Only use prev and next buttons for pagination on user dashboard (#33981)

The pagination on the user dashboard sounds unnecessary, this will
change it to a prev/next buttons. For instances with around `10 million`
records in the action table, this option affects how the user dashboard
is loaded on first visit.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

7 files changed, 65 insertions, 42 deletions

diff --git a/modules/paginator/paginator.go b/modules/paginator/paginator.go
index 8258d194c2..0f64e89d9a 100644
--- a/modules/paginator/paginator.go
+++ b/modules/paginator/paginator.go
@@ -4,6 +4,8 @@
 
 package paginator
 
+import "code.gitea.io/gitea/modules/util"
+
 /*
 In template:
 
@@ -32,25 +34,43 @@ Output:
 
 // Paginator represents a set of results of pagination calculations.
 type Paginator struct {
-	total     int // total rows count
+	total      int // total rows count, -1 means unknown
+	totalPages int // total pages count, -1 means unknown
+	current    int // current page number
+	curRows    int // current page rows count
+
 	pagingNum int // how many rows in one page
-	current   int // current page number
 	numPages  int // how many pages to show on the UI
 }
 
 // New initialize a new pagination calculation and returns a Paginator as result.
 func New(total, pagingNum, current, numPages int) *Paginator {
-	if pagingNum <= 0 {
-		pagingNum = 1
+	pagingNum = max(pagingNum, 1)
+	totalPages := util.Iif(total == -1, -1, (total+pagingNum-1)/pagingNum)
+	if total >= 0 {
+		current = min(current, totalPages)
 	}
-	if current <= 0 {
-		current = 1
+	current = max(current, 1)
+	return &Paginator{
+		total:      total,
+		totalPages: totalPages,
+		current:    current,
+		pagingNum:  pagingNum,
+		numPages:   numPages,
 	}
-	p := &Paginator{total, pagingNum, current, numPages}
-	if p.current > p.TotalPages() {
-		p.current = p.TotalPages()
+}
+
+func (p *Paginator) SetCurRows(rows int) {
+	// For "unlimited paging", we need to know the rows of current page to determine if there is a next page.
+	// There is still an edge case: when curRows==pagingNum, then the "next page" will be an empty page.
+	// Ideally we should query one more row to determine if there is really a next page, but it's impossible in current framework.
+	p.curRows = rows
+	if p.total == -1 && p.current == 1 && !p.HasNext() {
+		// if there is only one page for the "unlimited paging", set total rows/pages count
+		// then the tmpl could decide to hide the nav bar.
+		p.total = rows
+		p.totalPages = util.Iif(p.total == 0, 0, 1)
 	}
-	return p
 }
 
 // IsFirst returns true if current page is the first page.
@@ -72,7 +92,10 @@ func (p *Paginator) Previous() int {
 
 // HasNext returns true if there is a next page relative to current page.
 func (p *Paginator) HasNext() bool {
-	return p.total > p.current*p.pagingNum
+	if p.total == -1 {
+		return p.curRows >= p.pagingNum
+	}
+	return p.current*p.pagingNum < p.total
 }
 
 func (p *Paginator) Next() int {
@@ -84,10 +107,7 @@ func (p *Paginator) Next() int {
 
 // IsLast returns true if current page is the last page.
 func (p *Paginator) IsLast() bool {
-	if p.total == 0 {
-		return true
-	}
-	return p.total > (p.current-1)*p.pagingNum && !p.HasNext()
+	return !p.HasNext()
 }
 
 // Total returns number of total rows.
@@ -97,10 +117,7 @@ func (p *Paginator) Total() int {
 
 // TotalPages returns number of total pages.
 func (p *Paginator) TotalPages() int {
-	if p.total == 0 {
-		return 1
-	}
-	return (p.total + p.pagingNum - 1) / p.pagingNum
+	return p.totalPages
 }
 
 // Current returns current page number.
@@ -135,10 +152,10 @@ func getMiddleIdx(numPages int) int {
 // If value is -1 means "..." that more pages are not showing.
 func (p *Paginator) Pages() []*Page {
 	if p.numPages == 0 {
-		return []*Page{}
-	} else if p.numPages == 1 && p.TotalPages() == 1 {
+		return nil
+	} else if p.total == -1 || (p.numPages == 1 && p.TotalPages() == 1) {
 		// Only show current page.
-		return []*Page{{1, true}}
+		return []*Page{{p.current, true}}
 	}
 
 	// Total page number is less or equal.
diff --git a/modules/paginator/paginator_test.go b/modules/paginator/paginator_test.go
index 8a56ee5121..ed46ecea94 100644
--- a/modules/paginator/paginator_test.go
+++ b/modules/paginator/paginator_test.go
@@ -76,9 +76,7 @@ func TestPaginator(t *testing.T) {
 	t.Run("Only current page", func(t *testing.T) {
 		p := New(0, 10, 1, 1)
 		pages := p.Pages()
-		assert.Len(t, pages, 1)
-		assert.Equal(t, 1, pages[0].Num())
-		assert.True(t, pages[0].IsCurrent())
+		assert.Empty(t, pages) // no "total", so no pages
 
 		p = New(1, 10, 1, 1)
 		pages = p.Pages()
diff --git a/routers/web/user/home.go b/routers/web/user/home.go
index 864a2831d1..44e2a5ec71 100644
--- a/routers/web/user/home.go
+++ b/routers/web/user/home.go
@@ -137,11 +137,10 @@ func Dashboard(ctx *context.Context) {
 		return
 	}
 
-	ctx.Data["Feeds"] = feeds
-
-	pager := context.NewPagination(int(count), setting.UI.FeedPagingNum, page, 5)
+	pager := context.NewPagination(count, setting.UI.FeedPagingNum, page, 5).WithCurRows(len(feeds))
 	pager.AddParamFromRequest(ctx.Req)
 	ctx.Data["Page"] = pager
+	ctx.Data["Feeds"] = feeds
 
 	ctx.HTML(http.StatusOK, tplDashboard)
 }
diff --git a/services/context/pagination.go b/services/context/pagination.go
index d33dd217d0..25a9298e01 100644
--- a/services/context/pagination.go
+++ b/services/context/pagination.go
@@ -21,12 +21,18 @@ type Pagination struct {
 
 // NewPagination creates a new instance of the Pagination struct.
 // "pagingNum" is "page size" or "limit", "current" is "page"
+// total=-1 means only showing prev/next
 func NewPagination(total, pagingNum, current, numPages int) *Pagination {
 	p := &Pagination{}
 	p.Paginater = paginator.New(total, pagingNum, current, numPages)
 	return p
 }
 
+func (p *Pagination) WithCurRows(n int) *Pagination {
+	p.Paginater.SetCurRows(n)
+	return p
+}
+
 func (p *Pagination) AddParamFromRequest(req *http.Request) {
 	for key, values := range req.URL.Query() {
 		if key == "page" || len(values) == 0 || (len(values) == 1 && values[0] == "") {
diff --git a/services/feed/feed.go b/services/feed/feed.go
index 41a918f00e..214e9b5765 100644
--- a/services/feed/feed.go
+++ b/services/feed/feed.go
@@ -15,24 +15,17 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 )
 
 func userFeedCacheKey(userID int64) string {
 	return fmt.Sprintf("user_feed_%d", userID)
 }
 
-func GetFeedsForDashboard(ctx context.Context, opts activities_model.GetFeedsOptions) (activities_model.ActionList, int64, error) {
+func GetFeedsForDashboard(ctx context.Context, opts activities_model.GetFeedsOptions) (activities_model.ActionList, int, error) {
 	opts.DontCount = opts.RequestedTeam == nil && opts.Date == ""
 	results, cnt, err := activities_model.GetFeeds(ctx, opts)
-	if err != nil {
-		return nil, 0, err
-	}
-	if opts.DontCount {
-		cnt, err = cache.GetInt64(userFeedCacheKey(opts.Actor.ID), func() (int64, error) {
-			return activities_model.CountUserFeeds(ctx, opts.Actor.ID)
-		})
-	}
-	return results, cnt, err
+	return results, util.Iif(opts.DontCount, -1, int(cnt)), err
 }
 
 // GetFeeds returns actions according to the provided options
diff --git a/templates/base/paginate.tmpl b/templates/base/paginate.tmpl
index 253892c009..f6c1785ccf 100644
--- a/templates/base/paginate.tmpl
+++ b/templates/base/paginate.tmpl
@@ -2,32 +2,42 @@
 {{$paginationLink := $.Link}}
 {{if eq $paginationLink AppSubUrl}}{{$paginationLink = print $paginationLink "/"}}{{end}}
 {{with .Page.Paginater}}
-	{{if gt .TotalPages 1}}
+	{{if or (eq .TotalPages -1) (gt .TotalPages 1)}}
+		{{$showFirstLast := gt .TotalPages 1}}
 		<div class="center page buttons">
 			<div class="ui borderless pagination menu">
+				{{if $showFirstLast}}
 				<a class="{{if .IsFirst}}disabled{{end}} item navigation" {{if not .IsFirst}}href="{{$paginationLink}}{{if $paginationParams}}?{{$paginationParams}}{{end}}"{{end}}>
 					{{svg "gitea-double-chevron-left" 16 "tw-mr-1"}}
 					<span class="navigation_label">{{ctx.Locale.Tr "admin.first_page"}}</span>
 				</a>
+				{{end}}
+
 				<a class="{{if not .HasPrevious}}disabled{{end}} item navigation" {{if .HasPrevious}}href="{{$paginationLink}}?page={{.Previous}}{{if $paginationParams}}&{{$paginationParams}}{{end}}"{{end}}>
 					{{svg "octicon-chevron-left" 16 "tw-mr-1"}}
 					<span class="navigation_label">{{ctx.Locale.Tr "repo.issues.previous"}}</span>
 				</a>
-				{{range .Pages}}
+				{{$pages := .Pages}}
+				{{$pagesLen := len $pages}}
+				{{range $pages}}
 					{{if eq .Num -1}}
 						<a class="disabled item">...</a>
 					{{else}}
-						<a class="{{if .IsCurrent}}active {{end}}item" {{if not .IsCurrent}}href="{{$paginationLink}}?page={{.Num}}{{if $paginationParams}}&{{$paginationParams}}{{end}}"{{end}}>{{.Num}}</a>
+						{{/* do not highlight the current page if there is only one page */}}
+						<a class="{{if and .IsCurrent (gt $pagesLen 1)}}active {{end}}item" {{if not .IsCurrent}}href="{{$paginationLink}}?page={{.Num}}{{if $paginationParams}}&{{$paginationParams}}{{end}}"{{end}}>{{.Num}}</a>
 					{{end}}
 				{{end}}
 				<a class="{{if not .HasNext}}disabled{{end}} item navigation" {{if .HasNext}}href="{{$paginationLink}}?page={{.Next}}{{if $paginationParams}}&{{$paginationParams}}{{end}}"{{end}}>
 					<span class="navigation_label">{{ctx.Locale.Tr "repo.issues.next"}}</span>
 					{{svg "octicon-chevron-right" 16 "tw-ml-1"}}
 				</a>
+
+				{{if $showFirstLast}}
 				<a class="{{if .IsLast}}disabled{{end}} item navigation" {{if not .IsLast}}href="{{$paginationLink}}?page={{.TotalPages}}{{if $paginationParams}}&{{$paginationParams}}{{end}}"{{end}}>
 					<span class="navigation_label">{{ctx.Locale.Tr "admin.last_page"}}</span>
 					{{svg "gitea-double-chevron-right" 16 "tw-ml-1"}}
 				</a>
+				{{end}}
 			</div>
 		</div>
 	{{end}}
diff --git a/templates/user/dashboard/dashboard.tmpl b/templates/user/dashboard/dashboard.tmpl
index 3ce3c1eb73..666dd78073 100644
--- a/templates/user/dashboard/dashboard.tmpl
+++ b/templates/user/dashboard/dashboard.tmpl
@@ -5,7 +5,7 @@
 		<div class="flex-container-main">
 			{{template "base/alert" .}}
 			{{template "user/heatmap" .}}
-			{{if .Feeds}}
+			{{if .Page.Paginater.TotalPages}}
 				{{template "user/dashboard/feeds" .}}
 			{{else}}
 				{{template "user/dashboard/guide" .}}