Files
mangaBookmark/backend/internal/web/cover.go
T
sulthan d1800d0707 Prefetch Kagane covers during latest polling (#51)
## Summary
- Add an optional browser-backed cover fetcher to the latest-chapter poller.
- Prefetch missing Kagane covers during the existing due-series cycle and persist them before a Reader opens the web UI.
- Keep chapter polling, cooldown stamping, and on-first-view fallback independent from cover failures.

## Behavior and safety
- Stored Kagane covers are detected before browser work, so later poll cycles do not refetch them.
- Nil cover fetchers and non-Kagane series retain the existing behavior.
- Shared Kagane image-id and content-type validation prevents challenge or non-image responses from poisoning persistent cover storage.
- The browser is wired into both the chapter and cover poller paths from the composition root.

## Verification
- `go test ./...`
- Focused latest, store, and web package tests
- Deterministic tests cover missing covers, cached covers, failed fetches, invalid content types, nil fetchers, and non-Kagane series.

Closes #45

Reviewed-on: #51
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>
2026-08-09 14:58:59 +07:00

88 lines
3.0 KiB
Go

package web
import (
"bookmarkmanager/backend/internal/store"
"context"
"log"
"net/http"
"regexp"
"time"
)
// CoverFetcher retrieves one kagane cover by image id. Satisfied by
// latest.BrowserFetcher. It is nil when BROWSER_WS_URL is unset; uncached
// covers are then unavailable, while covers already stored by the backend
// remain available without a browser.
type CoverFetcher interface {
Image(ctx context.Context, imageID string) (body []byte, contentType string, err error)
}
// coverIDRe matches the request path segment that becomes part of an outbound
// URL. The proxy is session-gated, but the id still reaches a headless browser,
// so it is validated at the boundary rather than passed through.
var coverIDRe = regexp.MustCompile(`^[0-9a-f-]{36}$`)
// coverTimeout bounds one proxied cover. Shorter than the fetcher's own
// challenge budget on purpose: a browser page is waiting on this, and a cover
// that has not arrived by now is better left as a broken slot than as a request
// holding a connection open.
const coverTimeout = 20 * time.Second
// kaganeCover serves a kagane cover from the backend's own origin.
//
// kagane answers image requests with a Cloudflare challenge and
// `cross-origin-resource-policy: same-origin`, so the web UI cannot render one
// directly under any combination of referrer policy or crossorigin attribute
// (verified 2026-08-08). Fetching it through the headless browser that already
// clears the challenge, and re-serving it here, is what puts the bytes on an
// origin the page may load from.
func (h *Handler) kaganeCover(w http.ResponseWriter, r *http.Request) {
id := r.PathValue("id")
if !coverIDRe.MatchString(id) {
http.NotFound(w, r)
return
}
body, contentType, ok, err := h.store.GetKaganeCover(id)
if err != nil {
log.Printf("read kagane cover %s: %v", id, err)
http.Error(w, "internal error", http.StatusInternalServerError)
return
}
if ok {
writeCover(w, body, contentType)
return
}
if h.covers == nil {
http.NotFound(w, r)
return
}
ctx, cancel := context.WithTimeout(r.Context(), coverTimeout)
defer cancel()
body, contentType, err = h.covers.Image(ctx, id)
if err != nil {
log.Printf("kagane cover %s: %v", id, err)
http.NotFound(w, r)
return
}
if !store.IsKaganeCoverContentType(contentType) {
log.Printf("kagane cover %s: unexpected content type %q", id, contentType)
http.NotFound(w, r)
return
}
if err := h.store.PutKaganeCover(id, body, contentType); err != nil {
log.Printf("persist kagane cover %s: %v", id, err)
http.Error(w, "internal error", http.StatusInternalServerError)
return
}
writeCover(w, body, contentType)
}
// writeCover sends the bytes with a long cache life: an image id names one
// immutable rendering, so a client that has it never needs to ask again.
func writeCover(w http.ResponseWriter, body []byte, contentType string) {
w.Header().Set("Content-Type", contentType)
w.Header().Set("Cache-Control", "private, max-age=604800, immutable")
w.Write(body)
}