#!/bin/bash

# Build a minideb image for each supported dist
#
# First we build the image as a tarball, then we import it and tag it.
#
# However we aim to allow our images to be reproduced. That means
# we need more control over the import process. We also build and import
# each image twice to confirm that our images are still reproducible.
#
# To reproduce an image you have to:
#
#   - Produce exactly the same base tarball. `mkimage` will take care of that
#     for the same package inputs.
#   - Import the image with the same config (`CMD` etc.)
#   - Have the same creation date on the image.
#
# That last requirement leads us to some extra work to re-use timestamps.
#
# The steps are:
#
# 1. Pull image from Dockerhub and save creation date and image_id
# 2. Build image locally and import it, setting creation date to the pulled one
# 3. Build the image again and import it, also setting creation date to the pulled one
# 4. Compare the built image ids. Error if they are not the same (Docker thinks images are different, thanks to checksum)
# 5. Compare built image id with pulled image id. Both will have same creation date but may differ in checksum so ids may be different
#    - If the image is the same as the pulled one then nothing changed in this build
#    - If the image differs from the pulled one then:
#      - Re-import the locally built image with the current timestamp so it will be shown as a new image
#      - Tag the built image with the target tag, ready to push.

set -e
set -u
set -o pipefail

DISTS="jessie
unstable
"
LATEST=jessie

BASENAME=bitnami/minideb
GCR_BASENAME=gcr.io/bitnami-containers/minideb

mkdir -p build

log() {
    echo "$@" >&2
}

for DIST in $DISTS; do
   [ -f debootstrap/$DIST ] || (echo "buildall: Unknown distribution: $DIST" && exit 1)
   current_ts="$(date -u +%Y-%m-%dT%H:%M:%S.%NZ)"
   if docker pull $BASENAME:$DIST > /dev/null; then
       target_ts="$(docker inspect $BASENAME:$DIST | jq --raw-output ".[0].Created")"
       pulled_image_id="$(docker inspect $BASENAME:$DIST | jq --raw-output ".[0].Id")"
   else
       target_ts="$current_ts"
       pulled_image_id=
   fi
   log "============================================"
   log "Building $BASENAME:$DIST"
   log "============================================"
   ./mkimage build/$DIST.tar $DIST
   built_image_id=$(./import build/$DIST.tar "$target_ts")
   log "============================================"
   log "Running tests for $BASENAME:$DIST"
   log "============================================"
   ./test $built_image_id
   log "============================================"
   log "Rebuilding $BASENAME:$DIST to test reproducibility"
   log "============================================"
   ./mkimage build/${DIST}-repro.tar $DIST
   repro_image_id=$(./import build/${DIST}-repro.tar "$target_ts")
   if [ "$repro_image_id" != "$built_image_id" ]; then
       log "$BASENAME:$DIST differs after a rebuild. Examine $built_image_id and $repro_image_id"
       log "to find the differences and fix the build to be reproducible again."
       log "Running \`./dockerdiff $built_image_id $repro_image_id\` might be useful."
       exit 1
   fi
   rm build/${DIST}-repro.tar
   if [ -n "$pulled_image_id" ]; then
       if [ "$built_image_id" != "$pulled_image_id" ]; then
           log "Image changed $built_image_id (new) != $pulled_image_id (old)"
           # Re-import with the current timestamp so that the image shows
           # as new
           built_image_id="$(./import build/$DIST.tar "$current_ts")"
       else
           log "Image didn't change"
           continue
       fi
   fi
   docker tag $built_image_id $BASENAME:$DIST
   docker tag $built_image_id $GCR_BASENAME:$DIST
   log "Tagged $built_image_id as $BASENAME:$DIST $GCR_BASENAME:$DIST"
done
docker tag $BASENAME:$LATEST $BASENAME:latest
docker tag $GCR_BASENAME:$LATEST $GCR_BASENAME:latest