agson/src/agson/traversals.coffee

Querying and manipulating JSON graphs

{Just, Nothing, fromNullable} = require 'data.maybe'
{maybeMap, maybeMapValues, isArray, isObject} = require './util'

Traversal = require './Traversal'
traversal = Traversal.of

nothing =
  modify: Nothing
  get: Nothing

list = traversal "list", (mta) ->
  modify: (f) ->
    mta.chain (ta) ->
      unless isArray ta
        Nothing()
      else
        Just maybeMap ta, (a) ->
          f fromNullable a

  get: ->
    mta.chain (ta) ->
      unless isArray ta
        Nothing()
      else
        Just ta


object = traversal "object", (mo) ->
  modify: (f) ->
    mo.map (object) ->
      unless isObject object
        Nothing()
      else
        maybeMapValues object, (value) ->
          f fromNullable value
  get: ->
    mo.chain (object) ->
      unless isObject object
        Nothing()
      else
        Just object

module.exports = {
  list
  object
}