Here's the README for implementing the Receipt Processor web service using Go. This includes setup instructions, code explanations, and Docker setup:

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Receipt Processor (Go)

This is a web service written in Go that processes receipts and awards points based on specific rules. It includes two main endpoints:

1. To process a receipt and generate an ID.
2. To retrieve the points awarded based on that receipt ID.

Installation and Setup

Requirements

• Go 1.18+ installed
• Docker (optional, if you prefer Dockerized setup)

Installation

1. Clone the repository:

   git clone https://github.com/Harshil-Gupta/receipt-processor.git
   cd receipt-processor

2. Install dependencies: Since this service uses Go’s built-in libraries for HTTP handling and UUID generation, there are no external dependencies.

3. Build the application: Run the following command to build the Go service:

   go build -o receipt-processor main.go

4. Run the application: After building the application, start the server using:

   ./receipt-processor

   The service will be available at http://localhost:8080.

Docker Setup (Optional)

1. Build the Docker image: Create a Docker image to containerize the application.

   docker build -t receipt-processor .

2. Run the Docker container: Start the Docker container to run the web service.

   docker run -p 8080:8080 receipt-processor

   The service should now be available at http://localhost:8080.

API Documentation

1. Process Receipt

• Endpoint: /receipts/process
• Method: POST
• Payload: JSON object representing a receipt.
• Response: JSON object with a unique ID for the receipt.

Example Payload:

{
  "retailer": "Target",
  "purchaseDate": "2022-01-01",
  "purchaseTime": "13:01",
  "items": [
    { "shortDescription": "Mountain Dew 12PK", "price": "6.49" },
    { "shortDescription": "Emils Cheese Pizza", "price": "12.25" }
  ],
  "total": "35.35"
}

Example Response:

{ "id": "7fb1377b-b223-49d9-a31a-5a02701dd310" }

2. Get Points

• Endpoint: /receipts/{id}/points
• Method: GET
• Response: JSON object containing the points awarded for the receipt.

Example Response:

{ "points": 32 }

Points Calculation Rules

The points for each receipt are calculated based on the following rules:

1. Retailer Name: 1 point for each alphanumeric character.
2. Round Dollar Total: 50 points if the total has no cents (e.g., 9.00).
3. Multiple of $0.25: 25 points if the total is a multiple of 0.25.
4. Items: 5 points for every two items on the receipt.
5. Item Description Length: For each item whose description length is a multiple of 3, multiply the item price by 0.2 and round up to the nearest integer. The result is added as points.
6. Odd Purchase Day: 6 points if the day is odd.
7. Purchase Time: 10 points if the purchase time is between 2:00 PM and 4:00 PM.

Code Explanation

• main.go: This is the entry point of the service. It sets up the HTTP server, defines the routes, and handles the logic for both endpoints:

  • /receipts/process: Accepts receipt data, generates an ID, and stores the receipt in memory.
  • /receipts/{id}/points: Retrieves the stored receipt by its ID and calculates the points based on the defined rules.

• In-Memory Storage: The application uses a simple in-memory map to store receipt data temporarily. The data will be reset every time the application is restarted.

• Helper Functions:

  • calculatePoints: A function that calculates points for each receipt based on the rules.
  • generateID: A function that generates a unique ID for each processed receipt using the UUID library.
  • isOddDay, isBetweenTimes: Helper functions to check if the purchase day is odd or if the purchase time is between 2:00 PM and 4:00 PM.

Running Tests

1. Test API: Use a tool like curl or Postman to test the service.
   • POST /receipts/process: Send the receipt JSON to this endpoint to get a unique ID. Example curl command:

     curl -X POST http://localhost:8080/receipts/process -H "Content-Type: application/json" -d @receipt.json

   • GET /receipts/{id}/points: Retrieve the points for the generated receipt ID. Example curl command:

     curl http://localhost:8080/receipts/{id}/points

Example Walkthrough

1. POST /receipts/process with a sample receipt to generate an ID.
2. GET /receipts/{id}/points to retrieve the points for the generated receipt ID.

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This README provides a comprehensive guide to building, running, and testing the Receipt Processor web service in Go. It also includes a Docker setup for easier deployment and testing.