#!/bin/sh
set -eu

ROOT=$(CDPATH='' cd -- "$(dirname -- "$0")/.." && pwd)
env_file=${1:-"$ROOT/.env"}
template_file=${2:-"$ROOT/.env.example"}

case "$env_file" in
  /*) ;;
  *) env_file="$ROOT/$env_file" ;;
esac

case "$template_file" in
  /*) ;;
  *) template_file="$ROOT/$template_file" ;;
esac

if [ ! -f "$env_file" ]; then
  echo "Environment file does not exist: $env_file" >&2
  exit 1
fi

if [ ! -f "$template_file" ]; then
  echo "Environment template does not exist: $template_file" >&2
  exit 1
fi

if [ "$(stat -c '%a' "$env_file")" != 600 ]; then
  echo "Environment file must have mode 0600: $env_file" >&2
  exit 1
fi

env_dir=$(CDPATH='' cd -- "$(dirname -- "$env_file")" && pwd)
env_name=$(basename -- "$env_file")
temporary_env=$(mktemp "$env_dir/$env_name.tmp.XXXXXX")
trap 'rm -f "$temporary_env"' EXIT HUP INT TERM
chmod 600 "$temporary_env"

if ! awk '
  BEGIN {
    current_file = 1
  }

  FNR == 1 && NR != 1 {
    current_file = 0
  }

  current_file {
    separator = index($0, "=")

    if (separator > 1) {
      key = substr($0, 1, separator - 1)

      if (key ~ /^[A-Z][A-Z0-9_]*$/) {
        if (key in current) {
          exit 40
        }

        current[key] = substr($0, separator + 1)
        current_order[++current_count] = key
      }
    }

    next
  }

  {
    separator = index($0, "=")

    if (separator > 1) {
      key = substr($0, 1, separator - 1)

      if (key ~ /^[A-Z][A-Z0-9_]*$/) {
        if (key in template_seen) {
          exit 41
        }

        template_seen[key] = 1

        if (key in current) {
          print key "=" current[key]
          emitted[key] = 1
          next
        }
      }
    }

    print
  }

  END {
    unknown_count = 0

    for (position = 1; position <= current_count; position++) {
      key = current_order[position]

      if (!(key in emitted) && !(key in template_seen)) {
        unknown[++unknown_count] = key
      }
    }

    if (unknown_count > 0) {
      print ""
      print "# Local keys not present in the current template."

      for (position = 1; position <= unknown_count; position++) {
        key = unknown[position]
        print key "=" current[key]
      }
    }
  }
' "$env_file" "$template_file" >"$temporary_env"; then
  echo "Refusing to synchronize the environment: invalid or duplicate keys were found." >&2
  exit 1
fi

mv "$temporary_env" "$env_file"
trap - EXIT HUP INT TERM

echo "Environment synchronized with the template without printing values: $env_file"