require 'big_decimal_patch'

module CostQuery::Result
  class Base
    attr_accessor :parent
    attr_reader :value
    alias values value

    def initialize(value)
      @value = value
    end

    def recursive_each_with_level(level = 0, &block)
      block.call(level, self)
    end

    def recursive_each
      recursive_each_with_level { |level, result| yield result }
    end

    def [](key)
      fields[key]
    end
  end

  class DirectResult < Base
    alias fields values

    def has_children?
      false
    end

    def count
      self["count"].to_i
    end

    def units
      self["units"].to_d
    end

    def real_costs
      self["real_costs"].to_d
    end

    ##
    # @return [Integer] Number of child results
    def size
      0
    end
  end

  class WrappedResult < Base
    include Enumerable

    def has_children?
      true
    end

    def count
      sum_for :count
    end

    def units
      sum_for :units
    end

    def real_costs
      sum_for :real_costs
    end

    def sum_for(field)
      @sum_for ||= {}
      @sum_for[field] ||= inject(0) { |a,v| a + v.send(field) }
    end

    def recursive_each_with_level(level = 0, &block)
      super
      each { |c| c.recursive_each_with_level(level + 1, &block) }
    end

    def each(&block)
      values.each(&block)
    end

    def fields
      @fields ||= {}.with_indifferent_access
    end

    ##
    # @return [Integer] Number of child results
    def size
      values.size
    end
  end

  def self.new(value, fields = {})
    result = begin
      case value
      when Array then WrappedResult.new value.map { |e| new e }
      when Hash  then DirectResult.new value.with_indifferent_access
      when Base  then value
      else raise ArgumentError, "Cannot create Result from #{value.inspect}"
      end
    end
    result.fields.merge! fields
    result
  end
end