use std::mem::size_of;

use identities::Zero;
use bounds::Bounded;

/// A generic trait for converting a value to a number.
pub trait ToPrimitive {
    /// Converts the value of `self` to an `isize`.
    #[inline]
    fn to_isize(&self) -> Option<isize> {
        self.to_i64().and_then(|x| x.to_isize())
    }

    /// Converts the value of `self` to an `i8`.
    #[inline]
    fn to_i8(&self) -> Option<i8> {
        self.to_i64().and_then(|x| x.to_i8())
    }

    /// Converts the value of `self` to an `i16`.
    #[inline]
    fn to_i16(&self) -> Option<i16> {
        self.to_i64().and_then(|x| x.to_i16())
    }

    /// Converts the value of `self` to an `i32`.
    #[inline]
    fn to_i32(&self) -> Option<i32> {
        self.to_i64().and_then(|x| x.to_i32())
    }

    /// Converts the value of `self` to an `i64`.
    fn to_i64(&self) -> Option<i64>;

    /// Converts the value of `self` to a `usize`.
    #[inline]
    fn to_usize(&self) -> Option<usize> {
        self.to_u64().and_then(|x| x.to_usize())
    }

    /// Converts the value of `self` to an `u8`.
    #[inline]
    fn to_u8(&self) -> Option<u8> {
        self.to_u64().and_then(|x| x.to_u8())
    }

    /// Converts the value of `self` to an `u16`.
    #[inline]
    fn to_u16(&self) -> Option<u16> {
        self.to_u64().and_then(|x| x.to_u16())
    }

    /// Converts the value of `self` to an `u32`.
    #[inline]
    fn to_u32(&self) -> Option<u32> {
        self.to_u64().and_then(|x| x.to_u32())
    }

    /// Converts the value of `self` to an `u64`.
    #[inline]
    fn to_u64(&self) -> Option<u64>;

    /// Converts the value of `self` to an `f32`.
    #[inline]
    fn to_f32(&self) -> Option<f32> {
        self.to_f64().and_then(|x| x.to_f32())
    }

    /// Converts the value of `self` to an `f64`.
    #[inline]
    fn to_f64(&self) -> Option<f64> {
        self.to_i64().and_then(|x| x.to_f64())
    }
}

macro_rules! impl_to_primitive_int_to_int {
    ($SrcT:ty, $DstT:ty, $slf:expr) => (
        {
            if size_of::<$SrcT>() <= size_of::<$DstT>() {
                Some($slf as $DstT)
            } else {
                let n = $slf as i64;
                let min_value: $DstT = Bounded::min_value();
                let max_value: $DstT = Bounded::max_value();
                if min_value as i64 <= n && n <= max_value as i64 {
                    Some($slf as $DstT)
                } else {
                    None
                }
            }
        }
    )
}

macro_rules! impl_to_primitive_int_to_uint {
    ($SrcT:ty, $DstT:ty, $slf:expr) => (
        {
            let zero: $SrcT = Zero::zero();
            let max_value: $DstT = Bounded::max_value();
            if zero <= $slf && $slf as u64 <= max_value as u64 {
                Some($slf as $DstT)
            } else {
                None
            }
        }
    )
}

macro_rules! impl_to_primitive_int {
    ($T:ty) => (
        impl ToPrimitive for $T {
            #[inline]
            fn to_isize(&self) -> Option<isize> { impl_to_primitive_int_to_int!($T, isize, *self) }
            #[inline]
            fn to_i8(&self) -> Option<i8> { impl_to_primitive_int_to_int!($T, i8, *self) }
            #[inline]
            fn to_i16(&self) -> Option<i16> { impl_to_primitive_int_to_int!($T, i16, *self) }
            #[inline]
            fn to_i32(&self) -> Option<i32> { impl_to_primitive_int_to_int!($T, i32, *self) }
            #[inline]
            fn to_i64(&self) -> Option<i64> { impl_to_primitive_int_to_int!($T, i64, *self) }

            #[inline]
            fn to_usize(&self) -> Option<usize> { impl_to_primitive_int_to_uint!($T, usize, *self) }
            #[inline]
            fn to_u8(&self) -> Option<u8> { impl_to_primitive_int_to_uint!($T, u8, *self) }
            #[inline]
            fn to_u16(&self) -> Option<u16> { impl_to_primitive_int_to_uint!($T, u16, *self) }
            #[inline]
            fn to_u32(&self) -> Option<u32> { impl_to_primitive_int_to_uint!($T, u32, *self) }
            #[inline]
            fn to_u64(&self) -> Option<u64> { impl_to_primitive_int_to_uint!($T, u64, *self) }

            #[inline]
            fn to_f32(&self) -> Option<f32> { Some(*self as f32) }
            #[inline]
            fn to_f64(&self) -> Option<f64> { Some(*self as f64) }
        }
    )
}

impl_to_primitive_int!(isize);
impl_to_primitive_int!(i8);
impl_to_primitive_int!(i16);
impl_to_primitive_int!(i32);
impl_to_primitive_int!(i64);

macro_rules! impl_to_primitive_uint_to_int {
    ($DstT:ty, $slf:expr) => (
        {
            let max_value: $DstT = Bounded::max_value();
            if $slf as u64 <= max_value as u64 {
                Some($slf as $DstT)
            } else {
                None
            }
        }
    )
}

macro_rules! impl_to_primitive_uint_to_uint {
    ($SrcT:ty, $DstT:ty, $slf:expr) => (
        {
            if size_of::<$SrcT>() <= size_of::<$DstT>() {
                Some($slf as $DstT)
            } else {
                let zero: $SrcT = Zero::zero();
                let max_value: $DstT = Bounded::max_value();
                if zero <= $slf && $slf as u64 <= max_value as u64 {
                    Some($slf as $DstT)
                } else {
                    None
                }
            }
        }
    )
}

macro_rules! impl_to_primitive_uint {
    ($T:ty) => (
        impl ToPrimitive for $T {
            #[inline]
            fn to_isize(&self) -> Option<isize> { impl_to_primitive_uint_to_int!(isize, *self) }
            #[inline]
            fn to_i8(&self) -> Option<i8> { impl_to_primitive_uint_to_int!(i8, *self) }
            #[inline]
            fn to_i16(&self) -> Option<i16> { impl_to_primitive_uint_to_int!(i16, *self) }
            #[inline]
            fn to_i32(&self) -> Option<i32> { impl_to_primitive_uint_to_int!(i32, *self) }
            #[inline]
            fn to_i64(&self) -> Option<i64> { impl_to_primitive_uint_to_int!(i64, *self) }

            #[inline]
            fn to_usize(&self) -> Option<usize> {
                impl_to_primitive_uint_to_uint!($T, usize, *self)
            }
            #[inline]
            fn to_u8(&self) -> Option<u8> { impl_to_primitive_uint_to_uint!($T, u8, *self) }
            #[inline]
            fn to_u16(&self) -> Option<u16> { impl_to_primitive_uint_to_uint!($T, u16, *self) }
            #[inline]
            fn to_u32(&self) -> Option<u32> { impl_to_primitive_uint_to_uint!($T, u32, *self) }
            #[inline]
            fn to_u64(&self) -> Option<u64> { impl_to_primitive_uint_to_uint!($T, u64, *self) }

            #[inline]
            fn to_f32(&self) -> Option<f32> { Some(*self as f32) }
            #[inline]
            fn to_f64(&self) -> Option<f64> { Some(*self as f64) }
        }
    )
}

impl_to_primitive_uint!(usize);
impl_to_primitive_uint!(u8);
impl_to_primitive_uint!(u16);
impl_to_primitive_uint!(u32);
impl_to_primitive_uint!(u64);

macro_rules! impl_to_primitive_float_to_float {
    ($SrcT:ident, $DstT:ident, $slf:expr) => (
        if size_of::<$SrcT>() <= size_of::<$DstT>() {
            Some($slf as $DstT)
        } else {
            // Make sure the value is in range for the cast.
            // NaN and +-inf are cast as they are.
            let n = $slf as f64;
            let max_value: $DstT = ::std::$DstT::MAX;
            if !n.is_finite() || (-max_value as f64 <= n && n <= max_value as f64) {
                Some($slf as $DstT)
            } else {
                None
            }
        }
    )
}

macro_rules! impl_to_primitive_float {
    ($T:ident) => (
        impl ToPrimitive for $T {
            #[inline]
            fn to_isize(&self) -> Option<isize> { Some(*self as isize) }
            #[inline]
            fn to_i8(&self) -> Option<i8> { Some(*self as i8) }
            #[inline]
            fn to_i16(&self) -> Option<i16> { Some(*self as i16) }
            #[inline]
            fn to_i32(&self) -> Option<i32> { Some(*self as i32) }
            #[inline]
            fn to_i64(&self) -> Option<i64> { Some(*self as i64) }

            #[inline]
            fn to_usize(&self) -> Option<usize> { Some(*self as usize) }
            #[inline]
            fn to_u8(&self) -> Option<u8> { Some(*self as u8) }
            #[inline]
            fn to_u16(&self) -> Option<u16> { Some(*self as u16) }
            #[inline]
            fn to_u32(&self) -> Option<u32> { Some(*self as u32) }
            #[inline]
            fn to_u64(&self) -> Option<u64> { Some(*self as u64) }

            #[inline]
            fn to_f32(&self) -> Option<f32> { impl_to_primitive_float_to_float!($T, f32, *self) }
            #[inline]
            fn to_f64(&self) -> Option<f64> { impl_to_primitive_float_to_float!($T, f64, *self) }
        }
    )
}

impl_to_primitive_float!(f32);
impl_to_primitive_float!(f64);

/// A generic trait for converting a number to a value.
pub trait FromPrimitive: Sized {
    /// Convert an `isize` to return an optional value of this type. If the
    /// value cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_isize(n: isize) -> Option<Self> {
        FromPrimitive::from_i64(n as i64)
    }

    /// Convert an `i8` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_i8(n: i8) -> Option<Self> {
        FromPrimitive::from_i64(n as i64)
    }

    /// Convert an `i16` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_i16(n: i16) -> Option<Self> {
        FromPrimitive::from_i64(n as i64)
    }

    /// Convert an `i32` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_i32(n: i32) -> Option<Self> {
        FromPrimitive::from_i64(n as i64)
    }

    /// Convert an `i64` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    fn from_i64(n: i64) -> Option<Self>;

    /// Convert a `usize` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_usize(n: usize) -> Option<Self> {
        FromPrimitive::from_u64(n as u64)
    }

    /// Convert an `u8` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_u8(n: u8) -> Option<Self> {
        FromPrimitive::from_u64(n as u64)
    }

    /// Convert an `u16` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_u16(n: u16) -> Option<Self> {
        FromPrimitive::from_u64(n as u64)
    }

    /// Convert an `u32` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_u32(n: u32) -> Option<Self> {
        FromPrimitive::from_u64(n as u64)
    }

    /// Convert an `u64` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    fn from_u64(n: u64) -> Option<Self>;

    /// Convert a `f32` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_f32(n: f32) -> Option<Self> {
        FromPrimitive::from_f64(n as f64)
    }

    /// Convert a `f64` to return an optional value of this type. If the
    /// type cannot be represented by this value, the `None` is returned.
    #[inline]
    fn from_f64(n: f64) -> Option<Self> {
        FromPrimitive::from_i64(n as i64)
    }
}

macro_rules! impl_from_primitive {
    ($T:ty, $to_ty:ident) => (
        #[allow(deprecated)]
        impl FromPrimitive for $T {
            #[inline] fn from_i8(n: i8) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_i16(n: i16) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_i32(n: i32) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_i64(n: i64) -> Option<$T> { n.$to_ty() }

            #[inline] fn from_u8(n: u8) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_u16(n: u16) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_u32(n: u32) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_u64(n: u64) -> Option<$T> { n.$to_ty() }

            #[inline] fn from_f32(n: f32) -> Option<$T> { n.$to_ty() }
            #[inline] fn from_f64(n: f64) -> Option<$T> { n.$to_ty() }
        }
    )
}

impl_from_primitive!(isize, to_isize);
impl_from_primitive!(i8,    to_i8);
impl_from_primitive!(i16,   to_i16);
impl_from_primitive!(i32,   to_i32);
impl_from_primitive!(i64,   to_i64);
impl_from_primitive!(usize, to_usize);
impl_from_primitive!(u8,    to_u8);
impl_from_primitive!(u16,   to_u16);
impl_from_primitive!(u32,   to_u32);
impl_from_primitive!(u64,   to_u64);
impl_from_primitive!(f32,   to_f32);
impl_from_primitive!(f64,   to_f64);

/// Cast from one machine scalar to another.
///
/// # Examples
///
/// ```
/// # use num_traits as num;
/// let twenty: f32 = num::cast(0x14).unwrap();
/// assert_eq!(twenty, 20f32);
/// ```
///
#[inline]
pub fn cast<T: NumCast, U: NumCast>(n: T) -> Option<U> {
    NumCast::from(n)
}

/// An interface for casting between machine scalars.
pub trait NumCast: Sized + ToPrimitive {
    /// Creates a number from another value that can be converted into
    /// a primitive via the `ToPrimitive` trait.
    fn from<T: ToPrimitive>(n: T) -> Option<Self>;
}

macro_rules! impl_num_cast {
    ($T:ty, $conv:ident) => (
        impl NumCast for $T {
            #[inline]
            #[allow(deprecated)]
            fn from<N: ToPrimitive>(n: N) -> Option<$T> {
                // `$conv` could be generated using `concat_idents!`, but that
                // macro seems to be broken at the moment
                n.$conv()
            }
        }
    )
}

impl_num_cast!(u8,    to_u8);
impl_num_cast!(u16,   to_u16);
impl_num_cast!(u32,   to_u32);
impl_num_cast!(u64,   to_u64);
impl_num_cast!(usize, to_usize);
impl_num_cast!(i8,    to_i8);
impl_num_cast!(i16,   to_i16);
impl_num_cast!(i32,   to_i32);
impl_num_cast!(i64,   to_i64);
impl_num_cast!(isize, to_isize);
impl_num_cast!(f32,   to_f32);
impl_num_cast!(f64,   to_f64);


#[test]
fn to_primitive_float() {
    use std::f32;
    use std::f64;

    let f32_toolarge = 1e39f64;
    assert_eq!(f32_toolarge.to_f32(), None);
    assert_eq!((f32::MAX as f64).to_f32(), Some(f32::MAX));
    assert_eq!((-f32::MAX as f64).to_f32(), Some(-f32::MAX));
    assert_eq!(f64::INFINITY.to_f32(), Some(f32::INFINITY));
    assert_eq!((f64::NEG_INFINITY).to_f32(), Some(f32::NEG_INFINITY));
    assert!((f64::NAN).to_f32().map_or(false, |f| f.is_nan()));
}
