unrar / midb

    # This class handles engine-dependent database operations

    class Dbengine

      # @!attribute engine

      #   @return [Symbol] The database engine being used

      # @!attribute host

      #   @return [String] Host name where the database is located

      # @!attribute uname

      #   @return [String] Username for the database

      # @!attribute pwd

      #   @return [String] Password for the database.

      # @!attribute port

      #   @return [Fixnum] Port for the database

      # @!attribute db

      #   @return [String] Name of the database  

      attr_accessor :engine, :host, :uname, :pwd, :port, :db

      # Constructor - initializes the attributes with the configuration from ServerController

      #

      # @param cnf [Array<String>] The configuration array.

      # @param db  [String] Database name.

      def initialize(cnf, db)

        @engine = cnf["dbengine"]

        @host = cnf["dbhost"]

        @port = cnf["dbport"]

        @uname = cnf["dbuser"]

        @pwd = cnf["dbpassword"]

        @db = db

      end

      # Connect to the specified database

      #

      # @return [SQLite3::Database, Mysql2::Client] A resource referencing to the database

      def connect()

        begin

          # Connect to an SQLite3 database

          if @engine == :sqlite3

            sq = SQLite3::Database.open("./db/#{@db}.db")

            sq.results_as_hash = true

            return sq

          # Connect to a MySQL database

          elsif @engine == :mysql

            return Mysql2::Client.new(:host => @host, :username => @uname, :password => @pwd, :database => @db)

          end

        rescue

          MIDB::Interface::Errors.exception(:database_error, $!)

          return false

        end

      end

      # Perform a query to the database.

      #

      # @param res [SQLite3::Database, Mysql2::Client] An existing database resource.

      # @param query [String] The SQL query to be ran.

      #

      # @return [Array, Hash] Returns an array of hashes for SQLite3 or a hash for MySQL

      def query(res, query)

        begin

          if @engine == :sqlite3

            return res.execute(query)

          elsif @engine == :mysql

            return res.query(query)

          end

        rescue

          MIDB::Interface::Errors.exception(:query_error, $!)

          return false

        end

      end

      # Extract a field from a query, because different engines return different types (see #query)

      #

      # @param result [Array, Hash] The result of a query obtained via #query

      # @param field [String] The name of the field to be extracted.

      #

      # @return [String, Fixnum] The field extracted from a query

      def extract(result, field)

        if @engine == :sqlite3

          return result[0][field] || result[field]

        elsif @engine == :mysql

          result.each do |row|

            return row[field]

          end

        end

      end

      # Returns the length of a result, because different engines return diferent types (see #query)

      #

      # @param result [Array, Hash] The result of a query obtained via #query

      # 

      # @return [Fixnum] Length of the result.

      def length(result)

        if @engine == :sqlite3

          return result.length

        elsif @engine == :mysql 

          return result.count

        end

      end

end