```typescript
export function parseSemver(version: string): { major: number; minor: number; patch: number; prerelease: string | null; build: string | null } {
  const regex = /^(\d{1,})\.(\d{1,})\.(\d{1,})(?:-(.+?))?(?:\+(.+?))?$/;
  const match = version.match(regex);
  if (!match) {
    throw new Error('Invalid semver string');
  }
  return {
    major: parseInt(match[1], 10),
    minor: parseInt(match[2], 10),
    patch: parseInt(match[3], 10),
    prerelease: match[4] || null,
    build: match[5] || null
  };
}
```