sharp-error-handler/README.md

an error handler that integrates with Hapi/boom to manage all server errors through JSON file

## Sharp-Error-Handler

A NodeJS module that integrates with [HapiJS Server Framework](https://hapijs.com/) & uses [Boom](https://www.npmjs.com/package/boom) to return custom error messages, error codes & custom error fields.

First define a json object containing where the key is the error name, value is an object containing the required statusCode & message (you may use also use [extraFields](#extrafields)

```json

{
	"invalidId": {
		"statusCode": 400,
		"message": "This Id is invalid"
	},
	
	"notAuthorized": {
		"statusCode": 403,
		"message": "You're not authorized to access this item"
	}
}
```

Then create your custom error objects 
```javascript

const errorHandler = require('sharp-error-handler');
const ServerErrors = errorHandler.createServerErrors(errorsData);
```
Then inside your code
```javascript

throw new ServerErrors.InvalidId();
```
and in the catch function
```javascript

catch(error) {
	return errorHandler.wrapError(null, error);
}
```
This makes Hapi Server returns 

```json

{
    "statusCode": 400,
    "message": "This Id is invalid",
    "error": "Bad Request Error"
}
```

### Features
- `wrapError` function takes two arguments, the first is a log class & the second is the error object itself.
  the module calls the log function of the first argument, this is helpful if your server uses a default logging library like winston. You can also provide the `console` class

- Some modules use logging with tag, example
  ```javascript
  
  class.log(tag, message)
  ```
  Then you can use the other function which is `wrapErrorWithTag` which takes three arguments. `loggerClass`, `tag`, `error`

- The arrangement of arguments is made this way to facilitate the usage of `curry` functions.

- a flag called `isCreatedServerError` is added on the error object if the user needs to know whether the error was thrown on purpose or not
  ```javascript
  
  const wrappedError = errorHandler.wrapError(null, error);
  console.log(wrappedError.isCreatedServerError); //true if the error was created by errorHandler.createServerErrors
  ```

- Error names are defaulted to first letter capital
  example: if errors.json is
  ```json
  
  {
  	"invalidId": {
  		"statusCode": 400,
  		"message": "This Id is invalid"
      }
  }
  ```
  Then the error will to throw will be
  ```javascript
  
  ServerErrors.InvalidId()
  ```

- If data is provided in the constructor object of the error it will be added by default to the error message
  example: if errors.json is
  ```json
  
  {
  	"invalidId": {
  		"statusCode": 400,
  		"message": "This Id is invalid: "
  	}
  }
  ```
  and the error is 
  ```javascript
  
  throw new ServerErrors.InvalidId("122");
  ```
  The message returned will be
  ```
  
  "This Id is invalid: 122"
  ```
  

### extraFields:

- adds all keyValue pairs written inside it to the default output object of Hapi

- must be an object

- example:

  errors.json

  ```json
  
  {
  	"invalidId": {
  		"statusCode": 400,
  		"message": "This Id is invalid",
  		"extraFields": {
  			"ERROR_CODE": 112
  		}
  	}
  }
  ```

  

  Hapi final result will be

  ```json
  
  {
      "statusCode": 400,
      "message": "This Id is invalid",
      "error": "Bad Request Error",
      "ERROR_CODE": 112
  }
  ```