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Helper Functions

Space Cloud comes packed with quite a few helper functions that you can in transformations.

Helper functions in go templates

There are two sets of helper functions available in go templates for transformations in Space Cloud:

Functions made by us.
Sprig functions - A popular library for useful functions in go templates.

Below we are going to explain the functions made by us before giving a summary of the sprig functions:

hash

The hash function generates an SHA-256 hash of the provided string.

Example: Hash the password field recieved in the request body:

{{ $hashedPassword := hash .args.password }}

generateId

The generateId function simply returns a ksuid (K-Sortable Unique ID) string.

You can use this function to generate unique IDs in your templates.

Example:

{{ $id := generateId }}

marshalJSON

The marshalJSON function stringifies a given JSON object.

Many times while using go templates, we found ourselves simply shifting a JSON object up or down. For example, let’s say we want to transform the following response object:

{
  "result": {
    "user": {
      "id": "1",
      "name": "John"
    }
  }
}

to:

{
  "user": {
    "id": "1",
    "name": "John"
  }
}

The template for such transformation would look like this:

{
  "user": {
    "id": "{{ .args.result.user.id }}",
    "name": "{{ .args.result.user.name }}"
  }
}

As you can see, this use case will quickly become very tedious if the user object has a lot of fields.

With marshalJSON, we can simply generate the stringified version of the user object and use it instead of generating the string manually for each field. Here’s an example of how to achieve this with marshalJSON:

{
  "user": {{ marshalJSON .args.result.user }}
}

copy

The copy function creates a deep copy of the given object.

Example:

{{ $object2 := copy args.object1 }}

parseTimeInMillis

The parseTimeInMillis takes an integer (number of milliseconds since epoch) and converts it into a time object. This time object can then be used by other date functions in sprig for performing various operations like converting it into a date string or adding/subtracting time, etc.

Example: Convert time in milliseconds to a string with the format YEAR-MONTH-DAY with the help of parseTimeInMillis and date ( sprig function):

{{ $d := parseTimeInMillis .args.millis }}
{{ $dateString := date .d "2006-01-02" }}

If you are wondering what’s the 2006-01-02, its because date formatting in Golang is a little bit different.

sprig functions

Space Cloud supports Sprig functions in its go templates. Sprig is a library of useful functions for Go templates. It has tons of functions for working with strings, arrays, dates, etc.

Example: Uppercase a string:

{{ $name := "john" }}
{{ $uppercasedName = upper .name }}

Check out the documentation of Sprig functions to learn all the functions in details.

Helper functions in header modifications

All the utils functions in security rules are available for use in header modifications as well.

For example, let’s say you want to set a header Billing-Enabled to true based on whether the JWT claims contains a field called billingId. Here’s the header modification config for it using the exists function:

op: set
key: Billing-Enabled
value: utils.exists(auth.billingId)