@tangle/overwrite-fields

This strategy can be used to handle transformations which are objects which have arbitrarily set keys and values (potentially conforming to some pattern):

const T = {
  '@mix': 'mix irving',
  '@colin': 'Colin Pilborow'
}

Using concat, subfields can be given new values and additional subfields can be added.

overwrite.concat(
  {
    '@mix': 'mixmix',
    '@colin': 'Colin Pilborow'
  },
  {
    '@mix': 'Mix Irving',
    '@cherese': 'Cherese Epinu'
  }
)
// => {
//   '@mix': 'Mix Irving',        // overwrite
//   '@colin': 'Colin Pilborow'
//   '@cherese': 'Cherese Epinu'
// }

The internal implementation means that once a subfield is set, it cannot be unset. If you must erase a field you may want to allow values such as null and then choose to ignore that. This strategy is noncommutative, so it conflicts if the same subfield is set to different values in different branches. A merge is valid if it overwrites all conflicting subfields. see tests for examples.

API

Overwrite(opts) => overwrite

opts Object (optional) can have properties:

• opts.keyPattern String
  • add a JSON-schema string pattern
  • default: '^.+$'
• opts.valueSchema Object
  • add a JSON-schema to validate the values which are allowed to be passed in
  • default: { type: 'string' }

overwrite.schema

overwrite.isValid

overwrite.identity() => I

overwrite.concat(R, S) => T

overwrite.mapFromInput(input, currentTips) => T

overwrite.mapToOutput(T) => state

overwrite.isConflict(graph, nodeIds, field) => Boolean

where:

• graph is a @tangle/graph instance
• nodeIds is an Array of nodeIds you're wanting to check for conflict
• field String contains the the data fields node.data[field] you're checking for conflicts

overwrite.isValidMerge(graph, mergeNode, field) => Boolean

where:

• graph is a @tangle/graph instance
• mergeNode is the proposed merge-node
• field String contains the the data fields node.data[field] you're checking for merge validity

overwrite.merge(graph, mergeNode, field) => T

similar to isValidMerge, but return a transformation, T If it cannot, an error is thrown!