module MJ; module Tools

    module SubProcess

        class CoreDumpError < StandardError; end

        module ClassMethods

            # Executes command
            #
            # Executes the given command and yields each line of output.
            # Returns +$?+ .
            def execute( command, wd = ENV["HOME"], env = nil )
                cwd ||= Dir.getwd
                logger.trace "(#{wd}) > #{command} 2>&1"
                if !$noop
                    adjust_environment( wd, env ) {
                        IO.popen( "#{command} 2>&1" ) {
                            |f|
                            begin
                                while
                                    line = f.readline
                                    if line.start_with?( "error:" )
                                        logger.error line.chomp
                                    elsif line.start_with?( "warning:" )
                                        logger.warn line.chomp
                                    elsif line.start_with?( "trace:" )
                                        logger.trace line.chomp
                                    elsif line.start_with?( "info:" )
                                        logger.info line.chomp
                                    else
                                        logger.verbose line.chomp
                                    end
                                    yield line.chomp if block_given?
                                end
                            rescue EOFError
                                # Expected. Do nothing
                            end
                        }
                        if $?.coredump? or $?.signaled?
                            raise CoreDumpError, "Command '#{command}' core dumped because of signal #{$?.termsig}!"
                        end
                        logger.trace "= #{$?.exitstatus}"
                        return $?.exitstatus
                    }
                else
                    adjust_environment( wd, env ) {
                        logger.trace "= 0 # noop" 
                    }
                    return 0
                end

            end

            # Helper method to adjust LANG to "C"
            def adjust_environment( wd=nil, env=nil, lang="C" )
                if wd and !$noop
                    cwd = Dir.getwd
                    Dir.chdir(wd)
                end
                # Set the environment the user wants
                oldenv = Hash.new
                if env
                    env.each do |var, value|
                        oldenv[var] = ENV[var]
                        logger.verbose  "#{var} = #{value}"
                        ENV[var] = value
                    end
                end
                # Save old LANG setting and switch to 'C'
                oldlang = ENV['LANG']
                ENV['LANG'] = lang
                yield
                # Reset the old LANG setting
                ENV['LANG'] = oldlang
                # Reset our changes to ENV
                oldenv.each do |var, value|
                    ENV[var] = value
                end
                # Reset the current working directory
                if wd and !$noop
                    Dir.chdir(cwd)
                end
            end
        end

        #########
        protected
        #########

        def self.included( klass )
            klass.extend( ClassMethods )
        end

    end

end; end