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// Copyright 2015 The Noise-rs Developers.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! An ultra-light private math library to make our short lives easier as we
//! implement super-complex noise stuff.

use num::{self, Float, NumCast};
use std::ops::{Add, Sub, Mul};

/// Cast a numeric type without having to unwrap - we don't expect any overflow
/// errors...
pub fn cast<T: NumCast, U: NumCast>(x: T) -> U {
    num::traits::cast(x).unwrap()
}

/// Raises the number to the power of `4`
pub fn pow4<T: Float>(x: T) -> T { x * x * x * x }

/// A 2-dimensional point. This is a fixed sized array, so should be compatible
/// with most linear algebra libraries.
pub type Point2<T> = [T; 2];

/// A 3-dimensional point. This is a fixed sized array, so should be compatible
/// with most linear algebra libraries.
pub type Point3<T> = [T; 3];

/// A 4-dimensional point. This is a fixed sized array, so should be compatible
/// with most linear algebra libraries.
pub type Point4<T> = [T; 4];

/// A 2-dimensional vector, for internal use.
pub type Vector2<T> = [T; 2];
/// A 3-dimensional vector, for internal use.
pub type Vector3<T> = [T; 3];
/// A 4-dimensional vector, for internal use.
pub type Vector4<T> = [T; 4];

pub fn map2<T: Copy, U, F: Fn(T) -> U>(a: Vector2<T>, f: F) -> Vector2<U> {
    let (ax, ay) = (a[0], a[1]);
    [f(ax), f(ay)]
}
pub fn map3<T: Copy, U, F: Fn(T) -> U>(a: Vector3<T>, f: F) -> Vector3<U> {
    let (ax, ay, az) = (a[0], a[1], a[2]);
    [f(ax), f(ay), f(az)]
}
pub fn map4<T: Copy, U, F: Fn(T) -> U>(a: Vector4<T>, f: F) -> Vector4<U> {
    let (ax, ay, az, aw) = (a[0], a[1], a[2], a[3]);
    [f(ax), f(ay), f(az), f(aw)]
}

pub fn zip_with2<T: Copy, U: Copy, V, F: Fn(T, U) -> V>(a: Vector2<T>, b: Vector2<U>, f: F) -> Vector2<V> {
    let (ax, ay) = (a[0], a[1]);
    let (bx, by) = (b[0], b[1]);
    [f(ax, bx), f(ay, by)]
}
pub fn zip_with3<T: Copy, U: Copy, V, F: Fn(T, U) -> V>(a: Vector3<T>, b: Vector3<U>, f: F) -> Vector3<V> {
    let (ax, ay, az) = (a[0], a[1], a[2]);
    let (bx, by, bz) = (b[0], b[1], b[2]);
    [f(ax, bx), f(ay, by), f(az, bz)]
}
pub fn zip_with4<T: Copy, U: Copy, V, F: Fn(T, U) -> V>(a: Vector4<T>, b: Vector4<U>, f: F) -> Vector4<V> {
    let (ax, ay, az, aw) = (a[0], a[1], a[2], a[3]);
    let (bx, by, bz, bw) = (b[0], b[1], b[2], b[3]);
    [f(ax, bx), f(ay, by), f(az, bz), f(aw, bw)]
}

pub fn fold2<T: Copy, F: Fn(T, T) -> T>(a: Vector2<T>, f: F) -> T {
    let (ax, ay) = (a[0], a[1]);
    f(ax, ay)
}
pub fn fold3<T: Copy, F: Fn(T, T) -> T>(a: Vector3<T>, f: F) -> T {
    let (ax, ay, az) = (a[0], a[1], a[2]);
    f(f(ax, ay), az)
}
pub fn fold4<T: Copy, F: Fn(T, T) -> T>(a: Vector4<T>, f: F) -> T {
    let (ax, ay, az, aw) = (a[0], a[1], a[2], a[3]);
    f(f(f(ax, ay), az), aw)
}

pub fn add2<T: Copy + Add<T, Output = T>>(a: Point2<T>, b: Vector2<T>) -> Point2<T> { zip_with2(a, b, Add::add) }
pub fn add3<T: Copy + Add<T, Output = T>>(a: Point3<T>, b: Vector3<T>) -> Point3<T> { zip_with3(a, b, Add::add) }
pub fn add4<T: Copy + Add<T, Output = T>>(a: Point4<T>, b: Vector4<T>) -> Point4<T> { zip_with4(a, b, Add::add) }

pub fn sub2<T: Copy + Sub<T, Output = T>>(a: Point2<T>, b: Point2<T>) -> Vector2<T> { zip_with2(a, b, Sub::sub) }
pub fn sub3<T: Copy + Sub<T, Output = T>>(a: Point3<T>, b: Point3<T>) -> Vector3<T> { zip_with3(a, b, Sub::sub) }
pub fn sub4<T: Copy + Sub<T, Output = T>>(a: Point4<T>, b: Point4<T>) -> Vector4<T> { zip_with4(a, b, Sub::sub) }

pub fn mul2<T: Copy + Mul<T, Output = T> + Copy>(a: Vector2<T>, b: T) -> Vector2<T> { zip_with2(a, const2(b), Mul::mul) }
pub fn mul3<T: Copy + Mul<T, Output = T> + Copy>(a: Vector3<T>, b: T) -> Vector3<T> { zip_with3(a, const3(b), Mul::mul) }
pub fn mul4<T: Copy + Mul<T, Output = T> + Copy>(a: Vector4<T>, b: T) -> Vector4<T> { zip_with4(a, const4(b), Mul::mul) }

pub fn dot2<T: Float>(a: Vector2<T>, b: Vector2<T>) -> T { fold2(zip_with2(a, b, Mul::mul), Add::add) }
pub fn dot3<T: Float>(a: Vector3<T>, b: Vector3<T>) -> T { fold3(zip_with3(a, b, Mul::mul), Add::add) }
pub fn dot4<T: Float>(a: Vector4<T>, b: Vector4<T>) -> T { fold4(zip_with4(a, b, Mul::mul), Add::add) }

pub fn const2<T: Copy>(x: T) -> Vector2<T> { [x, x] }
pub fn const3<T: Copy>(x: T) -> Vector3<T> { [x, x, x] }
pub fn const4<T: Copy>(x: T) -> Vector4<T> { [x, x, x, x] }

pub fn one2<T: Copy + NumCast>() -> Vector2<T> { cast2(const2(1)) }
pub fn one3<T: Copy + NumCast>() -> Vector3<T> { cast3(const3(1)) }
pub fn one4<T: Copy + NumCast>() -> Vector4<T> { cast4(const4(1)) }

pub fn cast2<T: NumCast + Copy, U: NumCast + Copy>(x: Point2<T>) -> Point2<U> { map2(x, cast) }
pub fn cast3<T: NumCast + Copy, U: NumCast + Copy>(x: Point3<T>) -> Point3<U> { map3(x, cast) }
pub fn cast4<T: NumCast + Copy, U: NumCast + Copy>(x: Point4<T>) -> Point4<U> { map4(x, cast) }