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/compress/compress.go

@@ -0,0 +1,79 @@
+/*
+ * 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 compress
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/minio/minio/cmd/config"
+	"github.com/minio/minio/pkg/env"
+)
+
+// Config represents the compression settings.
+type Config struct {
+	Enabled    bool     `json:"enabled"`
+	Extensions []string `json:"extensions"`
+	MimeTypes  []string `json:"mime-types"`
+}
+
+// Compression environment variables
+const (
+	EnvMinioCompress           = "MINIO_COMPRESS"
+	EnvMinioCompressExtensions = "MINIO_COMPRESS_EXTENSIONS"
+	EnvMinioCompressMimeTypes  = "MINIO_COMPRESS_MIMETYPES"
+)
+
+// Parses the given compression exclude list `extensions` or `content-types`.
+func parseCompressIncludes(includes []string) ([]string, error) {
+	for _, e := range includes {
+		if len(e) == 0 {
+			return nil, config.ErrInvalidCompressionIncludesValue(nil).Msg("extension/mime-type (%s) cannot be empty", e)
+		}
+	}
+	return includes, nil
+}
+
+// LookupConfig - lookup compression config.
+func LookupConfig(cfg Config) (Config, error) {
+	const compressEnvDelimiter = ","
+	if compress := env.Get(EnvMinioCompress, strconv.FormatBool(cfg.Enabled)); compress != "" {
+		cfg.Enabled = strings.EqualFold(compress, "true")
+	}
+
+	compressExtensions := env.Get(EnvMinioCompressExtensions, strings.Join(cfg.Extensions, ","))
+	compressMimeTypes := env.Get(EnvMinioCompressMimeTypes, strings.Join(cfg.MimeTypes, ","))
+	if compressExtensions != "" || compressMimeTypes != "" {
+		if compressExtensions != "" {
+			extensions, err := parseCompressIncludes(strings.Split(compressExtensions, compressEnvDelimiter))
+			if err != nil {
+				return cfg, fmt.Errorf("%s: Invalid MINIO_COMPRESS_EXTENSIONS value (`%s`)", err, extensions)
+			}
+			cfg.Extensions = extensions
+		}
+		if compressMimeTypes != "" {
+			contenttypes, err := parseCompressIncludes(strings.Split(compressMimeTypes, compressEnvDelimiter))
+			if err != nil {
+				return cfg, fmt.Errorf("%s: Invalid MINIO_COMPRESS_MIMETYPES value (`%s`)", err, contenttypes)
+			}
+			cfg.MimeTypes = contenttypes
+		}
+	}
+
+	return cfg, nil
+}