class ActiveRecord::PredicateBuilder

def self.build(attribute, value)
  case value
  when Array
    values = value.to_a.map {|x| x.is_a?(Base) ? x.id : x}
    ranges, values = values.partition {|v| v.is_a?(Range)}
    values_predicate = if values.include?(nil)
      values = values.compact
      case values.length
      when 0
        attribute.eq(nil)
      when 1
        attribute.eq(values.first).or(attribute.eq(nil))
      else
        attribute.in(values).or(attribute.eq(nil))
      end
    else
      attribute.in(values)
    end
    array_predicates = ranges.map { |range| attribute.in(range) }
    array_predicates << values_predicate
    array_predicates.inject { |composite, predicate| composite.or(predicate) }
  when ActiveRecord::Relation
    value = value.select(value.klass.arel_table[value.klass.primary_key]) if value.select_values.empty?
    attribute.in(value.arel.ast)
  when Range
    attribute.in(value)
  when ActiveRecord::Base
    attribute.eq(value.id)
  when Class
    # FIXME: I think we need to deprecate this behavior
    attribute.eq(value.name)
  else
    attribute.eq(value)
  end
end

def self.build_from_hash(klass, attributes, default_table)
  queries = []
  attributes.each do |column, value|
    table = default_table
    if value.is_a?(Hash)
      if value.empty?
        queries << '1=0'
      else
        table       = Arel::Table.new(column, default_table.engine)
        association = klass.reflect_on_association(column.to_sym)
        value.each do |k, v|
          queries.concat expand(association && association.klass, table, k, v)
        end
      end
    else
      column = column.to_s
      if column.include?('.')
        table_name, column = column.split('.', 2)
        table = Arel::Table.new(table_name, default_table.engine)
      end
      queries.concat expand(klass, table, column, value)
    end
  end
  queries
end

def self.expand(klass, table, column, value)
  queries = []
  # Find the foreign key when using queries such as:
  # Post.where(author: author)
  #
  # For polymorphic relationships, find the foreign key and type:
  # PriceEstimate.where(estimate_of: treasure)
  if klass && value.class < Base && reflection = klass.reflect_on_association(column.to_sym)
    if reflection.polymorphic?
      queries << build(table[reflection.foreign_type], value.class.base_class)
    end
    column = reflection.foreign_key
  end
  queries << build(table[column], value)
  queries
end

def self.references(attributes)
  attributes.map do |key, value|
    if value.is_a?(Hash)
      key
    else
      key = key.to_s
      key.split('.').first if key.include?('.')
    end
  end.compact
end