module Tabulatr::JsonBuilder
  def self.build(data, klass, requested_attributes, id)
    if klass && ActiveModel.const_defined?(:ArraySerializer)
      ActiveModel::ArraySerializer.new(data,
        { root: "data", meta: data.__pagination,
          each_serializer: klass
        }).as_json
    else
      id_included = false
      attrs = build_hash_from requested_attributes, id
      result = []
      data.each do |f|
        tmp = {}
        attrs.each do |at|
          insert_attribute_in_hash(at, f, tmp)
        end
        result << tmp
      end
      { data: result, meta: data.__pagination }
    end
  end

  private

  def self.build_hash_from requested_attributes, id
    attrs = []
    id_included = false
    requested_attributes.split(',').each do |par|
      if par.include? ':'
        relation, action = par.split(':')
        attrs << {action: action, relation: relation}
      else
        id_included = true if par == id
        attrs << {action: par}
      end
    end
    attrs << {action: id} unless id_included
    attrs
  end

  def self.insert_attribute_in_hash at, f, r={}
    if at.has_key? :relation
      if f.class.reflect_on_association(at[:relation].to_sym).collection?
        if at[:action].to_sym == :count
          r["#{at[:relation]}:#{at[:action]}"] = f.try(at[:relation]).count
        else
          r["#{at[:relation]}:#{at[:action]}"] = f.try(at[:relation]).map(&at[:action].to_sym).join(', ')
        end
      else
        r["#{at[:relation]}:#{at[:action]}"] = f.try(at[:relation]).try(at[:action])
      end
    else
      r[at[:action]] = f.send at[:action]
    end
    r
  end
end