/*

 * // Copyright (c) Radzivon Bartoshyk 6/2025. All rights reserved.

 * //

 * // Redistribution and use in source and binary forms, with or without modification,

 * // are permitted provided that the following conditions are met:

 * //

 * // 1.  Redistributions of source code must retain the above copyright notice, this

 * // list of conditions and the following disclaimer.

 * //

 * // 2.  Redistributions in binary form must reproduce the above copyright notice,

 * // this list of conditions and the following disclaimer in the documentation

 * // and/or other materials provided with the distribution.

 * //

 * // 3.  Neither the name of the copyright holder nor the names of its

 * // contributors may be used to endorse or promote products derived from

 * // this software without specific prior written permission.

 * //

 * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

 * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE

 * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

 * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

 * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

use crate::common::f_fmla;

/// Hyperbolic tangent

///

/// Max found ULP 0.4999994

#[inline]

pub fn f_tanhf(x: f32) -> f32 {

    let z = x as f64;

    let t = x.to_bits();

    let ux = t;

    let e = ux.wrapping_shr(23) & 0xff;

    if e == 0xff {

        if ux << 9 != 0 {

            return x + x;

        } // x = nan

        const IR: [f32; 2] = [1.0, -1.0];

        return IR[ux.wrapping_shr(31) as usize]; // x = +-inf

    }

    if e < 115 {

        // |x| < 2^-13

        if e < 102 {

            // |x| < 2^-26

            if ux.wrapping_shl(1) == 0 {

                return x;

            }

            #[cfg(any(

                all(

                    any(target_arch = "x86", target_arch = "x86_64"),

                    target_feature = "fma"

                ),

                target_arch = "aarch64"

            ))]

            {

                use crate::common::f_fmlaf;

                let res = f_fmlaf(-x, x.abs(), x);

                return res;

            }

            #[cfg(not(any(

                all(

                    any(target_arch = "x86", target_arch = "x86_64"),

                    target_feature = "fma"

                ),

                target_arch = "aarch64"

            )))]

            {

                let dx = x as f64;

                let res = crate::common::f_fmla(-dx, dx.abs(), dx);

                return res as f32;

            }

        }

        #[cfg(any(

            all(

                any(target_arch = "x86", target_arch = "x86_64"),

                target_feature = "fma"

            ),

            target_arch = "aarch64"

        ))]

        {

            use crate::common::f_fmlaf;

            let x2 = x * x;

            return f_fmlaf(x, -f64::from_bits(0x3fd5555560000000) as f32 * x2, x);

        }

        #[cfg(not(any(

            all(

                any(target_arch = "x86", target_arch = "x86_64"),

                target_feature = "fma"

            ),

            target_arch = "aarch64"

        )))]

        {

            let dx = x as f64;

            let x2 = dx * dx;

            return f_fmla(dx, -f64::from_bits(0x3fd5555560000000) * x2, dx) as f32;

        }

    }

    if ux.wrapping_shl(1) > (0x41102cb3u32 << 1) {

        return f32::copysign(1.0, x) - f32::copysign(f64::from_bits(0x3e60000000000000) as f32, x);

    }

    let z2 = z * z;

    let z4 = z2 * z2;

    let z8 = z4 * z4;

    const CN: [u64; 8] = [

        0x3ff0000000000000,

        0x3fc30877b8b72d33,

        0x3f7694aa09ae9e5e,

        0x3f14101377abb729,

        0x3e9e0392b1db0018,

        0x3e12533756e546f7,

        0x3d6d62e5abe6ae8a,

        0x3c9b06be534182de,

    ];

    const CD: [u64; 8] = [

        0x3ff0000000000000,

        0x3fded99131b0ebea,

        0x3fa0d27ed6c95a69,

        0x3f47cbdaca0e9fcc,

        0x3edb4e60b892578e,

        0x3e5a6f707c5c71ab,

        0x3dc35a8b6e2cd94c,

        0x3d0ca8230677aa01,

    ];

    let mut n0 = f_fmla(z2, f64::from_bits(CN[1]), f64::from_bits(CN[0]));

    let n2 = f_fmla(z2, f64::from_bits(CN[3]), f64::from_bits(CN[2]));

    let mut n4 = f_fmla(z2, f64::from_bits(CN[5]), f64::from_bits(CN[4]));

    let n6 = f_fmla(z2, f64::from_bits(CN[7]), f64::from_bits(CN[6]));

    n0 = f_fmla(z4, n2, n0);

    n4 = f_fmla(z4, n6, n4);

    n0 = f_fmla(z8, n4, n0);

    let mut d0 = f_fmla(z2, f64::from_bits(CD[1]), f64::from_bits(CD[0]));

    let d2 = f_fmla(z2, f64::from_bits(CD[3]), f64::from_bits(CD[2]));

    let mut d4 = f_fmla(z2, f64::from_bits(CD[5]), f64::from_bits(CD[4]));

    let d6 = f_fmla(z2, f64::from_bits(CD[7]), f64::from_bits(CD[6]));

    d0 = f_fmla(z4, d2, d0);

    d4 = f_fmla(z4, d6, d4);

    d0 = f_fmla(z8, d4, d0);

    let r = z * n0 / d0;

    r as f32

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test_tanhf() {

        assert_eq!(f_tanhf(-0.5), -0.46211717);

        assert_eq!(f_tanhf(0.5), 0.46211717);

        assert_eq!(f_tanhf(7.), 0.99999833);

    }

}