Fix ranking pagination: sliding ±2 window around current page

rankingPageNums now takes a current page parameter and always renders
first 2, last 2, and current±2 — so navigating to page 3 shows
1 2 3 4 5 … 80 81 instead of only the fixed quarter-mark anchors.

scraper/internal/server/ui.go

@@ -881,47 +881,38 @@ type pageNum struct {
 	Num int
 }
 
-// rankingPageNums builds the dynamic pagination list for 100 pages with
-// smart ellipsis: always show the first 3, last 3, and a sliding window of
-// 3 around the ends — compressed with "…" separators between runs.
-//
-// For a flat 100-page list it produces:
-//
-//	1 2 3 … 6 7 8 … 93 94 95 … 98 99 100
-//
-// (The middle range is omitted intentionally; users click individual pages.)
-func rankingPageNums(total int) []pageNum {
+// rankingPageNums builds a pagination list with smart ellipsis.
+// It always shows: first 2, last 2, and a ±2 window around current.
+// Gaps between non-consecutive runs are filled with a sentinel (Num==0) for "…".
+// Pass current=0 when there is no concept of a current page (e.g. fetch bar).
+func rankingPageNums(total, current int) []pageNum {
 	if total <= 0 {
 		return nil
 	}
-	// Build the set of visible page numbers using a sliding-window approach.
 	show := make(map[int]bool)
-	// Always show first 3 and last 3.
-	for i := 1; i <= 3 && i <= total; i++ {
+	// First 2 and last 2.
+	for i := 1; i <= 2 && i <= total; i++ {
 		show[i] = true
 	}
-	for i := total - 2; i <= total; i++ {
+	for i := total - 1; i <= total; i++ {
 		if i >= 1 {
 			show[i] = true
 		}
 	}
-	// For large ranges, show a few pages near the 1/4 and 3/4 marks.
-	if total > 12 {
-		q1 := total / 4
-		q3 := total * 3 / 4
-		for _, p := range []int{q1 - 1, q1, q1 + 1, q3 - 1, q3, q3 + 1} {
-			if p >= 1 && p <= total {
-				show[p] = true
+	// ±2 window around current page.
+	if current > 0 {
+		for i := current - 2; i <= current+2; i++ {
+			if i >= 1 && i <= total {
+				show[i] = true
 			}
 		}
 	}
 
-	// Collect sorted visible pages.
+	// Collect and sort.
 	pages := make([]int, 0, len(show))
 	for p := range show {
 		pages = append(pages, p)
 	}
-	// Sort pages slice.
 	for i := 0; i < len(pages); i++ {
 		for j := i + 1; j < len(pages); j++ {
 			if pages[j] < pages[i] {
@@ -930,11 +921,11 @@ func rankingPageNums(total int) []pageNum {
 		}
 	}
 
-	// Build output with ellipsis sentinels (Num==0) between non-consecutive pages.
+	// Build output with ellipsis sentinels between non-consecutive pages.
 	out := make([]pageNum, 0, len(pages)*2)
 	for i, p := range pages {
 		if i > 0 && p > pages[i-1]+1 {
-			out = append(out, pageNum{0}) // ellipsis
+			out = append(out, pageNum{0})
 		}
 		out = append(out, pageNum{p})
 	}
@@ -1015,8 +1006,8 @@ func (s *Server) handleRanking(w http.ResponseWriter, r *http.Request) {
 	}{
 		Books:       toRankingViewItems(pageItems, s.writer.LocalSlugs()),
 		CachedAt:    cachedAt,
-		FetchNums:   rankingPageNums(100),
-		DisplayNums: rankingPageNums(totalPages),
+		FetchNums:   rankingPageNums(100, 0),
+		DisplayNums: rankingPageNums(totalPages, currentPage),
 		CurrentPage: currentPage,
 		TotalPages:  totalPages,
 		TotalItems:  totalItems,