package hostwrite

import (
	"context"
	"errors"
	"strings"
)

var ErrUnavailable = errors.New("hostwrite: lifecycle provider unavailable")

type Identity struct {
	Config  string
	Release string
}

type Work interface {
	With(context.Context, Identity, func() error) error
}

type Selector interface {
	Select(context.Context, string, string) (Work, error)
}

type Config struct {
	Enabled  bool
	Selector Selector
}

func Enabled(getenv func(string) string) bool {
	return strings.TrimSpace(getenv("CARLOS_HOST_CLAIM")) != ""
}

func (c Config) Select(ctx context.Context, host, action string) (Work, error) {
	if !c.Enabled {
		return legacy{}, nil
	}
	if c.Selector == nil {
		return nil, ErrUnavailable
	}
	return c.Selector.Select(ctx, host, action)
}

type legacy struct{}

// Legacy reports whether w is the flag-off pass-through work, so callers
// can keep their exact pre-claim behaviour when the flag is unset.
func Legacy(w Work) bool {
	_, ok := w.(legacy)
	return ok
}

func (legacy) With(_ context.Context, _ Identity, fn func() error) error { return fn() }