feat: multiple search indexes (#2514)

* refactor: abstract search interface

* wip: ~

* fix cycle import

* objs update hook

* wip: ~

* Delete search/none

* auto update index while cache changed

* db searcher

TODO: bleve init issue

cannot open index, metadata missing

* fix size type

why float64??

* fix typo

* fix nil pointer using

* api adapt ui

* bleve: fix clear & change struct

internal/search/search.go

@@ -0,0 +1,54 @@
+package search
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/alist-org/alist/v3/internal/conf"
+	"github.com/alist-org/alist/v3/internal/db"
+	"github.com/alist-org/alist/v3/internal/model"
+	"github.com/alist-org/alist/v3/internal/search/searcher"
+	log "github.com/sirupsen/logrus"
+)
+
+var instance searcher.Searcher = nil
+
+// Init or reset index
+func Init(mode string) error {
+	if instance != nil {
+		err := instance.Release(context.Background())
+		if err != nil {
+			log.Errorf("release instance err: %+v", err)
+		}
+		instance = nil
+	}
+	if Running {
+		return fmt.Errorf("index is running")
+	}
+	if mode == "none" {
+		log.Warnf("not enable search")
+		return nil
+	}
+	s, ok := searcher.NewMap[mode]
+	if !ok {
+		return fmt.Errorf("not support index: %s", mode)
+	}
+	i, err := s()
+	if err != nil {
+		log.Errorf("init searcher error: %+v", err)
+	} else {
+		instance = i
+	}
+	return err
+}
+
+func Search(ctx context.Context, req model.SearchReq) ([]model.SearchNode, int64, error) {
+	return instance.Search(ctx, req)
+}
+
+func init() {
+	db.RegisterSettingItemHook(conf.SearchIndex, func(item *model.SettingItem) error {
+		log.Debugf("searcher init, mode: %s", item.Value)
+		return Init(item.Value)
+	})
+}