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use {
    crate::types::*,
    std::{
        cmp::Ordering,
        fmt,
        ops::{Index, IndexMut, Range, RangeFrom},
        slice::Iter,
    },
};

/// API for Clause, providing literal accessors.
pub trait ClauseIF {
    /// return true if it contains no literals; a clause after unit propagation.
    fn is_empty(&self) -> bool;
    /// return an iterator over its literals.
    fn iter(&self) -> Iter<'_, Lit>;
    /// return the number of literals.
    fn len(&self) -> usize;
}

impl Default for Clause {
    fn default() -> Clause {
        Clause {
            lits: vec![],
            rank: 0,
            search_from: 2,
            reward: 0.0,
            flags: Flag::empty(),
        }
    }
}

impl Index<usize> for Clause {
    type Output = Lit;
    #[inline]
    fn index(&self, i: usize) -> &Lit {
        unsafe { self.lits.get_unchecked(i) }
    }
}

impl IndexMut<usize> for Clause {
    #[inline]
    fn index_mut(&mut self, i: usize) -> &mut Lit {
        unsafe { self.lits.get_unchecked_mut(i) }
    }
}

impl Index<Range<usize>> for Clause {
    type Output = [Lit];
    #[inline]
    fn index(&self, r: Range<usize>) -> &[Lit] {
        &self.lits[r]
    }
}

impl Index<RangeFrom<usize>> for Clause {
    type Output = [Lit];
    #[inline]
    fn index(&self, r: RangeFrom<usize>) -> &[Lit] {
        &self.lits[r]
    }
}

impl IndexMut<Range<usize>> for Clause {
    #[inline]
    fn index_mut(&mut self, r: Range<usize>) -> &mut [Lit] {
        &mut self.lits[r]
    }
}

impl IndexMut<RangeFrom<usize>> for Clause {
    #[inline]
    fn index_mut(&mut self, r: RangeFrom<usize>) -> &mut [Lit] {
        &mut self.lits[r]
    }
}

impl<'a> IntoIterator for &'a Clause {
    type Item = &'a Lit;
    type IntoIter = Iter<'a, Lit>;
    fn into_iter(self) -> Self::IntoIter {
        self.lits.iter()
    }
}

impl<'a> IntoIterator for &'a mut Clause {
    type Item = &'a Lit;
    type IntoIter = Iter<'a, Lit>;
    fn into_iter(self) -> Self::IntoIter {
        self.lits.iter()
    }
}

impl From<&Clause> for Vec<i32> {
    fn from(c: &Clause) -> Vec<i32> {
        c.lits.iter().map(|l| i32::from(*l)).collect::<Vec<i32>>()
    }
}

impl ClauseIF for Clause {
    fn is_empty(&self) -> bool {
        self.lits.is_empty()
    }
    fn iter(&self) -> Iter<'_, Lit> {
        self.lits.iter()
    }
    fn len(&self) -> usize {
        self.lits.len()
    }
}

impl FlagIF for Clause {
    fn is(&self, flag: Flag) -> bool {
        self.flags.contains(flag)
    }
    fn set(&mut self, f: Flag, b: bool) {
        self.flags.set(f, b);
    }
    fn turn_off(&mut self, flag: Flag) {
        self.flags.remove(flag);
    }
    fn turn_on(&mut self, flag: Flag) {
        self.flags.insert(flag);
    }
}

impl PartialEq for Clause {
    fn eq(&self, other: &Clause) -> bool {
        self == other
    }
}

impl Eq for Clause {}

impl PartialOrd for Clause {
    fn partial_cmp(&self, other: &Clause) -> Option<Ordering> {
        if self.rank < other.rank {
            Some(Ordering::Less)
        } else if other.rank < self.rank {
            Some(Ordering::Greater)
        } else if self.reward > other.reward {
            Some(Ordering::Less)
        } else if other.reward > self.reward {
            Some(Ordering::Greater)
        } else {
            Some(Ordering::Equal)
        }
    }
}

impl Ord for Clause {
    fn cmp(&self, other: &Clause) -> Ordering {
        if self.rank < other.rank {
            Ordering::Less
        } else if other.rank > self.rank {
            Ordering::Greater
        } else if self.reward > other.reward {
            Ordering::Less
        } else if other.reward > self.reward {
            Ordering::Greater
        } else {
            Ordering::Equal
        }
    }
}

impl fmt::Display for Clause {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let st = |flag, mes| if self.is(flag) { mes } else { "" };
        write!(
            f,
            "{{{:?}{}{}{}}}",
            i32s(&self.lits),
            st(Flag::LEARNT, ", learnt"),
            st(Flag::DEAD, ", dead"),
            st(Flag::ENQUEUED, ", enqueued"),
        )
    }
}