#!/usr/bin/bash

# Generates single-file from-scratch and delta update files for all or some of the
# refs in an OSTree repo.
#
# To use it run "generate-deltas REPODIR DESTDIR" which will look at all the refs in the
# repo and make updates to the latest version putting them in the DESTDIR directory.

# To apply these on a live system, do something like:
# $ ostree static-delta apply-offline cs9-x86_64-qemu-upgrade-demo-79da0b2f1b119e99137eaef9680fae9820a9edcd5cac4f6d7c23279498c578f6.update
# $ rpm-ostree rebase 79da0b2f1b119e99137eaef9680fae9820a9edcd5cac4f6d7c23279498c578f6

if [ "$#" -lt 2 ]; then
    echo "Usage generate-deltas REPODIR DESTDIR [REFS..]"
    exit 1
fi

REPO=$1
DIR=$2

shift 2

if [ "$#" -gt 0 ]; then
    REFS="$@"
else
    REFS=$(ostree --repo=$REPO refs)
fi

mkdir -p $DIR

NUM_DELTAS=3
for REF in $REFS; do
    REF_AS_FILE=$(echo $REF | sed "s%/%-%g" )
    HEAD=$(ostree --repo=$REPO rev-parse $REF)

    # Generate full update for HEAD:
    echo Generating non-delta update for $REF commit $HEAD
    ostree static-delta generate --repo=$REPO  --inline --min-fallback-size=0 --empty --filename=$DIR/$REF_AS_FILE-$HEAD.update $HEAD

    # Generate deltas to HEAD from up to the last 3 parents
    PARENT=$HEAD
    for i in seq $NUM_DELTAS; do
        if ! PARENT=$(ostree --repo=$REPO rev-parse $PARENT^ 2>/dev/null); then
            break;
        fi
        echo Generating delta update for $REF commit $HEAD from commit $PARENT
        ostree static-delta generate --repo=$REPO  --inline --min-fallback-size=0 --from=$PARENT --filename=$DIR/$REF_AS_FILE-$PARENT-$HEAD.update $HEAD
    done

done