From da3654ec4ac3afce7bf2a721ba7611a8bb60b793 Mon Sep 17 00:00:00 2001
From: Uruk <contact@uruk.dev>
Date: Fri, 22 May 2026 01:43:40 +0200
Subject: [PATCH] fix: restore StreamRanker for cross-episode track matching

Removing StreamRanker reduced track matching to direct index reuse. When a
next episode has a different audio/subtitle track layout (common with anime
multi-sub releases or mixed sources), the stored index points at the wrong
track. StreamRanker scores by codec/language/title/relative index and only
applies a match above threshold, otherwise falls back to media defaults.

Restores utils/streamRanker.ts and its use in getDefaultPlaySettings so the
cleanup PR stays behavior-preserving for playback.
---
 utils/jellyfin/getDefaultPlaySettings.ts |  30 ++++-
 utils/streamRanker.ts                    | 159 +++++++++++++++++++++++
 2 files changed, 184 insertions(+), 5 deletions(-)
 create mode 100644 utils/streamRanker.ts

diff --git a/utils/jellyfin/getDefaultPlaySettings.ts b/utils/jellyfin/getDefaultPlaySettings.ts
index 3cafd0d0..d5ac5032 100644
--- a/utils/jellyfin/getDefaultPlaySettings.ts
+++ b/utils/jellyfin/getDefaultPlaySettings.ts
@@ -15,6 +15,11 @@ import type {
 } from "@jellyfin/sdk/lib/generated-client";
 import { BITRATES } from "@/components/BitrateSelector";
 import { type Settings } from "../atoms/settings";
+import {
+  AudioStreamRanker,
+  StreamRanker,
+  SubtitleStreamRanker,
+} from "../streamRanker";
 
 export interface PlaySettings {
   item: BaseItemDto;
@@ -49,27 +54,42 @@ export function getDefaultPlaySettings(
   }
 
   const mediaSource = item.MediaSources?.[0];
-  const _streams = mediaSource?.MediaStreams ?? [];
+  const streams = mediaSource?.MediaStreams ?? [];
 
   // Start with media source defaults
   let audioIndex = mediaSource?.DefaultAudioStreamIndex;
   let subtitleIndex = mediaSource?.DefaultSubtitleStreamIndex ?? -1;
 
   // Try to match previous selections (sequential play)
-  // Simplified: just use previous indexes if available
-  if (previous?.indexes && settings) {
+  if (previous?.indexes && previous?.source && settings) {
     if (
       settings.rememberSubtitleSelections &&
       previous.indexes.subtitleIndex !== undefined
     ) {
-      subtitleIndex = previous.indexes.subtitleIndex;
+      const ranker = new StreamRanker(new SubtitleStreamRanker());
+      const result = { DefaultSubtitleStreamIndex: subtitleIndex };
+      ranker.rankStream(
+        previous.indexes.subtitleIndex,
+        previous.source,
+        streams,
+        result,
+      );
+      subtitleIndex = result.DefaultSubtitleStreamIndex;
     }
 
     if (
       settings.rememberAudioSelections &&
       previous.indexes.audioIndex !== undefined
     ) {
-      audioIndex = previous.indexes.audioIndex;
+      const ranker = new StreamRanker(new AudioStreamRanker());
+      const result = { DefaultAudioStreamIndex: audioIndex };
+      ranker.rankStream(
+        previous.indexes.audioIndex,
+        previous.source,
+        streams,
+        result,
+      );
+      audioIndex = result.DefaultAudioStreamIndex;
     }
   }
 
diff --git a/utils/streamRanker.ts b/utils/streamRanker.ts
new file mode 100644
index 00000000..8121adea
--- /dev/null
+++ b/utils/streamRanker.ts
@@ -0,0 +1,159 @@
+import type {
+  MediaSourceInfo,
+  MediaStream,
+} from "@jellyfin/sdk/lib/generated-client";
+
+abstract class StreamRankerStrategy {
+  abstract streamType: string;
+
+  abstract rankStream(
+    prevIndex: number,
+    prevSource: MediaSourceInfo,
+    mediaStreams: MediaStream[],
+    trackOptions: any,
+  ): void;
+
+  protected rank(
+    prevIndex: number,
+    prevSource: MediaSourceInfo,
+    mediaStreams: MediaStream[],
+    trackOptions: any,
+  ): void {
+    if (prevIndex === -1) {
+      console.debug("AutoSet Subtitle - No Stream Set");
+      trackOptions[`Default${this.streamType}StreamIndex`] = -1;
+      return;
+    }
+
+    if (!prevSource.MediaStreams || !mediaStreams) {
+      console.debug(`AutoSet ${this.streamType} - No MediaStreams`);
+      return;
+    }
+
+    let bestStreamIndex = null;
+    let bestStreamScore = 0;
+
+    const prevStream = prevSource.MediaStreams[prevIndex];
+
+    if (!prevStream) {
+      console.debug(`AutoSet ${this.streamType} - No prevStream`);
+      return;
+    }
+
+    console.debug(
+      `AutoSet ${this.streamType} - Previous was ${prevStream.Index} - ${prevStream.DisplayTitle}`,
+    );
+
+    let prevRelIndex = 0;
+    for (const stream of prevSource.MediaStreams) {
+      if (stream.Type !== this.streamType) {
+        continue;
+      }
+
+      if (stream.Index === prevIndex) {
+        break;
+      }
+
+      prevRelIndex += 1;
+    }
+
+    let newRelIndex = 0;
+    for (const stream of mediaStreams) {
+      if (stream.Type !== this.streamType) {
+        continue;
+      }
+
+      let score = 0;
+
+      if (prevStream.Codec === stream.Codec) {
+        score += 1;
+      }
+      if (prevRelIndex === newRelIndex) {
+        score += 1;
+      }
+      if (
+        prevStream.DisplayTitle &&
+        prevStream.DisplayTitle === stream.DisplayTitle
+      ) {
+        score += 2;
+      }
+      if (
+        prevStream.Language &&
+        prevStream.Language !== "und" &&
+        prevStream.Language === stream.Language
+      ) {
+        score += 2;
+      }
+
+      console.debug(
+        `AutoSet ${this.streamType} - Score ${score} for ${stream.Index} - ${stream.DisplayTitle}`,
+      );
+      if (score > bestStreamScore && score >= 3) {
+        bestStreamScore = score;
+        bestStreamIndex = stream.Index;
+      }
+
+      newRelIndex += 1;
+    }
+
+    if (bestStreamIndex != null) {
+      console.debug(
+        `AutoSet ${this.streamType} - Using ${bestStreamIndex} score ${bestStreamScore}.`,
+      );
+      trackOptions[`Default${this.streamType}StreamIndex`] = bestStreamIndex;
+    } else {
+      console.debug(
+        `AutoSet ${this.streamType} - Threshold not met. Using default.`,
+      );
+    }
+  }
+}
+
+class SubtitleStreamRanker extends StreamRankerStrategy {
+  streamType = "Subtitle";
+
+  rankStream(
+    prevIndex: number,
+    prevSource: MediaSourceInfo,
+    mediaStreams: MediaStream[],
+    trackOptions: any,
+  ): void {
+    super.rank(prevIndex, prevSource, mediaStreams, trackOptions);
+  }
+}
+
+class AudioStreamRanker extends StreamRankerStrategy {
+  streamType = "Audio";
+
+  rankStream(
+    prevIndex: number,
+    prevSource: MediaSourceInfo,
+    mediaStreams: MediaStream[],
+    trackOptions: any,
+  ): void {
+    super.rank(prevIndex, prevSource, mediaStreams, trackOptions);
+  }
+}
+
+class StreamRanker {
+  private strategy: StreamRankerStrategy;
+
+  constructor(strategy: StreamRankerStrategy) {
+    this.strategy = strategy;
+  }
+
+  setStrategy(strategy: StreamRankerStrategy) {
+    this.strategy = strategy;
+  }
+
+  rankStream(
+    prevIndex: number,
+    prevSource: MediaSourceInfo,
+    mediaStreams: MediaStream[],
+    trackOptions: any,
+  ) {
+    this.strategy.rankStream(prevIndex, prevSource, mediaStreams, trackOptions);
+  }
+}
+
+export { StreamRanker, SubtitleStreamRanker, AudioStreamRanker };