Funeral service newbie

I could not recall an instance in the past that I have to go to a funeral wake/service.  When my father and paternal grandmother passed, I was here in the States and did not go home for the funeral.  I was still a toddler when my paternal grandfather passed.  I was a kid shipped to my dad when my maternal grandmother passed.   When my dear aunt and uncle passed, I was also here in the States and was unable to go home for their wake.  I did not know anybody who passed away that necessitate my going to a funeral wake/service here in the States.    So before the funeral of my friend Jasmine, I did not have the experience on how to dress for a funeral wake/service.  When I went to my friend Jasmine's funeral service, I decided to wear jeans, gym shoe and a dark casual light coat.  Upon arriving at the funeral home, I came to the realization that I was underdressed.  Every man at the funeral service were dressed in a dark suit.  Some wore a tie and others did not but they all wore dress pants, sport coat and formal shoes.  It did not occur to me to dress formally.  It did not occur to me to search my memory on what I have seen in the movie/TV on how men dress for funeral.  I was just a friend paying my last respect to my deceased friend and had no special role to play in the funeral service so I just dressed casually.  And  even if I knew that I needed a suit for a funeral service, I don't think I have one to use anyway.  I got rid of my out of style suits and don't own a dark suit.  I would have to resort to wearing a dark dress pant, dark dress shirt and dark leather shoe in lieu of a suit.