use std::mem;
use num::FromPrimitive;
use na::{self, Real, DefaultAllocator};

use aliases::{Vec, Mat};
use traits::{Number, Dimension, Alloc};

/// For each matrix or vector component `x` if `x >= 0`; otherwise, it returns `-x`.
pub fn abs<N: Number, R: Dimension, C: Dimension>(x: &Mat<N, R, C>) -> Mat<N, R, C>
    where DefaultAllocator: Alloc<N, R, C> {
     x.abs()
}

/// For each matrix or vector component returns a value equal to the nearest integer that is greater than or equal to `x`.
pub fn ceil<N: Real, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.ceil())
}


/// Returns `min(max(x, min_val), max_val)`.
pub fn clamp_scalar<N: Number>(x: N, min_val: N, max_val: N) -> N {
    na::clamp(x, min_val, max_val)
}

/// Returns `min(max(x[i], min_val), max_val)` for each component in `x` using the floating-point values `min_val and `max_val`.
pub fn clamp<N: Number, D: Dimension>(x: &Vec<N, D>, min_val: N, max_val: N) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| na::clamp(x, min_val, max_val))
}

/// Returns `min(max(x[i], min_val[i]), max_val[i])` for each component in `x` using the components of `min_val` and `max_val` as bounds.
pub fn clamp_vec<N: Number, D: Dimension>(x: &Vec<N, D>, min_val: &Vec<N, D>, max_val: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    na::clamp(x.clone(), min_val.clone(), max_val.clone())
}

/// Returns a signed integer value representing the encoding of a floating-point value.
///
/// The floating-point value's bit-level representation is preserved.
pub fn float_bits_to_int(v: f32) -> i32 {
    unsafe { mem::transmute(v) }
}

/// Returns a signed integer value representing the encoding of each component of `v`.
///
/// The floating point value's bit-level representation is preserved.
pub fn float_bits_to_int_vec<D: Dimension>(v: &Vec<f32, D>) -> Vec<i32, D>
    where DefaultAllocator: Alloc<f32, D> {
    v.map(|v| float_bits_to_int(v))
}

/// Returns an unsigned integer value representing the encoding of a floating-point value.
///
/// The floating-point value's bit-level representation is preserved.
pub fn float_bits_to_uint(v: f32) -> u32 {
    unsafe { mem::transmute(v) }
}

/// Returns an unsigned integer value representing the encoding of each component of `v`.
///
/// The floating point value's bit-level representation is preserved.
pub fn float_bits_to_uint_vec<D: Dimension>(v: &Vec<f32, D>) -> Vec<u32, D>
    where DefaultAllocator: Alloc<f32, D> {
    v.map(|v| float_bits_to_uint(v))
}

/// Returns componentwise a value equal to the nearest integer that is less then or equal to `x`.
pub fn floor<N: Real, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.floor())
}

//// FIXME: should be implemented for Vec/Mat?
//pub fn fma<N: Number>(a: N, b: N, c: N) -> N {
//    // FIXME: use an actual FMA
//    a * b + c
//}

/// Returns the fractional part of each component of `x`.
pub fn fract<N: Real, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.fract())
}

//// FIXME: should be implemented for Vec/Mat?
///// Returns the (significant, exponent) of this float number.
//pub fn frexp<N: Real>(x: N, exp: N) -> (N, N) {
//    // FIXME: is there a better approach?
//    let e = x.log2().ceil();
//    (x * (-e).exp2(), e)
//}

/// Returns a floating-point value corresponding to a signed integer encoding of a floating-point value.
///
/// If an inf or NaN is passed in, it will not signal, and the resulting floating point value is unspecified. Otherwise, the bit-level representation is preserved.
pub fn int_bits_to_float(v: i32) -> f32 {
    unsafe { mem::transmute(v) }

}

/// For each components of `v`, returns a floating-point value corresponding to a signed integer encoding of a floating-point value.
///
/// If an inf or NaN is passed in, it will not signal, and the resulting floating point value is unspecified. Otherwise, the bit-level representation is preserved.
pub fn int_bits_to_float_vec<D: Dimension>(v: &Vec<i32, D>) -> Vec<f32, D>
    where DefaultAllocator: Alloc<f32, D> {
    v.map(|v| int_bits_to_float(v))
}

//pub fn isinf<N: Scalar, D: Dimension>(x: &Vec<N, D>) -> Vec<bool, D>
//    where DefaultAllocator: Alloc<N, D> {
//        unimplemented!()
//
//}
//
//pub fn isnan<N: Scalar, D: Dimension>(x: &Vec<N, D>) -> Vec<bool, D>
//    where DefaultAllocator: Alloc<N, D> {
//        unimplemented!()
//
//}

///// Returns the (significant, exponent) of this float number.
//pub fn ldexp<N: Real>(x: N, exp: N) -> N {
//    // FIXME: is there a better approach?
//    x * (exp).exp2()
//}

/// Returns `x * (1.0 - a) + y * a`, i.e., the linear blend of x and y using the floating-point value a.
///
/// The value for a is not restricted to the range `[0, 1]`.
pub fn mix<N: Number>(x: N, y: N, a: N) -> N {
    x * (N::one() - a) + y * a
}

/// Component-wise modulus.
///
/// Returns `x - y * floor(x / y)` for each component in `x` using the corresponding component of `y`.
pub fn modf_vec<N: Number, D: Dimension>(x: &Vec<N, D>, y: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.zip_map(y, |x, y| x % y)
}

/// Modulus between two values.
pub fn modf<N: Number>(x: N, i: N) -> N {
    x % i
}

/// Component-wise rounding.
///
/// Values equal to `0.5` are rounded away from `0.0`.
pub fn round<N: Real, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.round())

}

//pub fn roundEven<N: Scalar, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
//    where DefaultAllocator: Alloc<N, D> {
//        unimplemented!()
//}

/// Returns 1 if `x > 0`, 0 if `x == 0`, or -1 if `x < 0`.
pub fn sign<N: Number, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.signum())
}

/// Returns 0.0 if `x <= edge0` and `1.0 if x >= edge1` and performs smooth Hermite interpolation between 0 and 1 when `edge0 < x < edge1`.
///
/// This is useful in cases where you would want a threshold function with a smooth transition.
/// This is equivalent to: `let result = clamp((x - edge0) / (edge1 - edge0), 0, 1); return t * t * (3 - 2 * t);` Results are undefined if `edge0 >= edge1`.
pub fn smoothstep<N: Number>(edge0: N, edge1: N, x: N) -> N {
    let _3: N = FromPrimitive::from_f64(3.0).unwrap();
    let _2: N = FromPrimitive::from_f64(2.0).unwrap();
    let t = na::clamp((x - edge0) / (edge1 - edge0), N::zero(), N::one());
    t * t * (_3 - t * _2)
}

/// Returns 0.0 if `x < edge`, otherwise it returns 1.0.
pub fn step_scalar<N: Number>(edge: N, x: N) -> N {
    if edge > x {
        N::zero()
    } else {
        N::one()
    }
}

/// Returns 0.0 if `x[i] < edge`, otherwise it returns 1.0.
pub fn step<N: Number, D: Dimension>(edge: N, x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| step_scalar(edge, x))
}

/// Returns 0.0 if `x[i] < edge[i]`, otherwise it returns 1.0.
pub fn step_vec<N: Number, D: Dimension>(edge: &Vec<N, D>, x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    edge.zip_map(x, |edge, x| step_scalar(edge, x))
}

/// Returns a value equal to the nearest integer to `x` whose absolute value is not larger than the absolute value of `x`.
pub fn trunc<N: Real, D: Dimension>(x: &Vec<N, D>) -> Vec<N, D>
    where DefaultAllocator: Alloc<N, D> {
    x.map(|x| x.trunc())
}

/// Returns a floating-point value corresponding to a unsigned integer encoding of a floating-point value.
///
/// If an `inf` or `NaN` is passed in, it will not signal, and the resulting floating point value is unspecified. Otherwise, the bit-level representation is preserved.
pub fn uint_bits_to_float_scalar(v: u32) -> f32 {
    unsafe { mem::transmute(v) }

}

/// For each component of `v`, returns a floating-point value corresponding to a unsigned integer encoding of a floating-point value.
///
/// If an inf or NaN is passed in, it will not signal, and the resulting floating point value is unspecified. Otherwise, the bit-level representation is preserved.
pub fn uint_bits_to_float<D: Dimension>(v: &Vec<u32, D>) -> Vec<f32, D>
    where DefaultAllocator: Alloc<f32, D> {
    v.map(|v| uint_bits_to_float_scalar(v))
}