feat: add ASS subtitle cue parser

src/core/services/subtitle-cue-parser.ts

@@ -53,11 +53,76 @@ export function parseSrtCues(content: string): SubtitleCue[] {
   return cues;
 }
 
-// Stub exports — will be implemented in subsequent tasks
-export function parseAssCues(_content: string): SubtitleCue[] {
-  throw new Error('parseAssCues not yet implemented');
+const ASS_OVERRIDE_TAG_PATTERN = /\{[^}]*\}/g;
+
+const ASS_TIMING_PATTERN = /^(\d+):(\d{2}):(\d{2})\.(\d{1,2})$/;
+
+function parseAssTimestamp(raw: string): number | null {
+  const match = ASS_TIMING_PATTERN.exec(raw.trim());
+  if (!match) {
+    return null;
+  }
+  const hours = Number(match[1]);
+  const minutes = Number(match[2]);
+  const seconds = Number(match[3]);
+  const centiseconds = Number(match[4]!.padEnd(2, '0'));
+  return hours * 3600 + minutes * 60 + seconds + centiseconds / 100;
 }
 
+export function parseAssCues(content: string): SubtitleCue[] {
+  const cues: SubtitleCue[] = [];
+  const lines = content.split(/\r?\n/);
+  let inEventsSection = false;
+
+  for (const line of lines) {
+    const trimmed = line.trim();
+
+    if (trimmed.startsWith('[') && trimmed.endsWith(']')) {
+      inEventsSection = trimmed.toLowerCase() === '[events]';
+      continue;
+    }
+
+    if (!inEventsSection) {
+      continue;
+    }
+
+    if (!trimmed.startsWith('Dialogue:')) {
+      continue;
+    }
+
+    // Split on first 9 commas (ASS v4+ has 10 fields; last is Text which can contain commas)
+    const afterPrefix = trimmed.slice('Dialogue:'.length);
+    const fields: string[] = [];
+    let remaining = afterPrefix;
+    for (let fieldIndex = 0; fieldIndex < 9; fieldIndex += 1) {
+      const commaIndex = remaining.indexOf(',');
+      if (commaIndex < 0) {
+        break;
+      }
+      fields.push(remaining.slice(0, commaIndex));
+      remaining = remaining.slice(commaIndex + 1);
+    }
+
+    if (fields.length < 9) {
+      continue;
+    }
+
+    const startTime = parseAssTimestamp(fields[1]!);
+    const endTime = parseAssTimestamp(fields[2]!);
+    if (startTime === null || endTime === null) {
+      continue;
+    }
+
+    const rawText = remaining.replace(ASS_OVERRIDE_TAG_PATTERN, '').trim();
+    if (rawText) {
+      cues.push({ startTime, endTime, text: rawText });
+    }
+  }
+
+  return cues;
+}
+
+// Stub export — will be implemented in Task 6
 export function parseSubtitleCues(_content: string, _filename: string): SubtitleCue[] {
   throw new Error('parseSubtitleCues not yet implemented');
 }