wip: refactor offline download (#5331)

* base tool

* working: aria2

internal/offline_download/aria2/notify.go

@@ -0,0 +1,70 @@
+package aria2
+
+import (
+	"github.com/alist-org/alist/v3/pkg/aria2/rpc"
+	"github.com/alist-org/alist/v3/pkg/generic_sync"
+)
+
+const (
+	Downloading = iota
+	Paused
+	Stopped
+	Completed
+	Errored
+)
+
+type Notify struct {
+	Signals generic_sync.MapOf[string, chan int]
+}
+
+func NewNotify() *Notify {
+	return &Notify{Signals: generic_sync.MapOf[string, chan int]{}}
+}
+
+func (n *Notify) OnDownloadStart(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Downloading
+		}
+	}
+}
+
+func (n *Notify) OnDownloadPause(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Paused
+		}
+	}
+}
+
+func (n *Notify) OnDownloadStop(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Stopped
+		}
+	}
+}
+
+func (n *Notify) OnDownloadComplete(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Completed
+		}
+	}
+}
+
+func (n *Notify) OnDownloadError(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Errored
+		}
+	}
+}
+
+func (n *Notify) OnBtDownloadComplete(events []rpc.Event) {
+	for _, e := range events {
+		if signal, ok := n.Signals.Load(e.Gid); ok {
+			signal <- Completed
+		}
+	}
+}