fix(youtube): parse mpv EDL stream URLs with byte-length guards (#134)

2026-08-14 13:55:55 -07:00 · 2026-07-02 01:37:37 -07:00
parent 359cb0a301
commit 36a3704815
9 changed files with 312 additions and 46 deletions
@@ -0,0 +1,195 @@
+const EDL_URI_PREFIX = 'edl://';
+
+const BYTE_COMMA = ','.charCodeAt(0);
+const BYTE_CR = '\r'.charCodeAt(0);
+const BYTE_EQUALS = '='.charCodeAt(0);
+const BYTE_EXCLAMATION = '!'.charCodeAt(0);
+const BYTE_LF = '\n'.charCodeAt(0);
+const BYTE_PERCENT = '%'.charCodeAt(0);
+const BYTE_SEMICOLON = ';'.charCodeAt(0);
+
+function isDigitByte(value: number | undefined): value is number {
+  return value !== undefined && value >= 48 && value <= 57;
+}
+
+function isEntrySeparator(value: number | undefined): boolean {
+  return value === BYTE_SEMICOLON || value === BYTE_LF || value === BYTE_CR;
+}
+
+function isParamSeparator(value: number | undefined): boolean {
+  return value === BYTE_COMMA || isEntrySeparator(value);
+}
+
+function decodeBytes(buffer: Buffer, start: number, end: number): string {
+  return buffer.subarray(start, end).toString('utf8');
+}
+
+function isHttpUrl(value: string): boolean {
+  return /^https?:\/\//i.test(value);
+}
+
+function toEdlDataBuffer(source: string): Buffer {
+  const data = source.startsWith(EDL_URI_PREFIX) ? source.slice(EDL_URI_PREFIX.length) : source;
+  return Buffer.from(data, 'utf8');
+}
+
+function parseLengthGuardedValue(
+  buffer: Buffer,
+  position: number,
+): { value: string; end: number } | null {
+  if (buffer[position] !== BYTE_PERCENT) {
+    return null;
+  }
+
+  let cursor = position + 1;
+  if (!isDigitByte(buffer[cursor])) {
+    return null;
+  }
+
+  let byteLength = 0;
+  while (true) {
+    const digit = buffer[cursor];
+    if (!isDigitByte(digit)) {
+      break;
+    }
+    byteLength = byteLength * 10 + (digit - 48);
+    cursor += 1;
+  }
+
+  if (buffer[cursor] !== BYTE_PERCENT) {
+    return null;
+  }
+
+  const valueStart = cursor + 1;
+  const valueEnd = valueStart + byteLength;
+  if (valueEnd > buffer.length) {
+    return null;
+  }
+
+  return {
+    value: decodeBytes(buffer, valueStart, valueEnd),
+    end: valueEnd,
+  };
+}
+
+function skipEntrySeparators(buffer: Buffer, position: number): number {
+  let cursor = position;
+  while (cursor < buffer.length && isEntrySeparator(buffer[cursor])) {
+    cursor += 1;
+  }
+  return cursor;
+}
+
+function skipEntry(buffer: Buffer, position: number): number {
+  let cursor = position;
+  while (cursor < buffer.length) {
+    const guardedValue = parseLengthGuardedValue(buffer, cursor);
+    if (guardedValue) {
+      cursor = guardedValue.end;
+      continue;
+    }
+    if (isEntrySeparator(buffer[cursor])) {
+      break;
+    }
+    cursor += 1;
+  }
+  return cursor;
+}
+
+function parseRawValue(buffer: Buffer, position: number): { value: string; end: number } {
+  let cursor = position;
+  while (
+    cursor < buffer.length &&
+    !isParamSeparator(buffer[cursor]) &&
+    buffer[cursor] !== BYTE_EXCLAMATION
+  ) {
+    cursor += 1;
+  }
+  return {
+    value: decodeBytes(buffer, position, cursor),
+    end: cursor,
+  };
+}
+
+function parseParamValue(buffer: Buffer, position: number): { value: string; end: number } {
+  return parseLengthGuardedValue(buffer, position) ?? parseRawValue(buffer, position);
+}
+
+function parseOptionalParamName(
+  buffer: Buffer,
+  position: number,
+): { name: string | null; valueStart: number } {
+  let cursor = position;
+  while (
+    cursor < buffer.length &&
+    !isParamSeparator(buffer[cursor]) &&
+    buffer[cursor] !== BYTE_PERCENT &&
+    buffer[cursor] !== BYTE_EXCLAMATION
+  ) {
+    if (buffer[cursor] === BYTE_EQUALS) {
+      return {
+        name: decodeBytes(buffer, position, cursor),
+        valueStart: cursor + 1,
+      };
+    }
+    cursor += 1;
+  }
+
+  return { name: null, valueStart: position };
+}
+
+function parseSegmentEntry(buffer: Buffer, position: number): { urls: string[]; end: number } {
+  const urls: string[] = [];
+  let cursor = position;
+  let unnamedParamIndex = 0;
+
+  while (cursor < buffer.length && !isEntrySeparator(buffer[cursor])) {
+    const { name, valueStart } = parseOptionalParamName(buffer, cursor);
+    const value = parseParamValue(buffer, valueStart);
+    const lowerName = name?.toLowerCase() ?? null;
+    const isFileParam = lowerName === 'file' || (lowerName === null && unnamedParamIndex === 0);
+
+    if (isFileParam && isHttpUrl(value.value)) {
+      urls.push(value.value);
+    }
+
+    if (lowerName === null) {
+      unnamedParamIndex += 1;
+    }
+
+    cursor = value.end;
+    if (buffer[cursor] === BYTE_COMMA) {
+      cursor += 1;
+      continue;
+    }
+    if (!isEntrySeparator(buffer[cursor])) {
+      cursor = skipEntry(buffer, cursor);
+    }
+  }
+
+  return { urls, end: cursor };
+}
+
+export function extractFileUrlsFromMpvEdlSource(source: string): string[] {
+  const buffer = toEdlDataBuffer(source);
+  const urls: string[] = [];
+  let cursor = 0;
+
+  while (cursor < buffer.length) {
+    cursor = skipEntrySeparators(buffer, cursor);
+    if (cursor >= buffer.length) {
+      break;
+    }
+
+    if (buffer[cursor] === BYTE_EXCLAMATION) {
+      cursor = skipEntry(buffer, cursor);
+      continue;
+    }
+
+    const segment = parseSegmentEntry(buffer, cursor);
+    urls.push(...segment.urls);
+    cursor = segment.end;
+  }
+
+  return urls;
+}