use std::collections::HashSet;

#[derive(Clone, Debug, Copy, Hash, Eq, PartialEq)]
pub enum CellValue {
    One,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Eight,
    Nine,
}

pub struct Cell {
    value: Option<CellValue>,
    candidates: HashSet<CellValue>,
}

impl Cell {
    pub fn value(&self) -> Option<CellValue> {
        self.value
    }

    pub fn set_value(&mut self, value: CellValue) {
        self.value = Some(value);
    }

    pub fn candidates(&self) -> HashSet<CellValue> {
        self.candidates.clone()
    }

    pub fn remove_candidate(&mut self, value: CellValue) {
        self.candidates.remove(&value);
    }
}

impl Default for Cell {
    fn default() -> Cell {
        let mut candidates = HashSet::new();
        candidates.insert(CellValue::One);
        candidates.insert(CellValue::Two);
        candidates.insert(CellValue::Three);
        candidates.insert(CellValue::Four);
        candidates.insert(CellValue::Five);
        candidates.insert(CellValue::Six);
        candidates.insert(CellValue::Seven);
        candidates.insert(CellValue::Eight);
        candidates.insert(CellValue::Nine);
        Cell {
            value: None,
            candidates,
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use assertables::{assert_contains, assert_not_contains};

    #[test]
    fn inits_empty() {
        let cell = Cell::default();
        assert!(cell.value().is_none());
    }

    #[test]
    fn has_all_candidates() {
        let cell = Cell::default();
        assert_contains!(cell.candidates(), &CellValue::One);
        assert_contains!(cell.candidates(), &CellValue::Two);
        assert_contains!(cell.candidates(), &CellValue::Three);
        assert_contains!(cell.candidates(), &CellValue::Four);
        assert_contains!(cell.candidates(), &CellValue::Five);
        assert_contains!(cell.candidates(), &CellValue::Six);
        assert_contains!(cell.candidates(), &CellValue::Seven);
        assert_contains!(cell.candidates(), &CellValue::Eight);
        assert_contains!(cell.candidates(), &CellValue::Nine);
    }

    #[test]
    fn removed_candidate_is_gone() {
        let mut cell = Cell::default();
        cell.remove_candidate(CellValue::One);
        assert_not_contains!(cell.candidates(), &CellValue::One);
        assert_contains!(cell.candidates(), &CellValue::Two);
        assert_contains!(cell.candidates(), &CellValue::Three);
        assert_contains!(cell.candidates(), &CellValue::Four);
        assert_contains!(cell.candidates(), &CellValue::Five);
        assert_contains!(cell.candidates(), &CellValue::Six);
        assert_contains!(cell.candidates(), &CellValue::Seven);
        assert_contains!(cell.candidates(), &CellValue::Eight);
        assert_contains!(cell.candidates(), &CellValue::Nine);
    }
}