```typescript
export function parseSemver(version: string): { major: number; minor: number; patch: number; prerelease: string | null; build: string | null } {
  const regex = /^(\d+)\.(\d+)\.(\d+)(?:-(\w+))?(?:\+(\w+))?$/;
  const match = version.match(regex);

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

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

  // Convert to numbers
  const parsedMajor = parseInt(major, 10);
  const parsedMinor = parseInt(minor, 10);
  const parsedPatch = parseInt(patch, 10);

  // Validate numeric parts
  if (isNaN(parsedMajor) || isNaN(parsedMinor) || isNaN(parsedPatch)) {
    throw new Error(`Invalid semver format: ${version}`);
  }

  return { major: parsedMajor, minor: parsedMinor, patch: parsedPatch, prerelease, build };
}
```