require 'active_record'
require 'active_record/connection_adapters/abstract_adapter'
require 'active_record/connection_adapters/sqlserver_adapter/core_ext/active_record'
require 'base64'

module ActiveRecord
  
  class Base
    
    def self.sqlserver_connection(config) #:nodoc:
      config = config.dup.symbolize_keys!
      config.reverse_merge! :mode => :dblib, :host => 'localhost', :username => 'sa', :password => ''
      mode = config[:mode].to_s.downcase.underscore.to_sym
      case mode
      when :dblib
        require_library_or_gem 'tiny_tds'
        warn("TinyTds v0.4.3 or higher required. Using #{TinyTds::VERSION}") unless TinyTds::Client.instance_methods.map(&:to_s).include?("active?")
      when :odbc
        require_library_or_gem 'odbc' unless defined?(ODBC)
        require 'active_record/connection_adapters/sqlserver_adapter/core_ext/odbc'
        raise ArgumentError, 'Missing :dsn configuration.' unless config.has_key?(:dsn)
      when :adonet
        require 'System.Data'
        raise ArgumentError, 'Missing :database configuration.' unless config.has_key?(:database)
      when :ado
        raise NotImplementedError, 'Please use version 2.3.1 of the adapter for ADO connections. Future versions support ADO.NET.'
        raise ArgumentError, 'Missing :database configuration.' unless config.has_key?(:database)
      else
        raise ArgumentError, "Unknown connection mode in #{config.inspect}."
      end
      ConnectionAdapters::SQLServerAdapter.new(logger,config.merge(:mode=>mode))
    end
    
    protected
    
    def self.did_retry_sqlserver_connection(connection,count)
      logger.info "CONNECTION RETRY: #{connection.class.name} retry ##{count}."
    end
    
    def self.did_lose_sqlserver_connection(connection)
      logger.info "CONNECTION LOST: #{connection.class.name}"
    end
    
  end
  
  module ConnectionAdapters
    
    class SQLServerColumn < Column
            
      def initialize(name, default, sql_type = nil, null = true, sqlserver_options = {})
        @sqlserver_options = sqlserver_options.symbolize_keys
        super(name, default, sql_type, null)
      end
      
      class << self
        
        def string_to_binary(value)
         "0x#{value.unpack("H*")[0]}"
        end
        
        def binary_to_string(value)
          value =~ /[^[:xdigit:]]/ ? value : [value].pack('H*')
        end
        
      end
      
      def is_identity?
        @sqlserver_options[:is_identity]
      end
      
      def is_special?
        @sql_type =~ /^text|ntext|image$/
      end
      
      def is_utf8?
        @sql_type =~ /nvarchar|ntext|nchar/i
      end
      
      def default_function
        @sqlserver_options[:default_function]
      end
      
      def table_name
        @sqlserver_options[:table_name]
      end
      
      def table_klass
        @table_klass ||= begin
          table_name.classify.constantize
        rescue StandardError, NameError, LoadError
          nil
        end
        (@table_klass && @table_klass < ActiveRecord::Base) ? @table_klass : nil
      end
      
      def database_year
        @sqlserver_options[:database_year]
      end
      
      
      private
      
      def extract_limit(sql_type)
        case sql_type
        when /^smallint/i
          2
        when /^int/i
          4
        when /^bigint/i
          8
        when /\(max\)/, /decimal/, /numeric/
          nil
        else
          super
        end
      end
      
      def simplified_type(field_type)
        case field_type
          when /real/i              then :float
          when /money/i             then :decimal
          when /image/i             then :binary
          when /bit/i               then :boolean
          when /uniqueidentifier/i  then :string
          when /datetime/i          then simplified_datetime
          when /varchar\(max\)/     then :text
          when /timestamp/          then :binary
          else super
        end
      end
      
      def simplified_datetime
        if database_year >= 2008
          :datetime
        elsif table_klass && table_klass.coerced_sqlserver_date_columns.include?(name)
          :date
        elsif table_klass && table_klass.coerced_sqlserver_time_columns.include?(name)
          :time
        else
          :datetime
        end
      end
      
    end #SQLServerColumn
    

    class SQLServerAdapter < AbstractAdapter
      
      ADAPTER_NAME                = 'SQLServer'.freeze
      VERSION                     = '2.3.21'.freeze
      DATABASE_VERSION_REGEXP     = /Microsoft SQL Server\s+(\d{4})/
      SUPPORTED_VERSIONS          = [2000,2005,2008].freeze
      LIMITABLE_TYPES             = ['string','integer','float','char','nchar','varchar','nvarchar'].to_set.freeze
      QUOTED_TRUE, QUOTED_FALSE   = '1', '0'
      LOST_CONNECTION_EXCEPTIONS  = {
        :dblib  => ['TinyTds::Error'],
        :odbc   => ['ODBC::Error'],
        :adonet => ['TypeError','System::Data::SqlClient::SqlException']
      }
      LOST_CONNECTION_MESSAGES    = {
        :dblib  => [/closed connection/, /dead or not enabled/, /server failed/i],
        :odbc   => [/link failure/, /server failed/, /connection was already closed/, /invalid handle/i],
        :adonet => [/current state is closed/, /network-related/]
      }
      
      attr_reader    :database_version, :database_year,
                     :connection_supports_native_types
      cattr_accessor :native_text_database_type, :native_binary_database_type, :native_string_database_type,
                     :log_info_schema_queries, :enable_default_unicode_types, :auto_connect
      
      class << self
        
        def type_limitable?(type)
          LIMITABLE_TYPES.include?(type.to_s)
        end
        
      end
      
      def initialize(logger,config)
        @connection_options = config
        connect
        super(@connection, logger)
        @database_version = info_schema_query { select_value('SELECT @@version') }
        @database_year = DATABASE_VERSION_REGEXP.match(@database_version)[1].to_i rescue 0
        initialize_sqlserver_caches
        use_database
        unless SUPPORTED_VERSIONS.include?(@database_year)
          raise NotImplementedError, "Currently, only #{SUPPORTED_VERSIONS.to_sentence} are supported."
        end
      end
      
      # ABSTRACT ADAPTER =========================================#
      
      def adapter_name
        ADAPTER_NAME
      end
      
      def supports_migrations?
        true
      end
      
      def supports_ddl_transactions?
        true
      end
      
      def supports_savepoints?
        true
      end
      
      def sqlserver?
        true
      end
      
      def sqlserver_2000?
        @database_year == 2000
      end
      
      def sqlserver_2005?
        @database_year == 2005
      end
      
      def sqlserver_2008?
        @database_year == 2008
      end
      
      def version
        self.class::VERSION
      end
      
      def inspect
        "#<#{self.class} version: #{version}, year: #{@database_year}, connection_options: #{@connection_options.inspect}>"
      end
      
      def auto_connect
        @@auto_connect.is_a?(FalseClass) ? false : true
      end
      
      def native_string_database_type
        @@native_string_database_type || (enable_default_unicode_types ? 'nvarchar' : 'varchar') 
      end
      
      def native_text_database_type
        @@native_text_database_type || 
        if sqlserver_2005? || sqlserver_2008?
          enable_default_unicode_types ? 'nvarchar(max)' : 'varchar(max)'
        else
          enable_default_unicode_types ? 'ntext' : 'text'
        end
      end
      
      def native_time_database_type
        sqlserver_2008? ? 'time' : 'datetime'
      end
      
      def native_date_database_type
        sqlserver_2008? ? 'date' : 'datetime'
      end
      
      def native_binary_database_type
        @@native_binary_database_type || ((sqlserver_2005? || sqlserver_2008?) ? 'varbinary(max)' : 'image')
      end
      
      
      # QUOTING ==================================================#
      
      def quote(value, column = nil)
        case value
        when String, ActiveSupport::Multibyte::Chars
          if column && column.type == :binary
            column.class.string_to_binary(value)
          elsif value.is_utf8? || (column && column.type == :string)
            "N'#{quote_string(value)}'"
          else
            super
          end
        else
          super
        end
      end
      
      def quote_string(string)
        string.to_s.gsub(/\'/, "''")
      end
      
      def quote_column_name(name)
        @sqlserver_quoted_column_and_table_names[name] ||= 
          name.to_s.split('.').map{ |n| n =~ /^\[.*\]$/ ? n : "[#{n.to_s.gsub(']', ']]')}]" }.join('.')
      end
      
      def quote_table_name(name)
        quote_column_name(name)
      end
      
      def quoted_true
        QUOTED_TRUE
      end

      def quoted_false
        QUOTED_FALSE
      end
      
      def quoted_date(value)
        if value.acts_like?(:time) && value.respond_to?(:usec)
          "#{super}.#{sprintf("%03d",value.usec/1000)}"
        else
          super
        end
      end
      
      # REFERENTIAL INTEGRITY ====================================#
      
      def disable_referential_integrity
        do_execute "EXEC sp_MSforeachtable 'ALTER TABLE ? NOCHECK CONSTRAINT ALL'"
        yield
      ensure
        do_execute "EXEC sp_MSforeachtable 'ALTER TABLE ? CHECK CONSTRAINT ALL'"
      end
      
      # CONNECTION MANAGEMENT ====================================#
      
      def active?
        case @connection_options[:mode]
        when :dblib
          @connection.active?
        end
        raw_connection_do("SELECT 1")
        true
      rescue *lost_connection_exceptions
        false
      end

      def reconnect!
        disconnect!
        connect
        active?
      end

      def disconnect!
        case @connection_options[:mode]
        when :dblib
          @connection.close rescue nil
        when :odbc
          @connection.disconnect rescue nil
        else :adonet
          @connection.close rescue nil
        end
      end
      
      # DATABASE STATEMENTS ======================================#
      
      def user_options
        info_schema_query do
          select_rows("dbcc useroptions").inject(HashWithIndifferentAccess.new) do |values,row| 
            set_option = row[0].gsub(/\s+/,'_')
            user_value = row[1]
            values[set_option] = user_value
            values
          end
        end
      end
      
      VALID_ISOLATION_LEVELS = ["READ COMMITTED", "READ UNCOMMITTED", "REPEATABLE READ", "SERIALIZABLE", "SNAPSHOT"]
      
      def run_with_isolation_level(isolation_level)
        raise ArgumentError, "Invalid isolation level, #{isolation_level}. Supported levels include #{VALID_ISOLATION_LEVELS.to_sentence}." if !VALID_ISOLATION_LEVELS.include?(isolation_level.upcase)
        initial_isolation_level = user_options[:isolation_level] || "READ COMMITTED"
        do_execute "SET TRANSACTION ISOLATION LEVEL #{isolation_level}"
        begin
          yield 
        ensure
          do_execute "SET TRANSACTION ISOLATION LEVEL #{initial_isolation_level}"
        end if block_given?
      end
      
      def select_one(sql, name = nil)
        result = raw_select sql, name, :fetch => :one
        (result && result.first.present?) ? result.first : nil
      end
      
      def select_one_with_query_cache(*args)
        if @query_cache_enabled
          cache_sql(args.first) { select_one_without_query_cache(*args) }
        else
          select_one_without_query_cache(*args)
        end
      end
      alias_method_chain :select_one, :query_cache
      
      def select_rows(sql, name = nil)
        raw_select sql, name, :fetch => :rows
      end
      
      def execute(sql, name = nil, skip_logging = false)
        if id_insert_table_name = query_requires_identity_insert?(sql)
          with_identity_insert_enabled(id_insert_table_name) { do_execute(sql,name) }
        else
          do_execute(sql,name)
        end
      end
      
      def execute_procedure(proc_name, *variables)
        vars = variables.map{ |v| quote(v) }.join(', ')
        sql = "EXEC #{proc_name} #{vars}".strip
        name = 'Execute Procedure'
        log(sql, name) do
          case @connection_options[:mode]
          when :dblib
            result = @connection.execute(sql)
            result.each(:as => :hash, :cache_rows => true) do |row|
              r = row.with_indifferent_access
              yield(r) if block_given?
            end
            result.each.map{ |row| row.is_a?(Hash) ? row.with_indifferent_access : row }
          when :odbc
            results = []
            raw_connection_run(sql) do |handle|
              get_rows = lambda {
                rows = handle_to_names_and_values handle, :fetch => :all
                rows.each_with_index { |r,i| rows[i] = r.with_indifferent_access }
                results << rows
              }
              get_rows.call
              while handle_more_results?(handle)
                get_rows.call
              end
            end
            results.many? ? results : results.first
          when :adonet
            results = []
            results << select(sql, name).map { |r| r.with_indifferent_access }
            results.many? ? results : results.first
          end
        end
      end
      
      def use_database(database=nil)
        database ||= @connection_options[:database]
        do_execute "USE #{quote_table_name(database)}" unless database.blank?
      end
      
      def outside_transaction?
        info_schema_query { select_value("SELECT @@TRANCOUNT") == 0 }
      end
      
      def begin_db_transaction
        do_execute "BEGIN TRANSACTION"
      end

      def commit_db_transaction
        do_execute "COMMIT TRANSACTION"
      end

      def rollback_db_transaction
        do_execute "ROLLBACK TRANSACTION" rescue nil
      end
      
      def create_savepoint
        do_execute "SAVE TRANSACTION #{current_savepoint_name}"
      end

      def release_savepoint
      end
      
      def rollback_to_savepoint
        do_execute "ROLLBACK TRANSACTION #{current_savepoint_name}"
      end
      
      def add_limit_offset!(sql, options)
        # Validate and/or convert integers for :limit and :offets options.
        if options[:offset]
          raise ArgumentError, "offset should have a limit" unless options[:limit]
          unless options[:offset].kind_of?(Integer)
            if options[:offset] =~ /^\d+$/
              options[:offset] = options[:offset].to_i
            else
              raise ArgumentError, "offset should be an integer"
            end
          end
        end
        if options[:limit] && !(options[:limit].kind_of?(Integer))
          if options[:limit] =~ /^\d+$/
            options[:limit] = options[:limit].to_i
          else
            raise ArgumentError, "limit should be an integer"
          end
        end
        # The business of adding limit/offset
        if options[:limit] and options[:offset]
          tally_sql = "SELECT count(*) as TotalRows from (#{sql.sub(/\bSELECT(\s+DISTINCT)?\b/i, "SELECT#{$1} TOP 1000000000")}) tally"
          add_lock! tally_sql, options
          total_rows = select_value(tally_sql).to_i
          if (options[:limit] + options[:offset]) >= total_rows
            options[:limit] = (total_rows - options[:offset] >= 0) ? (total_rows - options[:offset]) : 0
          end
          # Make sure we do not need a special limit/offset for association limiting. http://gist.github.com/25118
          add_limit_offset_for_association_limiting!(sql,options) and return if sql_for_association_limiting?(sql)
          # Wrap the SQL query in a bunch of outer SQL queries that emulate proper LIMIT,OFFSET support.
          sql.sub!(/^\s*SELECT(\s+DISTINCT)?/i, "SELECT * FROM (SELECT TOP #{options[:limit]} * FROM (SELECT#{$1} TOP #{options[:limit] + options[:offset]}")
          sql << ") AS tmp1"
          if options[:order]
            order = options[:order].split(',').map do |field|
              order_by_column, order_direction = field.split(" ")
              order_by_column = quote_column_name(order_by_column)
              # Investigate the SQL query to figure out if the order_by_column has been renamed.
              if sql =~ /#{Regexp.escape(order_by_column)} AS (t\d+_r\d+)/
                # Fx "[foo].[bar] AS t4_r2" was found in the SQL. Use the column alias (ie 't4_r2') for the subsequent orderings
                order_by_column = $1
              elsif order_by_column =~ /\w+\.\[?(\w+)\]?/
                order_by_column = $1
              else
                # It doesn't appear that the column name has been renamed as part of the query. Use just the column
                # name rather than the full identifier for the outer queries.
                order_by_column = order_by_column.split('.').last
              end
              # Put the column name and eventual direction back together
              [order_by_column, order_direction].join(' ').strip
            end.join(', ')
            sql << " ORDER BY #{change_order_direction(order)}) AS tmp2 ORDER BY #{order}"
          else
            sql << ") AS tmp2"
          end
        elsif options[:limit] && sql !~ /^\s*SELECT (@@|COUNT\()/i
          if md = sql.match(/^(\s*SELECT)(\s+DISTINCT)?(.*)/im)
            sql.replace "#{md[1]}#{md[2]} TOP #{options[:limit]}#{md[3]}"
          else
            # Account for building SQL fragments without SELECT yet. See #update_all and #limited_update_conditions.
            sql.replace "TOP #{options[:limit]} #{sql}"
          end
        end
      end
      
      def add_lock!(sql, options)
        # http://blog.sqlauthority.com/2007/04/27/sql-server-2005-locking-hints-and-examples/
        return unless options[:lock]
        lock_type = options[:lock] == true ? 'WITH(HOLDLOCK, ROWLOCK)' : options[:lock]
        sql.gsub! %r|LEFT OUTER JOIN\s+(.*?)\s+ON|im, "LEFT OUTER JOIN \\1 #{lock_type} ON"
        sql.gsub! %r{FROM\s([\w\[\]\.]+)}im, "FROM \\1 #{lock_type}"
      end
      
      def empty_insert_statement(table_name)
        "INSERT INTO #{quote_table_name(table_name)} DEFAULT VALUES"
      end
      
      def case_sensitive_equality_operator
        "COLLATE Latin1_General_CS_AS ="
      end
      
      def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
        match_data = where_sql.match(/^(.*?[\]\) ])WHERE[\[\( ]/)
        limit = match_data[1]
        where_sql.sub!(limit,'')
        "WHERE #{quoted_primary_key} IN (SELECT #{limit} #{quoted_primary_key} FROM #{quoted_table_name} #{where_sql})"
      end
      
      def newid_function
        select_value "SELECT NEWID()"
      end
      
      def newsequentialid_function
        select_value "SELECT NEWSEQUENTIALID()"
      end
      
      # SCHEMA STATEMENTS ========================================#
      
      def native_database_types
        @native_database_types ||= initialize_native_database_types.freeze
      end
      
      def table_alias_length
        128
      end
      
      def tables(name = nil)
        info_schema_query do
          select_values "SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_NAME <> 'dtproperties'"
        end
      end
      
      def views(name = nil)
        @sqlserver_views_cache ||= 
          info_schema_query { select_values("SELECT TABLE_NAME FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME NOT IN ('sysconstraints','syssegments')") }
      end
      
      def view_information(table_name)
        table_name = unqualify_table_name(table_name)
        @sqlserver_view_information_cache[table_name] ||= begin
          view_info = info_schema_query { select_one("SELECT * FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME = '#{table_name}'") }
          if view_info
            view_info = view_info.with_indifferent_access
            if view_info[:VIEW_DEFINITION].blank? || view_info[:VIEW_DEFINITION].length == 4000
              view_info[:VIEW_DEFINITION] = info_schema_query do
                                              begin
                                                select_values("EXEC sp_helptext #{quote_table_name(table_name)}").join
                                              rescue
                                                warn "No view definition found, possible permissions problem.\nPlease run GRANT VIEW DEFINITION TO your_user;"
                                              end
                                            end
            end
          end
          view_info
        end
      end
      
      def view_table_name(table_name)
        view_info = view_information(table_name)
        view_info ? get_table_name(view_info['VIEW_DEFINITION']) : table_name
      end
      
      def table_exists?(table_name)
        super || tables.include?(unqualify_table_name(table_name)) || views.include?(table_name.to_s)
      end
      
      def indexes(table_name, name = nil)
        unquoted_table_name = unqualify_table_name(table_name)
        select("EXEC sp_helpindex #{quote_table_name(unquoted_table_name)}",name).inject([]) do |indexes,index|
          index = index.with_indifferent_access
          if index[:index_description] =~ /primary key/
            indexes
          else
            name    = index[:index_name]
            unique  = index[:index_description] =~ /unique/
            columns = index[:index_keys].split(',').map do |column|
              column.strip!
              column.gsub! '(-)', '' if column.ends_with?('(-)')
              column
            end
            indexes << IndexDefinition.new(table_name, name, unique, columns)
          end
        end
      end
      
      def columns(table_name, name = nil)
        return [] if table_name.blank?
        cache_key = unqualify_table_name(table_name)
        @sqlserver_columns_cache[cache_key] ||= column_definitions(table_name).collect do |ci|
          sqlserver_options = ci.except(:name,:default_value,:type,:null).merge(:database_year=>database_year)
          SQLServerColumn.new ci[:name], ci[:default_value], ci[:type], ci[:null], sqlserver_options
        end
      end
      
      def create_table(table_name, options = {})
        super
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def rename_table(table_name, new_name)
        do_execute "EXEC sp_rename '#{table_name}', '#{new_name}'"
      end
      
      def drop_table(table_name, options = {})
        super
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def add_column(table_name, column_name, type, options = {})
        super
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def remove_column(table_name, *column_names)
        raise ArgumentError.new("You must specify at least one column name.  Example: remove_column(:people, :first_name)") if column_names.empty?
        column_names.flatten.each do |column_name|
          remove_check_constraints(table_name, column_name)
          remove_default_constraint(table_name, column_name)
          remove_indexes(table_name, column_name)
          do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP COLUMN #{quote_column_name(column_name)}"
        end
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def change_column(table_name, column_name, type, options = {})
        sql_commands = []
        column_object = columns(table_name).detect { |c| c.name.to_s == column_name.to_s }
        change_column_sql = "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
        change_column_sql << " NOT NULL" if options[:null] == false
        sql_commands << change_column_sql
        if options_include_default?(options) || (column_object && column_object.type != type.to_sym)
         	remove_default_constraint(table_name,column_name)
        end
        if options_include_default?(options)
          remove_sqlserver_columns_cache_for(table_name)
          sql_commands << "ALTER TABLE #{quote_table_name(table_name)} ADD CONSTRAINT #{default_name(table_name,column_name)} DEFAULT #{quote(options[:default])} FOR #{quote_column_name(column_name)}"
        end
        sql_commands.each { |c| do_execute(c) }
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def change_column_default(table_name, column_name, default)
        remove_default_constraint(table_name, column_name)
        do_execute "ALTER TABLE #{quote_table_name(table_name)} ADD CONSTRAINT #{default_name(table_name, column_name)} DEFAULT #{quote(default)} FOR #{quote_column_name(column_name)}"
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def rename_column(table_name, column_name, new_column_name)
        column_for(table_name,column_name)
        do_execute "EXEC sp_rename '#{table_name}.#{column_name}', '#{new_column_name}', 'COLUMN'"
        remove_sqlserver_columns_cache_for(table_name)
      end
      
      def remove_index(table_name, options = {})
        do_execute "DROP INDEX #{table_name}.#{quote_column_name(index_name(table_name, options))}" rescue nil
      end
      
      def type_to_sql(type, limit = nil, precision = nil, scale = nil)
        limit = nil unless self.class.type_limitable?(type)
        case type.to_s
        when 'integer'
          case limit
            when 1..2       then  'smallint'
            when 3..4, nil  then  'integer'
            when 5..8       then  'bigint'
            else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
          end
        else
          super
        end
      end
      
      def add_order_by_for_association_limiting!(sql, options)
        # Disertation http://gist.github.com/24073
        # Information http://weblogs.sqlteam.com/jeffs/archive/2007/12/13/select-distinct-order-by-error.aspx
        return sql if options[:order].blank?
        columns = sql.match(/SELECT\s+DISTINCT(.*?)FROM/)[1].strip
        sql.sub!(/SELECT\s+DISTINCT/,'SELECT')
        sql << "GROUP BY #{columns} ORDER BY #{order_to_min_set(options[:order])}"
      end
      
      def change_column_null(table_name, column_name, null, default = nil)
        column = column_for(table_name,column_name)
        unless null || default.nil?
          do_execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
        end
        sql = "ALTER TABLE #{table_name} ALTER COLUMN #{quote_column_name(column_name)} #{type_to_sql column.type, column.limit, column.precision, column.scale}"
        sql << " NOT NULL" unless null
        do_execute sql
      end
      
      def pk_and_sequence_for(table_name)
        idcol = identity_column(table_name)
        idcol ? [idcol.name,nil] : nil
      end
      
      # RAKE UTILITY METHODS =====================================#
      
      def recreate_database
        remove_database_connections_and_rollback do
          do_execute "EXEC sp_MSforeachtable 'DROP TABLE ?'"
        end
      end
      
      def recreate_database!(database=nil)
        current_db = current_database
        database ||= current_db
        this_db = database.to_s == current_db
        do_execute 'USE master' if this_db
        drop_database(database)
        create_database(database)
      ensure
        use_database(current_db) if this_db
      end
      
      # Remove existing connections and rollback any transactions if we received the message
      # 'Cannot drop the database 'test' because it is currently in use'
      def drop_database(database)
        retry_count = 0
        max_retries = 1
        begin
          do_execute "DROP DATABASE #{quote_table_name(database)}"
        rescue ActiveRecord::StatementInvalid => err
          if err.message =~ /because it is currently in use/i
            raise if retry_count >= max_retries
            retry_count += 1
            remove_database_connections_and_rollback(database)
            retry
          elsif err.message =~ /does not exist/i
            nil
          else
            raise
          end
        end
      end

      def create_database(database)
        do_execute "CREATE DATABASE #{quote_table_name(database)}"
      end
      
      def current_database
        select_value 'SELECT DB_NAME()'
      end
      
      def charset
        select_value "SELECT SERVERPROPERTY('SqlCharSetName')"
      end
      
      # This should disconnect all other users and rollback any transactions for SQL 2000 and 2005
      # http://sqlserver2000.databases.aspfaq.com/how-do-i-drop-a-sql-server-database.html
      def remove_database_connections_and_rollback(database=nil)
        database ||= current_database
        do_execute "ALTER DATABASE #{quote_table_name(database)} SET SINGLE_USER WITH ROLLBACK IMMEDIATE"
        begin
          yield
        ensure
          do_execute "ALTER DATABASE #{quote_table_name(database)} SET MULTI_USER"
        end if block_given?
      end
      
      
      
      protected
      
      # CONNECTION MANAGEMENT ====================================#
      
      def connect
        config = @connection_options
        @connection = case @connection_options[:mode]
                      when :dblib
                        appname = config[:appname] || Rails.application.class.name.split('::').first rescue nil
                        login_timeout = config[:login_timeout].present? ? config[:login_timeout].to_i : nil
                        timeout = config[:timeout].present? ? config[:timeout].to_i/1000 : nil
                        encoding = config[:encoding].present? ? config[:encoding] : nil
                        TinyTds::Client.new({ 
                          :dataserver    => config[:dataserver],
                          :host          => config[:host],
                          :port          => config[:port],
                          :username      => config[:username],
                          :password      => config[:password],
                          :database      => config[:database],
                          :appname       => appname,
                          :login_timeout => login_timeout,
                          :timeout       => timeout,
                          :encoding      => encoding
                        }).tap do |client|
                          client.execute("SET ANSI_DEFAULTS ON").do
                          client.execute("SET IMPLICIT_TRANSACTIONS OFF").do
                          client.execute("SET CURSOR_CLOSE_ON_COMMIT OFF").do
                        end
                      when :odbc
                        if config[:dsn].include?(';')
                          driver = ODBC::Driver.new.tap do |d|
                            d.name = config[:dsn_name] || 'Driver1'
                            d.attrs = config[:dsn].split(';').map{ |atr| atr.split('=') }.reject{ |kv| kv.size != 2 }.inject({}){ |h,kv| k,v = kv ; h[k] = v ; h }
                          end
                          ODBC::Database.new.drvconnect(driver)
                        else
                          ODBC.connect config[:dsn], config[:username], config[:password]
                        end.tap do |c|
                          if c.respond_to?(:use_time)
                            c.use_time = true
                            c.use_utc = ActiveRecord::Base.default_timezone == :utc
                            @connection_supports_native_types = true
                          end
                        end
                      when :adonet
                        System::Data::SqlClient::SqlConnection.new.tap do |connection|
                          connection.connection_string = System::Data::SqlClient::SqlConnectionStringBuilder.new.tap do |cs|
                            if config[:integrated_security]
                              cs.integrated_security = true
                            else
                              cs.user_i_d = config[:username]
                              cs.password = config[:password]
                            end
                            cs.add 'Server', config[:host].to_clr_string
                            cs.initial_catalog = config[:database]
                            cs.multiple_active_result_sets = false
                            cs.pooling = false
                          end.to_s
                          connection.open
                        end
                      end
      rescue
        raise unless @auto_connecting
      end
      
      def lost_connection_exceptions
        exceptions = LOST_CONNECTION_EXCEPTIONS[@connection_options[:mode]]
        @lost_connection_exceptions ||= exceptions ? exceptions.map(&:constantize) : []
      end
      
      def lost_connection_messages
        LOST_CONNECTION_MESSAGES[@connection_options[:mode]]
      end
      
      def with_auto_reconnect
        begin
          yield
        rescue *lost_connection_exceptions => e
          if lost_connection_messages.any? { |lcm| e.message =~ lcm }
            retry if auto_reconnected?
          end
          raise
        end
      end
      
      def auto_reconnected?
        return false unless auto_connect
        @auto_connecting = true
        count = 0
        while count <= 5
          sleep 2** count
          ActiveRecord::Base.did_retry_sqlserver_connection(self,count)
          return true if reconnect!
          count += 1
        end
        ActiveRecord::Base.did_lose_sqlserver_connection(self)
        false
      ensure
        @auto_connecting = false
      end
      
      def raw_connection_run(sql)
        with_auto_reconnect do
          case @connection_options[:mode]
          when :dblib
            @connection.execute(sql)
          when :odbc
            block_given? ? @connection.run_block(sql) { |handle| yield(handle) } : @connection.run(sql)
          else :adonet
            @connection.create_command.tap{ |cmd| cmd.command_text = sql }.execute_reader
          end
        end
      end
      
      def raw_connection_do(sql)
        case @connection_options[:mode]
        when :dblib
          @insert_sql ? @connection.execute(sql).insert : @connection.execute(sql).do
        when :odbc
          @connection.do(sql)
        else :adonet
          @connection.create_command.tap{ |cmd| cmd.command_text = sql }.execute_non_query
        end
      end
      
      def finish_statement_handle(handle)
        case @connection_options[:mode]
        when :dblib
        when :odbc
          handle.drop if handle && handle.respond_to?(:drop) && !handle.finished?
        when :adonet
          handle.close if handle && handle.respond_to?(:close) && !handle.is_closed
          handle.dispose if handle && handle.respond_to?(:dispose)
        end
        handle
      end
      
      # DATABASE STATEMENTS ======================================
      
      def select(sql, name = nil)
        raw_select sql, name, :fetch => :all
      end
      
      def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
        @insert_sql = true
        case @connection_options[:mode]
        when :dblib
          execute(sql, name) || id_value
        else
          super || select_value("SELECT CAST(SCOPE_IDENTITY() AS bigint) AS Ident")
        end
      ensure
        @insert_sql = false
      end
      
      def update_sql(sql, name = nil)
        @update_sql = true
        case @connection_options[:mode]
        when :dblib
          sqlserver_2000? ? execute(sql, name) && select_value('SELECT @@ROWCOUNT AS AffectedRows') : execute(sql, name)
        else
          execute(sql, name)
          select_value('SELECT @@ROWCOUNT AS AffectedRows')
        end
      ensure
        @update_sql = false
      end
      
      def info_schema_query
        log_info_schema_queries ? yield : ActiveRecord::Base.silence{ yield }
      end
      
      def do_execute(sql,name=nil)
        log(sql, name || 'EXECUTE') do
          with_auto_reconnect { raw_connection_do(sql) }
        end
      end
      
      def raw_select(sql, name=nil, options={})
        log(sql,name) do
          begin
            handle = raw_connection_run(sql)
            handle_to_names_and_values(handle, options)
          ensure
            finish_statement_handle(handle)
          end
        end
      end
      
      def handle_more_results?(handle)
        case @connection_options[:mode]
        when :dblib
        when :odbc
          handle.more_results
        when :adonet
          handle.next_result
        end
      end
      
      def handle_to_names_and_values(handle, options={})
        case @connection_options[:mode]
        when :dblib
          handle_to_names_and_values_dblib(handle, options)
        when :odbc
          handle_to_names_and_values_odbc(handle, options)
        when :adonet
          handle_to_names_and_values_adonet(handle, options)
        end
      end
      
      def handle_to_names_and_values_dblib(handle, options={})
        query_options = {}.tap do |qo|
          qo[:timezone] = ActiveRecord::Base.default_timezone || :utc
          qo[:first] = true if options[:fetch] == :one
          qo[:as] = options[:fetch] == :rows ? :array : :hash
        end
        handle.each(query_options)
      end

      def handle_to_names_and_values_odbc(handle, options={})
        @connection.use_utc = ActiveRecord::Base.default_timezone == :utc if @connection_supports_native_types
        case options[:fetch]
        when :all, :one
          if @connection_supports_native_types
            if options[:fetch] == :all
              handle.each_hash || []
            else
              row = handle.fetch_hash
              rows = row ? [row] : [[]]                    
            end
          else
            rows = if options[:fetch] == :all
                     handle.fetch_all || []
                   else
                     row = handle.fetch
                     row ? [row] : [[]]                     
                   end
            names = handle.columns(true).map{ |c| c.name }
            names_and_values = []
            rows.each do |row|
              h = {}
              i = 0
              while i < row.size
                v = row[i]
                h[names[i]] = v.respond_to?(:to_sqlserver_string) ? v.to_sqlserver_string : v
                i += 1
              end
              names_and_values << h
            end
            names_and_values
          end
        when :rows
          rows = handle.fetch_all || []
          return rows if @connection_supports_native_types
          rows.each do |row|
            i = 0
            while i < row.size
              v = row[i]
              row[i] = v.to_sqlserver_string if v.respond_to?(:to_sqlserver_string)
              i += 1
            end
          end
          rows
        end
      end

      def handle_to_names_and_values_adonet(handle, options={})
        if handle.has_rows
          names = []
          rows = []
          fields_named = options[:fetch] == :rows
          one_row_only = options[:fetch] == :one
          while handle.read
            row = []
            handle.visible_field_count.times do |row_index|
              value = handle.get_value(row_index)
              value = case value
                      when System::String
                        value.to_s
                      when System::DBNull
                        nil
                      when System::DateTime
                        value.to_string("yyyy-MM-dd HH:mm:ss.fff").to_s
                      when @@array_of_bytes ||= System::Array[System::Byte]
                        String.new(value)
                      else
                        value
                      end
              row << value
              names << handle.get_name(row_index).to_s unless fields_named
              break if one_row_only
            end
            rows << row
            fields_named = true
          end
        else
          rows = []
        end
        if options[:fetch] != :rows
          names_and_values = []
          rows.each do |row|
            h = {}
            i = 0
            while i < row.size
              h[names[i]] = row[i]
              i += 1
            end
            names_and_values << h
          end
          names_and_values
        else
          rows
        end
      end
      
      def add_limit_offset_for_association_limiting!(sql, options)
        sql.replace %|
          SET NOCOUNT ON
          DECLARE @row_number TABLE (row int identity(1,1), id int)
          INSERT INTO @row_number (id)
            #{sql}
          SET NOCOUNT OFF
          SELECT id FROM (
            SELECT TOP #{options[:limit]} * FROM (
              SELECT TOP #{options[:limit] + options[:offset]} * FROM @row_number ORDER BY row
            ) AS tmp1 ORDER BY row DESC
          ) AS tmp2 ORDER BY row
        |.gsub(/[ \t\r\n]+/,' ')
      end
      
      # SCHEMA STATEMENTS ========================================#
      
      def remove_check_constraints(table_name, column_name)
        constraints = info_schema_query { select_values("SELECT CONSTRAINT_NAME FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE where TABLE_NAME = '#{quote_string(table_name)}' and COLUMN_NAME = '#{quote_string(column_name)}'") }
        constraints.each do |constraint|
          do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP CONSTRAINT #{quote_column_name(constraint)}"
        end
      end
      
      def remove_default_constraint(table_name, column_name)
        select_all("EXEC sp_helpconstraint '#{quote_string(table_name)}','nomsg'").flatten.select do |row|
          row['constraint_type'] == "DEFAULT on column #{column_name}"
        end.each do |row|
          do_execute "ALTER TABLE #{quote_table_name(table_name)} DROP CONSTRAINT #{row['constraint_name']}"
        end
      end
      
      def remove_indexes(table_name, column_name)
        indexes(table_name).select{ |index| index.columns.include?(column_name.to_s) }.each do |index|
          remove_index(table_name, {:name => index.name})
        end
      end
      
      def default_name(table_name, column_name)
        "DF_#{table_name}_#{column_name}"
      end
      
      # IDENTITY INSERTS =========================================#
      
      def with_identity_insert_enabled(table_name)
        table_name = quote_table_name(table_name_or_views_table_name(table_name))
        set_identity_insert(table_name, true)
        yield
      ensure
        set_identity_insert(table_name, false)
      end
      
      def set_identity_insert(table_name, enable = true)
        sql = "SET IDENTITY_INSERT #{table_name} #{enable ? 'ON' : 'OFF'}"
        do_execute(sql,'IDENTITY_INSERT')
      rescue Exception => e
        raise ActiveRecordError, "IDENTITY_INSERT could not be turned #{enable ? 'ON' : 'OFF'} for table #{table_name}"
      end
      
      def query_requires_identity_insert?(sql)
        if insert_sql?(sql)
          table_name = get_table_name(sql)
          id_column = identity_column(table_name)
          id_column && sql =~ /^\s*INSERT[^(]+\([^)]*\b(#{id_column.name})\b,?[^)]*\)/i ? quote_table_name(table_name) : false
        else
          false
        end
      end
      
      def identity_column(table_name)
        columns(table_name).detect(&:is_identity?)
      end
      
      def table_name_or_views_table_name(table_name)
        unquoted_table_name = unqualify_table_name(table_name)
        views.include?(unquoted_table_name) ? view_table_name(unquoted_table_name) : unquoted_table_name
      end
      
      # HELPER METHODS ===========================================#
      
      def insert_sql?(sql)
        !(sql =~ /^\s*INSERT/i).nil?
      end
      
      def unqualify_table_name(table_name)
        table_name.to_s.split('.').last.gsub(/[\[\]]/,'')
      end
      
      def unqualify_db_name(table_name)
        table_names = table_name.to_s.split('.')
        table_names.length == 3 ? table_names.first.tr('[]','') : nil
      end
      
      def get_table_name(sql)
        if sql =~ /^\s*insert\s+into\s+([^\(\s]+)\s*|^\s*update\s+([^\(\s]+)\s*/i
          $1 || $2
        elsif sql =~ /from\s+([^\(\s]+)\s*/i
          $1
        else
          nil
        end
      end
      
      def orders_and_dirs_set(order)
        orders = order.sub('ORDER BY','').split(',').map(&:strip).reject(&:blank?)
        orders_dirs = orders.map do |ord|
          dir = nil
          ord.sub!(/\b(asc|desc)$/i) do |match|
            if match
              dir = match.upcase.strip
              ''
            end
          end
          [ord.strip, dir]
        end
      end
      
      def views_real_column_name(table_name,column_name)
        view_definition = view_information(table_name)[:VIEW_DEFINITION]
        match_data = view_definition.match(/([\w-]*)\s+as\s+#{column_name}/im)
        match_data ? match_data[1] : column_name
      end
      
      def order_to_min_set(order)
        orders_dirs = orders_and_dirs_set(order)
        orders_dirs.map do |o,d|
          "MIN(#{o}) #{d}".strip
        end.join(', ')
      end
      
      def sql_for_association_limiting?(sql)
        if md = sql.match(/^\s*SELECT(.*)FROM.*GROUP BY.*ORDER BY.*/im)
          select_froms = md[1].split(',')
          select_froms.size == 1 && !select_froms.first.include?('*')
        end
      end
      
      def remove_sqlserver_columns_cache_for(table_name)
        cache_key = unqualify_table_name(table_name)
        @sqlserver_columns_cache[cache_key] = nil
        initialize_sqlserver_caches(false)
      end
      
      def initialize_sqlserver_caches(reset_columns=true)
        @sqlserver_columns_cache = {} if reset_columns
        @sqlserver_views_cache = nil
        @sqlserver_view_information_cache = {}
        @sqlserver_quoted_column_and_table_names = {}
      end
      
      def initialize_native_database_types
        {
          :primary_key  => "int NOT NULL IDENTITY(1,1) PRIMARY KEY",
          :string       => { :name => native_string_database_type, :limit => 255  },
          :text         => { :name => native_text_database_type },
          :integer      => { :name => "int", :limit => 4 },
          :float        => { :name => "float", :limit => 8 },
          :decimal      => { :name => "decimal" },
          :datetime     => { :name => "datetime" },
          :timestamp    => { :name => "datetime" },
          :time         => { :name => native_time_database_type },
          :date         => { :name => native_date_database_type },
          :binary       => { :name => native_binary_database_type },
          :boolean      => { :name => "bit"},
          # These are custom types that may move somewhere else for good schema_dumper.rb hacking to output them.
          :char         => { :name => 'char' },
          :varchar_max  => { :name => 'varchar(max)' },
          :nchar        => { :name => "nchar" },
          :nvarchar     => { :name => "nvarchar", :limit => 255 },
          :nvarchar_max => { :name => "nvarchar(max)" },
          :ntext        => { :name => "ntext" },
          :ss_timestamp => { :name => 'timestamp'}
        }
      end
      
      def column_definitions(table_name)
        db_name = unqualify_db_name(table_name)
        db_name_with_period = "#{db_name}." if db_name
        table_name = unqualify_table_name(table_name)
        sql = %{
          SELECT
          columns.TABLE_NAME as table_name,
          columns.COLUMN_NAME as name,
          columns.DATA_TYPE as type,
          columns.COLUMN_DEFAULT as default_value,
          columns.NUMERIC_SCALE as numeric_scale,
          columns.NUMERIC_PRECISION as numeric_precision,
          CASE
            WHEN columns.DATA_TYPE IN ('nchar','nvarchar') THEN columns.CHARACTER_MAXIMUM_LENGTH
            ELSE COL_LENGTH(columns.TABLE_SCHEMA+'.'+columns.TABLE_NAME, columns.COLUMN_NAME)
          END as length,
          CASE
            WHEN columns.IS_NULLABLE = 'YES' THEN 1
            ELSE NULL
          END as is_nullable,
          CASE
            WHEN COLUMNPROPERTY(OBJECT_ID(columns.TABLE_SCHEMA+'.'+columns.TABLE_NAME), columns.COLUMN_NAME, 'IsIdentity') = 0 THEN NULL
            ELSE 1
          END as is_identity
          FROM #{db_name_with_period}INFORMATION_SCHEMA.COLUMNS columns
          WHERE columns.TABLE_NAME = '#{table_name}'
          ORDER BY columns.ordinal_position
        }.gsub(/[ \t\r\n]+/,' ')
        results = info_schema_query { select(sql,nil) }
        results.collect do |ci|
          ci = ci.symbolize_keys
          ci[:type] = case ci[:type]
                      when /^bit|image|text|ntext|datetime$/
                        ci[:type]
                      when /^numeric|decimal$/i
                        "#{ci[:type]}(#{ci[:numeric_precision]},#{ci[:numeric_scale]})"
                      when /^float|real$/i
                        "#{ci[:type]}(#{ci[:numeric_precision]})"
                      when /^char|nchar|varchar|nvarchar|varbinary|bigint|int|smallint$/
                        ci[:length].to_i == -1 ? "#{ci[:type]}(max)" : "#{ci[:type]}(#{ci[:length]})"
                      else
                        ci[:type]
                      end
          if ci[:default_value].nil? && views.include?(table_name)
            real_table_name = table_name_or_views_table_name(table_name)
            real_column_name = views_real_column_name(table_name,ci[:name])
            col_default_sql = "SELECT c.COLUMN_DEFAULT FROM #{db_name_with_period}INFORMATION_SCHEMA.COLUMNS c WHERE c.TABLE_NAME = '#{real_table_name}' AND c.COLUMN_NAME = '#{real_column_name}'"
            ci[:default_value] = info_schema_query { select_value(col_default_sql) }
          end
          ci[:default_value] = case ci[:default_value]
                               when nil, '(null)', '(NULL)'
                                 nil
                               when /\A\((\w+\(\))\)\Z/
                                 ci[:default_function] = $1
                                 nil
                               else
                                 match_data = ci[:default_value].match(/\A\(+N?'?(.*?)'?\)+\Z/m)
                                 match_data ? match_data[1] : nil
                               end
          ci[:null] = ci[:is_nullable].to_i == 1 ; ci.delete(:is_nullable)
          ci
        end
      end
      
      def column_for(table_name, column_name)
        unless column = columns(table_name).detect { |c| c.name == column_name.to_s }
          raise ActiveRecordError, "No such column: #{table_name}.#{column_name}"
        end
        column
      end
      
      def change_order_direction(order)
        order.split(",").collect {|fragment|
          case fragment
            when  /\bDESC\b/i     then fragment.gsub(/\bDESC\b/i, "ASC")
            when  /\bASC\b/i      then fragment.gsub(/\bASC\b/i, "DESC")
            else                  String.new(fragment).split(',').join(' DESC,') + ' DESC'
          end
        }.join(",")
      end
      
      def special_columns(table_name)
        columns(table_name).select(&:is_special?).map(&:name)
      end
      
      def repair_special_columns(sql)
        special_cols = special_columns(get_table_name(sql))
        for col in special_cols.to_a
          sql.gsub!(/((\.|\s|\()\[?#{col.to_s}\]?)\s?=\s?/, '\1 LIKE ')
          sql.gsub!(/ORDER BY #{col.to_s}/i, '')
        end
        sql
      end
            
    end #class SQLServerAdapter < AbstractAdapter
    
  end #module ConnectionAdapters
  
end #module ActiveRecord