1

[ArkS0001]

Okay, let's get this Flask app ready for deployment on Netlify Functions.

Here's the plan:

1. Adapt the Python Code:
   • Remove the app.run() block (serverless functions don't run a persistent server).
   • Add the serverless-wsgi wrapper.
   • Define the main entry point (handler) that Netlify will call.
   • Refine request handling/validation within the Flask route for better HTTP practices.
2. Create requirements.txt: List the necessary Python packages.
3. Create netlify.toml: Configure Netlify builds and function routing (rewrites).
4. Explain Deployment: Outline the steps to deploy using Git and the Netlify UI/CLI.

---

1. Modified Python Code (api.py)

Save this code in a file, for example, inside a netlify/functions/ directory. Let's call the file api.py.

import math
import itertools
import json # For request body check
from flask import Flask, request, jsonify # Removed render_template as not used in API part
# Import serverless_wsgi to wrap the app
import serverless_wsgi

app = Flask(__name__)

# --- Data Definitions (Same as before) ---
PRODUCTS = {
    "A": {"center": "C1", "weight": 3.0}, "B": {"center": "C1", "weight": 2.0},
    "C": {"center": "C1", "weight": 8.0}, "D": {"center": "C2", "weight": 12.0},
    "E": {"center": "C2", "weight": 25.0}, "F": {"center": "C2", "weight": 15.0},
    "G": {"center": "C3", "weight": 0.5}, "H": {"center": "C3", "weight": 1.0},
    "I": {"center": "C3", "weight": 2.0},
}
DISTANCES = {
    ("C1", "L1"): 3.0, ("L1", "C1"): 3.0, ("C2", "L1"): 2.5, ("L1", "C2"): 2.5,
    ("C3", "L1"): 2.0, ("L1", "C3"): 2.0, ("C1", "C2"): 4.0, ("C2", "C1"): 4.0,
    ("C2", "C3"): 3.0, ("C3", "C2"): 3.0,
}
CENTERS = ["C1", "C2", "C3"]
LOCATIONS = ["C1", "C2", "C3", "L1"]
# Small epsilon for float comparisons
EPSILON = 1e-9

# --- Helper Functions (Slightly improved cost calculation clarity) ---
def get_distance(loc1, loc2):
    if loc1 == loc2: return 0.0
    # Check both directions directly
    dist = DISTANCES.get((loc1, loc2))
    if dist is None: dist = DISTANCES.get((loc2, loc1))
    # Return distance or infinity if not found
    return dist if dist is not None else float('inf')

def calculate_segment_cost(weight, distance):
    if distance <= 0 or distance == float('inf'):
        return 0.0 # No cost for zero or infinite distance travel

    if weight <= EPSILON: # Treat near-zero weight as deadhead
        cost_per_unit = 10.0
    elif weight <= 5.0 + EPSILON:
        cost_per_unit = 10.0
    else:
        # Calculate blocks needed *beyond* the initial 5kg block
        additional_weight = max(0.0, weight - 5.0 - EPSILON)
        additional_blocks = math.ceil(additional_weight / 5.0)
        cost_per_unit = 10.0 + 8.0 * additional_blocks

    return cost_per_unit * distance

def _calculate_travel_cost_between_stops(loc_a, loc_b, weight_carried):
    # Direct path cost
    direct_dist = get_distance(loc_a, loc_b)
    cost_direct = calculate_segment_cost(weight_carried, direct_dist)

    # Indirect path via C2 (specifically for C1 <-> C3)
    cost_indirect = float('inf')
    if (loc_a, loc_b) in [("C1", "C3"), ("C3", "C1")]:
        # Check if C2 is reachable from both ends
        dist_a_c2 = get_distance(loc_a, "C2")
        dist_c2_b = get_distance("C2", loc_b)

        if dist_a_c2 != float('inf') and dist_c2_b != float('inf'):
            cost_a_c2 = calculate_segment_cost(weight_carried, dist_a_c2)
            cost_c2_b = calculate_segment_cost(weight_carried, dist_c2_b)
            cost_indirect = cost_a_c2 + cost_c2_b

    # Return the minimum valid cost (direct might be infinity)
    return min(cost_direct, cost_indirect)


# --- Core Calculation Logic (_calculate_overall_minimum_cost - Mostly same) ---
def _calculate_overall_minimum_cost(order_data):
    # Input: validated_order - {product_code: quantity > 0}
    # Output: (cost, None) or (None, error_message)

    items_needed = order_data # Already validated
    if not items_needed:
        return 0, None # No items, no cost

    needed_centers = set()
    weight_from_center = {c: 0.0 for c in CENTERS}
    total_weight = 0.0

    # 1. Calculate weights per center based on the validated order
    for product_code, quantity in items_needed.items():
        product_info = PRODUCTS[product_code] # Assumes product exists (validated earlier)
        center = product_info["center"]
        weight = product_info["weight"]
        item_total_weight = weight * quantity
        needed_centers.add(center)
        weight_from_center[center] += item_total_weight
        total_weight += item_total_weight

    min_overall_cost = float('inf')

    # 2. Iterate through possible starting centers and strategies
    for start_center in CENTERS:
        # Strategy 1: Simple Pickup (Start -> Visit others -> L1)
        cost_simple = float('inf')
        pickup_centers_to_visit = list(needed_centers - {start_center})

        if not pickup_centers_to_visit:
            # Only need items from start_center (or no items needed from this start - handled by check below)
             if start_center in needed_centers:
                 cost_simple = _calculate_travel_cost_between_stops(start_center, 'L1', total_weight)
        else:
            # Iterate through permutations of remaining centers to visit
            min_perm_cost = float('inf')
            for order in itertools.permutations(pickup_centers_to_visit):
                current_perm_cost = 0.0
                current_perm_weight = weight_from_center.get(start_center, 0.0) # Weight leaving start_center
                loc_a = start_center
                valid_path = True

                # Travel through the permutation of pickup centers
                for loc_b in order:
                    segment_cost = _calculate_travel_cost_between_stops(loc_a, loc_b, current_perm_weight)
                    if segment_cost == float('inf'):
                        valid_path = False
                        break
                    current_perm_cost += segment_cost
                    current_perm_weight += weight_from_center.get(loc_b, 0.0) # Add weight picked up at loc_b
                    loc_a = loc_b # Move to the next location

                if not valid_path:
                    continue # Try next permutation if this one is impossible

                # Final leg from the last pickup center to L1
                # Note: current_perm_weight should now equal total_weight
                final_leg_cost = _calculate_travel_cost_between_stops(loc_a, 'L1', total_weight)
                if final_leg_cost == float('inf'):
                    continue # This permutation doesn't allow final delivery

                min_perm_cost = min(min_perm_cost, current_perm_cost + final_leg_cost)

            cost_simple = min_perm_cost # Assign the minimum cost found for this start_center

        # Strategy 2: Partial Delivery (Start -> L1 -> Visit others -> L1)
        cost_partial = float('inf')
        # Condition: Must have items at start_center and need items from elsewhere
        if weight_from_center.get(start_center, 0) > EPSILON and len(needed_centers) > 1:
            weight_leg1 = weight_from_center[start_center]
            cost_leg1 = _calculate_travel_cost_between_stops(start_center, "L1", weight_leg1)

            if cost_leg1 != float('inf'):
                # Calculate cost for the second trip (L1 -> pickup remaining -> L1)
                remaining_centers = list(needed_centers - {start_center})
                weight_remaining = total_weight - weight_leg1
                cost_pickup_and_final_leg = float('inf')

                if remaining_centers: # Check if there are remaining centers to visit
                    min_perm_pickup_cost = float('inf')
                    for order in itertools.permutations(remaining_centers):
                        current_pickup_cost = 0.0
                        current_pickup_weight = 0.0 # Start empty from L1 for the second trip
                        loc_a = "L1"
                        valid_pickup_path = True

                        # Travel through the permutation of remaining centers
                        for loc_b in order:
                            segment_cost = _calculate_travel_cost_between_stops(loc_a, loc_b, current_pickup_weight)
                            if segment_cost == float('inf'):
                                valid_pickup_path = False
                                break
                            current_pickup_cost += segment_cost
                            current_pickup_weight += weight_from_center.get(loc_b, 0.0)
                            loc_a = loc_b

                        if not valid_pickup_path:
                            continue

                        # Final delivery leg for the second trip (last pickup -> L1)
                        # Note: current_pickup_weight should equal weight_remaining
                        final_delivery_cost = _calculate_travel_cost_between_stops(loc_a, 'L1', weight_remaining)
                        if final_delivery_cost == float('inf'):
                            continue

                        min_perm_pickup_cost = min(min_perm_pickup_cost, current_pickup_cost + final_delivery_cost)

                    cost_pickup_and_final_leg = min_perm_pickup_cost
                else:
                    # This case shouldn't happen if len(needed_centers) > 1 and start_center had weight,
                    # but handle defensively. If no remaining centers, second trip cost is 0.
                     cost_pickup_and_final_leg = 0.0

                # Combine cost of first delivery and the second trip if valid
                if cost_pickup_and_final_leg != float('inf'):
                    cost_partial = cost_leg1 + cost_pickup_and_final_leg

        # Update overall minimum cost considering both strategies for this start_center
        min_overall_cost = min(min_overall_cost, cost_simple, cost_partial)

    # 3. Return Result
    if min_overall_cost == float('inf'):
        return None, "No valid delivery path found for the given order."

    # Round to nearest integer for the final cost
    return round(min_overall_cost), None

# --- Flask Routes ---

# IMPORTANT: This single route '/' will handle POST requests routed to the function.
# Netlify rewrites (in netlify.toml) will map a user-facing path (e.g., /api/calculate)
# to this function's root.
@app.route('/', methods=['POST'])
def handle_calculate():
    """ Handles POST requests for calculating the minimum delivery cost. """
    # 1. Check Content-Type
    content_type = request.headers.get('Content-Type')
    if not content_type or 'application/json' not in content_type.lower():
         return jsonify({"error": "Request Content-Type must be application/json"}), 415

    # 2. Get and Validate JSON Body
    try:
        order_data = request.get_json()
        if order_data is None: # Handles empty body or non-JSON parse result
             raise ValueError("No JSON body found or failed to parse.") # Use ValueError for clarity
    except Exception as e: # Catch JSONDecodeError and other potential issues
        return jsonify({"error": f"Invalid JSON data in request body: {str(e)}"}), 400

    # 3. Validate JSON Structure (must be an object/dict)
    if not isinstance(order_data, dict):
         return jsonify({"error": "Request JSON data must be an object (key-value pairs)."}), 400

    # 4. Validate Order Items (Product Codes and Quantities)
    validated_order = {}
    validation_errors = []
    for product_code, quantity in order_data.items():
        # Ensure product code is a string (JSON keys are always strings)
        if not isinstance(product_code, str):
             validation_errors.append(f"Invalid product code format: {product_code}. Must be a string.")
             continue # Skip further checks for this item

        if product_code not in PRODUCTS:
            validation_errors.append(f"Product code '{product_code}' not found.")
            continue # Skip quantity check if product doesn't exist

        if not isinstance(quantity, int):
             validation_errors.append(f"Invalid quantity for {product_code}: '{quantity}'. Must be an integer.")
        elif quantity < 0:
             validation_errors.append(f"Invalid quantity for {product_code}: {quantity}. Cannot be negative.")
        elif quantity > 0:
             validated_order[product_code] = quantity # Only add items with quantity > 0

    if validation_errors:
        # Return a single error message with all validation failures
        return jsonify({"error": "Order validation failed.", "details": validation_errors}), 400

    # 5. Handle Empty Validated Order (all quantities were 0 or invalid)
    if not validated_order:
        return jsonify({"minimum_cost": 0}), 200 # No cost if no valid items ordered

    # 6. Call the Core Calculation Logic
    cost, error_msg = _calculate_overall_minimum_cost(validated_order)

    # 7. Return Result or Error
    if error_msg:
        # Use 400 for calculation errors like "no path found" as it stems from the request input
        return jsonify({"error": error_msg}), 400
    else:
        return jsonify({"minimum_cost": cost}), 200

# Optional: Add a simple GET handler for the root for basic "is it alive?" checks
@app.route('/', methods=['GET'])
def handle_root_get():
    """ Basic health check endpoint. """
    return jsonify({"message": "Logistics Cost API Function is running. Use POST to calculate costs."}), 200

# --- Serverless Handler ---
# This is the entry point for Netlify Functions (AWS Lambda)
def handler(event, context):
    """
    AWS Lambda handler function that integrates with Flask using serverless-wsgi.
    """
    # Use serverless_wsgi to translate the Lambda event/context into a WSGI request
    # and call the Flask app (`app`) to handle it.
    return serverless_wsgi.handle(app, event, context)

# DO NOT INCLUDE app.run() for serverless deployment
# if __name__ == '__main__':
#     app.run(debug=True) # Only for local development testing

Key Changes in api.py:

• Removed app.run(): Essential for serverless.
• Added import serverless_wsgi.
• Added handler(event, context) function: This is the function Netlify will execute. It uses serverless_wsgi.handle(app, event, context) to pass the request to your Flask app.
• Enhanced Route Validation: Moved input validation (JSON format, product codes, quantities) into the / POST route handler (handle_calculate) before calling _calculate_overall_minimum_cost. This is better practice for separating concerns (HTTP handling vs. core logic) and provides more specific error messages with correct HTTP status codes (400, 415).
• Simplified Routes: The Flask app now only defines routes starting from /. The mapping from the public URL (like /api/calculate) to this function's / route will be done in netlify.toml.
• Added GET / route: A simple endpoint to check if the function is deployed and responding.
• Improved Cost Calculation Comments/Clarity: Added comments and small refinements to the cost calculation functions for better readability. Added EPSILON for float comparisons.

---

2. Create requirements.txt

Create this file in the root directory of your project (the same level as the netlify.toml file).

Flask
serverless-wsgi

---

3. Create netlify.toml

Create this file in the root directory of your project.

# netlify.toml

[build]
  # Command to build your project (not needed for simple Python function)
  # command = "echo 'No build command needed'"

  # Directory containing the serverless functions
  functions = "netlify/functions"

  # Directory with static files to publish (if you had a frontend)
  # publish = "public" # Example if you had a 'public' folder

# Optional: Specify Python version if needed (check Netlify docs for available versions)
[build.environment]
  PYTHON_VERSION = "3.9" # Or 3.8, 3.10, 3.11 etc.

# --- Function Routing (Redirects/Rewrites) ---

# Rule for the POST request to calculate cost
[[redirects]]
  # The public URL path users will POST to
  from = "/api/calculate"
  # The internal path to your function. Netlify automatically maps this
  # to /.netlify/functions/<function_filename_without_py>
  to = "/.netlify/functions/api"
  # Status 200 indicates a rewrite (proxy), not a redirect
  status = 200
  # Force the rewrite even if a file exists at the 'from' path
  force = true
  # Only apply this rule for POST requests
  methods = ["POST"]

# Rule for the GET request to check status
[[redirects]]
  # The public URL path users will GET
  from = "/api/status" # Or could be the same as POST path if you prefer
  # The internal path to your function
  to = "/.netlify/functions/api"
  status = 200
  force = true
  methods = ["GET"]

# You could potentially combine the above GET/POST rules using a wildcard
# if your Flask app handles multiple methods on the same route internally,
# but separate rules are often clearer.

# Example of a broader rewrite if your Flask app had more routes under /api/:
# [[redirects]]
#   from = "/api/*"
#   to = "/.netlify/functions/api/:splat"
#   status = 200
#   force = true

Explanation of netlify.toml:

• [build] functions: Tells Netlify where to find your function code (netlify/functions directory).
• [build.environment] PYTHON_VERSION: Good practice to specify the Python version you developed with.
• [[redirects]]: These rules are crucial. They map user-friendly URLs (/api/calculate, /api/status) to the internal Netlify function path (/.netlify/functions/api).
  • from: The public URL path.
  • to: The internal function path. If your function file is api.py, the path is /.netlify/functions/api.
  • status = 200: Makes it a rewrite (like a proxy), so the URL in the user's browser doesn't change.
  • force = true: Ensures the rule applies.
  • methods = ["POST"] / methods = ["GET"]: Restricts the rule to specific HTTP methods.

---

4. Project Structure

Your project directory should look something like this:

your-project-root/
├── netlify.toml
├── requirements.txt
└── netlify/
    └── functions/
        └── api.py   # Your Flask app code

---

5. Deployment Steps

1. Initialize Git: If you haven't already, navigate to your-project-root in your terminal and run:

   git init
   git add .
   git commit -m "Initial commit of logistics API function"

2. Push to Repository: Create a new repository on GitHub, GitLab, or Bitbucket and push your code:

   # Add the remote repository URL (replace with your actual URL)
   git remote add origin <your-repository-url.git>
   git branch -M main # Or master depending on your default
   git push -u origin main

3. Connect to Netlify:

   • Log in to your Netlify account (or sign up).
   • Click "Add new site" -> "Import an existing project".
   • Connect to your Git provider (GitHub, GitLab, Bitbucket).
   • Select the repository you just pushed.

4. Configure Build Settings (Netlify UI):

   • Netlify should automatically detect netlify.toml.
   • Base directory: Leave blank (or /) if netlify.toml is in the root.
   • Build command: Can usually be left blank as specified in netlify.toml.
   • Publish directory: Can usually be left blank unless you have static files.
   • Functions directory: Should be detected as netlify/functions.
   • Ensure the correct Python version is selected (it should pick up from netlify.toml, but double-check under "Deploy settings" -> "Environment" -> "Environment variables" if needed, or in the build settings).

5. Deploy: Click "Deploy site". Netlify will clone your repo, install dependencies from requirements.txt, discover the function in netlify/functions, apply the netlify.toml settings, and deploy.

6. Test: Once deployed, Netlify will give you a site URL (e.g., https://your-site-name.netlify.app). You can then test your API endpoints:

   • Status Check (GET): https://your-site-name.netlify.app/api/status (using a browser or curl)
   • Calculation (POST): Use curl or a tool like Postman/Insomnia to send a POST request to https://your-site-name.netlify.app/api/calculate with a JSON body like {"A": 1, "D": 2} and the Content-Type: application/json header.

   # Example using curl
   curl -X POST \
     https://your-site-name.netlify.app/api/calculate \
     -H 'Content-Type: application/json' \
     -d '{"A": 1, "D": 2}'
   
   # Expected output (example): {"minimum_cost": 138}

That's it! Your Flask application is now packaged as a serverless function and deployed online using Netlify.

[Banner-19]

https://minimum-delivery-cost.onrender.com

[ArkS0001]

import requests
import json

api_url = "https://minimum-delivery-cost.onrender.com/"

# Your order data as a Python dictionary
order_data = {
    "A": 1,
    "F": 3,
    "H": 5
}

# Set the headers
headers = {
    'Content-Type': 'application/json'
}

try:
    # Send the POST request
    # The `json` parameter automatically serializes the dict to JSON
    # and sets the Content-Type header to application/json
    response = requests.post(api_url, json=order_data) # Using json= is preferred

    # Raise an exception for bad status codes (4xx or 5xx)
    response.raise_for_status()

    # Get the JSON response from the server
    result = response.json()
    print("Calculation successful:")
    print(result)

except requests.exceptions.RequestException as e:
    print(f"An error occurred: {e}")
    # You might want to print response.text to see error details from the server
    if hasattr(e, 'response') and e.response is not None:
        print("Server Response:", e.response.text)

except json.JSONDecodeError:
     print("Failed to decode JSON response from server.")
     print("Server Response:", response.text)

[ArkS0001]

# In a Colab code cell:

!curl -X POST \
  https://minimum-delivery-cost.onrender.com/ \
  -H 'Content-Type: application/json' \
  -d '{"A": 1, "F": 3, "H": 5}'