1 files changed, 98 insertions, 0 deletions
diff --git a/apps/web/src/lib/subtitles/srt.ts b/apps/web/src/lib/subtitles/srt.ts
new file mode 100644
index 00000000..197e96f9
--- /dev/null
+++ b/apps/web/src/lib/subtitles/srt.ts
@@ -0,0 +1,98 @@
+import type { ParseSubtitleResult, SubtitleCue } from "./types";
+
+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 function parseSrt({ input }: { input: string }): ParseSubtitleResult {
+	const normalized = input.replace(/\r\n?/g, "\n").trim();
+	if (!normalized) {
+		return {
+			captions: [],
+			skippedCueCount: 0,
+			warnings: [],
+		};
+	}
+
+	const blocks = normalized.split(/\n{2,}/);
+	const cues: SubtitleCue[] = [];
+	let skippedCueCount = 0;
+
+	for (const block of blocks) {
+		const lines = block
+			.split("\n")
+			.map((line) => line.trim())
+			.filter((line) => line.length > 0);
+
+		if (lines.length < 2) {
+			skippedCueCount += 1;
+			continue;
+		}
+
+		const timestampIndex = TIMESTAMP_SEPARATOR.test(lines[0]) ? 0 : 1;
+		const timestampLine = lines[timestampIndex];
+		if (!timestampLine || !TIMESTAMP_PATTERN.test(timestampLine)) {
+			skippedCueCount += 1;
+			continue;
+		}
+
+		const textLines = lines.slice(timestampIndex + 1);
+		const text = textLines.join("\n").trim();
+		if (!text) {
+			skippedCueCount += 1;
+			continue;
+		}
+
+		const [rawStart, rawEnd] = timestampLine.split(TIMESTAMP_SEPARATOR);
+		if (!rawStart || !rawEnd) {
+			skippedCueCount += 1;
+			continue;
+		}
+
+		const startTime = parseSrtTimestamp({ input: rawStart });
+		const endTime = parseSrtTimestamp({ input: rawEnd });
+		const duration = endTime - startTime;
+
+		if (
+			!Number.isFinite(startTime) ||
+			!Number.isFinite(endTime) ||
+			duration <= 0
+		) {
+			skippedCueCount += 1;
+			continue;
+		}
+
+		cues.push({
+			text,
+			startTime,
+			duration,
+		});
+	}
+
+	return {
+		captions: cues,
+		skippedCueCount,
+		warnings: [],
+	};
+}
+
+function parseSrtTimestamp({ input }: { input: string }): number {
+	const normalized = input.trim().replace(",", ".");
+	const match = normalized.match(/^(\d{2}):(\d{2}):(\d{2})\.(\d{1,3})$/);
+	if (!match) {
+		return Number.NaN;
+	}
+
+	const [, hours, minutes, seconds, milliseconds] = match;
+	const parsedHours = Number.parseInt(hours, 10);
+	const parsedMinutes = Number.parseInt(minutes, 10);
+	const parsedSeconds = Number.parseInt(seconds, 10);
+	const parsedMilliseconds = Number.parseInt(milliseconds.padEnd(3, "0"), 10);
+
+	return (
+		parsedHours * 3600 +
+		parsedMinutes * 60 +
+		parsedSeconds +
+		parsedMilliseconds / 1000
+	);
+}