From 5e63c3551d8fbf90ee905ec82f924f83f5226424 Mon Sep 17 00:00:00 2001
From: mkelvers <mikkelelvers@outlook.com>
Date: Wed, 6 May 2026 14:09:11 +0200
Subject: [PATCH] jikan: add parallel episode fetching

---
 api/playback/handler.go        | 32 +++++------------------
 integrations/jikan/episodes.go | 48 ++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 26 deletions(-)

diff --git a/api/playback/handler.go b/api/playback/handler.go
index f00dfae..042c714 100644
--- a/api/playback/handler.go
+++ b/api/playback/handler.go
@@ -56,20 +56,9 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Fetch episodes sequentially (pages are in correct order: 1-100, 101-200, etc.)
-	pageSize := 100
-	var allEpisodes []jikan.Episode
-	for page := 1; ; page++ {
-		resp, err := h.jikanClient.GetEpisodes(r.Context(), id, page)
-		if err != nil || len(resp.Data) == 0 {
-			break
-		}
-		allEpisodes = append(allEpisodes, resp.Data...)
-
-		// If we got fewer than pageSize, we've reached the end
-		if len(resp.Data) < pageSize {
-			break
-		}
+	allEpisodes, err := h.jikanClient.GetAllEpisodes(r.Context(), id)
+	if err != nil {
+		log.Printf("failed to fetch episodes: %v", err)
 	}
 
 	user := middleware.GetUser(r.Context())
@@ -419,18 +408,9 @@ func (h *Handler) HandleEpisodeThumbnails(w http.ResponseWriter, r *http.Request
 		return
 	}
 
-	// Fetch episodes sequentially
-	pageSize := 100
-	var allEpisodes []jikan.Episode
-	for page := 1; ; page++ {
-		resp, err := h.jikanClient.GetEpisodes(r.Context(), id, page)
-		if err != nil || len(resp.Data) == 0 {
-			break
-		}
-		allEpisodes = append(allEpisodes, resp.Data...)
-		if len(resp.Data) < pageSize {
-			break
-		}
+	allEpisodes, err := h.jikanClient.GetAllEpisodes(r.Context(), id)
+	if err != nil {
+		log.Printf("failed to fetch thumbnails/episodes: %v", err)
 	}
 
 	// Fill gaps if anime has known total
diff --git a/integrations/jikan/episodes.go b/integrations/jikan/episodes.go
index b1c1d0d..c202ec4 100644
--- a/integrations/jikan/episodes.go
+++ b/integrations/jikan/episodes.go
@@ -3,6 +3,7 @@ package jikan
 import (
 	"context"
 	"fmt"
+	"sync"
 	"time"
 )
 
@@ -19,6 +20,53 @@ func (c *Client) GetEpisodes(ctx context.Context, animeID int, page int) (Episod
 	return result, err
 }
 
+func (c *Client) GetAllEpisodes(ctx context.Context, animeID int) ([]Episode, error) {
+	// First page to get total pages
+	first, err := c.GetEpisodes(ctx, animeID, 1)
+	if err != nil {
+		return nil, err
+	}
+
+	if first.Pagination.LastVisiblePage <= 1 {
+		return first.Data, nil
+	}
+
+	all := make([][]Episode, first.Pagination.LastVisiblePage)
+	all[0] = first.Data
+
+	var wg sync.WaitGroup
+	errs := make(chan error, first.Pagination.LastVisiblePage-1)
+
+	// Fetch remaining pages in parallel
+	// Note: Client.getWithCache handles rate limiting (3 req/sec)
+	for p := 2; p <= first.Pagination.LastVisiblePage; p++ {
+		wg.Add(1)
+		go func(page int) {
+			defer wg.Done()
+			resp, err := c.GetEpisodes(ctx, animeID, page)
+			if err != nil {
+				errs <- err
+				return
+			}
+			all[page-1] = resp.Data
+		}(p)
+	}
+
+	wg.Wait()
+	close(errs)
+
+	if err := <-errs; err != nil {
+		return nil, err
+	}
+
+	var result []Episode
+	for _, pageData := range all {
+		result = append(result, pageData...)
+	}
+
+	return result, nil
+}
+
 func (c *Client) GetEpisodesRange(ctx context.Context, animeID int, startPage, endPage int) ([]Episode, error) {
 	var all []Episode
 	for page := startPage; page <= endPage; page++ {