add: parser srt files

src/utils/subtitles/parseSrt.ts

@@ -0,0 +1,62 @@
+export interface SubtitleCue {
+  index: number;
+  startTime: number;
+  endTime: number;
+  text: string;
+}
+
+const SRT_TIME_SEPARATOR = " --> ";
+const SRT_TIME_PATTERN = /^(\d{2}):(\d{2}):(\d{2}),(\d{3})$/;
+
+export function parseSrt(srtContent: string): SubtitleCue[] {
+  return srtContent
+    .replace(/^\uFEFF/, "")
+    .replace(/\r/g, "")
+    .trim()
+    .split(/\n{2,}/)
+    .map(parseSrtBlock)
+    .filter((cue): cue is SubtitleCue => cue !== null);
+}
+
+function parseSrtBlock(block: string): SubtitleCue | null {
+  const lines = block
+    .split("\n")
+    .map((line) => line.trim())
+    .filter(Boolean);
+
+  if (lines.length < 3) return null;
+
+  const index = Number(lines[0]);
+  if (!Number.isInteger(index)) return null;
+
+  const [start, end] = lines[1]?.split(SRT_TIME_SEPARATOR) ?? [];
+  if (!start || !end) return null;
+
+  const startTime = parseSrtTime(start);
+  const endTime = parseSrtTime(end);
+  if (startTime === null || endTime === null || endTime <= startTime) {
+    return null;
+  }
+
+  return {
+    index,
+    startTime,
+    endTime,
+    text: lines.slice(2).join("\n"),
+  };
+}
+
+function parseSrtTime(value: string): number | null {
+  const match = value.match(SRT_TIME_PATTERN);
+  if (!match) return null;
+
+  const [, hours, minutes, seconds, milliseconds] = match;
+  if (!hours || !minutes || !seconds || !milliseconds) return null;
+
+  return (
+    Number(hours) * 3600 +
+    Number(minutes) * 60 +
+    Number(seconds) +
+    Number(milliseconds) / 1000
+  );
+}