class Middleman::Sitemap::Queryable::Query

def all
  result = @model.select(:where => @where, :order_by => @order_by)
  if @offset.present?
    result = result.last([result.size - @offset, 0].max)
  end
  if @limit.present?
    result = result.first(@limit)
  end
  result
end

def first
  self.all.first
end

def initialize(model)
  @model = model
  @where = {}
end

def last
  self.all.last
end

def limit(number)
  @limit = number
  self
end

def offset(number)
  @offset = number
  self
end

def order_by(field)
  @order_by = field.is_a?(Symbol) ? {field => :asc} : field
  self
end

def where(constraints_hash)
  selector_hash = constraints_hash.reject { |key, value| !key.is_a? Selector }
  symbol_hash = constraints_hash.reject { |key, value| key.is_a? Selector }
  symbol_hash.each do |attribute, value|
    selector = Selector.new(:attribute => attribute, :operator => 'equal')
    selector_hash.update({ selector => value })
  end
  @where.merge! selector_hash
  self
end