require 'set'

module Arel
  class TypecastError < StandardError ; end
  class Attribute
    attr_reader :relation, :name, :alias, :ancestor, :hash
    attr_reader :history

    def initialize(relation, name, options = {})
      @relation = relation # this is actually a table (I think)
      @name     = name
      @alias    = options[:alias]
      @ancestor = options[:ancestor]
      @history  = [self] + (@ancestor ? @ancestor.history : [])
      @root = @history.last
      @original_relation = nil
      @original_attribute = nil

      # FIXME: I think we can remove this eventually
      @hash     = name.hash + root.relation.class.hash
    end

    def engine
      @relation.engine
    end

    def christener
      @relation.christener
    end

    def == other
      super ||
        Attribute === other &&
        @name      == other.name &&
        @alias     == other.alias &&
        @ancestor  == other.ancestor &&
        @relation  == other.relation
    end

    alias :eql? :==

    def named?(hypothetical_name)
      (@alias || name).to_s == hypothetical_name.to_s
    end

    def aggregation?
      false
    end

    def eval(row)
      row[self]
    end

    def as(aliaz = nil)
      Attribute.new(relation, name, :alias => aliaz, :ancestor => self)
    end

    def bind(new_relation)
      relation == new_relation ? self : Attribute.new(new_relation, name, :alias => @alias, :ancestor => self)
    end

    def to_attribute(relation)
      bind(relation)
    end

    def join?
      relation.join?
    end

    def root
      history.last
    end

    def original_relation
      @original_relation ||= original_attribute.relation
    end

    def original_attribute
      @original_attribute ||= history.detect { |a| !a.join? }
    end

    def find_correlate_in(relation)
      relation[self] || self
    end

    def descends_from?(other)
      history.include?(other)
    end

    def /(other)
      other ? (history & other.history).size : 0
    end

    PREDICATES = [
      :eq, :eq_any, :eq_all, :not_eq, :not_eq_any, :not_eq_all, :lt, :lt_any,
      :lt_all, :lteq, :lteq_any, :lteq_all, :gt, :gt_any, :gt_all, :gteq,
      :gteq_any, :gteq_all, :matches, :matches_any, :matches_all, :not_matches,
      :not_matches_any, :not_matches_all, :in, :in_any, :in_all, :not_in,
      :not_in_any, :not_in_all
    ]

    Predications = Class.new do
      def self.instance_methods *args
        warn "this module is deprecated, please use the PREDICATES constant"
        PREDICATES
      end
    end

    def eq(other)
      Predicates::Equality.new(self, other)
    end

    def eq_any(*others)
      Predicates::Any.build(Predicates::Equality, self, *others)
    end

    def eq_all(*others)
      Predicates::All.build(Predicates::Equality, self, *others)
    end

    def not_eq(other)
      Predicates::Inequality.new(self, other)
    end

    def not_eq_any(*others)
      Predicates::Any.build(Predicates::Inequality, self, *others)
    end

    def not_eq_all(*others)
      Predicates::All.build(Predicates::Inequality, self, *others)
    end

    def lt(other)
      Predicates::LessThan.new(self, other)
    end

    def lt_any(*others)
      Predicates::Any.build(Predicates::LessThan, self, *others)
    end

    def lt_all(*others)
      Predicates::All.build(Predicates::LessThan, self, *others)
    end

    def lteq(other)
      Predicates::LessThanOrEqualTo.new(self, other)
    end

    def lteq_any(*others)
      Predicates::Any.build(Predicates::LessThanOrEqualTo, self, *others)
    end

    def lteq_all(*others)
      Predicates::All.build(Predicates::LessThanOrEqualTo, self, *others)
    end

    def gt(other)
      Predicates::GreaterThan.new(self, other)
    end

    def gt_any(*others)
      Predicates::Any.build(Predicates::GreaterThan, self, *others)
    end

    def gt_all(*others)
      Predicates::All.build(Predicates::GreaterThan, self, *others)
    end

    def gteq(other)
      Predicates::GreaterThanOrEqualTo.new(self, other)
    end

    def gteq_any(*others)
      Predicates::Any.build(Predicates::GreaterThanOrEqualTo, self, *others)
    end

    def gteq_all(*others)
      Predicates::All.build(Predicates::GreaterThanOrEqualTo, self, *others)
    end

    def matches(other)
      Predicates::Match.new(self, other)
    end

    def matches_any(*others)
      Predicates::Any.build(Predicates::Match, self, *others)
    end

    def matches_all(*others)
      Predicates::All.build(Predicates::Match, self, *others)
    end

    def not_matches(other)
      Predicates::NotMatch.new(self, other)
    end

    def not_matches_any(*others)
      Predicates::Any.build(Predicates::NotMatch, self, *others)
    end

    def not_matches_all(*others)
      Predicates::All.build(Predicates::NotMatch, self, *others)
    end

    def in(other)
      Predicates::In.new(self, other)
    end

    def in_any(*others)
      Predicates::Any.build(Predicates::In, self, *others)
    end

    def in_all(*others)
      Predicates::All.build(Predicates::In, self, *others)
    end

    def not_in(other)
      Predicates::NotIn.new(self, other)
    end

    def not_in_any(*others)
      Predicates::Any.build(Predicates::NotIn, self, *others)
    end

    def not_in_all(*others)
      Predicates::All.build(Predicates::NotIn, self, *others)
    end

    module Expressions
      def count(distinct = false)
        distinct ?  Distinct.new(self).count :  Count.new(self)
      end

      def sum
        Sum.new(self)
      end

      def maximum
        Maximum.new(self)
      end

      def minimum
        Minimum.new(self)
      end

      def average
        Average.new(self)
      end
    end
    include Expressions

    module Orderings
      def asc
        Ascending.new(self)
      end

      def desc
        Descending.new(self)
      end

      alias_method :to_ordering, :asc
    end
    include Orderings

    module Types
      def type_cast(value)
        if root == self
          raise NotImplementedError, "#type_cast should be implemented in a subclass."
        else
          root.type_cast(value)
        end
      end

      def type_cast_to_numeric(value, method)
        return unless value
        if value.respond_to?(:to_str)
          str = value.to_str.strip
          return if str.empty?
          return $1.send(method) if str =~ /\A(-?(?:0|[1-9]\d*)(?:\.\d+)?|(?:\.\d+))\z/
        elsif value.respond_to?(method)
          return value.send(method)
        end
        raise typecast_error(value)
      end

      def typecast_error(value)
        raise TypecastError, "could not typecast #{value.inspect} to #{self.class.name.split('::').last}"
      end
    end
    include Types

    def column
      original_relation.column_for(self)
    end

    def format(object)
      object.to_sql(Sql::Attribute.new(self))
    end

    def to_sql(formatter = Sql::WhereCondition.new(relation))
      formatter.attribute self
    end
  end
end