Web-calculator | English | Русский

web-calculator is a web service that allows users to send arithmetic expressions via HTTP and receive their results.

Functionality

• Supports addition, subtraction, multiplication, division operations, and expressions in parentheses
• Expressions can be entered with or without spaces between numbers and operands
• The calculator accepts positive integers as input

Requirements

• Go version 1.22 or newer

⚠️ Warning

Dear Yandex Practicum Reviewers The comments in the code, from start to finish, were written by me and comply with the requirements of go-lint, which I use in my project to adhere to the code style.

Installation

1. Clone the repository

git clone https://github.com/bulbosaur/web-calculator-golang

2. Run the server from the project repository

go run cmd/main.go

Environment Variables

Variable	Description	Default Value
PORT	Port for running the server	8080
HOST	Host for running the server	localhost
TIME_ADDITION_MS	Execution time for the addition operation in milliseconds	100
TIME_SUBTRACTION_MS	Execution time for the subtraction operation in milliseconds	100
TIME_MULTIPLICATIONS_MS	Execution time for the multiplication operation in milliseconds	100
TIME_DIVISIONS_MS	Execution time for the division operation in milliseconds	100
DATABASE_PATH	Path to the database

To change the values of the environment variables, you need to create a file named config.yaml (or edit the existing file example_config.yaml).

Example of a Config File

# web-calculator-golang/config/config.yaml
server:
  host: localhost
  port: 8080

time:
  TIME_ADDITION_MS: 100
  TIME_SUBTRACTION_MS: 100
  TIME_MULTIPLICATIONS_MS: 100
  TIME_DIVISIONS_MS: 100

database:
  DATABASE_PATH: ./db/calc.db

API

Default base URL: http://localhost:8080

API endpoint	Method	Request Body	Server Response	Response Code
/api/v1/calculate	POST	{"expression": "2 * 2"}	{"result":"4"}	200
/api/v1/calculate	POST	"expression": "2 * 2"	{"error":"Bad request","error_message":"invalid request body"}	400
/api/v1/calculate	GET	{"expression": "2 * 2"}	Method Not Allowed	405
/coffee			I'm a teapot	418
/api/v1/tea			404 page not found	404

Response Codes

• 200 - Successful request
• 400 - Bad request
• 404 - Resource not found
• 405 - Method not allowed
• 422 - Invalid expression (e.g., English letter instead of a number)
• 500 - Internal server error

Usage Examples

For sending POST requests, it's most convenient to use Postman.

1. StatusOK 200

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "42 + 5 * 2"
}'

# {"result":52}

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "6-8"
}'

# {"result":-2}

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "123(3/2)"
}'

# {"result":184.5}

2. Bad Request 400

curl 'localhost/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "2 * 2
}'

# {"error":"Bad request","error_message":"invalid request body"}

3. Unprocessable Entity 422

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "cat + 100500"
}'

# {"error":"Expression is not valid","error_message":"invalid characters in expression"}

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "()"
}'

# {"error":"Expression is not valid","error_message":"the brackets are empty"}

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "1/(2 - 3 + 1)"
}'

# {"error":"Expression is not valid","error_message":"division by zero is not allowed"}

curl 'localhost:8080/api/v1/calculate' \
--header 'Content-Type: application/json' \
--data '{
  "expression": "1 000 000 + 6"
}'

# {"error":"Expression is not valid","error_message":"missing operand"}