fix: separate golang license caches from mod dir (#2852)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

cmd/syft/internal/options/cache.go

@@ -0,0 +1,122 @@
+package options
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/adrg/xdg"
+	"github.com/mitchellh/go-homedir"
+
+	"github.com/anchore/clio"
+	"github.com/anchore/syft/internal/cache"
+	"github.com/anchore/syft/internal/log"
+)
+
+// Cache provides configuration for the Syft caching behavior
+type Cache struct {
+	Dir string `yaml:"dir" mapstructure:"dir"`
+	TTL string `yaml:"ttl" mapstructure:"ttl"`
+}
+
+func (c *Cache) DescribeFields(descriptions clio.FieldDescriptionSet) {
+	descriptions.Add(&c.Dir, "root directory to cache any downloaded content")
+	descriptions.Add(&c.TTL, "time to live for cached data")
+}
+
+func (c *Cache) PostLoad() error {
+	if c.Dir != "" {
+		ttl, err := parseDuration(c.TTL)
+		if err != nil {
+			log.Warnf("unable to parse duration '%v', using default (%s) due to: %v", c.TTL, durationToString(defaultTTL()), err)
+			ttl = defaultTTL()
+		}
+		dir, err := homedir.Expand(c.Dir)
+		if err != nil {
+			log.Warnf("unable to expand cache directory %s: %v", c.Dir, err)
+			cache.SetManager(cache.NewInMemory(ttl))
+		} else {
+			m, err := cache.NewFromDir(dir, ttl)
+			if err != nil {
+				log.Warnf("unable to get filesystem cache at %s: %v", c.Dir, err)
+				cache.SetManager(cache.NewInMemory(ttl))
+			} else {
+				cache.SetManager(m)
+			}
+		}
+	}
+	return nil
+}
+
+var _ interface {
+	clio.PostLoader
+	clio.FieldDescriber
+} = (*Cache)(nil)
+
+func DefaultCache() Cache {
+	return Cache{
+		Dir: defaultDir(),
+		TTL: durationToString(defaultTTL()),
+	}
+}
+
+func defaultTTL() time.Duration {
+	return 7 * 24 * time.Hour
+}
+
+func defaultDir() string {
+	var err error
+	cacheRoot := xdg.CacheHome
+	if cacheRoot == "" {
+		cacheRoot, err = homedir.Dir()
+		if err != nil {
+			cacheRoot = os.TempDir()
+			log.Debugf("unable to get stable cache directory due to: %v, defaulting cache to temp dir: %s", err, cacheRoot)
+		} else {
+			cacheRoot = filepath.Join(cacheRoot, ".cache")
+		}
+	}
+
+	return filepath.Join(cacheRoot, "syft")
+}
+
+func durationToString(duration time.Duration) string {
+	days := int64(duration / (24 * time.Hour))
+	remain := duration % (24 * time.Hour)
+	out := ""
+	if days > 0 {
+		out = fmt.Sprintf("%vd", days)
+	}
+	if remain != 0 {
+		out += remain.String()
+	}
+	if out == "" {
+		return "0"
+	}
+	return out
+}
+
+var whitespace = regexp.MustCompile(`\s+`)
+
+func parseDuration(duration string) (time.Duration, error) {
+	duration = strings.ToLower(whitespace.ReplaceAllString(duration, ""))
+	parts := strings.SplitN(duration, "d", 2)
+	var days time.Duration
+	var remain time.Duration
+	var err error
+	if len(parts) > 1 {
+		numDays, daysErr := strconv.Atoi(parts[0])
+		if daysErr != nil {
+			return 0, daysErr
+		}
+		days = time.Duration(numDays) * 24 * time.Hour
+		remain, err = time.ParseDuration(parts[1])
+	} else {
+		remain, err = time.ParseDuration(duration)
+	}
+	return days + remain, err
+}