build: split buildflags package

Planned to be imported by nerdctl in future.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

util/buildflags/cache.go

@@ -0,0 +1,81 @@
+package buildflags
+
+import (
+	"encoding/csv"
+	"os"
+	"strings"
+
+	"github.com/moby/buildkit/client"
+	"github.com/pkg/errors"
+)
+
+func ParseCacheEntry(in []string) ([]client.CacheOptionsEntry, error) {
+	imports := make([]client.CacheOptionsEntry, 0, len(in))
+	for _, in := range in {
+		csvReader := csv.NewReader(strings.NewReader(in))
+		fields, err := csvReader.Read()
+		if err != nil {
+			return nil, err
+		}
+		if isRefOnlyFormat(fields) {
+			for _, field := range fields {
+				imports = append(imports, client.CacheOptionsEntry{
+					Type:  "registry",
+					Attrs: map[string]string{"ref": field},
+				})
+			}
+			continue
+		}
+		im := client.CacheOptionsEntry{
+			Attrs: map[string]string{},
+		}
+		for _, field := range fields {
+			parts := strings.SplitN(field, "=", 2)
+			if len(parts) != 2 {
+				return nil, errors.Errorf("invalid value %s", field)
+			}
+			key := strings.ToLower(parts[0])
+			value := parts[1]
+			switch key {
+			case "type":
+				im.Type = value
+			default:
+				im.Attrs[key] = value
+			}
+		}
+		if im.Type == "" {
+			return nil, errors.Errorf("type required form> %q", in)
+		}
+		if !addGithubToken(&im) {
+			continue
+		}
+		imports = append(imports, im)
+	}
+	return imports, nil
+}
+
+func isRefOnlyFormat(in []string) bool {
+	for _, v := range in {
+		if strings.Contains(v, "=") {
+			return false
+		}
+	}
+	return true
+}
+
+func addGithubToken(ci *client.CacheOptionsEntry) bool {
+	if ci.Type != "gha" {
+		return true
+	}
+	if _, ok := ci.Attrs["token"]; !ok {
+		if v, ok := os.LookupEnv("ACTIONS_RUNTIME_TOKEN"); ok {
+			ci.Attrs["token"] = v
+		}
+	}
+	if _, ok := ci.Attrs["url"]; !ok {
+		if v, ok := os.LookupEnv("ACTIONS_CACHE_URL"); ok {
+			ci.Attrs["url"] = v
+		}
+	}
+	return ci.Attrs["token"] != "" && ci.Attrs["url"] != ""
+}