module env import os import toml // The prefix that every environment variable should have const prefix = 'VIETER_' // The suffix an environment variable in order for it to be loaded from a file // instead const file_suffix = '_FILE' pub struct ServerConfig { pub: log_level string [default: WARN] log_file string [default: 'vieter.log'] pkg_dir string download_dir string api_key string repo_dir string repos_file string } pub struct BuildConfig { pub: api_key string address string } fn get_env_var(field_name string) ?string { env_var_name := '$env.prefix$field_name.to_upper()' env_file_name := '$env.prefix$field_name.to_upper()$env.file_suffix' env_var := os.getenv(env_var_name) env_file := os.getenv(env_file_name) // If both are missing, we return an empty string if env_var == '' && env_file == '' { return '' } // If they're both set, we report a conflict if env_var != '' && env_file != '' { return error('Only one of $env_var_name or $env_file_name can be defined.') } // If it's the env var itself, we return it. // I'm pretty sure this also prevents variable ending in _FILE (e.g. // VIETER_LOG_FILE) from being mistakingely read as an _FILE suffixed env // var. if env_var != '' { return env_var } // Otherwise, we process the file return os.read_file(env_file) or { error('Failed to read file defined in $env_file_name: ${err.msg}.') } } // load attempts to create the given type from environment variables. For // each field, the corresponding env var is its name in uppercase prepended // with the hardcoded prefix. If this one isn't present, it looks for the env // var with the file_suffix suffix. pub fn load(path string) ?T { mut res := T{} if os.exists(path) { res = toml.parse_file(path) ?.reflect() } $for field in T.fields { $if field.typ is string { env_value := get_env_var(field.name) ? // The value of the env var will always be chosen over the config // file if env_value != '' { res.$(field.name) = env_value } // If there's no value from the toml file either, we try to find a // default value else if res.$(field.name) == '' { // We use the default instead, if it's present mut default := '' for attr in field.attrs { if attr.starts_with('default: ') { default = attr[9..] break } } if default == '' { return error("Missing config variable '$field.name' with no provided default. Either add it to the config file or provide it using an environment variable.") } res.$(field.name) = default } } } return res }