```ts
export function parseSemver(version: string): { major: number; minor: number; patch: number; prerelease: string | null; build: string | null } {
  if (!/^\d+\.\d+(\.\d+)?(-[\w-]+)?$/.test(version)) {
    throw new Error('Invalid semantic version format');
  }

  const parts = version.split('.');
  const major = parseInt(parts[0], 10);
  const minor = parseInt(parts[1], 10);
  const patch = parseInt(parts[2] || '0', 10);

  let prerelease: string | null = null;
  if (parts.length > 3 && parts[3].startsWith('-')) {
    prerelease = parts.slice(3).join('.');
  }

  let build: string | null = null;
  if (parts.length > 4 && parts[4].startsWith('+')) {
    build = parts.slice(4).join('');
  }

  return { major, minor, patch, prerelease, build };
}
```