#!/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

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:-""}

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
        # WARNING: The mattdm image has the root filesystem on the second
        #          partition (p2). If he changes the image the MAGIC_BIT
        #          might also need to change.
        # UPDATE to above warning alluding to Fedora18:
        # F19 images have the rootfs partition on p1
        MAGIC_BIT=p1
        # 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.
        # NOTE: On F17 (parted-3.0-10.fc17.x86_64), partprobe of
        #       /dev/loop0 does not create /dev/loop0p2, while kpartx at
        #       least creates /dev/mapper/loop0p2.
        LOOPDEV=$(sudo kpartx -av $WORKING/$RAW_FILE | awk "/loop[0-9]+$MAGIC_BIT/ {print \$3}")
        if ! timeout 5 sh -c "while ! [ -e /dev/mapper/$LOOPDEV ]; do sleep 1; done"; then
            echo "Error: Could not find /dev/mapper/$LOOPDEV"
            exit 1
        fi
        EACTION="sudo kpartx -d $WORKING/$RAW_FILE;$EACTION"
        trap "$EACTION" EXIT
        mkdir $WORKING/mnt
        sudo mount /dev/mapper/$LOOPDEV $WORKING/mnt
        EACTION="sudo umount -f $WORKING/mnt;$EACTION"
        trap "$EACTION" EXIT
        # 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 $CACHED_TAR
if [ -e "$TARGET_ROOT/lost+found" ]; then
  sudo rmdir $TARGET_ROOT/lost+found
fi