Refactor config and split them in packages (#8351)

This change is related to larger config migration PR
change, this is a first stage change to move our
configs to `cmd/config/` - divided into its subsystems

cmd/config/cache/config.go

@@ -0,0 +1,118 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cache
+
+import (
+	"encoding/json"
+	"errors"
+	"path/filepath"
+	"strings"
+
+	"github.com/minio/minio/cmd/config"
+	"github.com/minio/minio/pkg/ellipses"
+)
+
+// Config represents cache config settings
+type Config struct {
+	Drives  []string `json:"drives"`
+	Expiry  int      `json:"expiry"`
+	MaxUse  int      `json:"maxuse"`
+	Exclude []string `json:"exclude"`
+}
+
+// UnmarshalJSON - implements JSON unmarshal interface for unmarshalling
+// json entries for CacheConfig.
+func (cfg *Config) UnmarshalJSON(data []byte) (err error) {
+	type Alias Config
+	var _cfg = &struct {
+		*Alias
+	}{
+		Alias: (*Alias)(cfg),
+	}
+	if err = json.Unmarshal(data, _cfg); err != nil {
+		return err
+	}
+
+	if _cfg.Expiry < 0 {
+		return errors.New("config expiry value should not be negative")
+	}
+
+	if _cfg.MaxUse < 0 {
+		return errors.New("config max use value should not be null or negative")
+	}
+
+	if _, err = parseCacheDrives(_cfg.Drives); err != nil {
+		return err
+	}
+	if _, err = parseCacheExcludes(_cfg.Exclude); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Parses given cacheDrivesEnv and returns a list of cache drives.
+func parseCacheDrives(drives []string) ([]string, error) {
+	if len(drives) == 0 {
+		return drives, nil
+	}
+	var endpoints []string
+	for _, d := range drives {
+		if ellipses.HasEllipses(d) {
+			s, err := parseCacheDrivePaths(d)
+			if err != nil {
+				return nil, err
+			}
+			endpoints = append(endpoints, s...)
+		} else {
+			endpoints = append(endpoints, d)
+		}
+	}
+
+	for _, d := range endpoints {
+		if !filepath.IsAbs(d) {
+			return nil, config.ErrInvalidCacheDrivesValue(nil).Msg("cache dir should be absolute path: %s", d)
+		}
+	}
+	return endpoints, nil
+}
+
+// Parses all arguments and returns a slice of drive paths following the ellipses pattern.
+func parseCacheDrivePaths(arg string) (ep []string, err error) {
+	patterns, perr := ellipses.FindEllipsesPatterns(arg)
+	if perr != nil {
+		return []string{}, config.ErrInvalidCacheDrivesValue(nil).Msg(perr.Error())
+	}
+
+	for _, lbls := range patterns.Expand() {
+		ep = append(ep, strings.Join(lbls, ""))
+	}
+
+	return ep, nil
+}
+
+// Parses given cacheExcludesEnv and returns a list of cache exclude patterns.
+func parseCacheExcludes(excludes []string) ([]string, error) {
+	for _, e := range excludes {
+		if len(e) == 0 {
+			return nil, config.ErrInvalidCacheExcludesValue(nil).Msg("cache exclude path (%s) cannot be empty", e)
+		}
+		if strings.HasPrefix(e, "/") {
+			return nil, config.ErrInvalidCacheExcludesValue(nil).Msg("cache exclude pattern (%s) cannot start with / as prefix", e)
+		}
+	}
+	return excludes, nil
+}