#!/bin/bash

# Bring in the variables from SOLUTION file, supporting
# nested substitution
. SOLUTION
. MANIFEST

VARS=($(sed -nE "s,(^[^#][^=]*).*$,\1,pg" SOLUTION))
VARS+=($(sed -nE "s,(^[^#][^=]*).*$,\1,pg" MANIFEST))
for var in ${VARS[@]}; do
  export ${var}
done

SOLUTION_SUFFIX=".${OS_DISTRO}-${OS_RELEASE}"
[[ -d "templates/${OS_DISTRO}" ]] || {
  echo "Unrecognized OS_DISTRO: '${OS_DISTRO}'"
  exit -1
}

[[ ! -e "Dockerfile.solution${SOLUTION_SUFFIX}" ]] && {
  cat << EOF

OS_DISTRO and OS_RELEASE creates a solution suffix of '${OS_DISTRO}-${OS_RELEASE}'.
However, Dockerfile.solution${SOLUTION_SUFFIX} does not exist.

Using 'Dockerfile.solution' as default.

EOF

  SOLUTION_SUFFIX=""
}

export DOCKERFILE="Dockerfile${SOLUTION_SUFFIX}"
export SOLUTION="Dockerfile.solution${SOLUTION_SUFFIX}"
VARS+=("DOCKERFILE")
VARS+=("SOLUTION")

cat << EOF
Using:

  ${SOLUTION}

To generate:

  ${DOCKERFILE}
EOF

# Build a SHELL-FORMAT value to pass to envsubst.
# Only those variables matched in SHELL-FORMAT will
# be escaped by envsubst.
ENV=''
for var in ${VARS[@]}; do
  ENV=${ENV}'$'${var}
done

# Remove the Dockerfile if it exists; should check
# if it is clean first, and abort if not.
#
[ -e ${DOCKERFILE} ] && rm ${DOCKERFILE}

cat << EOM > ${DOCKERFILE}
#
# DO NOT EDIT THIS DOCKERFILE
#
# This file is auto-generated via scripts/build-dockerfile
# by using environment substitution while concatenating the
# contents of templates/*, and then adding the contents
# of ${SOLUTION}
#
# Most solution specific changes should be isolated in
# ${SOLUTION}. After making changes, you can then re-run
# scripts/build-dockerfile
#
EOM

for snippet in templates/${OS_DISTRO}/??-*.in; do
  cat << EOM >> ${DOCKERFILE}

#
# Template from ${snippet}
#
EOM
  envsubst ${ENV} < $snippet >> ${DOCKERFILE}
done

cat << EOM >> ${DOCKERFILE}

#
# Solution begins here (from ${SOLUTION})
#
EOM

envsubst ${ENV} < ${SOLUTION} >> ${DOCKERFILE}

cat << EOM >> ${DOCKERFILE}

#
# Standard ending begins here (from templates/ending.in)
#
EOM

envsubst ${ENV} < templates/ending.in >> ${DOCKERFILE}

cat << EOM

${DOCKERFILE} has been updated.

To build the image, you can run:

  OS_DISTRO=${OS_DISTRO} OS_RELEASE=${OS_RELEASE} scripts/build-image.sh

EOM