github.com/gmaschi/log-exp-eval

Logical Expression Evaluator

Assumptions

The current implementation of the logical expression evaluator assumes that:

1. the given expression characters (and logical operators) must only be separated by spaces ;
2. the given expression must contain only lowercase variables, such as x AND y;
3. the given expression must be a valid logical expression (expression validation is not yet implemented -- see TODOs section).

Running the application

Required applications

• make
• docker:
  • docker-compose engine if running an older version of docker. You may also need to change the docker compose commands throughout the application to docker-compose.

Run make server to spin the database and server. The server runs at port 8080.

Stopping the application

To stop the application and clean all resources, run make server-down.

Running tests

There are three commands to run the application tests:

• make unit-test: runs only unit tests;
• make integration-test: runs only integration tests;
• make test: runs both unit and integration tests.

Integration tests will run in their own containers.

API

The full API documentation can be seen through the swagger document at internal/docs/generated/swagger.json. You can also run directly from the application by running make swag-serve. It will install go-swagger through brew if you don't have it.

There is also a postman collection at internal/docs/postman/exp-eval-postman-collection.json for convenience with all the main requests.

There are some important mentions regarding the challenge's requirements that need to be made:

1. a v1 prefix was used to version the endpoints, so, the endpoint /evaluate/{expression_id}?x=1,y=0,z=1 described in the requirements is at v1/evaluate/{expression_id}?x=1,y=0,z=1. This rule applies to every endpoint;
2. the create and update endpoints were designed separately, instead of a POST at v1/expressions to perform both depending on the payload, we leverage the HTTP methods to differentiate between these two actions. POST to create and PATCH to update and expression.
3. some additional endpoints were added to the API, such as:
   1. GET v1/expressions/{id}: get expression by ID;
   2. DELETE v1/expressions/{id}: delete expression by ID;
   3. PATCH v1/expressions: updates an existing expression.

The API requires authentication for all endpoints. There are two mocked bearer tokens that can be used to run requests against the server:

token 1: 74edf612f393b4eb01fbc2c29dd96671
token 2: d88b4b1e77c70ba780b56032db1c259b

Each token is tied to a specific user, and there are operations in the system that can only be performed by the author of the expression e.g.: updating/deleting/getting by id.

Some Sample Requests/Responses for each endpoint:

Create expression

Request:

curl --location --request POST 'http://localhost:8080/v1/expressions' \
--header 'Authorization: Bearer 74edf612f393b4eb01fbc2c29dd96671' \
--header 'Content-Type: application/json' \
--data-raw '{
    "expression": "((x OR y) AND (z OR k) OR j)"
}'

Response:

{
    "expressionID": "659f9c60-9056-4ba2-ae12-bb70533d8671",
    "expression": "((x OR y) AND (z OR k) OR j)",
    "username": "John Doe",
    "createdAt": "2023-02-05T18:03:59.41586Z",
    "updatedAt": "2023-02-05T18:03:59.41586Z"
}

Get expression by ID

Request:

curl --location --request GET 'http://localhost:8080/v1/expressions/659f9c60-9056-4ba2-ae12-bb70533d8671' \
--header 'Authorization: Bearer 74edf612f393b4eb01fbc2c29dd96671'

Response:

{
    "expressionID": "659f9c60-9056-4ba2-ae12-bb70533d8671",
    "expression": "((x OR y) AND (z OR k) OR j)",
    "username": "John Doe",
    "createdAt": "2023-02-05T18:03:59.41586Z",
    "updatedAt": "2023-02-05T18:03:59.41586Z"
}

List expressions

List expressions endpoint was built with support for pagination by sending page_id and page_size as query parameters. PageID must be greater than 0. Pagination information (page number, page items and total number of pages will be added to the header response)

Request:

curl --location --request GET 'http://localhost:8080/v1/expressions?page_id=1&page_size=2' \
--header 'Authorization: Bearer 74edf612f393b4eb01fbc2c29dd96671'

Response:

[
    {
        "rowID": 1,
        "expressionID": "659f9c60-9056-4ba2-ae12-bb70533d8671",
        "expression": "((x OR y) AND (z OR k) OR j)",
        "username": "John Doe",
        "createdAt": "2023-02-05T18:03:59.41586Z",
        "updatedAt": "2023-02-05T18:03:59.41586Z"
    },
    {
        "rowID": 2,
        "expressionID": "11625fa6-cb11-491d-97fa-089fa94d43b5",
        "expression": "((x OR y) AND (z OR k) OR j)",
        "username": "John Doe",
        "createdAt": "2023-02-05T18:05:44.774641Z",
        "updatedAt": "2023-02-05T18:05:44.774641Z"
    }
]

Delete expression

Request:

curl --location --request DELETE 'http://localhost:8080/v1/expressions/11625fa6-cb11-491d-97fa-089fa94d43b5' \
--header 'Authorization: Bearer 74edf612f393b4eb01fbc2c29dd96671'

Response: A success response will return a 204 (status no content) http status.

Evaluate expression

Request:

curl --location --request GET 'http://localhost:8080/v1/evaluate/11625fa6-cb11-491d-97fa-089fa94d43b5?X=1&y=0&z=1&k=0&j=1' \
--header 'Authorization: Bearer 74edf612f393b4eb01fbc2c29dd96671' \
--header 'Content-Type: application/json' \
--data-raw '{
    "expression": "((x OR y) AND (z OR k) OR j)"
}'

Response:

{
    "result": true
}

TODOs

The logical expression evaluator method used is not complete, leading to some misleading results for some edge cases. The following must still be implemented:

1. validate a given logical expression before saving/evaluating its value, so we know that we will always have reliable expressions;
2. implement support for ! (NOT) operator;
3. take the operators' order of precedence into account when performing an evaluation;