#!/bin/sh -e

lang=$1
validated_language=

test -n "$lang" || exit 1

langtoolsdir=/usr/share/language-tools

#
# discard possible fallback languages
#
lang=${lang%%:*}

#
# remove possible encoding part
#
if [ $lang != ${lang%.utf8*} ]; then
lang=${lang%.*}${lang#*.utf8}
elif [ $lang != ${lang%.UTF-8*} ]; then
lang=${lang%.*}${lang#*.UTF-8}
fi

#
# make sure that the output is a valid language option
#
options=$( $langtoolsdir/language-options )

# exact match
for opt in $options; do
if [ $opt = $lang ]; then
validated_language=$lang
break
fi
done

if [ -z "$validated_language" ]; then
langcode=${lang%%[_@]*}

# try the "main" country code if any
main_country=
while read line; do
if [ "${line%%[[:space:]]*}" = $langcode ]; then
main_country=${line##*[[:space:]]}
if [ $lang != ${lang#*@} ]; then
main_country=$main_country@${lang#*@}
is_variant=true
fi
break
fi
done < $langtoolsdir/main-countries
if [ -n "$main_country" ]; then
for opt in $options; do
if [ $main_country = $opt ]; then
validated_language=$main_country
break
fi
done
fi

# try out fitting language option without paying regard to
# country code or variant
if [ -z "$validated_language" ]; then
for opt in $options; do
if [ "${opt%%[_@]*}" = $langcode -a $langcode != 'zh' ]; then
validated_language=$opt
break
fi
done
fi
fi

if [ -z "$validated_language" ]; then
validated_language='en'
fi

echo $validated_language