[chore] Make paging logic more generic (#901)

* make paging logic more generic
not just for timelines!

* linty linterson

6 files changed, 134 insertions, 77 deletions

diff --git a/internal/processing/account.go b/internal/processing/account.go
index 6cba8b9c4..94f0dac89 100644
--- a/internal/processing/account.go
+++ b/internal/processing/account.go
@@ -55,11 +55,11 @@ func (p *processor) AccountUpdate(ctx context.Context, authed *oauth.Auth, form
 	return p.accountProcessor.Update(ctx, authed.Account, form)
 }
 
-func (p *processor) AccountStatusesGet(ctx context.Context, authed *oauth.Auth, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinnedOnly bool, mediaOnly bool, publicOnly bool) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) AccountStatusesGet(ctx context.Context, authed *oauth.Auth, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinnedOnly bool, mediaOnly bool, publicOnly bool) (*apimodel.PageableResponse, gtserror.WithCode) {
 	return p.accountProcessor.StatusesGet(ctx, authed.Account, targetAccountID, limit, excludeReplies, excludeReblogs, maxID, minID, pinnedOnly, mediaOnly, publicOnly)
 }
 
-func (p *processor) AccountWebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) AccountWebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.PageableResponse, gtserror.WithCode) {
 	return p.accountProcessor.WebStatusesGet(ctx, targetAccountID, maxID)
 }
 
diff --git a/internal/processing/account/account.go b/internal/processing/account/account.go
index b18e705ca..d2c3cddbe 100644
--- a/internal/processing/account/account.go
+++ b/internal/processing/account/account.go
@@ -60,10 +60,10 @@ type Processor interface {
 	Update(ctx context.Context, account *gtsmodel.Account, form *apimodel.UpdateCredentialsRequest) (*apimodel.Account, gtserror.WithCode)
 	// StatusesGet fetches a number of statuses (in time descending order) from the given account, filtered by visibility for
 	// the account given in authed.
-	StatusesGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinned bool, mediaOnly bool, publicOnly bool) (*apimodel.TimelineResponse, gtserror.WithCode)
+	StatusesGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinned bool, mediaOnly bool, publicOnly bool) (*apimodel.PageableResponse, gtserror.WithCode)
 	// WebStatusesGet fetches a number of statuses (in descending order) from the given account. It selects only
 	// statuses which are suitable for showing on the public web profile of an account.
-	WebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.TimelineResponse, gtserror.WithCode)
+	WebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.PageableResponse, gtserror.WithCode)
 	// FollowersGet fetches a list of the target account's followers.
 	FollowersGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string) ([]apimodel.Account, gtserror.WithCode)
 	// FollowingGet fetches a list of the accounts that target account is following.
diff --git a/internal/processing/account/getstatuses.go b/internal/processing/account/getstatuses.go
index 7dbe68462..9c78917c3 100644
--- a/internal/processing/account/getstatuses.go
+++ b/internal/processing/account/getstatuses.go
@@ -26,11 +26,10 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
-	"github.com/superseriousbusiness/gotosocial/internal/timeline"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
-func (p *processor) StatusesGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinnedOnly bool, mediaOnly bool, publicOnly bool) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) StatusesGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinnedOnly bool, mediaOnly bool, publicOnly bool) (*apimodel.PageableResponse, gtserror.WithCode) {
 	if requestingAccount != nil {
 		if blocked, err := p.db.IsBlocked(ctx, requestingAccount.ID, targetAccountID, true); err != nil {
 			return nil, gtserror.NewErrorInternalError(err)
@@ -42,7 +41,7 @@ func (p *processor) StatusesGet(ctx context.Context, requestingAccount *gtsmodel
 	statuses, err := p.db.GetAccountStatuses(ctx, targetAccountID, limit, excludeReplies, excludeReblogs, maxID, minID, pinnedOnly, mediaOnly, publicOnly)
 	if err != nil {
 		if err == db.ErrNoEntries {
-			return util.EmptyTimelineResponse(), nil
+			return util.EmptyPageableResponse(), nil
 		}
 		return nil, gtserror.NewErrorInternalError(err)
 	}
@@ -55,25 +54,37 @@ func (p *processor) StatusesGet(ctx context.Context, requestingAccount *gtsmodel
 		}
 	}
 
-	if len(filtered) == 0 {
-		return util.EmptyTimelineResponse(), nil
+	count := len(filtered)
+
+	if count == 0 {
+		return util.EmptyPageableResponse(), nil
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, i := range filtered {
-		apiStatus, err := p.tc.StatusToAPIStatus(ctx, i, requestingAccount)
+	items := []interface{}{}
+	nextMaxIDValue := ""
+	prevMinIDValue := ""
+	for i, s := range filtered {
+		item, err := p.tc.StatusToAPIStatus(ctx, s, requestingAccount)
 		if err != nil {
 			return nil, gtserror.NewErrorInternalError(fmt.Errorf("error converting status to api: %s", err))
 		}
 
-		timelineables = append(timelineables, apiStatus)
+		if i == count-1 {
+			nextMaxIDValue = item.GetID()
+		}
+
+		if i == 0 {
+			prevMinIDValue = item.GetID()
+		}
+
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:          timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:          items,
 		Path:           fmt.Sprintf("/api/v1/accounts/%s/statuses", targetAccountID),
-		NextMaxIDValue: timelineables[len(timelineables)-1].GetID(),
-		PrevMinIDValue: timelineables[0].GetID(),
+		NextMaxIDValue: nextMaxIDValue,
+		PrevMinIDValue: prevMinIDValue,
 		Limit:          limit,
 		ExtraQueryParams: []string{
 			fmt.Sprintf("exclude_replies=%t", excludeReplies),
@@ -85,7 +96,7 @@ func (p *processor) StatusesGet(ctx context.Context, requestingAccount *gtsmodel
 	})
 }
 
-func (p *processor) WebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) WebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.PageableResponse, gtserror.WithCode) {
 	acct, err := p.db.GetAccountByID(ctx, targetAccountID)
 	if err != nil {
 		if err == db.ErrNoEntries {
@@ -103,26 +114,42 @@ func (p *processor) WebStatusesGet(ctx context.Context, targetAccountID string,
 	statuses, err := p.db.GetAccountWebStatuses(ctx, targetAccountID, 10, maxID)
 	if err != nil {
 		if err == db.ErrNoEntries {
-			return util.EmptyTimelineResponse(), nil
+			return util.EmptyPageableResponse(), nil
 		}
 		return nil, gtserror.NewErrorInternalError(err)
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, i := range statuses {
-		apiStatus, err := p.tc.StatusToAPIStatus(ctx, i, nil)
+	count := len(statuses)
+
+	if count == 0 {
+		return util.EmptyPageableResponse(), nil
+	}
+
+	items := []interface{}{}
+	nextMaxIDValue := ""
+	prevMinIDValue := ""
+	for i, s := range statuses {
+		item, err := p.tc.StatusToAPIStatus(ctx, s, nil)
 		if err != nil {
 			return nil, gtserror.NewErrorInternalError(fmt.Errorf("error converting status to api: %s", err))
 		}
 
-		timelineables = append(timelineables, apiStatus)
+		if i == count-1 {
+			nextMaxIDValue = item.GetID()
+		}
+
+		if i == 0 {
+			prevMinIDValue = item.GetID()
+		}
+
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:            timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:            items,
 		Path:             "/@" + acct.Username,
-		NextMaxIDValue:   timelineables[len(timelineables)-1].GetID(),
-		PrevMinIDValue:   timelineables[0].GetID(),
+		NextMaxIDValue:   nextMaxIDValue,
+		PrevMinIDValue:   prevMinIDValue,
 		ExtraQueryParams: []string{},
 	})
 }
diff --git a/internal/processing/notification.go b/internal/processing/notification.go
index fd2651d4a..7e748bdc3 100644
--- a/internal/processing/notification.go
+++ b/internal/processing/notification.go
@@ -25,36 +25,48 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/oauth"
-	"github.com/superseriousbusiness/gotosocial/internal/timeline"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
-func (p *processor) NotificationsGet(ctx context.Context, authed *oauth.Auth, excludeTypes []string, limit int, maxID string, sinceID string) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) NotificationsGet(ctx context.Context, authed *oauth.Auth, excludeTypes []string, limit int, maxID string, sinceID string) (*apimodel.PageableResponse, gtserror.WithCode) {
 	notifs, err := p.db.GetNotifications(ctx, authed.Account.ID, excludeTypes, limit, maxID, sinceID)
 	if err != nil {
 		return nil, gtserror.NewErrorInternalError(err)
 	}
 
-	if len(notifs) == 0 {
-		return util.EmptyTimelineResponse(), nil
+	count := len(notifs)
+
+	if count == 0 {
+		return util.EmptyPageableResponse(), nil
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, n := range notifs {
-		apiNotif, err := p.tc.NotificationToAPINotification(ctx, n)
+	items := []interface{}{}
+	nextMaxIDValue := ""
+	prevMinIDValue := ""
+	for i, n := range notifs {
+		item, err := p.tc.NotificationToAPINotification(ctx, n)
 		if err != nil {
 			log.Debugf("got an error converting a notification to api, will skip it: %s", err)
 			continue
 		}
-		timelineables = append(timelineables, apiNotif)
+
+		if i == count-1 {
+			nextMaxIDValue = item.GetID()
+		}
+
+		if i == 0 {
+			prevMinIDValue = item.GetID()
+		}
+
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:          timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:          items,
 		Path:           "api/v1/notifications",
-		NextMaxIDValue: timelineables[len(timelineables)-1].GetID(),
+		NextMaxIDValue: nextMaxIDValue,
 		PrevMinIDKey:   "since_id",
-		PrevMinIDValue: timelineables[0].GetID(),
+		PrevMinIDValue: prevMinIDValue,
 		Limit:          limit,
 	})
 }
diff --git a/internal/processing/processor.go b/internal/processing/processor.go
index 09bb579ba..c76b1623b 100644
--- a/internal/processing/processor.go
+++ b/internal/processing/processor.go
@@ -89,10 +89,10 @@ type Processor interface {
 	AccountUpdate(ctx context.Context, authed *oauth.Auth, form *apimodel.UpdateCredentialsRequest) (*apimodel.Account, gtserror.WithCode)
 	// AccountStatusesGet fetches a number of statuses (in time descending order) from the given account, filtered by visibility for
 	// the account given in authed.
-	AccountStatusesGet(ctx context.Context, authed *oauth.Auth, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinned bool, mediaOnly bool, publicOnly bool) (*apimodel.TimelineResponse, gtserror.WithCode)
+	AccountStatusesGet(ctx context.Context, authed *oauth.Auth, targetAccountID string, limit int, excludeReplies bool, excludeReblogs bool, maxID string, minID string, pinned bool, mediaOnly bool, publicOnly bool) (*apimodel.PageableResponse, gtserror.WithCode)
 	// AccountWebStatusesGet fetches a number of statuses (in descending order) from the given account. It selects only
 	// statuses which are suitable for showing on the public web profile of an account.
-	AccountWebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.TimelineResponse, gtserror.WithCode)
+	AccountWebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.PageableResponse, gtserror.WithCode)
 	// AccountFollowersGet fetches a list of the target account's followers.
 	AccountFollowersGet(ctx context.Context, authed *oauth.Auth, targetAccountID string) ([]apimodel.Account, gtserror.WithCode)
 	// AccountFollowingGet fetches a list of the accounts that target account is following.
@@ -160,7 +160,7 @@ type Processor interface {
 	MediaUpdate(ctx context.Context, authed *oauth.Auth, attachmentID string, form *apimodel.AttachmentUpdateRequest) (*apimodel.Attachment, gtserror.WithCode)
 
 	// NotificationsGet
-	NotificationsGet(ctx context.Context, authed *oauth.Auth, excludeTypes []string, limit int, maxID string, sinceID string) (*apimodel.TimelineResponse, gtserror.WithCode)
+	NotificationsGet(ctx context.Context, authed *oauth.Auth, excludeTypes []string, limit int, maxID string, sinceID string) (*apimodel.PageableResponse, gtserror.WithCode)
 	// NotificationsClear
 	NotificationsClear(ctx context.Context, authed *oauth.Auth) gtserror.WithCode
 
@@ -192,11 +192,11 @@ type Processor interface {
 	StatusGetContext(ctx context.Context, authed *oauth.Auth, targetStatusID string) (*apimodel.Context, gtserror.WithCode)
 
 	// HomeTimelineGet returns statuses from the home timeline, with the given filters/parameters.
-	HomeTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.TimelineResponse, gtserror.WithCode)
+	HomeTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.PageableResponse, gtserror.WithCode)
 	// PublicTimelineGet returns statuses from the public/local timeline, with the given filters/parameters.
-	PublicTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.TimelineResponse, gtserror.WithCode)
+	PublicTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.PageableResponse, gtserror.WithCode)
 	// FavedTimelineGet returns faved statuses, with the given filters/parameters.
-	FavedTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, minID string, limit int) (*apimodel.TimelineResponse, gtserror.WithCode)
+	FavedTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, minID string, limit int) (*apimodel.PageableResponse, gtserror.WithCode)
 
 	// AuthorizeStreamingRequest returns a gotosocial account in exchange for an access token, or an error if the given token is not valid.
 	AuthorizeStreamingRequest(ctx context.Context, accessToken string) (*gtsmodel.Account, gtserror.WithCode)
diff --git a/internal/processing/statustimeline.go b/internal/processing/statustimeline.go
index b7313818c..4491308f3 100644
--- a/internal/processing/statustimeline.go
+++ b/internal/processing/statustimeline.go
@@ -137,40 +137,47 @@ func StatusSkipInsertFunction() timeline.SkipInsertFunction {
 	}
 }
 
-func (p *processor) HomeTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) HomeTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.PageableResponse, gtserror.WithCode) {
 	preparedItems, err := p.statusTimelines.GetTimeline(ctx, authed.Account.ID, maxID, sinceID, minID, limit, local)
 	if err != nil {
 		return nil, gtserror.NewErrorInternalError(err)
 	}
 
-	if len(preparedItems) == 0 {
-		return util.EmptyTimelineResponse(), nil
+	count := len(preparedItems)
+
+	if count == 0 {
+		return util.EmptyPageableResponse(), nil
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, i := range preparedItems {
-		status, ok := i.(*apimodel.Status)
-		if !ok {
-			return nil, gtserror.NewErrorInternalError(errors.New("error converting prepared timeline entry to api status"))
+	items := []interface{}{}
+	nextMaxIDValue := ""
+	prevMinIDValue := ""
+	for i, item := range preparedItems {
+		if i == count-1 {
+			nextMaxIDValue = item.GetID()
 		}
-		timelineables = append(timelineables, status)
+
+		if i == 0 {
+			prevMinIDValue = item.GetID()
+		}
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:          timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:          items,
 		Path:           "api/v1/timelines/home",
-		NextMaxIDValue: timelineables[len(timelineables)-1].GetID(),
-		PrevMinIDValue: timelineables[0].GetID(),
+		NextMaxIDValue: nextMaxIDValue,
+		PrevMinIDValue: prevMinIDValue,
 		Limit:          limit,
 	})
 }
 
-func (p *processor) PublicTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) PublicTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, sinceID string, minID string, limit int, local bool) (*apimodel.PageableResponse, gtserror.WithCode) {
 	statuses, err := p.db.GetPublicTimeline(ctx, authed.Account.ID, maxID, sinceID, minID, limit, local)
 	if err != nil {
 		if err == db.ErrNoEntries {
 			// there are just no entries left
-			return util.EmptyTimelineResponse(), nil
+			return util.EmptyPageableResponse(), nil
 		}
 		// there's an actual error
 		return nil, gtserror.NewErrorInternalError(err)
@@ -181,30 +188,41 @@ func (p *processor) PublicTimelineGet(ctx context.Context, authed *oauth.Auth, m
 		return nil, gtserror.NewErrorInternalError(err)
 	}
 
-	if len(filtered) == 0 {
-		return util.EmptyTimelineResponse(), nil
+	count := len(filtered)
+
+	if count == 0 {
+		return util.EmptyPageableResponse(), nil
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, i := range filtered {
-		timelineables = append(timelineables, i)
+	items := []interface{}{}
+	nextMaxIDValue := ""
+	prevMinIDValue := ""
+	for i, item := range filtered {
+		if i == count-1 {
+			nextMaxIDValue = item.GetID()
+		}
+
+		if i == 0 {
+			prevMinIDValue = item.GetID()
+		}
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:          timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:          items,
 		Path:           "api/v1/timelines/public",
-		NextMaxIDValue: timelineables[len(timelineables)-1].GetID(),
-		PrevMinIDValue: timelineables[0].GetID(),
+		NextMaxIDValue: nextMaxIDValue,
+		PrevMinIDValue: prevMinIDValue,
 		Limit:          limit,
 	})
 }
 
-func (p *processor) FavedTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, minID string, limit int) (*apimodel.TimelineResponse, gtserror.WithCode) {
+func (p *processor) FavedTimelineGet(ctx context.Context, authed *oauth.Auth, maxID string, minID string, limit int) (*apimodel.PageableResponse, gtserror.WithCode) {
 	statuses, nextMaxID, prevMinID, err := p.db.GetFavedTimeline(ctx, authed.Account.ID, maxID, minID, limit)
 	if err != nil {
 		if err == db.ErrNoEntries {
 			// there are just no entries left
-			return util.EmptyTimelineResponse(), nil
+			return util.EmptyPageableResponse(), nil
 		}
 		// there's an actual error
 		return nil, gtserror.NewErrorInternalError(err)
@@ -216,16 +234,16 @@ func (p *processor) FavedTimelineGet(ctx context.Context, authed *oauth.Auth, ma
 	}
 
 	if len(filtered) == 0 {
-		return util.EmptyTimelineResponse(), nil
+		return util.EmptyPageableResponse(), nil
 	}
 
-	timelineables := []timeline.Timelineable{}
-	for _, i := range filtered {
-		timelineables = append(timelineables, i)
+	items := []interface{}{}
+	for _, item := range filtered {
+		items = append(items, item)
 	}
 
-	return util.PackageTimelineableResponse(util.TimelineableResponseParams{
-		Items:          timelineables,
+	return util.PackagePageableResponse(util.PageableResponseParams{
+		Items:          items,
 		Path:           "api/v1/favourites",
 		NextMaxIDValue: nextMaxID,
 		PrevMinIDValue: prevMinID,