@qrvey/function-gateway/README.md

 

# @qrvey/function-gateway

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The `@qrvey/function-gateway` package provides a unified interface for invoking lambda and REST functions based on the specific configurations of the service.

## Installation

You can install the package using npm or yarn:

```bash
npm install @qrvey/function-gateway
```

Or with yarn:

```bash
yarn add @qrvey/function-gateway
```

Note: If the application does not have @aws-sdk/client-lambda installed, it must be installed manually. @qrvey/function-gateway requires it to make Lambda invoke calls.

### Conditions for Lambda or REST call

The function gateway in the `@qrvey/function-gateway` package can invoke functions either as a Lambda function or as a REST API call, depending on certain conditions. These conditions are determined by:

1. **REST Invocation**:
    - If the environment variable `PLATFORM_TYPE` is set to `'CONTAINER'` and the function mapping contains a REST configuration.
    - If the `options.mappingType` parameter is explicitly set to `'rest'`.

2. **Lambda Invocation**:
    - If the `options.mappingType` parameter is explicitly set to `'lambda'`.
    - In the absence of `options.mappingType` being specified, the function gateway will default to Lambda invocation unless there is a REST configuration and no Lambda configuration.


## Usage Example

```javascript
const { FunctionGatewayService } = require("@qrvey/function-gateway");
const mapper = require("./fnGwMapping");

class MyFunctionGateway extends FunctionGatewayService {
  getInfoById(id) {
    const headers: {
        'x-api-key': 'my-api-key'
    }
    const params = { headers, dataId: id };
    return MyFunctionGateway.invoke("getData", params, mapper);
  }
}

const myFunctionGw = new MyFunctionGateway();
myFunctionGw
  .getInfoById("my_id")
  .then((res) => {
    // Handle successful result
    console.log(JSON.parse(res.Payload));
  })
  .catch((error) => {
    // Handle errors
    console.log(error);
  });
```

## API

### Class
`FunctionGatewayService`

#### Function
`static invoke(functionName: string, params: unknown, functionMapping: IFunctionMapping, options: IFunctionOptions): Promise<any>`

-   **`functionName`**: The name of the function to invoke.
-   **`params`**: Parameters to be provided to the corresponding property in the functionMapping definition.
-   **`functionMapping`**: An object that maps function names to function implementations.
-   **`options`**: An object containing additional options for invoking the function.
-   **Returns**: A promise that resolves with the result of the invoked function or rejects with an error if the invocation fails.

#### `functionMapping param`

Defines the mapping of function names to their corresponding implementations.

Example

This example demonstrates how to configure both a Lambda function and a REST API call:

```javascript
const mapper = {
    // Define a mapping for a function named 'getData'
    getData: (param) => {
        return {
            // Configuration for a Lambda invocation
            lambda: {
                // [required] The name of the Lambda function
                name: process.env.SERVER_PREFIX + '_getDataFunction',
                // [required] The payload to send to the Lambda function
                payload: {
                    headers: param.headers,
                    method: 'get', // HTTP method for the request
                    body: {
                        pathParameters: {
                            dataID: param.dataID, // Parameters to pass to the Lambda function
                        },
                    },
                },
                // [optional]
                options: {
                    asHttp: false,
                    //invocationParams defines the additional params to be passed in lambda.invoke call
                    invocationParams: {
                        Qualifier: 'my_lambda_alias' //should be the name of the property used in lambda.invoke of @aws-sdk/client-lambda library
                    },
                },
                // A callback function to handle the Lambda response
                callback: (res) => {
                    const responseObj = JSON.parse(res.Payload);
                    return responseObj.data; // Extracting and returning the data from the response
                },
            },
            // Configuration for REST API invocation
            rest: {
                // The URL for the REST API call
                endpoint: `/api/service-data/${param.dataID}`,
                // The HTTP method for the request
                method: 'get',
                // Additional options for the REST API call
                options: {
                    baseDomain: process.env.API_DOMAIN,
                    headers: param.headers, // Headers to include in the request
                },
            },
        };
    }
};
```