Move subtitle parsing into a shared interface

[Modified from e84404b7857f8c611eda7a65b5d61ee6c9823d75, 2026-03-28 09:52:31 -0400]

Extracted the srt specific extraction behind a generic shared interface to allow easier adding of other subtitle formats in the future.

apps/web/src/components/editor/panels/assets/views/captions.tsx

@@ -23,7 +23,7 @@ import { transcriptionService } from "@/services/transcription/service";
 import { decodeAudioToFloat32 } from "@/lib/media/audio";
 import { buildCaptionChunks } from "@/lib/transcription/caption";
 import { insertCaptionChunksAsTextTrack } from "@/lib/subtitles/insert";
-import { parseSrt } from "@/lib/subtitles/srt";
+import { parseSubtitleFile } from "@/lib/subtitles/parse";
 import { Spinner } from "@/components/ui/spinner";
 import {
 	Section,
@@ -121,7 +121,10 @@ export function Captions() {
 			setProcessingStep("Reading subtitle file...");
 
 			const input = await file.text();
-			const result = parseSrt({ input });
+			const result = parseSubtitleFile({
+				fileName: file.name,
+				input,
+			});
 
 			if (result.captions.length === 0) {
 				throw new Error("No valid subtitle cues were found in the .srt file");

apps/web/src/lib/subtitles/parse.ts

@@ -0,0 +1,33 @@
+import type { CaptionChunk } from "@/lib/transcription/types";
+import { parseSrt } from "./srt";
+
+export interface ParseSubtitleResult {
+	captions: CaptionChunk[];
+	skippedCueCount: number;
+}
+
+export function parseSubtitleFile({
+	fileName,
+	input,
+}: {
+	fileName: string;
+	input: string;
+}): ParseSubtitleResult {
+	const extension = getFileExtension({ fileName });
+
+	switch (extension) {
+		case "srt":
+			return parseSrt({ input });
+		default:
+			throw new Error("Unsupported subtitle format");
+	}
+}
+
+function getFileExtension({
+	fileName,
+}: {
+	fileName: string;
+}): string {
+	const extension = fileName.split(".").pop();
+	return extension?.toLowerCase() ?? "";
+}

apps/web/src/lib/subtitles/srt.ts

@@ -1,19 +1,15 @@
 import type { CaptionChunk } from "@/lib/transcription/types";
+import type { ParseSubtitleResult } from "./parse";
 
 const TIMESTAMP_SEPARATOR = /\s*-->\s*/;
 const TIMESTAMP_PATTERN =
 	/^(\d{2}:\d{2}:\d{2}[,.]\d{1,3})\s*-->\s*(\d{2}:\d{2}:\d{2}[,.]\d{1,3})/;
 
-export interface ParseSrtResult {
-	captions: CaptionChunk[];
-	skippedCueCount: number;
-}
-
 export function parseSrt({
 	input,
 }: {
 	input: string;
-}): ParseSrtResult {
+}): ParseSubtitleResult {
 	const normalized = input.replace(/\r\n?/g, "\n").trim();
 	if (!normalized) {
 		return {