#!/bin/sh

# -------------------------------------------------------------------------- #
# Copyright 2002-2022, OpenNebula Project, OpenNebula Systems                #
#                                                                            #
# Licensed under the Apache License, Version 2.0 (the "License"); you may    #
# not use this file except in compliance with the License. You may obtain    #
# a copy of the License at                                                   #
#                                                                            #
# http://www.apache.org/licenses/LICENSE-2.0                                 #
#                                                                            #
# Unless required by applicable law or agreed to in writing, software        #
# distributed under the License is distributed on an "AS IS" BASIS,          #
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   #
# See the License for the specific language governing permissions and        #
# limitations under the License.                                             #
#--------------------------------------------------------------------------- #

set -e

CMD=$(basename ${0})

# file path to the new qemu-kvm symlink
QEMU_ONE="/usr/bin/qemu-kvm-one"

#
# functions
#

print_usage()
{
    cat <<EOF
NAME:
    ${CMD} - System agnostic QEMU/KVM symlink generator

    It will try to find a qemu-kvm binary in the system from a list of known
    paths and if successful - it will create a proper symlink:
        '${QEMU_ONE}'

USAGE:
    ${CMD} [-f|--force]
        Find the system QEMU binary and create the symlink

        -f|--force: This option will overwrite existing symlink or file

    ${CMD} -h|--help
        Print this help
EOF
}

#
# main
#

FORCE_CREATE=
case "$1" in
    '')
        :
        ;;
    -h|--help)
        print_usage
        exit 0
        ;;
    -f|--force)
        FORCE_CREATE=yes
        ;;
    *)
        echo "ERROR: ${CMD}: Unknown option '${1}' !" >&2
        print_usage >&2
        exit 1
        ;;
esac

# find cpu arch or default to x86_64
if command -v arch >/dev/null 2>&1 ; then
    ARCH=$(arch)
else
    ARCH="x86_64"
fi

# verify that symlink is not already created
if [ -L "${QEMU_ONE}" ] ; then
    # symlink already exists

    qemu_target=$(readlink "${QEMU_ONE}")

    if [ -e "${qemu_target}" ] && [ -z "${FORCE_CREATE}" ] ; then
        # symlink is valid
        exit 0
    fi
elif [ -e "${QEMU_ONE}" ] ; then
    # there is a file of the same name and it is not a symlink

    if [ -z "${FORCE_CREATE}" ] ; then
        echo "ERROR: ${CMD}: File '${QEMU_ONE}' already exists but it is not a symlink !" >&2
        exit 1
    else
        # --force is used
        rm -f "${QEMU_ONE}"
    fi
fi

# search the known paths for qemu binary
#
# NOTE: you can add new supported paths here in the future
for QEMU_BIN in \
    /usr/libexec/qemu-kvm \
    /usr/bin/qemu-kvm \
    /usr/bin/qemu-system-${ARCH} \
    ;
do
    if [ -e "${QEMU_BIN}" ] ; then
        ln -s ${FORCE_CREATE:+-f} "${QEMU_BIN}" "${QEMU_ONE}"
        exit 0
    fi
done

# no qemu binary found -> we signal error and exit
echo "ERROR: ${CMD}: No qemu kvm binary found !" >&2
exit 1