########################################################################
#                                                                      #
#              This file is part of the ksh 93u+m package              #
#          Copyright (c) 2021-2024 Contributors to ksh 93u+m           #
#                      and is licensed under the                       #
#                 Eclipse Public License, Version 2.0                  #
#                                                                      #
#                A copy of the License is available at                 #
#      https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.html      #
#         (with md5 checksum 84283fa8859daf213bdda5a9f8d1be1d)         #
#                                                                      #
#                  Martijn Dekker <martijn@inlv.org>                   #
#                                                                      #
########################################################################

# This is a ksh implementation of an autocd feature like 'shopt -s autocd'
# in bash. Drop this file in a directory in your $FPATH, and type 'autocd'
# to activate. After that, you only need to type the name of an existing
# directory to change to it, without needing to type 'cd' first.
#
# This is implemented using the DEBUG trap. The exit status of an autocd
# is always 2 because this is necessary to stop the directory name from
# being executed as a command (see ksh(1) under Built-in Commands, 'trap').

_do_autocd()
{
	# do nothing if called from another function, or shell not interactive, or the
	# command is ((arithmetic)), or the command contains blanks but is not quoted
	if	[[ .sh.level -ne 1 || ! -o interactive || $1 == \(* \
			|| ($1 == *[[:blank:]]* && $1 != \'*\' && $1 != \$\'*\') ]]
	then	return
	fi
	# if command name is quoted (e.g. directory name containing spaces), unquote it
	if	[[ $1 == \'*\' || $1 == \$\'*\' ]]
	then	eval "set -- $1"
	fi
	# if the result is one word and it's not a command, then autocd
	if      (($#==1)) && ! whence -q "$1" && [[ -d $1 ]]
	then    printf 'cd -- %q\n' "$1" >&2
		CDPATH= cd -- "$1"
		return 2  # status 2 == do not execute original command
	fi
}

autocd()
{
	if	[[ ${1-} == '-d' ]]
	then	trap - DEBUG
		print "autocd deactivated"
	else	trap '_do_autocd "${.sh.command}"' DEBUG
		print "autocd activated -- type a directory path to cd, ~- to cd back"
		print "type 'autocd -d' to deactivate"
	fi
}

# Do a check at autoload time. This depends on a non-buggy DEBUG trap.
# It is horribly broken in every latter-years AT&T version of ksh93.
if	((.sh.version < 20210220))
then	print "WARNING: this may crash or break ksh ${.sh.version};" >&2
	print "         autocd requires ksh 93u+m 2021-02-20 or later" >&2
	sleep 1
fi
