--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bash-completion.sh	Sun Dec 27 21:57:52 2020 +0100
@@ -0,0 +1,78 @@
+# Relational pipes
+# Copyright © 2019 František Kučera (Frantovo.cz, GlobalCode.info)
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+_relpipe_tr_xpath_completion() {
+	local w0 w1 w2 w3
+
+	COMPREPLY=()
+	w0=${COMP_WORDS[COMP_CWORD]}
+	w1=${COMP_WORDS[COMP_CWORD-1]}
+	w2=${COMP_WORDS[COMP_CWORD-2]}
+	w3=${COMP_WORDS[COMP_CWORD-3]}
+
+	DATA_TYPE=(
+		"string"
+		"integer"
+		"boolean"
+	)
+
+	INPUT_ATTRIBUTE_POLICY=(
+		"append"
+		"prepend"
+		"auto"
+	)
+
+	# FIXME: user must type " and then press TAB otherwise the completion is broken due to the : colon
+	#
+	# can be fixed by global modification of environment variable:
+	#	COMP_WORDBREAKS=${COMP_WORDBREAKS//:}
+	# but it will affect other completions (where : is a separator)
+	#
+	# these functions should help:
+	#	_get_comp_words_by_ref -n : cur
+	#	__ltrim_colon_completions "$cur"
+	# but was not working (despite w0 renamed to cur)
+	XMLNS=(
+		"tag:globalcode.info,2018:relpipe"
+		"http://www.w3.org/1999/xhtml"
+		"http://www.w3.org/2000/svg"
+		"http://www.w3.org/2005/Atom"
+		"http://docbook.org/ns/docbook"
+	)
+
+
+	if   [[ "$w1" == "--relation"                      && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w1" == "--where"                         && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w1" == "--xml-attribute"                 && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w1" == "--output-attribute"              && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w2" == "--output-attribute"                               ]];    then COMPREPLY=($(compgen -W "${DATA_TYPE[*]}" -- "$w0"))
+	elif [[ "$w3" == "--output-attribute"              && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w1" == "--namespace"                     && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w2" == "--namespace"                                      ]];    then COMPREPLY=($(compgen -W "${XMLNS[*]}" -- "$w0"))
+	elif [[ "$w1" == "--input-attributes"                               ]];    then COMPREPLY=($(compgen -W "${INPUT_ATTRIBUTE_POLICY[*]}" -- "$w0"))
+	else
+		OPTIONS=(
+			"--namespace"
+			"--relation"
+			"--where"
+			"--output-attribute"
+			"--input-attributes"
+			"--xml-attribute"
+		)
+		COMPREPLY=($(compgen -W "${OPTIONS[*]}" -- "$w0"))
+	fi
+}
+
+complete -F _relpipe_tr_xpath_completion relpipe-tr-xpath