def handle_block(new_block):
    if not is_new_head(new_block):
        return
	
    set_head(new_block)
    if --casper-fork-choice is on:
        check_and_finalize_new_checkpoint(new_block)

		
def is_new_head(new_block):
    if --casper-fork-choice is off
        return new_block.total_difficuty > current_head.total_difficulty

    if new_block is in --exclude list or one of its descendants 
        return false

    # don't revert finalized blocks
    if db.last_finalized_block is not in new_block.ancestors:
        return false

    return highest_justified_epoch(new_block) * 10**40 + new_block.total_difficuty > 
        highest_justified_epoch(current_head) * 10**40 + current_head.total_difficulty

	
def highest_justified_epoch(block):
    casper = block.post_state.casper_contract
    return casper.highest_justified_epoch(NON_REVERT_MIN_DEPOSITS)

		
def check_and_finalize_new_checkpoint(new_block):
    casper = new_block.post_state.casper_contract

    # If no finalized blocks, db.last_finalized_epoch initialized to -1

    finalized_epoch = casper.highest_finalized_epoch(NON_REVERT_MIN_DEPOSITS)
    if finalized_epoch > db.last_finalized_epoch:
        finalized_hash = casper.checkpoint_hashes(finalized_epoch)
		
        # ensure not trivially finalized
        if finalized_hash == b'\x00' * 32:
            return
		
        db.last_finalized_epoch = finalized_epoch
        db.last_finalized_block = finalized_hash