[](https://www.npmjs.com/package/@nidomiro/relation-tuple-parser)
npm install @nidomiro/relation-tuple-parser
This library can parse a string representation of a Relation tuple to an object structure in typescript.
Relation tuples are used to evaluate permissions in "Zanzibar: Google's Consistent, Global Authorization System".
The BNF of a valid Relation tuple is as follows:
``BNF`
Examples of valid strings:
`
namespace:object#relation@subjectId
namespace:object#relation@(subjectId)
namespace:object#relation@subjectNamespace:subjectObject#subjectRelation
namespace:object#relation@(subjectNamespace:subjectObject#subjectRelation)
The different parts of the Relation tuple can contain any character but :#@().
A Relation tuple can easily be verbalised:
The Relation tuple sharedFiles:a.txt#access@(dirs:b#access) can be verbalised as "Anyone with access to dirs:b
has to sharedFiles:a.txt".
After Parsing you get an object in the format:
`ts
interface SubjectSet {
namespace: string
object: string
relation: string
}
interface RelationTuple {
namespace: string
object: string
relation: string
subjectIdOrSet: string | SubjectSet
}
`
`ts
import { parseRelationTuple } from '@nidomiro/relation-tuple-parser'
const result = parseRelationTuple('sharedFiles:a.txt#access@(dirs:b#access)')
const value = result.unwrapOrThrow()
/* value = {
namespace: 'sharedFiles',
object: 'a.txt',
relation: 'access',
subjectIdOrSet: {
namespace: 'dirs',
object: 'b',
relation: 'access',
},
}
*/
`
It is also possible to parse the Relation tuple in a structure where different placeholders can be replaced.
This is especially useful if you define a Guard via Decorators but require som dynamic replacements e.g. for the id of
the current user.
`ts
import { parseRelationTupleWithReplacements } from '@nidomiro/relation-tuple-parser'
const result = parseRelationTupleWithReplacements(({ userId }) => groups:admin#member@${userId})
/**
* Contains the "Template" of the Relation tuple with the replacements defined above.
* Calculate this once and use it on every evaluation.
*/
const valueWithreplacements = result.unwrapOrThrow()
/**
* Execute this at evaluation time (e.g. every incomming Request) to get the actual Relation tuple to evaluate against.
*/
const relationTuple = applyReplacements(valueWithreplacements, {
userId: 'my_user_id',
})
/* relationTuple = {
namespace: 'groups',
object: 'admin',
relation: 'member',
subjectIdOrSet: 'my_user_id',
}
*/
`
Run nx build typescript to build the library.
Run nx test typescript to execute the unit tests.
Make sure you are logged into npm.
Run nx publish typescript --tag latest --ver x.x.x` to publish to npm.