setting

type DefaultSource func() (string, error)

type EnvKey string

type FallbackSource struct {
	Source

	// Stored marks a value a person saved earlier, such as in a profile, so that the environment
	// overriding it with another value is warned of. Resolving looks it up only then, so it must
	// not prompt.
	Stored bool
}

type FrontendSource struct {
	Source
}

type LookupSource struct {
	MatchingKey string
	Description string
	Func        func(ctx context.Context) (string, error)
}

type Setting[T any] struct {
	Env EnvKey

	// Short is plain text for a cobra flag, Long is Markdown for the Terraform provider's schema.
	// Both state facts about the setting rather than about a front end, so neither says "flag",
	// "block" or "attribute".
	Short func(envKey string) string
	Long  func(envKey string) string

	Default DefaultSource
	// Parse always receives a non-empty string: Resolve trims what a source returned and skips
	// that source when nothing is left.
	Parse func(v string) (T, error)
}

type Source interface {
	// Lookup returns an empty string and no error when it carries no value. An error stops the
	// whole resolution, so return one only for a condition no other source can make up for.
	Lookup(ctx context.Context, key string) (string, error)
	// Describe names this source to a person, so that a failed resolution can list what to set.
	Describe(key string) string
}

type Sources []Source