package miner

import (
	"errors"
	"fmt"
	"os"
	"strings"

	"crypto-miner-agent/config"
)

// ErrNoImageTar is returned when docker_load tier is selected but no tarball is available.
var ErrNoImageTar = errors.New("no docker image tarball configured")

// imageTarFetcher resolves a worker OCI tarball from the server upload/channel stub.
// Tests and integrations override via SetImageTarFetcher.
var imageTarFetcher func(cfg config.RuntimeConfig) (string, error)

// SetImageTarFetcher restores the default when fn is nil.
func SetImageTarFetcher(fn func(cfg config.RuntimeConfig) (string, error)) {
	imageTarFetcher = fn
}

// HasImageTarPolicy reports whether server policy supplies a local tar for docker_load.
func HasImageTarPolicy(cfg config.RuntimeConfig) bool {
	_, err := ResolveImageTar(cfg)
	return err == nil
}

// ResolveImageTar returns a filesystem path to the worker image tar.
// Priority: injected fetcher → AETHERFORGE_DOCKER_IMAGE_TAR env → cfg.DockerImageTar.
func ResolveImageTar(cfg config.RuntimeConfig) (string, error) {
	if imageTarFetcher != nil {
		if p, err := imageTarFetcher(cfg); err == nil && strings.TrimSpace(p) != "" {
			return strings.TrimSpace(p), nil
		} else if err != nil && !errors.Is(err, ErrNoImageTar) {
			return "", err
		}
	}
	if p := strings.TrimSpace(os.Getenv("AETHERFORGE_DOCKER_IMAGE_TAR")); p != "" {
		if _, err := os.Stat(p); err != nil {
			return "", fmt.Errorf("docker image tar: %w", err)
		}
		return p, nil
	}
	if p := strings.TrimSpace(cfg.DockerImageTar); p != "" {
		if _, err := os.Stat(p); err != nil {
			return "", fmt.Errorf("docker image tar: %w", err)
		}
		return p, nil
	}
	return "", ErrNoImageTar
}