```ts
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.-]+))?(?:\+([^-.]+))?$/);
  
  if (!match) {
    throw new Error("Invalid semantic version format");
  }

  const [_, major, minor, patch, prerelease, build] = match;

  // Check if all parts are valid digits
  if (!/\d+$/.test(major) || !/\d+$/.test(minor) || !/\d+$/.test(patch)) {
    throw new Error("Invalid numeric version part");
  }

  return {
    major: parseInt(major, 10),
    minor: parseInt(minor, 10),
    patch: parseInt(patch, 10),
    prerelease,
    build
  };
}
```