Capabilities utils

Here are a number of useful utilities provided for managing lists of attenuations aka capabilities.

UCAN is a beautifully unopinionated standard, but in order to make this more turn-key usable, we have had to opine. The possible segments supported by these utilities are READ, WRITE, CREATE, DELETE and superuser *.

Some of these utilities are really just for the convenience of working with any sort of UI for these capabilities.

Ability Structure

export type AbilityTree = {
    'READ': Array<string>,
    'CREATE': Array<string>,
    'WRITE': Array<string>,
    '*': Array<string>
};
export const abilityTree: AbilityTree = {
    'READ': [],
    'CREATE': ['READ'],
    'WRITE': ['READ', 'CREATE'],
    '*': ['READ', 'WRITE', 'CREATE', 'DELETE']
};

Utilities

• abilityObj(abilities: Array):AbilityObj organizes a list of capabilities into an object keyed by the capability with stringified. Secondly each with space is organized into namespace keys. This allows object traversal of abilities for a given namespace.

• (obj: { [key:string]:Superuser|{[key:string]:string[]} }):Array simply flattens out an AbilityObj into an attenuations list

• stackedAbilities(abilities: Array):Array calls abilityObj and flattenAbilityObj to dedup a list of Capabilities.

• reduceAbilities(reduce: Array, abilities: Array):Array where the first argument is Capabilities you want to remove from a list of Capabilities. Returns the reduced Capability list.

• stackAbilities(abilities: Array):Array could almost seem redundant to stackedAbilities !!except!! there is an important functionality within UCANs that needs to be considered. If you consider that giving someone WRITE ability would normally assume READ and CREATE as well. However, there is no such etymology within the UCAN functions. That's where we opine. If you stack abilities, all lesser abilities will be added to each namespace that has a greater ability. So it lengthens the total list of Capabilities to match how UCAN verify functions. This way, for UI purposes, you only need the greatest possible ability to know all abilities. Of course UCAN is far more extensible than this, but this is a sound, time-tested, and simple approach to handling permissions. It only limits you inasmuch as you use these utilities - you can still do anything you wish with your UCAN implementation.