# frozen_string_literal: true

# Tableless model to handle updating multiple models at once from a single form
module Sets
  class ModelSet
    include ActiveModel::Conversion
    extend ActiveModel::Naming

    attr_accessor :collection

    def initialize(klass, collection, attributes = {}, reject_if = nil, delete_if = nil)
      @klass, @collection, @reject_if, @delete_if = klass, collection, reject_if, delete_if

      # Set here first, to ensure that we apply collection_attributes to the right collection
      @collection = attributes[:collection] if attributes[:collection]
      @collection = @collection.to_a

      attributes.each do |name, value|
        public_send("#{name}=", value)
      end
    end

    def collection_attributes=(collection_attributes)
      collection_attributes.each_value do |attributes|
        # attributes == {:id => 123, :next_collection_at => '...'}
        found_element = @collection.detect do |element|
          element.id.to_s == attributes[:id].to_s && !element.id.nil?
        end

        if found_element.nil?
          @collection << @klass.new(attributes) unless @reject_if&.call(attributes)
        else
          process(found_element, attributes)
        end
      end
    end

    # The request params are assigned to the fetched record here, becoming dirty and ready to
    # be persisted in DB as an UPDATE.
    #
    # This enables having different process strategies depending on the concrete model set class, if
    # we choose to. This will be the default implementation.
    def process(found_element, attributes)
      found_element.assign_attributes(attributes.except(:id))
    end

    def errors
      errors = ActiveModel::Errors.new self
      full_messages = @collection
        .map { |model| model.errors.full_messages }
        .flatten

      full_messages.each { |message| errors.add(:base, message) }
      errors
    end

    def invalid
      @collection.select { |model| model.errors.any? }
    end

    def save
      collection_to_delete.each(&:destroy)
      collection_to_keep.all?(&:save)
    end

    def collection_to_delete
      # Remove all elements to be deleted from collection and return them
      # Allows us to render @model_set.collection without deleted elements
      deleted = []
      @collection = collection.to_a
      collection.delete_if { |e| deleted << e if @delete_if&.call(e.attributes) }
      deleted
    end

    def collection_to_keep
      collection.reject { |e| @delete_if&.call(e.attributes) }
    end

    def persisted?
      false
    end

    def find_model(collection, model_id)
      collection.find do |model|
        model.id.to_s == model_id.to_s && model.persisted?
      end
    end
  end
end