# frozen_string_literal: true

module Phlexi
  module Form
    module Structure
      # Generates DOM IDs, names, etc. for a Field, Namespace, or Node based on
      # norms that were established by Rails. These can be used outsidef or Rails in
      # other Ruby web frameworks since it has now dependencies on Rails.
      class DOM
        def initialize(field:)
          @field = field
        end

        # Converts the value of the field to a String, which is required to work
        # with Phlex. Assumes that `Object#to_s` emits a format suitable for the web form.
        def value
          @field.value.to_s
        end

        # Walks from the current node to the parent node, grabs the names, and seperates
        # them with a `_` for a DOM ID. One limitation of this approach is if multiple forms
        # exist on the same page, the ID may be duplicate.
        def id
          lineage.map(&:key).join("_")
        end

        # The `name` attribute of a node, which is influenced by Rails (not sure where Rails got
        # it from). All node names, except the parent node, are wrapped in a `[]` and collections
        # are left empty. For example, `user[addresses][][street]` would be created for a form with
        # data shaped like `{user: {addresses: [{street: "Sesame Street"}]}}`.
        def name
          root, *names = keys
          names.map { |name| "[#{name}]" }.unshift(root).join
        end

        # Emit the id, name, and value in an HTML tag-ish that doesnt have an element.
        def inspect
          "<id=#{id.inspect} name=#{name.inspect} value=#{value.inspect}/>"
        end

        private

        def keys
          lineage.map do |node|
            # If the parent of a field is a field, the name should be nil.
            node.key unless node.parent.is_a? FieldBuilder
          end
        end

        # One-liner way of walking from the current node all the way up to the parent.
        def lineage
          Enumerator.produce(@field, &:parent).take_while(&:itself).reverse
        end
      end
    end
  end
end