Implement hostname-restricted web crawler

Implement a single-threaded web crawler that, given a starting URL startUrl and an interface getUrls(url) that returns all hyperlinks on the page at url, returns the set of all unique pages reachable whose hostname exactly matches the hostname of startUrl. Requirements: do not fetch pages outside the starting hostname; avoid duplicate fetches and infinite loops (handle cycles); choose BFS or DFS and justify your choice; state time and space complexity; explain how you parse the hostname from a URL; describe basic error handling for failed requests.