use shared::names::Site;

trait IndexArithmetic {
	fn index_add(self, length: usize, num: usize) -> usize;
	fn index_subtract(self, length: usize, num: usize) -> usize;
}

impl IndexArithmetic for usize {
	fn index_add(self, length: usize, num: usize) -> usize {
		if self > (length - 1) {
			return 0;
		}
		return self + num;
	}

	fn index_subtract(self, length: usize, num: usize) -> usize {
		match self.checked_sub(num) {
			Some(num) => num,
			None => length - 1,
		}
	}
}

pub fn previous_url(source_url: &String, names: &Vec<Site>) -> Option<String> {
	match names.iter().position(|r| &r.url == source_url) {
		Some(index) => Some(names[index.index_subtract(names.len(), 1)].url.clone()),
		None => None,
	}
}

pub fn next_url(source_url: &String, names: &Vec<Site>) -> Option<String> {
	// this is gay
	match names.iter().position(|r| &r.url == source_url) {
		Some(index) => Some(names[index.index_add(names.len(), 1)].url.clone()),
		None => None,
	}
}

pub fn previous_name(source_url: &String, names: &Vec<Site>) -> Option<String> {
	match names.iter().position(|r| &r.url == source_url) {
		Some(index) => match &names[index.index_subtract(names.len(), 1)].name {
			Some(name) => Some(name.clone()),
			None => previous_url(source_url, names),
		},
		None => None,
	}
}

pub fn next_name(source_url: &String, names: &Vec<Site>) -> Option<String> {
	match names.iter().position(|r| &r.url == source_url) {
		Some(index) => match &names[index.index_add(names.len(), 1)].name {
			Some(name) => Some(name.clone()),
			None => next_url(source_url, names),
		},
		None => None,
	}
}