package dockerfile
 
 import (
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/builder"

 	"github.com/sirupsen/logrus"

 )
 
 // ImageProber exposes an Image cache to the Builder. It supports resetting a
 // cache.
 type ImageProber interface {
 	Reset()
 	Probe(parentID string, runConfig *container.Config) (string, error)
 }
 
 type imageProber struct {
 	cache       builder.ImageCache
 	reset       func() builder.ImageCache
 	cacheBusted bool
 }
 

 func newImageProber(cacheBuilder builder.ImageCacheBuilder, cacheFrom []string, noCache bool) ImageProber {

 	if noCache {
 		return &nopProber{}
 	}
 
 	reset := func() builder.ImageCache {

 		return cacheBuilder.MakeImageCache(cacheFrom)

 	}
 	return &imageProber{cache: reset(), reset: reset}
 }
 
 func (c *imageProber) Reset() {
 	c.cache = c.reset()
 	c.cacheBusted = false
 }
 
 // Probe checks if cache match can be found for current build instruction.
 // It returns the cachedID if there is a hit, and the empty string on miss
 func (c *imageProber) Probe(parentID string, runConfig *container.Config) (string, error) {
 	if c.cacheBusted {
 		return "", nil
 	}
 	cacheID, err := c.cache.GetCache(parentID, runConfig)
 	if err != nil {
 		return "", err
 	}
 	if len(cacheID) == 0 {
 		logrus.Debugf("[BUILDER] Cache miss: %s", runConfig.Cmd)
 		c.cacheBusted = true
 		return "", nil
 	}
 	logrus.Debugf("[BUILDER] Use cached version: %s", runConfig.Cmd)
 	return cacheID, nil
 }
 
 type nopProber struct{}
 
 func (c *nopProber) Reset() {}
 
 func (c *nopProber) Probe(_ string, _ *container.Config) (string, error) {
 	return "", nil
 }