mbland/custom-links

#! /usr/local/env bash
#
# Access to configuration values in JSON files
#
# Requires that `jq` is installed on the system.

# Sets a variable based on an environment variable or configuration file entry
#
# Arguments:
#   config_file_path:   Path to the configuration file
#   config_entry_name:  Name of the configuration file entry, e.g. `REDIS_HOST`
#   result_var_name:    Name of caller's variable into which to store the value 
#   default_value:      Value to assign if neither env or config var is set
#
# Returns:
#   Zero if `result_var_name` has been set with either an env or config var
#     value; nonzero if it's been set using the default value
cl.get_config_variable() {
  local config_file_path="$1"
  local config_entry_name="$2"
  local result_var_name="$3"
  local default_value="$4"
  local env_var_name="CUSTOM_LINKS_${config_entry_name}"
  local config_value="${!env_var_name:-null}"
  local result='0'

  if [[ "$config_value" == 'null' ]]; then
    config_value="$(jq -r ".${config_entry_name}" "$config_file_path")"
  fi
  if [[ "$config_value" == 'null' ]]; then
    config_value="$default_value"
    result='1'
  fi
  printf -v "$result_var_name" '%s' "$config_value"
  return "$result"
}