# These are refinements to core classes that allow the Sequel
# DSL to be used without modifying the core classes directly.
# After loading the extension via:
#
#   Sequel.extension :core_refinements
#
# you can enable the refinements for particular files:
#
#   using Sequel::CoreRefinements

raise(Sequel::Error, "Refinements require ruby 2.0.0 or greater") unless RUBY_VERSION >= '2.0.0'

module Sequel::CoreRefinements
  refine Array do
    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this array, not matching all of the
    # conditions.
    #
    #   ~[[:a, true]] # SQL: a IS NOT TRUE
    #   ~[[:a, 1], [:b, [2, 3]]] # SQL: a != 1 OR b NOT IN (2, 3)
    def ~
      Sequel.~(self)
    end

    # Return a <tt>Sequel::SQL::CaseExpression</tt> with this array as the conditions and the given
    # default value and expression.
    #
    #   [[{:a=>[2,3]}, 1]].case(0) # SQL: CASE WHEN a IN (2, 3) THEN 1 ELSE 0 END
    #   [[:a, 1], [:b, 2]].case(:d, :c) # SQL: CASE c WHEN a THEN 1 WHEN b THEN 2 ELSE d END
    def case(*args)
      ::Sequel::SQL::CaseExpression.new(self, *args)
    end

    # Return a <tt>Sequel::SQL::ValueList</tt> created from this array.  Used if this array contains
    # all two element arrays and you want it treated as an SQL value list (IN predicate) 
    # instead of as a conditions specifier (similar to a hash).  This is not necessary if you are using
    # this array as a value in a filter, but may be necessary if you are using it as a
    # value with placeholder SQL:
    #
    #   DB[:a].filter([:a, :b]=>[[1, 2], [3, 4]]) # SQL: (a, b) IN ((1, 2), (3, 4))
    #   DB[:a].filter('(a, b) IN ?', [[1, 2], [3, 4]]) # SQL: (a, b) IN ((1 = 2) AND (3 = 4))
    #   DB[:a].filter('(a, b) IN ?', [[1, 2], [3, 4]].sql_value_list) # SQL: (a, b) IN ((1, 2), (3, 4))
    def sql_value_list
      ::Sequel::SQL::ValueList.new(self)
    end
    
    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this array, matching all of the
    # conditions.  Rarely do you need to call this explicitly, as Sequel generally
    # assumes that arrays of two element arrays specify this type of condition.  One case where
    # it can be necessary to use this is if you are using the object as a value in a filter hash
    # and want to use the = operator instead of the IN operator (which is used by default for
    # arrays of two element arrays).
    #
    #   [[:a, true]].sql_expr # SQL: a IS TRUE
    #   [[:a, 1], [:b, [2, 3]]].sql_expr # SQL: a = 1 AND b IN (2, 3)
    def sql_expr
      Sequel.expr(self)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this array, matching none
    # of the conditions.
    #
    #   [[:a, true]].sql_negate # SQL: a IS NOT TRUE
    #   [[:a, 1], [:b, [2, 3]]].sql_negate # SQL: a != 1 AND b NOT IN (2, 3)
    def sql_negate
      Sequel.negate(self)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this array, matching any of the
    # conditions.
    #
    #   [[:a, true]].sql_or # SQL: a IS TRUE
    #   [[:a, 1], [:b, [2, 3]]].sql_or # SQL: a = 1 OR b IN (2, 3)
    def sql_or
      Sequel.or(self)
    end

    # Return a <tt>Sequel::SQL::StringExpression</tt> representing an SQL string made up of the
    # concatenation of this array's elements.  If an argument is passed
    # it is used in between each element of the array in the SQL
    # concatenation.
    #
    #   [:a].sql_string_join # SQL: a
    #   [:a, :b].sql_string_join # SQL: a || b
    #   [:a, 'b'].sql_string_join # SQL: a || 'b'
    #   ['a', :b].sql_string_join(' ') # SQL: 'a' || ' ' || b
    def sql_string_join(joiner=nil)
      Sequel.join(self, joiner)
    end
  end

  refine Hash do
    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, matching
    # all of the conditions in this hash and the condition specified by
    # the given argument.
    #
    #   {:a=>1} & :b # SQL: a = 1 AND b
    #   {:a=>true} & ~:b # SQL: a IS TRUE AND NOT b
    def &(ce)
      ::Sequel::SQL::BooleanExpression.new(:AND, self, ce)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, matching
    # all of the conditions in this hash or the condition specified by
    # the given argument.
    #
    #   {:a=>1} | :b # SQL: a = 1 OR b
    #   {:a=>true} | ~:b # SQL: a IS TRUE OR NOT b
    def |(ce)
      ::Sequel::SQL::BooleanExpression.new(:OR, self, ce)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, not matching all of the
    # conditions.
    #
    #   ~{:a=>true} # SQL: a IS NOT TRUE
    #   ~{:a=>1, :b=>[2, 3]} # SQL: a != 1 OR b NOT IN (2, 3)
    def ~
      ::Sequel::SQL::BooleanExpression.from_value_pairs(self, :OR, true)
    end

    # Return a <tt>Sequel::SQL::CaseExpression</tt> with this hash as the conditions and the given
    # default value.  Note that the order of the conditions will be arbitrary on ruby 1.8, so all
    # conditions should be orthogonal.
    #
    #   {{:a=>[2,3]}=>1}.case(0) # SQL: CASE WHEN a IN (2, 3) THEN 1 ELSE 0 END
    #   {:a=>1, :b=>2}.case(:d, :c) # SQL: CASE c WHEN a THEN 1 WHEN b THEN 2 ELSE d END
    #                                 #  or: CASE c WHEN b THEN 2 WHEN a THEN 1 ELSE d END
    def case(*args)
      ::Sequel::SQL::CaseExpression.new(to_a, *args)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, matching all of the
    # conditions.  Rarely do you need to call this explicitly, as Sequel generally
    # assumes that hashes specify this type of condition.
    #
    #   {:a=>true}.sql_expr # SQL: a IS TRUE
    #   {:a=>1, :b=>[2, 3]}.sql_expr # SQL: a = 1 AND b IN (2, 3)
    def sql_expr
      ::Sequel::SQL::BooleanExpression.from_value_pairs(self)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, matching none
    # of the conditions.
    #
    #   {:a=>true}.sql_negate # SQL: a IS NOT TRUE
    #   {:a=>1, :b=>[2, 3]}.sql_negate # SQL: a != 1 AND b NOT IN (2, 3)
    def sql_negate
      ::Sequel::SQL::BooleanExpression.from_value_pairs(self, :AND, true)
    end

    # Return a <tt>Sequel::SQL::BooleanExpression</tt> created from this hash, matching any of the
    # conditions.
    #
    #   {:a=>true}.sql_or # SQL: a IS TRUE
    #   {:a=>1, :b=>[2, 3]}.sql_or # SQL: a = 1 OR b IN (2, 3)
    def sql_or
      ::Sequel::SQL::BooleanExpression.from_value_pairs(self, :OR)
    end
  end

  refine String do
    include Sequel::SQL::AliasMethods
    include Sequel::SQL::CastMethods

    # Converts a string into a <tt>Sequel::LiteralString</tt>, in order to override string
    # literalization, e.g.:
    #
    #   DB[:items].filter(:abc => 'def').sql #=>
    #     "SELECT * FROM items WHERE (abc = 'def')"
    #
    #   DB[:items].filter(:abc => 'def'.lit).sql #=>
    #     "SELECT * FROM items WHERE (abc = def)"
    #
    # You can also provide arguments, to create a <tt>Sequel::SQL::PlaceholderLiteralString</tt>:
    #
    #    DB[:items].select{|o| o.count('DISTINCT ?'.lit(:a))}.sql #=>
    #      "SELECT count(DISTINCT a) FROM items"
    def lit(*args)
      args.empty? ? Sequel::LiteralString.new(self) : Sequel::SQL::PlaceholderLiteralString.new(self, args)
    end
    
    # Returns a <tt>Sequel::SQL::Blob</tt> that holds the same data as this string. Blobs provide proper
    # escaping of binary data.
    def to_sequel_blob
      ::Sequel::SQL::Blob.new(self)
    end
  end

  refine Symbol do
    include Sequel::SQL::AliasMethods
    include Sequel::SQL::CastMethods
    include Sequel::SQL::OrderMethods
    include Sequel::SQL::BooleanMethods
    include Sequel::SQL::NumericMethods
    include Sequel::SQL::QualifyingMethods
    include Sequel::SQL::StringMethods
    include Sequel::SQL::SubscriptMethods
    include Sequel::SQL::ComplexExpressionMethods

    # Returns receiver wrapped in an <tt>Sequel::SQL::Identifier</tt>.  Usually used to
    # prevent splitting the symbol.
    #
    #   :a__b # SQL: "a"."b"
    #   :a__b.identifier # SQL: "a__b"
    def identifier
      Sequel::SQL::Identifier.new(self)
    end

    # Returns a <tt>Sequel::SQL::Function</tt> with this as the function name,
    # and the given arguments. This is aliased as <tt>Symbol#[]</tt> if the RUBY_VERSION
    # is less than 1.9.0. Ruby 1.9 defines <tt>Symbol#[]</tt>, and Sequel
    # doesn't override methods defined by ruby itself.
    #
    #   :now.sql_function # SQL: now()
    #   :sum.sql_function(:a) # SQL: sum(a)
    #   :concat.sql_function(:a, :b) # SQL: concat(a, b)
    def sql_function(*args)
      Sequel::SQL::Function.new(self, *args)
    end
  end
end
