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use crate::natural::Natural;
use malachite_base::num::arithmetic::traits::ShlRound;
use malachite_base::num::basic::floats::PrimitiveFloat;
use malachite_base::num::basic::traits::Zero;
use malachite_base::num::conversion::traits::{
    ConvertibleFrom, IntegerMantissaAndExponent, IsInteger, RoundingFrom,
};
use malachite_base::rounding_modes::RoundingMode;

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum NaturalFromPrimitiveFloatError {
    FloatInfiniteOrNan,
    FloatNegative,
    FloatNonInteger,
}

macro_rules! float_impls {
    ($f: ident) => {
        impl RoundingFrom<$f> for Natural {
            /// Converts a floating-point value to a [`Natural`], using the specified rounding
            /// mode.
            ///
            /// The floating-point value cannot be NaN or infinite, and it cannot round to a
            /// negative integer.
            ///
            /// # Worst-case complexity
            /// $T(n) = O(n)$
            ///
            /// $M(n) = O(n)$
            ///
            /// where $T$ is time, $M$ is additional memory, and $n$ is `value.sci_exponent()`.
            ///
            /// # Panics
            /// Panics if `value` is NaN or infinite, if it would round to a negative integer, or if
            /// the rounding mode is `Exact` and `value` is not an integer.
            ///
            /// # Examples
            /// See [here](super::from_primitive_float#rounding_from).
            fn rounding_from(value: $f, rm: RoundingMode) -> Self {
                if value.is_nan() || value == $f::POSITIVE_INFINITY {
                    panic!("Cannot convert {} to Natural", value);
                } else if value == 0.0 {
                    Natural::ZERO
                } else if value < 0.0 {
                    if rm == RoundingMode::Down
                        || rm == RoundingMode::Ceiling
                        || rm == RoundingMode::Nearest
                    {
                        Natural::ZERO
                    } else {
                        panic!("Result is negative and cannot be converted to a Natural");
                    }
                } else {
                    let (mantissa, exponent) = value.integer_mantissa_and_exponent();
                    Natural::from(mantissa).shl_round(exponent, rm)
                }
            }
        }

        impl TryFrom<$f> for Natural {
            type Error = NaturalFromPrimitiveFloatError;

            /// Converts a floating-point value to a [`Natural`].
            ///
            /// If the input isn't exactly equal to some [`Natural`], an error is returned.
            ///
            /// # Worst-case complexity
            /// $T(n) = O(n)$
            ///
            /// $M(n) = O(n)$
            ///
            /// where $T$ is time, $M$ is additional memory, and $n$ is `value.sci_exponent()`.
            ///
            /// # Examples
            /// See [here](super::from_primitive_float#try_from).
            fn try_from(value: $f) -> Result<Natural, Self::Error> {
                if value.is_nan() || value.is_infinite() {
                    Err(NaturalFromPrimitiveFloatError::FloatInfiniteOrNan)
                } else if value < 0.0 {
                    Err(NaturalFromPrimitiveFloatError::FloatNegative)
                } else if value == 0.0 {
                    Ok(Natural::ZERO)
                } else {
                    let (mantissa, exponent) = value.integer_mantissa_and_exponent();
                    if exponent >= 0 {
                        Ok(Natural::from(mantissa) << exponent)
                    } else {
                        Err(NaturalFromPrimitiveFloatError::FloatNonInteger)
                    }
                }
            }
        }

        impl ConvertibleFrom<$f> for Natural {
            /// Determines whether a floating-point value can be exactly converted to a
            /// [`Natural`].
            ///
            /// # Worst-case complexity
            /// Constant time and additional memory.
            ///
            /// # Examples
            /// See [here](super::from_primitive_float#convertible_from).
            #[inline]
            fn convertible_from(value: $f) -> bool {
                value >= 0.0 && value.is_integer()
            }
        }
    };
}
apply_to_primitive_floats!(float_impls);