#!/bin/bash
#  $HeadURL$ $LastChangedRevision$
set -e
PROGNAME=$(basename $0)

#  Load support functions
. $(pcms-config PCMS_SHARE_PREFIX)/scripts/support.sh

main()
{
    #  Defaults for options
    VERBOSELEVEL=2

    #  Process options
    while [ $# -ge 1 ]; do
        case $1 in
            -d)              VERBOSELEVEL=$2; shift ;;
            --debug=*)       VERBOSELEVEL=${1#*=} ;;
            -v|--verbose)    VERBOSELEVEL=3 ;;
            --)              shift; break ;;
            -*)              error "main: $1: bad option" ;;
            *)               break ;;
        esac
        shift
    done

    #  Process arguments
    [ $# = 1 ] || usage
    eval set -- $(encode --decode "$1")
    [ $# -eq 3 ] || usage
    SYMLINK="$1"
    TARGET="$2"
    MKDIR_FLAG="$3"
    debug 10 "main: SYMLINK=$SYMLINK, TARGET=$TARGET, MKDIR_FLAG=$MKDIR_FLAG"

    #  Sanity checks and derivations
    [[ $MKDIR_FLAG =~ ^(true|false)$ ]] || error "$MKDIR_FLAG: invalid value for MKDIR_FLAG"
    [[ $SYMLINK =~ ^/ ]] || error "$SYMLINK: not absolute"
    ! [[ $TARGET =~ ^/ ]] || error "$SYMLINK: not relative"

    #  Symlink
    if [ ! -h $SYMLINK -a ! -e $SYMLINK ]; then
        ln -s $TARGET $SYMLINK
    elif { [ ! -h $SYMLINK -a -e $SYMLINK ]; }; then
        error "$SYMLINK: exists but is not a symlink (hint: fix this manually)"
    elif { [ -h $SYMLINK ] && [ $(readlink $SYMLINK) != $TARGET ]; }; then
        warning "$SYMLINK: exists and is a symlink but points to $(readlink $SYMLINK) instead of $TARGET; removing ..."
        rm -f $SYMLINK
        ln -s $TARGET $SYMLINK
    fi
    #  Mkdir
    if $MKDIR_FLAG; then
        ABSOLUTE_TARGET=$(realpath -m $SYMLINK)
        if [ ! -h $ABSOLUTE_TARGET -a ! -e $ABSOLUTE_TARGET ]; then
            mkdir -p $ABSOLUTE_TARGET
        elif [ -h $ABSOLUTE_TARGET -o \( -e $ABSOLUTE_TARGET -a ! -d $ABSOLUTE_TARGET \) ]; then
            error "$ABSOLUTE_TARGET: exists but is not a directory (hint: fix this manually)"
        fi
    else
        #  It'd be nice to do this "if link's targer doesn't exist then error" test before we even create the
        #  symlink, but $ABSOLUTE_TARGET depends on the realpath command and I suspect that that won't work
        #  in the above call unless $SYMLINK actually exists. But perhaps it would e..g:
        #
        #      lagane# realpath /etc/a             #  where /etc/a does not exist!
        #      /etc/a
        #      lagane#
        #
        #  Nonetheless, for the time being, we do it this way: undo the just created symlink
        #  and return an error.
        if [ ! -e $ABSOLUTE_TARGET ]; then
            rm -f $SYMLINK
            error "$ABSOLUTE_TARGET: does not exist and you didn't request me to create it (as a directory); symlink has been removed"
        fi
    fi
}

usage() { echo "Usage: $PROGNAME <symlink>@<target>@<mkdir-flag>" >&2; exit 1; }

main "$@"