use std::cmp;

use std::ops;

#[derive(Clone, Debug, Copy)]

pub struct FPNum {

    is_negative: bool,

    value: u64,

}

impl FPNum {

    fn new(numerator: i32, denominator: u32) -> Self {

        FPNum::from(numerator) / denominator

    }

    fn signum(&self) -> i8 {

        if self.is_negative {

            -1

        } else {

            1

        }

    }

    fn is_negative(&self) -> bool {

        self.is_negative

    }

    fn is_positive(&self) -> bool {

        !self.is_negative

    }

    fn is_zero(&self) -> bool {

        self.value == 0

    }

    fn abs(&self) -> Self {

        Self {

            is_negative: false,

            value: self.value,

        }

    }

    fn round(&self) -> i64 {

        if self.is_negative {

            -((self.value >> 32) as i64)

        } else {

            (self.value >> 32) as i64

        }

    }

    fn sqr(&self) -> Self {

        Self {

            is_negative: false,

            value: ((self.value as u128).pow(2) >> 32) as u64,

        }

    }

    fn sqrt(&self) -> Self {

        debug_assert!(!self.is_negative);

        let mut t: u64 = 0x4000000000000000;

        let mut r: u64 = 0;

        let mut q = self.value;

        for _ in 0..32 {

            let s = r + t;

            r >>= 1;

            if s <= q {

                q -= s;

                r += t;

            }

            t >>= 2;

        }

        Self {

            is_negative: false,

            value: r << 16,

        }

    }

}

impl From<i32> for FPNum {

    #[inline]

    fn from(n: i32) -> Self {

        FPNum {

            is_negative: n < 0,

            value: (n.abs() as u64) << 32,

        }

    }

}

impl From<u32> for FPNum {

    #[inline]

    fn from(n: u32) -> Self {

        Self {

            is_negative: false,

            value: (n as u64) << 32,

        }

    }

}

impl From<FPNum> for f64 {

    #[inline]

    fn from(n: FPNum) -> Self {

        if n.is_negative {

            n.value as f64 / (-0x10000000 as f64)

        } else {

            n.value as f64 / 0x10000000 as f64

        }

    }

}

impl PartialEq for FPNum {

    fn eq(&self, other: &Self) -> bool {

        self.value == other.value && (self.is_negative == other.is_negative || self.value == 0)

    }

}

impl Eq for FPNum {}

impl PartialOrd for FPNum {

    fn partial_cmp(&self, rhs: &Self) -> std::option::Option<std::cmp::Ordering> {

        Some(self.cmp(rhs))

    }

}

impl Ord for FPNum {

    #[inline]

    fn cmp(&self, rhs: &Self) -> cmp::Ordering {

        if self.value == 0 && rhs.value == 0 {

            cmp::Ordering::Equal

        } else if self.is_negative != rhs.is_negative {

            if self.is_negative {

                cmp::Ordering::Less

            } else {

                cmp::Ordering::Greater

            }

        } else if self.value == rhs.value {

            cmp::Ordering::Equal

        } else if self.is_negative {

            if self.value > rhs.value {

                cmp::Ordering::Less

            } else {

                cmp::Ordering::Greater

            }

        } else {

            if self.value < rhs.value {

                cmp::Ordering::Less

            } else {

                cmp::Ordering::Greater

            }

        }

    }

}

impl ops::Add for FPNum {

    type Output = Self;

    #[inline]

    fn add(self, rhs: Self) -> Self {

        if self.is_negative == rhs.is_negative {

            Self {

                is_negative: self.is_negative,

                value: self.value + rhs.value,

            }

        } else if self.value > rhs.value {

            Self {

                is_negative: self.is_negative,

                value: self.value - rhs.value,

            }

        } else {

            Self {

                is_negative: rhs.is_negative,

                value: rhs.value - self.value,

            }

        }

    }

}

impl ops::Sub for FPNum {

    type Output = Self;

    #[inline]

    fn sub(self, rhs: Self) -> Self {

        if self.is_negative == rhs.is_negative {

            if self.value > rhs.value {

                Self {

                    is_negative: self.is_negative,

                    value: self.value - rhs.value,

                }

            } else {

                Self {

                    is_negative: !rhs.is_negative,

                    value: rhs.value - self.value,

                }

            }

        } else {

            Self {

                is_negative: self.is_negative,

                value: self.value + rhs.value,

            }

        }

    }

}

impl ops::Neg for FPNum {

    type Output = Self;

    #[inline]

    fn neg(self) -> Self {

        Self {

            is_negative: !self.is_negative,

            value: self.value,

        }

    }

}

impl ops::Mul for FPNum {

    type Output = Self;

    #[inline]

    fn mul(self, rhs: Self) -> Self {

        Self {

            is_negative: self.is_negative ^ rhs.is_negative,

            value: ((self.value as u128 * rhs.value as u128) >> 32) as u64,

        }

    }

}

impl ops::Mul<i32> for FPNum {

    type Output = Self;

    #[inline]

    fn mul(self, rhs: i32) -> Self {

        Self {

            is_negative: self.is_negative ^ (rhs < 0),

            value: self.value * rhs.abs() as u64,

        }

    }

}

impl ops::Div for FPNum {

    type Output = Self;

    #[inline]

    fn div(self, rhs: Self) -> Self {

        Self {

            is_negative: self.is_negative ^ rhs.is_negative,

            value: (((self.value as u128) << 32) / rhs.value as u128) as u64,

        }

    }

}

impl ops::Div<i32> for FPNum {

    type Output = Self;

    #[inline]

    fn div(self, rhs: i32) -> Self {

        Self {

            is_negative: self.is_negative ^ (rhs < 0),

            value: self.value / rhs.abs() as u64,

        }

    }

}

impl ops::Div<u32> for FPNum {

    type Output = Self;

    #[inline]

    fn div(self, rhs: u32) -> Self {

        Self {

            is_negative: self.is_negative,

            value: self.value / rhs as u64,

        }

    }

}

/* TODO:

 Distance

 DistanceI

 SignAs

 AngleSin

 AngleCos

*/

#[cfg(test)]

#[test]

fn basics() {

    let n = FPNum::new(15, 2);

    assert!(n.is_positive());

    assert!(!n.is_negative());

    assert!(!(-n).is_positive());

    assert!((-n).is_negative());

    assert_eq!(-(-n), n);

    assert_eq!((-n).abs(), n);

    assert_eq!(-n, FPNum::new(-15, 2));

    assert_eq!(n.round(), 7);

    assert_eq!((-n).round(), -7);

}

#[test]

fn zero() {

    let z = FPNum::from(0);

    let n = FPNum::new(15, 2);

    assert!(z.is_zero());

    assert!(z.is_positive());

    assert!((-z).is_negative);

    assert_eq!(n - n, z)

}

#[test]

fn arith() {

    let n1_5 = FPNum::new(3, 2);

    let n2_25 = FPNum::new(9, 4);

    assert_eq!(n1_5 + n1_5, FPNum::from(3));

    assert_eq!(-n1_5 - n1_5, FPNum::from(-3));

    assert_eq!(n1_5 * n1_5, n2_25);

    assert_eq!(-n1_5 * -n1_5, n2_25);

    assert_eq!(n1_5 * -n1_5, -n2_25);

    assert_eq!(-n1_5 * n1_5, -n2_25);

    assert_eq!(n1_5.sqr(), n2_25);

    assert_eq!((-n1_5).sqr(), n2_25);

    assert_eq!(n2_25.sqrt(), n1_5);

    assert_eq!((n1_5 * n1_5 * n1_5.sqr()).sqrt(), n2_25);

}