Init V4 community edition (#2265)

* Init V4 community edition

* Init V4 community edition

pkg/filemanager/fs/mime/mime.go

@@ -0,0 +1,40 @@
+package mime
+
+import (
+	"context"
+	"encoding/json"
+	"github.com/cloudreve/Cloudreve/v4/pkg/logging"
+	"github.com/cloudreve/Cloudreve/v4/pkg/setting"
+	"mime"
+	"path"
+)
+
+type MimeDetector interface {
+	// TypeByName returns the mime type by file name.
+	TypeByName(ext string) string
+}
+
+type mimeDetector struct {
+	mapping map[string]string
+}
+
+func NewMimeDetector(ctx context.Context, settings setting.Provider, l logging.Logger) MimeDetector {
+	mappingStr := settings.MimeMapping(ctx)
+	mapping := make(map[string]string)
+	if err := json.Unmarshal([]byte(mappingStr), &mapping); err != nil {
+		l.Error("Failed to unmarshal mime mapping: %s, fallback to empty mapping", err)
+	}
+
+	return &mimeDetector{
+		mapping: mapping,
+	}
+}
+
+func (d *mimeDetector) TypeByName(p string) string {
+	ext := path.Ext(p)
+	if m, ok := d.mapping[ext]; ok {
+		return m
+	}
+
+	return mime.TypeByExtension(ext)
+}