Complex sentence: Affleck co ‑ wrote the screenplay, based on the book by Dennis Lehane, with childhood friend Aaron Stockard, having first mentioned his intention to adapt the story in 2003.
Split into simpler sentences: Affleck co ‑ wrote the screenplay, based on the book by Dennis Lehane, with childhood friend Aaron Stockard. Affleck first mentioned his intention to adapt the story in 2003.