```ts
/**
 * Parse a semantic version string.
 *
 * @param version The semantic version string to parse.
 */
export function parseSemver(version: string): {
  major: number;
  minor: number;
  patch: number;
  prerelease: string | null;
  build: string | null;
} {
  const match = version.match(/^(\d+)\.(\d+)\.(\d+)(?:-([a-zA-Z0-9_-]+))?(?:\+([a-zA-Z0-9_-]+))?$/);

  if (!match) {
    throw new Error(`Invalid semver: ${version}`);
  }

  const [, major, minor, patch] = match.slice(1).map(Number);
  const prerelease = match[5];
  const build = match[6];

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