#!/bin/bash

# Determine if it is Mac OS and switch to use gxargs instead
CMD=xargs
if [ $(which system_profiler) ]; then
  CMD=gxargs
fi

# 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

# 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 Dockerfile.solution
#
# Most solution specific changes should be isolated in
# Dockerfile.solution. After making changes, you can
# then re-run scripts/build-dockerfile
#
EOM

for snippet in templates/??-*.in; do
  cat << EOM >> Dockerfile

#
# Template from templates/${snippet}
#
EOM
  envsubst ${ENV} < $snippet >> Dockerfile
done

cat << EOM >> Dockerfile

#
# Solution begins here (from Dockerfile.solution)
#
EOM

envsubst ${ENV} < Dockerfile.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 scripts/build-images

EOM