#!/bin/bash

# Intended to be called from the root.d cloud-image script as follows:
# $TMP_HOOKS_PATH/bin/extract-image $BASE_IMAGE_FILE $BASE_IMAGE_TAR $IMAGE_LOCATION $CACHED_IMAGE


set -eu
set -o pipefail

BASE_IMAGE_FILE=$1
BASE_IMAGE_TAR=$2
IMAGE_LOCATION=$3
CACHED_IMAGE=$4

CACHED_TAR=$DIB_IMAGE_CACHE/$BASE_IMAGE_TAR
DIB_LOCAL_IMAGE=${DIB_LOCAL_IMAGE:-""}
TAR_LOCK=$CACHED_TAR.lock

function extract_image() {
    if [ -n "$DIB_OFFLINE" -a -f "$CACHED_TAR" ] ; then
        echo "Not checking freshness of cached $CACHED_TAR."
    else
        if [ -z "$DIB_LOCAL_IMAGE" ]; then
            echo "Fetching Base Image"

            # There seems to be some bad Fedora mirrors returning http 404's for the cloud image.
            # If the image fails to download due to a 404 we retry once.
            set +e
            $TMP_HOOKS_PATH/bin/cache-url $IMAGE_LOCATION $CACHED_IMAGE
            RV=$?
            set -e

            if [ "$RV" == "44" ] ; then
                $TMP_HOOKS_PATH/bin/cache-url $IMAGE_LOCATION $CACHED_IMAGE
            elif [ "$RV" != "0" ] ; then
                exit 1
            fi
        fi

        if [ ! -f $CACHED_TAR -o \
            $CACHED_IMAGE -nt $CACHED_TAR ] ; then
            echo "Repacking base image as tarball."
            WORKING=$(mktemp -d)
            EACTION="rm -r $WORKING"
            trap "$EACTION" EXIT
            echo "Working in $WORKING"
            RAW_FILE=$(basename $BASE_IMAGE_FILE)
            RAW_FILE=${RAW_FILE#.qcow2}.raw
            qemu-img convert -f qcow2 -O raw $CACHED_IMAGE $WORKING/$RAW_FILE

            # F19 images have the rootfs partition on p1
            # Centos7 images on p3 (p1 boot, p2 swap)
            if [[ $DISTRO_NAME = "centos7" ]]; then
                ROOT_PARTITON=p3
            else
                ROOT_PARTITON=p1
            fi

            # kpartx fails if no /dev/loop* exists, "losetup -f" prints first unused
            # loop device and creates it if it doesn't exist
            sudo losetup -f

            # XXX: Parsing stdout is dangerous, would like a better way to discover
            #      the device used for the image.
            ROOT_LOOPDEV=$(sudo kpartx -av $WORKING/$RAW_FILE | \
                awk "/loop[0-9]+$ROOT_PARTITON/ {print \$3}")
            if ! timeout 5 sh -c "while ! [ -e /dev/mapper/$ROOT_LOOPDEV ]; do sleep 1; done"; then
                echo "Error: Could not find /dev/mapper/$ROOT_LOOPDEV"
                exit 1
            fi
            EACTION="sudo kpartx -d $WORKING/$RAW_FILE ; $EACTION"
            trap "$EACTION" EXIT
            mkdir $WORKING/mnt
            sudo mount /dev/mapper/$ROOT_LOOPDEV $WORKING/mnt
            EACTION="sudo umount -f $WORKING/mnt ; $EACTION"
            trap "$EACTION" EXIT

            # need to copy the contents of /boot into the image too, so
            # mount it
            if [[ $DISTRO_NAME = "centos7" ]]; then
                BOOT_LOOPDEV=${ROOT_LOOPDEV/p3/p1}
                sudo mount /dev/mapper/$BOOT_LOOPDEV $WORKING/mnt/boot
                EACTION="sudo umount -f $WORKING/mnt/boot ; $EACTION"
                trap "$EACTION" EXIT
            fi

            # Chroot in so that we get the correct uid/gid
            sudo chroot $WORKING/mnt bin/tar -cz . > $WORKING/tmp.tar
            mv $WORKING/tmp.tar $CACHED_TAR
        else
            echo "Using cached tar from $CACHED_TAR"
        fi
    fi

    # Extract the base image (use --numeric-owner to avoid UID/GID mismatch between
    # image tarball and host OS e.g. when building Fedora image on an openSUSE host)
    echo "Extracting base root image from $CACHED_TAR"
    sudo tar -C $TARGET_ROOT --numeric-owner -xzf $CACHED_TAR
}

(
    echo "Getting $TAR_LOCK: $(date)"
    # Wait up to 20 minutes for another process to download
    if ! flock -w 1200 9 ; then
        echo "Did not get $TAR_LOCK: $(date)"
        exit 1
    fi
    extract_image
) 9> $TAR_LOCK