feat: add pikpak offline download function (#6648)

* add pikpak offline download function

* 完善PikPak离线下载功能

* 删除多余的代码

* add task cache to avoid too many requests about API

* 优化Status函数

* 完善所有功能,目前测试无BUG

* 减少缓存时间，优化添加离线任务的参数

internal/offline_download/pikpak/util.go

@@ -0,0 +1,43 @@
+package pikpak
+
+import (
+	"context"
+	"time"
+
+	"github.com/Xhofe/go-cache"
+	"github.com/alist-org/alist/v3/drivers/pikpak"
+	"github.com/alist-org/alist/v3/internal/op"
+	"github.com/alist-org/alist/v3/pkg/singleflight"
+)
+
+var taskCache = cache.NewMemCache(cache.WithShards[[]pikpak.OfflineTask](16))
+var taskG singleflight.Group[[]pikpak.OfflineTask]
+
+func (p *PikPak) GetTasks(pikpakDriver *pikpak.PikPak) ([]pikpak.OfflineTask, error) {
+	key := op.Key(pikpakDriver, "/drive/v1/task")
+	if !p.refreshTaskCache {
+		if tasks, ok := taskCache.Get(key); ok {
+			return tasks, nil
+		}
+	}
+	p.refreshTaskCache = false
+	tasks, err, _ := taskG.Do(key, func() ([]pikpak.OfflineTask, error) {
+		ctx := context.Background()
+		phase := []string{"PHASE_TYPE_RUNNING", "PHASE_TYPE_ERROR", "PHASE_TYPE_PENDING", "PHASE_TYPE_COMPLETE"}
+		tasks, err := pikpakDriver.OfflineList(ctx, "", phase)
+		if err != nil {
+			return nil, err
+		}
+		// 添加缓存 10s
+		if len(tasks) > 0 {
+			taskCache.Set(key, tasks, cache.WithEx[[]pikpak.OfflineTask](time.Second*10))
+		} else {
+			taskCache.Del(key)
+		}
+		return tasks, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	return tasks, nil
+}