forked from vieter-v/vieter
83 lines
2.3 KiB
V
83 lines
2.3 KiB
V
module env
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import os
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import toml
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// The prefix that every environment variable should have
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const prefix = 'VIETER_'
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// The suffix an environment variable in order for it to be loaded from a file
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// instead
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const file_suffix = '_FILE'
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fn get_env_var(field_name string) ?string {
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env_var_name := '$env.prefix$field_name.to_upper()'
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env_file_name := '$env.prefix$field_name.to_upper()$env.file_suffix'
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env_var := os.getenv(env_var_name)
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env_file := os.getenv(env_file_name)
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// If both are missing, we return an empty string
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if env_var == '' && env_file == '' {
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return ''
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}
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// If they're both set, we report a conflict
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if env_var != '' && env_file != '' {
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return error('Only one of $env_var_name or $env_file_name can be defined.')
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}
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// If it's the env var itself, we return it.
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// I'm pretty sure this also prevents variable ending in _FILE (e.g.
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// VIETER_LOG_FILE) from being mistakingely read as an _FILE suffixed env
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// var.
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if env_var != '' {
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return env_var
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}
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// Otherwise, we process the file
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return os.read_file(env_file) or {
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error('Failed to read file defined in $env_file_name: ${err.msg}.')
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}
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}
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// load<T> attempts to create an object of type T from the given path to a toml
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// file & environment variables. For each field, it will select either a value
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// given from an environment variable, a value defined in the config file or a
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// configured default if present, in that order.
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pub fn load<T>(path string) ?T {
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mut res := T{}
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if os.exists(path) {
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// We don't use reflect here because reflect also sets any fields not
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// in the toml back to their zero value, which we don't want
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doc := toml.parse_file(path) ?
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$for field in T.fields {
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s := doc.value(field.name)
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// We currently only support strings
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if s.type_name() == 'string' {
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res.$(field.name) = s.string()
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}
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}
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}
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$for field in T.fields {
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$if field.typ is string {
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env_value := get_env_var(field.name) ?
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// The value of the env var will always be chosen over the config
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// file
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if env_value != '' {
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res.$(field.name) = env_value
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}
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// If there's no value from the toml file either, we try to find a
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// default value
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else if res.$(field.name) == '' {
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return error("Missing config variable '$field.name' with no provided default. Either add it to the config file or provide it using an environment variable.")
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}
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}
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}
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return res
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}
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