#!/bin/sh

# print a list of PostgreSQL versions that are supported for the platform this
# script runs on.
# Note: Newer installed versions than the highest one listed here are always
# considered supported, so that backports will not cause an "obsolete" warning.
#
# /usr/share/postgresql-common/supported-versions decides which PostgreSQL
# server versions are supported. This information is used
# 1) for notifying users of obsolete versions, suggesting to upgrade
# 2) by postgresql-common itself (in debian/rules) to determine the
#    dependencies of the postgresql meta packages (default version), and to
#    generate the list of postgresql-server-dev-* packages
#    postgresql-server-dev-all depends on
# 3) by the pg_buildext tool to decide which server versions to build extension
#    modules for
#
# The *last* version returned here will be considered the default version, the
# remaining lines list other supported versions in an undefined order.
#
# * PG_SUPPORTED_VERSIONS
# * DEB_PG_SUPPORTED_VERSIONS
# * ~/.pg_supported_versions
# * /etc/postgresql-common/supported_versions
# (in that order) can be used to override the defaults. (Tokens separated by
# newlines.)
#
# Recognized tokens:
# default: use the appropiate defaults for the current distribution
#          (as determined by os-release)
# debian: use Debian defaults
# debian-backports: use Debian Backports defaults
# ubuntu: use Ubuntu defaults
# pgdg: use defaults for apt.postgresql.org
# installed: consider all installed versions supported (determined by
#            postgresql-server-dev-X packages)
# X: consider this version supported
#
# (C) 2005-2016 Martin Pitt <mpitt@debian.org>
# (C) 2012-2022 Christoph Berg <myon@debian.org>

set -eu

DEFAULT="15"

# functions

default() {
    . /etc/os-release
    case "$ID" in
        [uU]buntu)
            ubuntu
            ;;
        [dD]ebian)
            debian
            ;;
        *)
            echo "supported-versions: WARNING! Unknown distribution ID in /etc/os-release: $ID" >&2
            if  echo $ID_LIKE | grep -E '(^| )ubuntu($| )' > /dev/null; then
                echo "ubuntu found in ID_LIKE, treating as Ubuntu" >&2
                ubuntu
            elif echo $ID_LIKE | grep -E '(^| )debian($| )' > /dev/null; then
                echo "debian found in ID_LIKE, treating as Debian" >&2
                debian
            else
                echo "Please submit this as a bug report to your distribution." >&2
                /bin/echo -e "$DEFAULT"
            fi
            ;;
    esac
}

ubuntu() {
    echo "$DEFAULT"
}

debian() {
    echo "$DEFAULT"
}

debian_backports() {
    echo "$DEFAULT"
}

pgdg() {
    cat <<-EOF
	10
	11
	12
	13
	14
	15
	EOF
}

installed() {
    dpkg -l 'postgresql-server-dev-[1-9]*' | \
        sed -ne 's/^ii *postgresql-server-dev-\([^ ]*\).*/\1/p' | \
        sort -V
}

# main

if [ "${PG_SUPPORTED_VERSIONS:-}" ] ; then
    SUPPORTED_VERSIONS=$(echo "$PG_SUPPORTED_VERSIONS" | xargs -n1)
elif [ "${DEB_PG_SUPPORTED_VERSIONS:-}" ] ; then
    SUPPORTED_VERSIONS=$(echo "$DEB_PG_SUPPORTED_VERSIONS" | xargs -n1)
elif [ -f ${HOME:-}/.pg_supported_versions ] ; then
    SUPPORTED_VERSIONS="$(cat ${HOME:-}/.pg_supported_versions)"
elif [ -f ${PGSYSCONFDIR:-/etc/postgresql-common}/supported_versions ] ; then
    SUPPORTED_VERSIONS="$(cat ${PGSYSCONFDIR:-/etc/postgresql-common}/supported_versions)"
else
    SUPPORTED_VERSIONS="default"
fi

echo "$SUPPORTED_VERSIONS" | while read version release; do
    COMMENT="#"
    case $version in
        "") ;;
        $COMMENT*) ;;
        default)
            default
            ;;
        debian)
            debian
            ;;
        debian-backports)
            debian_backports
            ;;
        ubuntu)
            ubuntu
            ;;
        pgdg) # apt.postgresql.org
            pgdg
            ;;
        installed)
            installed
            ;;
        *)
            /bin/echo -e "$version"
            ;;
    esac
done

exit 0