feat: ranking page pagination, popular URL, and per-page HTML disk cache

- Switch ScrapeRanking to novelfire.net/genre-all/sort-popular URL and updated DOM selectors (div.novel-item, h3.novel-title, div.genres)
- Replace 5 hardcoded refresh buttons with dynamic 100-page paginator (smart ellipsis via rankingPageNums)
- Add RankingPageCacher interface and writer methods to cache raw HTML per page under static/books/_ranking_cache/page-N.html
- ScrapeRanking serves from disk cache on hit and writes to cache on miss, skipping Browserless round-trip
- Thread writer as PageCacher through novelfire.New and main.go
- Add TestScrapeRanking_CacheHit and TestScrapeRanking_CacheMiss tests

scraper/internal/server/ui.go

@@ -546,25 +546,31 @@ const rankingTmpl = `
   </div>
 
   <!-- Pagination: fetch pages from novelfire -->
-  <div class="flex items-center gap-2 mb-6 flex-wrap">
-    <span class="text-xs text-zinc-500">Fetch pages:</span>
-    {{range .Pages}}
-    <form hx-post="/ranking/refresh"
-          hx-target="#ranking-refresh-status"
-          hx-swap="innerHTML">
-      <input type="hidden" name="pages" value="{{.Pages}}">
-      <button type="submit"
-        class="text-xs px-2.5 py-1 rounded-lg bg-zinc-800 hover:bg-amber-700 border border-zinc-700 hover:border-amber-600 text-zinc-300 hover:text-white transition-colors">
-        {{.Label}}
-      </button>
-    </form>
-    {{end}}
-    <span class="text-xs text-zinc-600 ml-1">
-      (source:
+  <div class="mb-6">
+    <div class="flex items-center gap-1.5 mb-2 flex-wrap">
+      <span class="text-xs text-zinc-500 mr-1">Fetch up to page:</span>
+      {{range .PageNums}}
+      {{if eq .Num 0}}
+      <span class="text-xs text-zinc-600 px-1 select-none">…</span>
+      {{else}}
+      <form hx-post="/ranking/refresh"
+            hx-target="#ranking-refresh-status"
+            hx-swap="innerHTML">
+        <input type="hidden" name="pages" value="{{.Num}}">
+        <button type="submit"
+          class="text-xs w-8 h-7 rounded-lg bg-zinc-800 hover:bg-amber-700 border border-zinc-700 hover:border-amber-600 text-zinc-300 hover:text-white transition-colors text-center">
+          {{.Num}}
+        </button>
+      </form>
+      {{end}}
+      {{end}}
+    </div>
+    <p class="text-xs text-zinc-600">
+      Each page = ~20 novels from
       <a href="https://novelfire.net/genre-all/sort-popular/status-all/all-novel?page=1"
          target="_blank" rel="noopener noreferrer"
-         class="text-zinc-500 hover:text-amber-400 underline underline-offset-2">novelfire.net</a>)
-    </span>
+         class="text-zinc-500 hover:text-amber-400 underline underline-offset-2">novelfire.net popular</a>
+    </p>
   </div>
 
   <!-- Book grid -->
@@ -693,21 +699,70 @@ func toRankingViewItems(items []writer.RankingItem, localSlugs map[string]bool)
 	return out
 }
 
-// refreshPage is one entry in the ranking refresh pagination bar.
-type refreshPage struct {
-	Label string
-	Pages int // 0 means "all pages"
+// pageNum is one entry in the ranking pagination bar.
+// Num == 0 is a sentinel that renders as an ellipsis gap.
+type pageNum struct {
+	Num int
 }
 
-// rankingRefreshPages defines the pagination buttons shown on the ranking page.
-// Each entry fetches that many pages from novelfire.net (100 novels per page).
-// Pages == 0 means fetch all pages.
-var rankingRefreshPages = []refreshPage{
-	{"p.1 (top 100)", 1},
-	{"p.1–3 (top 300)", 3},
-	{"p.1–5 (top 500)", 5},
-	{"p.1–10 (top 1000)", 10},
-	{"All", 0},
+// 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 {
+	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++ {
+		show[i] = true
+	}
+	for i := total - 2; 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
+			}
+		}
+	}
+
+	// Collect sorted visible pages.
+	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] {
+				pages[i], pages[j] = pages[j], pages[i]
+			}
+		}
+	}
+
+	// Build output with ellipsis sentinels (Num==0) 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{p})
+	}
+	return out
 }
 
 // handleRanking serves the ranking page from the cached ranking.md file.
@@ -728,11 +783,11 @@ func (s *Server) handleRanking(w http.ResponseWriter, r *http.Request) {
 	_ = t.Execute(&buf, struct {
 		Books    interface{}
 		CachedAt string
-		Pages    []refreshPage
+		PageNums []pageNum
 	}{
 		Books:    toRankingViewItems(rankingItems, s.writer.LocalSlugs()),
 		CachedAt: cachedAt,
-		Pages:    rankingRefreshPages,
+		PageNums: rankingPageNums(100),
 	})
 	s.respond(w, r, "Rankings", buf.String())
 }