houdini/app/models/concerns/model/jbuilder.rb

# frozen_string_literal: true

# License: AGPL-3.0-or-later WITH WTO-AP-3.0-or-later
# Full license explanation at https://github.com/houdiniproject/houdini/blob/master/LICENSE
module Model::Jbuilder
	extend ActiveSupport::Concern
	class_methods do
		#
		# Builder expansions address a common issue when using Jbuilder for generated JSON for object events work with `#init_builder`
		# In some situations, a model may reference another object but, depending on the situation, may not want to expand that object
		# 
		# As an example, consider an hypothetical Supporter class with a reference to a Nonprofit
		#
		# class Supporter < ApplicationRecord
		#		belongs_to :nonprofit
		#   belongs_to :group
		# 	def to_builder(*expand)
		#			 init_builder(*expand) do 
		#      # build you JBuilder object
		#			 end
		#   end
		# end
		#
		# When generating the the Jbuilder object, you may want to expand the nonprofit object or in other situations not expand it. To handle this
		# you would need to write the following code:
		# `
		#	if expand.include? :nonprofit
		#		json.nonprofit nonprofit.to_builder.attributes!
		#	else
		#		json.nonprofit nonprofit.to_id
		#	end
		#  `
		# You would have to write the same code for `group`. As your number of expandable attributes increase, your code gets filled with boilerplate code.
		# 
		# `add_builder_expansion` addresses this by autocreating this code in to_builder.
		# For example, if you want nonprofit to be expandable as in the nonprofit json attribute, and group into the group json attribute. You only need to write:
		# `add_builder_expansion :nonprofit, :group`
		# You can put as many expandable attributes there as you'd like.
		#
		# On the other hand, let's say you want to make group expandable BUT you want to assign it to the "supporter_group" json attribute. To do that, you
		# pass in the attribute you want to be expandable along with the "json_attribute" method key set to 'supporter_group': 
		# `add_builder_expansion :group, json_attribute: 'supporter_group'`
		#
		# For enumerable attributes (like a has_many or an array), there are two ways you may want to include them into your json output. If it's a set of simple values 
		# like, an array of strings or numbers, you may want to want to the array output as-is. For example, let's say you have a array of tags which are strings. You may want
		# it to be output like so:
		# ````
		# tags: [ 'founders circle', 'large donor']
		# ```
		# We call these `:flat` enumerable attribtes. Assuming the supporter class before has a tags attribute, you would add the tags builder_expansion using:
		# ```
		# add_builder_expansion :tags, enum_type: :flat
		# ```
		#
		# On the other hand, you may want to have an array of other Jbuilder created objects. Let's say your supporter has many groups. You may want these attributes expanded in
		# one of two ways: expanded or unexpanded.
		# 
		# For expanded, you would receive have something like this in your output:
		# 
		# {
		#		# ... some other parts of the supporter json
		# 	groups: [{ id: 546, name: 'group name 1'}, {id: 235, name: 'group name 2'}]
		# }
		# 
		# However, for unexpanded, you'd just want the ids:
		# 
		# {
		#		# ... some other parts of the supporter json
		# 	groups: [546, 235]
		# }
		#
		# For this type of builder expansion, you would use:
		# ```
		# add_builder expansion :groups, enum_type: :expandable
		# ```
		#
		# @param [Symbol] *attributes the attributes you'd like to make expandable. If you want to set options, there should only be a single attribute here.
		# @param  **options options for configuring the builder expansion. The options right now are:
		# - `json_attribute`: the json attribute name in the outputted Jbuilder. Defaults to the attribute name.
		# - `enum_type`: the type of enumerable for the attribute. pass :flat if the enumerable attribute is flat, or :expandable if it's expandable. ANy other value 
		# including the default of nil, means the attribute is not enumerable.
		#
		def add_builder_expansion(*attributes, **options)
			builder_expansions.add_builder_expansion(*attributes, **options)
		end

		#
		# A set of all the builder expansions configured for a class
		#
		# @return [Array] the builder expansions
		#
		def builder_expansions 
			@builder_expansions ||= BuilderExpansionSet.new
		end

		def init_builder(model, *expand)
			JbuilderWithExpansions.new(model, *expand) do | json|
				json.(model, :id)
				json.object model.class.name.underscore
				
				yield(json)
			end
		end
	end

	def to_id
		id
	end

	class BuilderExpansionSet < Set
		def add_builder_expansion(*args, **kwargs)
			be = nil
			if args.any? || kwargs.any?
				if (args.count == 1 && kwargs.any?)
					be = BuilderExpansion.new(**{key: args[0]}.merge(kwargs))
					add(be)
				else
					args.each do |a|
						be = BuilderExpansion.new(key: a)
						add(be)
					end
				end
			else
				raise ArgumentError
			end
		end

		def keys
			map{|i| i.key}
		end

		def get_by_key(key) 
			select{|i| i.key == key}.first
		end
	end

	class BuilderExpansion
		include ActiveModel::AttributeAssignment
		attr_accessor :key, :json_attribute, :enum_type

		def initialize(new_attributes)
			assign_attributes(new_attributes)
		end
		def enumerable?
			expandable_enum? || flat_enum?
		end

		def expandable_enum?
			enum_type == :expandable
		end

		def flat_enum?
			enum_type == :flat
		end

		def json_attribute
			(@json_attribute || key).to_s
		end

		def to_id
			return ->(model,be=self) {	
				value = be.get_attribute_value model
				if be.expandable_enum?
					value&.map do |i|
						id_result = i&.to_id
						if ::Jbuilder === id_result
						 	id_result.attributes!
						else
						 	id_result
						end
					end
				elsif be.flat_enum?
					value
				else
					value&.to_id
				end
			}	
		end

		def to_builder
			return ->(model,be=self) { 
				value = be.get_attribute_value model
				if be.expandable_enum?
					value&.map{|i| i&.to_builder.attributes!}
				elsif be.flat_enum?
					value
				else
					value&.to_builder
				end
			}
		end

		def get_attribute_value(model)
			if model.respond_to? key
				model.send(key)
			else
				raise ActiveModel::MissingAttributeError, "missing attribute: #{key}"
			end
		end
	end

	def init_builder(*expand, &block)
		self.class.init_builder(self, *expand, &block)
	end


	class JbuilderWithExpansions < ::Jbuilder
		attr_reader :model, :expand
		
		delegate_missing_to :@jbuilder
		
		def initialize(model, *expand, &block)
			@model = model
			@expand = expand
			super(&block)
		end

		def add_builder_expansion( ... )
			builder_expansions = BuilderExpansionSet.new
			builder_expansions.add_builder_expansion( ... )
			builder_expansions.keys.each do |k|
				if expand.include? k
					set! builder_expansions.get_by_key(k).json_attribute, builder_expansions.get_by_key(k).to_builder.(model)
				else
					set! builder_expansions.get_by_key(k).json_attribute, builder_expansions.get_by_key(k).to_id.(model)
				end
			end
		end
	end
end