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use crate::engine::{Engine, GfElement, NoSimd, ShardsRefMut, GF_ORDER};

#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
use crate::engine::{Avx2, Ssse3};

#[cfg(target_arch = "aarch64")]
use crate::engine::Neon;

// ======================================================================
// DefaultEngine - PUBLIC

/// [`Engine`] that at runtime selects the best Engine.
pub struct DefaultEngine(Box<dyn Engine + Send + Sync>);

impl DefaultEngine {
    /// Creates new [`DefaultEngine`] by chosing and initializing the underlying engine.
    ///
    /// On x86(-64) the engine is chosen in the following order of preference:
    /// 1. [`Avx2`]
    /// 2. [`Ssse3`]
    /// 3. [`NoSimd`]
    ///
    /// On AArch64 the engine is chosen in the following order of preference:
    /// 1. [`Neon`]
    /// 2. [`NoSimd`]
    pub fn new() -> Self {
        #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
        {
            if is_x86_feature_detected!("avx2") {
                return DefaultEngine(Box::new(Avx2::new()));
            }

            if is_x86_feature_detected!("ssse3") {
                return DefaultEngine(Box::new(Ssse3::new()));
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            if std::arch::is_aarch64_feature_detected!("neon") {
                return DefaultEngine(Box::new(Neon::new()));
            }
        }

        DefaultEngine(Box::new(NoSimd::new()))
    }
}

// ======================================================================
// DefaultEngine - IMPL Default

impl Default for DefaultEngine {
    fn default() -> Self {
        Self::new()
    }
}

// ======================================================================
// DefaultEngine - IMPL Engine

impl Engine for DefaultEngine {
    fn fft(
        &self,
        data: &mut ShardsRefMut,
        pos: usize,
        size: usize,
        truncated_size: usize,
        skew_delta: usize,
    ) {
        self.0.fft(data, pos, size, truncated_size, skew_delta)
    }

    fn ifft(
        &self,
        data: &mut ShardsRefMut,
        pos: usize,
        size: usize,
        truncated_size: usize,
        skew_delta: usize,
    ) {
        self.0.ifft(data, pos, size, truncated_size, skew_delta)
    }

    fn mul(&self, x: &mut [u8], log_m: GfElement) {
        self.0.mul(x, log_m)
    }

    fn xor(x: &mut [u8], y: &[u8]) {
        #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
        {
            if is_x86_feature_detected!("avx2") {
                return Avx2::xor(x, y);
            }

            if is_x86_feature_detected!("ssse3") {
                return Ssse3::xor(x, y);
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            if std::arch::is_aarch64_feature_detected!("neon") {
                return Neon::xor(x, y);
            }
        }

        NoSimd::xor(x, y)
    }

    fn eval_poly(erasures: &mut [GfElement; GF_ORDER], truncated_size: usize) {
        #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
        {
            if is_x86_feature_detected!("avx2") {
                return Avx2::eval_poly(erasures, truncated_size);
            }

            if is_x86_feature_detected!("ssse3") {
                return Ssse3::eval_poly(erasures, truncated_size);
            }
        }

        #[cfg(target_arch = "aarch64")]
        {
            if std::arch::is_aarch64_feature_detected!("neon") {
                return Neon::eval_poly(erasures, truncated_size);
            }
        }

        NoSimd::eval_poly(erasures, truncated_size)
    }
}