#!/usr/bin/env bash
set -e

# Create a new intermediate, guaranteed unique, build directory. The final step
# of this script will copy all the content from this directory to $OUT.
mkdir -p "/tmp/bootstrap-mix"
TMPOUT=$(mktemp -d -p "/tmp/bootstrap-mix")

if [ -z "$TMPOUT" ]; then
  >&2 echo "Failed to create temp directory"
  exit 1
fi

function cleanup {
  # Use basename with an explicit path prefix to ensure we never evaluate to `/`.
  # Here we already verify `$TMPOUT` isn't empty prior to registering this
  # cleanup function, but this is nonetheless a good habit to establish.
  rm -r "/tmp/bootstrap-mix/$(basename "$TMPOUT")"
}

trap cleanup EXIT

# Begin copying content over to our new directory.
cp -r template/. "$TMPOUT"

# Generate a new project with the specified name using `mix`. Pipe in `yes`
# since `mix` requires confirmation when writing out to a directory that already
# has content.
nix develop "$TMPOUT" --command bash -c "yes | mix new $TMPOUT --app '$APP'"

# Replace the template name of the flake.nix file with the new app name. The
# mix generator would fail if `$APP` does not consist of just lowercase ASCII
# letters, numbers, or underscores. Thus the following command is safe.
sed -i "s/<APP_NAME>/$APP/g" "$TMPOUT/flake.nix"

# Everything succeeded. Copy contents over.
cp -r "$TMPOUT/." "$OUT"