lang

#!/bin/bash
: ${DS_LANG_STRING:=en}

modlangsubst()
{
	# modlangsubst <lang> <file>
	#   Substitutes all $(lang de:"Deutscher Text" en:"English text" ...) occurrences
	#   in <file> with <text> of the corresponding <lang>:"<text>" section.

	val='\(\([^"\\]*\(\\.\)*\)*\)'
	entry="\w\+:\"${val}\""
	LC_CTYPE=C sed -i -e "
	    :a
	    s/\$(lang\(\s\+$entry\)*\s\+${1}:\"${val}\"\(\s\+$entry\)*\s*)/\$(lang:\"\5\")/g
	    s/\$(lang\(\s\+$entry\)*\s*)/*** error: language[${1}] not available ***/g
	    :n
	    s/\$(lang:\"\(\([^\"\\]\+\)\|[\\]\(.\)\)${val}\")/\2\3\$(lang:\"\4\")/g
	    tn
	    s/\$(lang:\"\")//g
	    /\$(lang\(\s\|\$\)/ {N; ba}
	" "$2"
}

modlangconf()
{
	# modlangconf <key> <file>
	#   Get <content> of a <key> { <content> } section in <file>

	sed -n -e ":n;N;\$!bn;s/^.*${1}[\s\n]\+{[\s\n]*\([^}]*\)[\s\n]*}.*$/\1/p" "$2"
}

modlang()
{
	# modlang <conffile> <dir>

	avail="$(modlangconf "languages" "$1")"
	default="$DS_LANG_STRING $(modlangconf "default" "$1") en de $avail"
	lang=""

	for i in $default
	do
		for j in $avail
		do
			if [ "$i" == "$j" ]
			then
				lang="$j"
				break 2
			fi
		done
	done

	if [ -z "$lang" ]
	then
		echo "ERROR: no language available" 1>&2
		exit 1
	fi

	[ "$lang" == "$DS_LANG_STRING" ] || \
		echo "NOTICE: language $DS_LANG_STRING not available; $lang chosen." 1>&2

	for i in $(modlangconf "files" "$1")
	do
		if [ -e "${2}/${i}" ]
		then
			modlangsubst "$lang" "${2}/${i}"
		else
			echo "WARNING: ${2}/${i} not found" 1>&2
		fi
	done
}

modlang "$@"