package logic

import (
	"context"

	"spark-server/internal/module/upload/entity"
	"spark-server/internal/pkg/errs"
	"spark-server/internal/pkg/i18n"
	"spark-server/internal/pkg/reqctx"
	"spark-server/internal/pkg/validate"
)

const maxDownloadBatch = 9

// BatchDownloadInput issues up to nine Presigned GETs (moment 九宫格) in one call.
type BatchDownloadInput struct {
	ObjectKeys []string `json:"object_keys" validate:"required,min=1,max=9,dive,required,max=512" label:"field.object_key" errmsg:"required:validate.upload.key_required;max:validate.upload.download_items_invalid"`
}

func (s *Service) CreateDownloads(ctx context.Context, userID int64, in *BatchDownloadInput) (*entity.DownloadSet, error) {
	if !s.ready() {
		return nil, errs.ErrAvailable
	}
	if userID <= 0 {
		return nil, errs.ErrUnauthorized
	}
	if in == nil {
		return nil, errs.ErrInvalidArgument
	}
	if err := validate.StructLang(reqctx.Lang(ctx), in); err != nil {
		return nil, err
	}
	if n := len(in.ObjectKeys); n < 1 || n > maxDownloadBatch {
		return nil, errs.ErrInvalidArgument
	}
	if !s.allow(userID) {
		return nil, errs.ErrRateLimited
	}
	items := make([]entity.Download, 0, len(in.ObjectKeys))
	for _, key := range in.ObjectKeys {
		got, err := s.issueGet(ctx, key)
		if err != nil {
			return nil, err
		}
		items = append(items, *got)
	}
	return &entity.DownloadSet{Items: items}, nil
}

func (s *Service) issueGet(ctx context.Context, key string) (*entity.Download, error) {
	if !entity.ValidObjectKey(key) {
		return nil, errs.ErrInvalidArgument.WithMsg(i18n.T(reqctx.Lang(ctx), i18n.KeyUploadKeyInvalid, nil))
	}
	url, err := s.store.PresignGet(ctx, key, s.ttl)
	if err != nil {
		return nil, err
	}
	return &entity.Download{
		ObjectKey:   key,
		DownloadURL: url,
		Method:      entity.MethodGET,
		ExpiresIn:   s.expiresIn(),
	}, nil
}