#! /bin/sh
#
# 	Figure out where to find pg_config.
#       Copyright (c) 2020 Marc Munro
#       Author:  Marc Munro
#	License: GPL V3
#
# This is primarily built for debian and debian-like systems where
# multiple versions of postgres may be installed.
#
# Usage ./find_pg_config
#



# Return a simplified (2-part) version string.
#
strip_version()
{
    sed 's/.*\([0-9][0-9]*\.[0-9][0-9]*\)\.[0-9][0-9]*.*/\1/'
}

# Attempt to read the postgres version by connecting to the database
# server. If that fails, use the contents of the PG_VERSION file, if it
# exists.
#
pgver()
{
    if [ "x$1" != "x" ]; then
        echo $1
    else
    	if ver=`psql --no-psqlrc --tuples-only \
    		  --command="select version()"`; then
    	    # All was well, so record the version in PG_VERSION for later
    	    # use by install (which is run from root and may not have access
    	    # to psql or postgres databases.
	    ver=`echo ${ver} | awk '{print $2}' | strip_version`
    	    echo $ver >PG_VERSION
    	    echo $ver
    	else
    	    if [ -f ./PG_VERSION ]; then
    		    cat ./PG_VERSION
    	    else
	        echo "Cannot establish postgres version..." 1>&2
    	        echo "Specify PG_VERSION explicitly in the make command." 1>&2
    	        exit 2
	    fi
    	fi
    fi
}

if [ -r PG_CONFIG ]; then
    cat PG_CONFIG
else
    # Maybe the correct pg_config is where it claims to be.
    #
    if ver=`pgver $1`; then
	major_ver=`echo "${ver}" | cut -d. -f1`
	if [ "0${major_ver}" -ge 10 ]; then
	    # This is a postgres version after pg 10, when version
	    # numbering changed.  We now only need the major part of
	    # the version number.
	    ver=${major_ver}
	fi
        if cver=`pg_config --version | strip_version`; then
            if [ "x${cver}" = "x${ver}" ]; then
                which pg_config > PG_CONFIG
                cat PG_CONFIG
        	exit 0
            fi
        fi

        # Or maybe, we can figure it out from the database version
        if [ -f /usr/lib/postgresql/${ver}/bin/pg_config ]; then
            echo /usr/lib/postgresql/${ver}/bin/pg_config  > PG_CONFIG
            cat PG_CONFIG
            exit 0
        fi

        # If we get here, we really have not much idea, nor anywhere else to
        # look.

        echo "Cannot find pg_config for postgres version ${ver}" 1>&2
        exit 2
    fi
fi