// Copyright © 2016–2020 University of Malta

// 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::{ext::xmpfr, Float};
use core::{
    cmp::Ordering,
    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},
    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][`AsRef`]&lt;[Float][`Float`]&gt;</code> which is
    /// provided for [`OrdFloat`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rug::{float::OrdFloat, 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);
    /// ```
    ///
    /// [`AsRef`]: https://doc.rust-lang.org/nightly/core/convert/trait.AsRef.html
    /// [`Float`]: ../struct.Float.html
    /// [`OrdFloat`]: struct.OrdFloat.html
    #[inline]
    pub fn as_float(&self) -> &Float {
        &self.inner
    }

    /// Extracts the underlying [`Float`].
    ///
    /// The same result can be obtained using the implementation of
    /// <code>[AsMut][`AsMut`]&lt;[Float][`Float`]&gt;</code> which is
    /// provided for [`OrdFloat`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// use rug::{float::OrdFloat, 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);
    /// ```
    ///
    /// [`AsMut`]: https://doc.rust-lang.org/nightly/core/convert/trait.AsMut.html
    /// [`Float`]: ../struct.Float.html
    /// [`OrdFloat`]: struct.OrdFloat.html
    #[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 {
        let s = &self.inner;
        let o = &other.inner;
        if s.is_zero() && o.is_zero() {
            s.is_sign_positive().cmp(&o.is_sign_positive())
        } else {
            match (s.is_nan(), o.is_nan()) {
                (false, true) => {
                    if o.is_sign_negative() {
                        Ordering::Greater
                    } else {
                        Ordering::Less
                    }
                }
                (true, false) => {
                    if o.is_sign_negative() {
                        Ordering::Less
                    } else {
                        Ordering::Greater
                    }
                }
                (true, true) => s.is_sign_positive().cmp(&o.is_sign_positive()),
                (false, false) => xmpfr::cmp(s, o),
            }
        }
    }
}

impl PartialEq for OrdFloat {
    #[inline]
    fn eq(&self, other: &OrdFloat) -> bool {
        let s = &self.inner;
        let o = &other.inner;
        if s.is_nan() {
            o.is_nan() && s.is_sign_negative() == o.is_sign_negative()
        } else if s.is_zero() {
            o.is_zero() && s.is_sign_negative() == o.is_sign_negative()
        } else {
            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()
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        float::{self, FreeCache, OrdFloat, Special},
        ops::NegAssign,
        Assign, Float,
    };
    use core::hash::{Hash, Hasher};
    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!(
            &f as *const Float as *const OrdFloat,
            f.as_ord() as *const OrdFloat
        );
        assert_eq!(
            &f as *const Float as *const OrdFloat,
            AsRef::<OrdFloat>::as_ref(&f) as *const OrdFloat
        );
        let mut o = OrdFloat::from(f);
        assert_eq!(
            &o as *const OrdFloat as *const Float,
            o.as_float() as *const Float
        );
        assert_eq!(
            &o as *const OrdFloat as *const Float,
            AsRef::<Float>::as_ref(&o) as *const Float
        );
        assert_eq!(
            &mut o as *mut OrdFloat as *mut Float,
            o.as_float_mut() as *mut Float
        );
        assert_eq!(
            &mut o as *mut OrdFloat as *mut Float,
            AsMut::<Float>::as_mut(&mut o) as *mut Float
        );
    }
}