class DeepPreloader::Spec

def self.parse(data)
  case data
  when Array
    data.inject(self.new) do |acc, v|
      acc.merge!(parse(v))
    end
  when Hash
    assoc_specs = data.each_with_object({}) do |(k, v), h|
      h[k.to_s] = parse(v)
    end
    self.new(assoc_specs)
  when String, Symbol
    self.new({ data.to_s => nil })
  when DeepPreloader::AbstractSpec
    data
  when nil
    nil
  else
    raise ArgumentError.new("Cannot parse invalid hash preload spec: #{hash.inspect}")
  end
end

def ==(other)
  self.class == other.class && self.association_specs == other.association_specs
end

def deep_dup
  self.class.new(association_specs.deep_dup)
end

def hash
  [self.class, self.association_specs].hash
end

def initialize(association_specs = {})
  @association_specs = association_specs.transform_keys(&:to_s)
end

def inspect
  "Spec#{association_specs.inspect}"
end

def merge!(other)
  case other
  when nil
    return
  when DeepPreloader::Spec
    other.association_specs.each do |k, v|
      if association_specs[k]
        association_specs[k].merge!(v)
      else
        association_specs[k] = v.deep_dup
      end
    end
  else
    raise ArgumentError.new("Cannot merge #{other.class.name} into #{self.inspect}")
  end
  self
end