#!/bin/bash
# These are useful, or at worst not harmful, for all images we build.

if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
    set -x
fi
set -eu
set -o pipefail

[ -n "$ARCH" ]
[ -n "$TARGET_ROOT" ]

shopt -s extglob

DIB_RELEASE=${DIB_RELEASE:-trusty}
DIB_CLOUD_IMAGES=${DIB_CLOUD_IMAGES:-http://cloud-images.ubuntu.com/$DIB_RELEASE/current}
if [ $DIB_RELEASE != "trusty" ] && [ $DIB_RELEASE != "xenial" ]; then
    BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-$DIB_RELEASE-server-cloudimg-$ARCH.squashfs}
else
    BASE_IMAGE_FILE=${BASE_IMAGE_FILE:-$DIB_RELEASE-server-cloudimg-$ARCH-root.tar.gz}
fi
SHA256SUMS=${SHA256SUMS:-https://${DIB_CLOUD_IMAGES##http?(s)://}/SHA256SUMS}
CACHED_FILE=$DIB_IMAGE_CACHE/$BASE_IMAGE_FILE
CACHED_FILE_LOCK=$DIB_LOCKFILES/$BASE_IMAGE_FILE.lock
CACHED_SUMS=$DIB_IMAGE_CACHE/SHA256SUMS.ubuntu.$DIB_RELEASE.$ARCH

function get_ubuntu_tarball() {
    if [ -n "$DIB_OFFLINE" -a -z "$DIB_LOCAL_IMAGE" ] ; then
        if [ -f "$CACHED_FILE" ] ; then
            echo "Not checking freshness of cached $CACHED_FILE."
        else
            echo "Fetching Base Image"
            $TMP_HOOKS_PATH/bin/cache-url $SHA256SUMS $CACHED_SUMS
            $TMP_HOOKS_PATH/bin/cache-url \
                $DIB_CLOUD_IMAGES/$BASE_IMAGE_FILE $CACHED_FILE
            pushd $DIB_IMAGE_CACHE
            if ! grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check - ; then
                # It is likely that an upstream http(s) proxy has given us a skewed
                # result - either a cached SHA file or a cached image. Use cache-busting
                # to get (as long as caches are compliant...) fresh files.
                # Try the sha256sum first, just in case that is the stale one (avoiding
                # downloading the larger image), and then if the sums still fail retry
                # the image.
                $TMP_HOOKS_PATH/bin/cache-url -f $SHA256SUMS $CACHED_SUMS
                if ! grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check - ; then
                    $TMP_HOOKS_PATH/bin/cache-url -f \
                        $DIB_CLOUD_IMAGES/$BASE_IMAGE_FILE $CACHED_FILE
                    grep "$BASE_IMAGE_FILE" $CACHED_SUMS | sha256sum --check -
                fi
            fi
            popd
        fi
    elif [ ! -f "$DIB_LOCAL_IMAGE" ] ; then
        echo "Unable to find image $DIB_LOCAL_IMAGE locally! Check path and file name to source image"
        exit 1
    fi
    # Extract the base image (use --numeric-owner to avoid UID/GID mismatch between
    # image tarball and host OS e.g. when building Ubuntu image on an openSUSE host)
    if [ "$DIB_RELEASE" != "trusty" ] && [ "$DIB_RELEASE" != "xenial" ] ; then
        if [ -n "$DIB_LOCAL_IMAGE"] ; then
            sudo unsquashfs -f -d $TARGET_ROOT $DIB_IMAGE_CACHE/$BASE_IMAGE_FILE
        else
            sudo unsquashfs -f -d $TARGET_ROOT $DIB_LOCAL_IMAGE
        fi
    else
        if [ -n "$DIB_LOCAL_IMAGE"] ; then
            sudo tar -C $TARGET_ROOT --numeric-owner -xzf $DIB_IMAGE_CACHE/$BASE_IMAGE_FILE
        else
            sudo tar -C $TARGET_ROOT --numeric-owner -xzf $DIB_LOCAL_IMAGE
        fi
    fi
}

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