module Arel
  class Table
    include Arel::Crud
    include Arel::FactoryMethods

    @engine = nil
    class << self; attr_accessor :engine; end

    attr_accessor :name, :engine, :aliases, :table_alias

    # TableAlias and Table both have a #table_name which is the name of the underlying table
    alias :table_name :name

    def initialize name, engine = Table.engine
      @name    = name.to_s
      @engine  = engine
      @columns = nil
      @aliases = []
      @table_alias = nil

      if Hash === engine
        @engine  = engine[:engine] || Table.engine

        # Sometime AR sends an :as parameter to table, to let the table know
        # that it is an Alias.  We may want to override new, and return a
        # TableAlias node?
        @table_alias = engine[:as] unless engine[:as].to_s == @name
      end
    end

    def alias name = "#{self.name}_2"
      Nodes::TableAlias.new(self, name).tap do |node|
        @aliases << node
      end
    end

    def from table
      SelectManager.new(@engine, table)
    end

    def join relation, klass = Nodes::InnerJoin
      return from(self) unless relation

      case relation
      when String, Nodes::SqlLiteral
        raise if relation.empty?
        klass = Nodes::StringJoin
      end

      from(self).join(relation, klass)
    end

    def outer_join relation
      join(relation, Nodes::OuterJoin)
    end

    def group *columns
      from(self).group(*columns)
    end

    def order *expr
      from(self).order(*expr)
    end

    def where condition
      from(self).where condition
    end

    def project *things
      from(self).project(*things)
    end

    def take amount
      from(self).take amount
    end

    def skip amount
      from(self).skip amount
    end

    def having expr
      from(self).having expr
    end

    def [] name
      ::Arel::Attribute.new self, name
    end

    def select_manager
      SelectManager.new(@engine)
    end

    def insert_manager
      InsertManager.new(@engine)
    end

    def update_manager
      UpdateManager.new(@engine)
    end

    def delete_manager
      DeleteManager.new(@engine)
    end

    def hash
      # Perf note: aliases, table alias and engine is excluded from the hash
      #  aliases can have a loop back to this table breaking hashes in parent
      #  relations, for the vast majority of cases @name is unique to a query
      @name.hash
    end

    def eql? other
      self.class == other.class &&
        self.name == other.name &&
        self.engine == other.engine &&
        self.aliases == other.aliases &&
        self.table_alias == other.table_alias
    end
    alias :== :eql?

    private

    def attributes_for columns
      return nil unless columns

      columns.map do |column|
        Attributes.for(column).new self, column.name.to_sym
      end
    end

  end
end