require 'benchmark'
require 'date'

# Method that requires a library, ensuring that rubygems is loaded
# This is used in the database adaptors to require DB drivers. Reasons:
# (1) database drivers are the only third-party library that Rails depend upon
# (2) they are often installed as gems
def require_library_or_gem(library_name)
  begin
    require library_name
  rescue LoadError => cannot_require
    # 1. Requiring the module is unsuccessful, maybe it's a gem and nobody required rubygems yet. Try.
    begin
      require 'rubygems'
    rescue LoadError => rubygems_not_installed
      raise cannot_require
    end
    # 2. Rubygems is installed and loaded. Try to load the library again
    begin 
      require library_name
    rescue LoadError => gem_not_installed
      raise cannot_require
    end
  end
end

module ActiveRecord
  class Base
    class ConnectionSpecification #:nodoc:
      attr_reader :config, :adapter_method
      def initialize (config, adapter_method)
        @config, @adapter_method = config, adapter_method
      end
    end
    
    # The class -> [adapter_method, config] map
    @@defined_connections = {}

    # Establishes the connection to the database. Accepts a hash as input where
    # the :adapter key must be specified with the name of a database adapter (in lower-case)
    # example for regular databases (MySQL, Postgresql, etc):
    #
    #   ActiveRecord::Base.establish_connection(
    #     :adapter  => "mysql",
    #     :host     => "localhost",
    #     :username => "myuser",
    #     :password => "mypass",
    #     :database => "somedatabase"
    #   )
    #
    # Example for SQLite database:
    #
    #   ActiveRecord::Base.establish_connection(
    #     :adapter => "sqlite",
    #     :dbfile  => "path/to/dbfile"
    #   )
    #
    # Also accepts keys as strings (for parsing from yaml for example):
    #   ActiveRecord::Base.establish_connection(
    #     "adapter" => "sqlite",
    #     "dbfile"  => "path/to/dbfile"
    #   )
    #
    # The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError
    # may be returned on an error.
    #
    # == Connecting to another database for a single model
    #
    # To support different connections for different classes, you can
    # simply call establish_connection with the classes you wish to have
    # different connections for:
    #
    #   class Courses < ActiveRecord::Base
    #    ...
    #   end
    #
    #   Courses.establish_connection( ... )
    def self.establish_connection(spec = nil)
      case spec
        when nil
          raise AdapterNotSpecified unless defined? RAILS_ENV
          establish_connection(RAILS_ENV)
        when ConnectionSpecification
          @@defined_connections[self] = spec
        when Symbol, String
          if configuration = configurations[spec.to_s]
            establish_connection(configuration)
          else
            raise AdapterNotSpecified, "#{spec} database is not configured"
          end
        else
          spec = symbolize_strings_in_hash(spec)
          unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
          adapter_method = "#{spec[:adapter]}_connection"
          unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
          remove_connection
          establish_connection(ConnectionSpecification.new(spec, adapter_method))
      end
    end

    # Locate the connection of the nearest super class. This can be an
    # active or defined connections: if it is the latter, it will be
    # opened and set as the active connection for the class it was defined
    # for (not necessarily the current class).
    def self.retrieve_connection #:nodoc:
      klass = self
      until klass == ActiveRecord::Base.superclass
        Thread.current['active_connections'] ||= {}
        if Thread.current['active_connections'][klass]
          return Thread.current['active_connections'][klass]
        elsif @@defined_connections[klass]
          klass.connection = @@defined_connections[klass]
          return self.connection
        end
        klass = klass.superclass
      end
      raise ConnectionNotEstablished
    end
    
    # Returns true if a connection that's accessible to this class have already been opened.
    def self.connected?
      klass = self
      until klass == ActiveRecord::Base.superclass
        if Thread.current['active_connections'].is_a?(Hash) && Thread.current['active_connections'][klass]
          return true 
        else
          klass = klass.superclass
        end
      end
      return false
    end
    
    # Remove the connection for this class. This will close the active
    # connection and the defined connection (if they exist). The result
    # can be used as argument for establish_connection, for easy
    # re-establishing of the connection.
    def self.remove_connection(klass=self)
      conn = @@defined_connections[klass]
      @@defined_connections.delete(klass)
      Thread.current['active_connections'] ||= {}
      Thread.current['active_connections'][klass] = nil
      conn.config if conn
    end
    
    # Set the connection for the class.
    def self.connection=(spec)
      raise ConnectionNotEstablished unless spec
      conn = self.send(spec.adapter_method, spec.config)
      Thread.current['active_connections'] ||= {}
      Thread.current['active_connections'][self] = conn
    end

    # Converts all strings in a hash to symbols.
    def self.symbolize_strings_in_hash(hash)
      hash.inject({}) do |hash_with_symbolized_strings, pair|
        hash_with_symbolized_strings[pair.first.to_sym] = pair.last
        hash_with_symbolized_strings
      end
    end
  end

  module ConnectionAdapters # :nodoc:
    class Column # :nodoc:
      attr_reader :name, :default, :type, :limit
      # The name should contain the name of the column, such as "name" in "name varchar(250)"
      # The default should contain the type-casted default of the column, such as 1 in "count int(11) DEFAULT 1"
      # The type parameter should either contain :integer, :float, :datetime, :date, :text, or :string
      # The sql_type is just used for extracting the limit, such as 10 in "varchar(10)"
      def initialize(name, default, sql_type = nil)
        @name, @default, @type = name, default, simplified_type(sql_type)
        @limit = extract_limit(sql_type) unless sql_type.nil?
      end

      def default
        type_cast(@default)
      end

      def klass
        case type
          when :integer       then Fixnum
          when :float         then Float
          when :datetime      then Time
          when :date          then Date
          when :timestamp     then Time
          when :time          then Time
          when :text, :string then String
          when :binary        then String
          when :boolean       then Object
        end
      end
      
      def type_cast(value)
        if value.nil? then return nil end
        case type
          when :string    then value
          when :text      then value
          when :integer   then value.to_i
          when :float     then value.to_f
          when :datetime  then string_to_time(value)
          when :timestamp then string_to_time(value)
          when :time      then string_to_dummy_time(value)
          when :date      then string_to_date(value)
          when :binary    then binary_to_string(value)
          when :boolean   then (value == "t" or value == true ? true : false)
          else value
        end
      end
      
      def human_name
        Base.human_attribute_name(@name)
      end
      
      def string_to_binary(value)
        value
      end     

      def binary_to_string(value)
        value
      end     

      private
        def string_to_date(string)
          return string if Date === string
          date_array = ParseDate.parsedate(string)
          # treat 0000-00-00 as nil
          Date.new(date_array[0], date_array[1], date_array[2]) rescue nil
        end
        
        def string_to_time(string)
          return string if Time === string
          time_array = ParseDate.parsedate(string).compact
          # treat 0000-00-00 00:00:00 as nil
          Time.send(Base.default_timezone, *time_array) rescue nil
        end

        def string_to_dummy_time(string)
          return string if Time === string
          time_array = ParseDate.parsedate(string)
          # pad the resulting array with dummy date information
          time_array[0] = 2000; time_array[1] = 1; time_array[2] = 1;
          Time.send(Base.default_timezone, *time_array) rescue nil
        end 
        
        def extract_limit(sql_type)
          $1.to_i if sql_type =~ /\((.*)\)/
        end
        
        def simplified_type(field_type)
          case field_type
            when /int/i
              :integer
            when /float|double|decimal|numeric/i
              :float
            when /datetime/i
              :datetime
            when /timestamp/i
              :timestamp
            when /time/i
              :time
            when /date/i
              :date
            when /clob/i, /text/i
              :text
            when /blob/i, /binary/i
              :binary
            when /char/i, /string/i
              :string
            when /boolean/i
              :boolean
          end
        end
    end

    # All the concrete database adapters follow the interface laid down in this class.
    # You can use this interface directly by borrowing the database connection from the Base with
    # Base.connection.
    class AbstractAdapter
      @@row_even = true

      include Benchmark

      def initialize(connection, logger = nil) # :nodoc:
        @connection, @logger = connection, logger
        @runtime = 0
      end

      # Returns an array of record hashes with the column names as a keys and fields as values.
      def select_all(sql, name = nil) end
      
      # Returns a record hash with the column names as a keys and fields as values.
      def select_one(sql, name = nil) end

      # Returns an array of column objects for the table specified by +table_name+.
      def columns(table_name, name = nil) end

      # Returns the last auto-generated ID from the affected table.
      def insert(sql, name = nil, pk = nil, id_value = nil) end

      # Executes the update statement and returns the number of rows affected.
      def update(sql, name = nil) end

      # Executes the delete statement and returns the number of rows affected.
      def delete(sql, name = nil) end

      def reset_runtime # :nodoc:
        rt = @runtime
        @runtime = 0
        return rt
      end

      # Wrap a block in a transaction.  Returns result of block.
      def transaction(start_db_transaction = true)
        begin
          if block_given?
            begin_db_transaction if start_db_transaction
            result = yield
            commit_db_transaction if start_db_transaction
            result
          end
        rescue Exception => database_transaction_rollback
          rollback_db_transaction if start_db_transaction
          raise
        end
      end

      # Begins the transaction (and turns off auto-committing).
      def begin_db_transaction()    end
      
      # Commits the transaction (and turns on auto-committing). 
      def commit_db_transaction()   end

      # Rollsback the transaction (and turns on auto-committing). Must be done if the transaction block
      # raises an exception or returns false.
      def rollback_db_transaction() end

      def quote(value, column = nil)
        case value
          when String                
            if column && column.type == :binary
              "'#{quote_string(column.string_to_binary(value))}'" # ' (for ruby-mode)
            else
              "'#{quote_string(value)}'" # ' (for ruby-mode)
            end
          when NilClass              then "NULL"
          when TrueClass             then (column && column.type == :boolean ? "'t'" : "1")
          when FalseClass            then (column && column.type == :boolean ? "'f'" : "0")
          when Float, Fixnum, Bignum then value.to_s
          when Date                  then "'#{value.to_s}'" 
          when Time, DateTime        then "'#{value.strftime("%Y-%m-%d %H:%M:%S")}'"
          else                            "'#{quote_string(value.to_yaml)}'"
        end
      end

      def quote_string(s)
        s.gsub(/\\/, '\&\&').gsub(/'/, "''") # ' (for ruby-mode)
      end

      def quote_column_name(name)
        return name
      end

      # Returns a string of the CREATE TABLE SQL statements for recreating the entire structure of the database.
      def structure_dump() end

      def add_limit!(sql, limit)
        sql << " LIMIT #{limit}"
      end

      protected
        def log(sql, name, connection, &action)
          begin
            if @logger.nil? || @logger.level > Logger::INFO
              action.call(connection)
            else
              result = nil
              bm = measure { result = action.call(connection) }
              @runtime += bm.real
              log_info(sql, name, bm.real)
              result
            end
          rescue => e
            log_info("#{e.message}: #{sql}", name, 0)
            raise ActiveRecord::StatementInvalid, "#{e.message}: #{sql}"
          end
        end

        def log_info(sql, name, runtime)
          if @logger.nil? then return end

          @logger.info(
            format_log_entry(
              "#{name.nil? ? "SQL" : name} (#{sprintf("%f", runtime)})", 
              sql.gsub(/ +/, " ")
            )
          )
        end

        def format_log_entry(message, dump = nil)
          if @@row_even then
            @@row_even = false; caller_color = "1;32"; message_color = "4;33"; dump_color = "1;37"
          else
            @@row_even = true; caller_color = "1;36"; message_color = "4;35"; dump_color = "0;37"
          end
          
          log_entry = "  \e[#{message_color}m#{message}\e[m"
          log_entry << "   \e[#{dump_color}m%s\e[m" % dump if dump.kind_of?(String) && !dump.nil?
          log_entry << "   \e[#{dump_color}m%p\e[m" % dump if !dump.kind_of?(String) && !dump.nil?
          log_entry
        end
    end
    
  end
end