#!/bin/bash

set -e -o pipefail

# Allow environment variables to be set by creating a file with the
# contents, and setting an environment variable with the suffix _FILE to
# point to it. This can be used to provide secrets to a container, without
# the values being specified explicitly when running the container.
#
# Note that only supported environment variables are processed, in order
# to avoid unexpected failures when an environment sets a "*_FILE" variable
# that doesn't contain a filename.
#
# This script is intended to be sourced, not executed, and modifies the
# environment.

for VAR_NAME_FILE in ELASTIC_PASSWORD_FILE KEYSTORE_PASSWORD_FILE ; do
  if [[ -n "${!VAR_NAME_FILE}" ]]; then
    VAR_NAME="${VAR_NAME_FILE%_FILE}"

    if env | grep "^${VAR_NAME}="; then
      echo "ERROR: Both $VAR_NAME_FILE and $VAR_NAME are set. These are mutually exclusive." >&2
      exit 1
    fi

    if [[ ! -e "${!VAR_NAME_FILE}" ]]; then
      echo "ERROR: File ${!VAR_NAME_FILE} from $VAR_NAME_FILE does not exist" >&2
      exit 1
    fi

    FILE_PERMS="$(stat -L -c '%a' ${!VAR_NAME_FILE})"

    if [[ "$FILE_PERMS" != "400" && "$FILE_PERMS" != "600" ]]; then
        if [[ -h "${!VAR_NAME_FILE}" ]]; then
            echo "ERROR: File $(readlink "${!VAR_NAME_FILE}") (target of symlink ${!VAR_NAME_FILE} from $VAR_NAME_FILE) must have file permissions 400 or 600, but actually has: $FILE_PERMS" >&2
        else
            echo "ERROR: File ${!VAR_NAME_FILE} from $VAR_NAME_FILE must have file permissions 400 or 600, but actually has: $FILE_PERMS" >&2
        fi
        exit 1
    fi

    echo "Setting $VAR_NAME from $VAR_NAME_FILE at ${!VAR_NAME_FILE}" >&2
    export "$VAR_NAME"="$(cat ${!VAR_NAME_FILE})"

    unset VAR_NAME
    # Unset the suffixed environment variable
    unset "$VAR_NAME_FILE"
  fi
done