expects a JSON payload containing property details and returns
    the predicted rental price as a JSON response.
    """
    # Get the JSON data from the request body
    try:                                                                        # Tries to decode the JSON data from the request body
        business_data = request.get_json()                                      # Attempts to retrieve the JSON data sent in the body of the POST request
        logging.debug(f"Received data: {business_data}")                        # Logs the received data at the DEBUG level
    except Exception as e:                                                      # Catches any exception that occurs during JSON decoding                                                      
        logging.error(f"Error decoding JSON: {e}")                              # Logs an error message containing the specific JSON decoding error
        return jsonify({'error': f'Invalid JSON: {e}'}), 400                    # Returns a JSON response with an error message and a 400 Bad Request status code

    # Extract relevant features from the JSON data
    try:                                                                        # Tries to decode the JSON data from the request body                            
        business_data_sample = {                                                # Creates a dictionary containing the features required for prediction, extracted from the received JSON data
            'Product_Weight': business_data['Product_Weight'],
            'Product_Sugar_Content': business_data['Product_Sugar_Content'],
            'Product_Type': business_data['Product_Type'],
            'Product_Allocated_Area': business_data['Product_Allocated_Area'],
            'Product_MRP': business_data['Product_MRP'],
            'Store_Size': business_data['Store_Size'],
            'Store_Id': business_data['Store_Id'],
            'Store_Location_City_Type': business_data['Store_Location_City_Type'],
            'Store_Type': business_data['Store_Type'],
            'Store_Current_Age': business_data['Store_Current_Age']  
        }
    except KeyError as e:                                                       # Catches a KeyError if a required key is missing from the input JSON data  
        logging.error(f"Missing key in JSON data: {e}")                         # Logs an error message containing the specific JSON decoding error                                                        
        return jsonify({'error': f'Missing key: {e}'}), 400                     # Returns a JSON response with an error message and a 400 Bad Request status code
    except TypeError as e:                                                      # Catches a TypeError if the data type of a value in the JSON data is incorrect
        logging.error(f"Error with data types: {e}")                            # Logs an error message containing the specific JSON decoding error
        return jsonify({'error': f'Incorrect data type: {e}'}), 400             # Returns a JSON response with an error message and a 400 Bad Request status code                

    # Convert the extracted data into a Pandas DataFrame
    try:                                                                        # Tries to decode the JSON data from the request body   
        business_df = pd.DataFrame(business_data_sample, index=[0])             # Creates a Pandas DataFrame from the extracted feature dictionary, with a single row
        logging.debug(f"DataFrame: {business_df.head().to_string()}")           # Logs the first few rows of the DataFrame as a string
    except Exception as e:                                                      # Catches any exception that occurs during DataFrame creation
        logging.error(f"Error creating DataFrame: {e}")                         # Logs an error message containing the DataFrame creation error                                      
        return jsonify({'error': f'Error creating DataFrame: {e}'}), 500        # Returns a JSON response with an error message and a 500 Internal Server Error status code

    # Make predictions using the loaded model
    try:                                                                        # Tries to make predictions using the loaded model
        prediction = model.predict(business_df)                                 # Uses the loaded machine learning model to predict the sales for the input data in the DataFrame
        logging.debug(f"Prediction: {prediction}")                              # Logs the prediction result
    except Exception as e:                                                      # Catches any exception that occurs during the prediction process
        logging.error(f"Error during prediction: {e}")                          # Logs an error message containing the specific prediction error
        return jsonify({'error': f'Prediction error: {e}'}), 500                # Returns a JSON response with an error message and a 500 Internal Server Error status code

    # Return the prediction as a JSON response
    return jsonify({'prediction': list(prediction)})                            # Returns the prediction as a JSON object
    
# Define an endpoint for batch prediction (POST request)
@sales_prediction.post('/v1/batch_predict')                                     # Decorator that registers the batch_predict() function to handle POST requests to the '/v1/batch_predict' endpoint
def batch_predict():                                                            
    """
    This function handles POST requests to the '/v1/batch_predict' endpoint.
    It expects a JSON payload containing a list of property details and returns
    the predicted rental prices for each property as a JSON response.
    """
    # Get the uploaded CSV file from the request
    try:
        file = request.files['file']                                            # Attempts to retrieve the uploaded file from the request
        logging.debug(f"Received file: {file.filename}")                        # Logs the filename of the uploaded file
    except Exception as e:                                                      # Catches any exception that occurs while getting the file
        logging.error(f"Error getting file: {e}")                               # Logs an error message containing the file retrieval error
        return jsonify({'error': f'Error getting file: {e}'}), 400              # Returns a JSON response with an error message and a 400 Bad Request status code

    # Read the CSV file into a Pandas DataFrame
    try:                                                                        # Tries to read the CSV file into a Pandas DataFrame
        df = pd.read_csv(file)                                                  # Reads the uploaded CSV file into a Pandas DataFrame                                                      
        logging.debug(f"DataFrame shape: {df.shape}")                           # Logs the shape of the DataFrame
    except Exception as e:                                                      # Catches any exception that occurs during CSV reading
        logging.error(f"Error reading CSV: {e}")                                # Logs an error message containing the CSV reading error
        return jsonify({'error': f'Error reading CSV file: {e}'}), 400          # Returns a JSON response with an error message and a 400 Bad Request status code

    # Make preductions using the loaded model
    try:                                                                        # Tries to make predictions using the loaded model
        prediction = model.predict(df)                                          # Uses the loaded machine learning model to predict sales for the data in the DataFrame
        logging.debug(f"Prediction: {prediction}")                              # Logs the prediction result
    except Exception as e:                                                      # Catches any exception that occurs during the prediction process
        logging.error(f"Error during prediction: {e}")                          # Logs an error message containing the prediction error
        return jsonify({'error': f'Prediction error: {e}'}), 500                # Returns a JSON response with an error message and a 500 Internal Server Error status code

    # Return the prediction as a JSON response
    return jsonify({'prediction': list(prediction)})                            # Returns the prediction as a JSON object                            

# Run the Flask app if this script is executed
if __name__ == '__main__':                                                      
    sales_prediction.run(debug=True)                                            # Starts the Flask development server if the script is run directly with debug mode enabled