Clean up main function

[sts10]

As noted in #14, I don't like how the main function looks right now. Specifically, how I need to have one variable for the built-in list and another for the user-submitted "custom" list.

phraze/src/main.rs

Lines 104 to 161 in d530eba

	// We need two different variables here, one for a user-inputted list and another for
	// the built-in list (whether chosen or the default). This is because we use different
	// variable types for each case.
	let (custom_list, built_in_list) = match opt.custom_list_file_path {
	Some(custom_list_file_path) => (Some(read_in_custom_list(&custom_list_file_path)?), None),
	None => (None, Some(fetch_list(opt.list_choice))),
	};
	// If a "custom_list" was given by the user, we're going to use that list.
	// Otherwise we use the built-in list (a default list if the user didn't choose one).
	// To get the length of the list we're going to use, we need to check if a
	// custom_list was given.
	let list_length = match custom_list {
	Some(ref custom_list) => custom_list.len(),
	None => built_in_list.unwrap().len(), // pretty sure we're safe to unwrap here...
	};
	// Since user can define a minimum entropy, we might have to do a little math to
	// figure out how many words we need to include in this passphrase.
	let number_of_words_to_put_in_passphrase = calculate_number_words_needed(
	opt.number_of_words,
	opt.minimum_entropy,
	opt.strength_count,
	list_length,
	);
	// If user enabled verbose option
	if opt.verbose {
	// print entropy information, but use eprint to only print it
	// to the terminal
	print_entropy(
	number_of_words_to_put_in_passphrase,
	list_length,
	opt.n_passphrases,
	);
	}
	// Now we can (finally) generate and print some number of passphrases
	for _ in 0..opt.n_passphrases {
	// Again, we have more code than we should because of this pesky list type situation...
	let passphrase = match (&custom_list, built_in_list) {
	(Some(ref custom_list), _) => generate_passphrase(
	number_of_words_to_put_in_passphrase,
	&opt.separator,
	opt.title_case,
	custom_list,
	),
	(None, Some(built_in_list)) => generate_passphrase(
	number_of_words_to_put_in_passphrase,
	&opt.separator,
	opt.title_case,
	built_in_list,
	),
	(None, None) => return Err("List selection error!".to_string()),
	};
	println!("{}", passphrase);
	}

Any ideas on how to refactor this would be appreciated!

For example, is there a way to make a single Type or Struct that can take both a &' static[& 'static str] and a Vec<String>?