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

  return {
    major: parseInt(match[1], 10),
    minor: parseInt(match[2], 10),
    patch: parseInt(match[3], 10),
    prerelease: match[4] ? match[4].toLowerCase() : null,
    build: match[5] ? match[5] : null
  };
}
```