// Copyright © 2016–2025 Trevor Spiteri

// This program is free software: you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option) any
// later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
// details.
//
// You should have received a copy of the GNU Lesser General Public License and
// a copy of the GNU General Public License along with this program. If not, see
// <https://www.gnu.org/licenses/>.

use crate::Float;
use core::cmp::Ordering;
use core::hash::{Hash, Hasher};

/**
A float that supports total ordering and hashing.

Negative zero is ordered as less than positive zero. Negative NaN is
ordered as less than negative infinity, while positive NaN is ordered
as greater than positive infinity. Comparing two negative NaNs or two
positive NaNs produces equality.

# Examples

```rust
use core::cmp::Ordering;
use rug::float::{OrdFloat, Special};
use rug::Float;

let pos_nan_f = Float::with_val(53, Special::Nan);
let pos_inf_f = Float::with_val(53, Special::Infinity);
let pos_zero_f = Float::with_val(53, Special::Zero);
let neg_zero_f = Float::with_val(53, Special::NegZero);
let neg_inf_f = Float::with_val(53, Special::NegInfinity);
let neg_nan_f = Float::with_val(53, -&pos_nan_f);
let pos_nan = OrdFloat::from(pos_nan_f);
let pos_inf = OrdFloat::from(pos_inf_f);
let pos_zero = OrdFloat::from(pos_zero_f);
let neg_zero = OrdFloat::from(neg_zero_f);
let neg_inf = OrdFloat::from(neg_inf_f);
let neg_nan = OrdFloat::from(neg_nan_f);

assert_eq!(pos_nan.cmp(&pos_nan), Ordering::Equal);
assert_eq!(neg_nan.cmp(&neg_nan), Ordering::Equal);
assert_eq!(neg_nan.cmp(&pos_nan), Ordering::Less);

assert_eq!(pos_nan.cmp(&pos_inf), Ordering::Greater);
assert_eq!(neg_nan.cmp(&neg_inf), Ordering::Less);

assert_eq!(pos_zero.cmp(&neg_zero), Ordering::Greater);
```
*/
#[derive(Clone, Debug)]
#[repr(transparent)]
pub struct OrdFloat {
    inner: Float,
}

static_assert_same_layout!(OrdFloat, Float);

impl OrdFloat {
    /// Extracts the underlying [`Float`].
    ///
    /// The same result can be obtained using the implementation of
    /// <code>[AsRef]\<[Float]></code> which is provided for
    /// [`OrdFloat`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rug::float::OrdFloat;
    /// use rug::Float;
    /// let f = Float::with_val(53, 1.5);
    /// let ord = OrdFloat::from(f);
    /// let f_ref = ord.as_float();
    /// assert_eq!(f_ref.to_f64(), 1.5);
    /// ```
    #[inline]
    pub const fn as_float(&self) -> &Float {
        &self.inner
    }

    /// Extracts the underlying [`Float`].
    ///
    /// The same result can be obtained using the implementation of
    /// <code>[AsMut]\<[Float]></code> which is provided for
    /// [`OrdFloat`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rug::float::OrdFloat;
    /// use rug::Float;
    /// let f = Float::with_val(53, -1.5);
    /// let mut ord = OrdFloat::from(f);
    /// ord.as_float_mut().abs_mut();
    /// assert_eq!(ord.as_float().to_f64(), 1.5);
    /// ```
    #[inline]
    pub fn as_float_mut(&mut self) -> &mut Float {
        &mut self.inner
    }
}

impl Hash for OrdFloat {
    fn hash<H: Hasher>(&self, state: &mut H) {
        let float = &self.inner;
        float.inner().sign.hash(state);
        float.inner().exp.hash(state);

        let slice = float.inner_data();
        //   * Do not hash the least significant zero limbs, as
        //     equal numbers with different precisions must have
        //     equal hashes.
        //   * MPFR keeps unused bits set to zero, so there is no
        //     need to mask least significant limb.
        if let Some(first) = slice.iter().position(|&limb| limb != 0) {
            slice[first..].hash(state);
        }
    }
}

impl Eq for OrdFloat {}

impl Ord for OrdFloat {
    #[inline]
    fn cmp(&self, other: &OrdFloat) -> Ordering {
        self.inner.total_cmp(&other.inner)
    }
}

impl PartialEq for OrdFloat {
    #[inline]
    fn eq(&self, other: &OrdFloat) -> bool {
        let s = &self.inner;
        let o = &other.inner;
        if s.is_sign_negative() != o.is_sign_negative() {
            return false;
        }
        let o_nan = o.is_nan();
        if s.is_nan() {
            return o_nan;
        }
        if o_nan {
            return false;
        }
        // we have already handled zeros with different sign and NaNs
        s.eq(o)
    }
}

impl PartialOrd for OrdFloat {
    #[inline]
    fn partial_cmp(&self, other: &OrdFloat) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl From<Float> for OrdFloat {
    #[inline]
    fn from(src: Float) -> Self {
        OrdFloat { inner: src }
    }
}

impl From<OrdFloat> for Float {
    #[inline]
    fn from(src: OrdFloat) -> Self {
        src.inner
    }
}

impl AsRef<Float> for OrdFloat {
    #[inline]
    fn as_ref(&self) -> &Float {
        self.as_float()
    }
}

impl AsMut<Float> for OrdFloat {
    #[inline]
    fn as_mut(&mut self) -> &mut Float {
        self.as_float_mut()
    }
}

#[allow(clippy::eq_op)]
#[cfg(test)]
mod tests {
    use crate::float;
    use crate::float::{FreeCache, OrdFloat, Special};
    use crate::ops::NegAssign;
    use crate::{Assign, Float};
    use core::hash::{Hash, Hasher};
    use core::ptr;
    use std::collections::hash_map::DefaultHasher;

    fn calculate_hash<T: Hash>(t: &T) -> u64 {
        let mut s = DefaultHasher::new();
        t.hash(&mut s);
        s.finish()
    }

    #[test]
    fn check_zero() {
        let p = Float::with_val(53, Special::Zero);
        let n = Float::with_val(53, Special::NegZero);
        assert_eq!(p, n);
        let ord_p = p.as_ord();
        let ord_n = n.as_ord();
        assert_eq!(ord_p, ord_p);
        assert_eq!(ord_n, ord_n);
        assert_eq!(calculate_hash(ord_p), calculate_hash(ord_p));
        assert_eq!(calculate_hash(ord_n), calculate_hash(ord_n));
        assert_ne!(ord_p, ord_n);
        assert_ne!(calculate_hash(ord_p), calculate_hash(ord_n));

        float::free_cache(FreeCache::All);
    }

    fn hash(f: &OrdFloat) -> u64 {
        let mut hasher = DefaultHasher::new();
        f.hash(&mut hasher);
        hasher.finish()
    }

    #[test]
    fn check_hash_different_prec() {
        let mut f = Float::new(53);
        let mut g = Float::new(5301);
        assert_eq!(f, g);
        assert_eq!(f.as_ord(), g.as_ord());
        assert_eq!(hash(f.as_ord()), hash(g.as_ord()));

        g.neg_assign();
        assert_eq!(f, g);
        assert_ne!(f.as_ord(), g.as_ord());
        assert_ne!(hash(f.as_ord()), hash(g.as_ord()));

        f.assign(23.5);
        g.assign(23.5);
        assert_eq!(f, g);
        assert_eq!(f.as_ord(), g.as_ord());
        assert_eq!(hash(f.as_ord()), hash(g.as_ord()));

        g.neg_assign();
        assert_ne!(f, g);
        assert_ne!(f.as_ord(), g.as_ord());
        assert_ne!(hash(f.as_ord()), hash(g.as_ord()));

        f.assign(Special::Nan);
        g.assign(Special::Nan);
        assert_ne!(f, g);
        assert_eq!(f.as_ord(), g.as_ord());
        assert_eq!(hash(f.as_ord()), hash(g.as_ord()));

        g.neg_assign();
        assert_ne!(f, g);
        assert_ne!(f.as_ord(), g.as_ord());
        assert_ne!(hash(f.as_ord()), hash(g.as_ord()));
    }

    #[test]
    fn check_refs() {
        let f = Float::with_val(53, 23.5);
        assert_eq!(
            ptr::addr_of!(f).cast::<OrdFloat>(),
            f.as_ord() as *const OrdFloat
        );
        assert_eq!(
            ptr::addr_of!(f).cast::<OrdFloat>(),
            AsRef::<OrdFloat>::as_ref(&f) as *const OrdFloat
        );
        let mut o = OrdFloat::from(f);
        assert_eq!(
            ptr::addr_of!(o).cast::<Float>(),
            o.as_float() as *const Float
        );
        assert_eq!(
            ptr::addr_of!(o).cast::<Float>(),
            AsRef::<Float>::as_ref(&o) as *const Float
        );
        assert_eq!(
            ptr::addr_of_mut!(o).cast::<Float>(),
            o.as_float_mut() as *mut Float
        );
        assert_eq!(
            ptr::addr_of_mut!(o).cast::<Float>(),
            AsMut::<Float>::as_mut(&mut o) as *mut Float
        );
    }
}
