/* Much of this file is copied from https://github.com/qdrant/qdrant/blob/master/lib/segment/src/spaces/simple_sse.rs
copyright Qdrant, licensed under the Apache 2.0 license.

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#![allow(clippy::missing_safety_doc)]

#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;

#[cfg(target_feature = "sse")]
pub unsafe fn hsum128_ps_sse(x: __m128) -> f32 {
    let x64: __m128 = _mm_add_ps(x, _mm_movehl_ps(x, x));
    let x32: __m128 = _mm_add_ss(x64, _mm_shuffle_ps(x64, x64, 0x55));
    _mm_cvtss_f32(x32)
}

#[cfg(target_feature = "sse")]
pub unsafe fn cosine_distance(a: &[f32], b: &[f32]) -> f32 {
    let n = a.len();
    let m = n - (n % 16);
    let mut ptr1: *const f32 = a.as_ptr();
    let mut ptr2: *const f32 = b.as_ptr();
    let mut sum128_1: __m128 = _mm_setzero_ps();
    let mut sum128_2: __m128 = _mm_setzero_ps();
    let mut sum128_3: __m128 = _mm_setzero_ps();
    let mut sum128_4: __m128 = _mm_setzero_ps();

    let mut i: usize = 0;
    while i < m {
        sum128_1 = _mm_add_ps(_mm_mul_ps(_mm_loadu_ps(ptr1), _mm_loadu_ps(ptr2)), sum128_1);

        sum128_2 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(4)), _mm_loadu_ps(ptr2.add(4))),
            sum128_2,
        );

        sum128_3 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(8)), _mm_loadu_ps(ptr2.add(8))),
            sum128_3,
        );

        sum128_4 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(12)), _mm_loadu_ps(ptr2.add(12))),
            sum128_4,
        );

        ptr1 = ptr1.add(16);
        ptr2 = ptr2.add(16);
        i += 16;
    }

    let mut result = hsum128_ps_sse(sum128_1)
        + hsum128_ps_sse(sum128_2)
        + hsum128_ps_sse(sum128_3)
        + hsum128_ps_sse(sum128_4);
    for i in 0..n - m {
        result += (*ptr1.add(i)) * (*ptr2.add(i));
    }
    1.0_f32 - result
}

#[cfg(target_feature = "sse")]
pub unsafe fn inner_product(a: &[f32], b: &[f32]) -> f32 {
    let n = a.len();
    let m = n - (n % 16);
    let mut ptr1: *const f32 = a.as_ptr();
    let mut ptr2: *const f32 = b.as_ptr();
    let mut sum128_1: __m128 = _mm_setzero_ps();
    let mut sum128_2: __m128 = _mm_setzero_ps();
    let mut sum128_3: __m128 = _mm_setzero_ps();
    let mut sum128_4: __m128 = _mm_setzero_ps();

    let mut i: usize = 0;
    while i < m {
        sum128_1 = _mm_add_ps(_mm_mul_ps(_mm_loadu_ps(ptr1), _mm_loadu_ps(ptr2)), sum128_1);

        sum128_2 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(4)), _mm_loadu_ps(ptr2.add(4))),
            sum128_2,
        );

        sum128_3 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(8)), _mm_loadu_ps(ptr2.add(8))),
            sum128_3,
        );

        sum128_4 = _mm_add_ps(
            _mm_mul_ps(_mm_loadu_ps(ptr1.add(12)), _mm_loadu_ps(ptr2.add(12))),
            sum128_4,
        );

        ptr1 = ptr1.add(16);
        ptr2 = ptr2.add(16);
        i += 16;
    }

    let mut result = hsum128_ps_sse(sum128_1)
        + hsum128_ps_sse(sum128_2)
        + hsum128_ps_sse(sum128_3)
        + hsum128_ps_sse(sum128_4);
    for i in 0..n - m {
        result += (*ptr1.add(i)) * (*ptr2.add(i));
    }
    1.0_f32 - result
}

#[cfg(target_feature = "sse")]
pub unsafe fn euclidean_distance(a: &[f32], b: &[f32]) -> f32 {
    let n = a.len();
    let m = n - (n % 16);
    let mut ptr1: *const f32 = a.as_ptr();
    let mut ptr2: *const f32 = b.as_ptr();
    let mut sum128_1: __m128 = _mm_setzero_ps();
    let mut sum128_2: __m128 = _mm_setzero_ps();
    let mut sum128_3: __m128 = _mm_setzero_ps();
    let mut sum128_4: __m128 = _mm_setzero_ps();
    let mut i: usize = 0;
    while i < m {
        let sub128_1 = _mm_sub_ps(_mm_loadu_ps(ptr1), _mm_loadu_ps(ptr2));
        sum128_1 = _mm_add_ps(_mm_mul_ps(sub128_1, sub128_1), sum128_1);

        let sub128_2 = _mm_sub_ps(_mm_loadu_ps(ptr1.add(4)), _mm_loadu_ps(ptr2.add(4)));
        sum128_2 = _mm_add_ps(_mm_mul_ps(sub128_2, sub128_2), sum128_2);

        let sub128_3 = _mm_sub_ps(_mm_loadu_ps(ptr1.add(8)), _mm_loadu_ps(ptr2.add(8)));
        sum128_3 = _mm_add_ps(_mm_mul_ps(sub128_3, sub128_3), sum128_3);

        let sub128_4 = _mm_sub_ps(_mm_loadu_ps(ptr1.add(12)), _mm_loadu_ps(ptr2.add(12)));
        sum128_4 = _mm_add_ps(_mm_mul_ps(sub128_4, sub128_4), sum128_4);

        ptr1 = ptr1.add(16);
        ptr2 = ptr2.add(16);
        i += 16;
    }

    let mut result = hsum128_ps_sse(sum128_1)
        + hsum128_ps_sse(sum128_2)
        + hsum128_ps_sse(sum128_3)
        + hsum128_ps_sse(sum128_4);
    for i in 0..n - m {
        result += (*ptr1.add(i) - *ptr2.add(i)).powi(2);
    }
    result
}

#[cfg(test)]
mod tests {
    #[allow(unused_imports)]
    use super::*;
    #[allow(unused_imports)]
    use crate::distance::*;
    use rand::Rng;

    #[allow(dead_code)]
    fn generate_random_vector(size: usize) -> Vec<f32> {
        let mut rng = rand::thread_rng();
        (0..size).map(|_| rng.gen_range(-10.0..10.0)).collect()
    }

    #[cfg(target_feature = "sse")]
    fn test_distance_functions(v1: &[f32], v2: &[f32]) {
        // Test Euclidean distance
        let euclid_simd = unsafe { euclidean_distance(v1, v2) };
        let euclid = euclidean_distance_scalar(v1, v2);
        let euclid_tolerance = (euclid.abs() * 1e-4).max(1e-5) + (v1.len() as f32 * 1e-5);
        assert!(
            (euclid_simd - euclid).abs() < euclid_tolerance,
            "Euclidean distance mismatch: SIMD={}, Scalar={}, tolerance={}",
            euclid_simd,
            euclid,
            euclid_tolerance
        );

        // Test Cosine distance
        let cosine_simd = unsafe { cosine_distance(v1, v2) };
        let cosine = cosine_distance_scalar(v1, v2);
        let cosine_tolerance = (cosine.abs() * 5e-4).max(1e-4) + (v1.len() as f32 * 1e-5);
        assert!(
            (cosine_simd - cosine).abs() < cosine_tolerance,
            "Cosine distance mismatch: SIMD={}, Scalar={}, tolerance={}",
            cosine_simd,
            cosine,
            cosine_tolerance
        );

        // Test Inner product
        let inner_simd = unsafe { inner_product(v1, v2) };
        let inner = inner_product_scalar(v1, v2);
        let inner_tolerance = (inner.abs() * 5e-4).max(1e-4) + (v1.len() as f32 * 1e-5);
        assert!(
            (inner_simd - inner).abs() < inner_tolerance,
            "Inner product mismatch: SIMD={}, Scalar={}, tolerance={}",
            inner_simd,
            inner,
            inner_tolerance
        );
    }

    #[test]
    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "sse"
    ))]
    fn test_spaces_sse() {
        println!("Running SSE distance test...");
        if is_x86_feature_detected!("sse") {
            let v1: Vec<f32> = vec![
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                26., 27., 28., 29., 30., 31.,
            ];
            let v2: Vec<f32> = vec![
                40., 41., 42., 43., 44., 45., 46., 47., 48., 49., 50., 51., 52., 53., 54., 55.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.,
                56., 57., 58., 59., 60., 61.,
            ];

            test_distance_functions(&v1, &v2);
        } else {
            println!("sse test skipped");
        }
    }

    #[test]
    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "sse"
    ))]
    fn test_sse_random_sizes() {
        if !is_x86_feature_detected!("sse") {
            println!("sse random sizes test skipped");
            return;
        }

        println!("Running SSE random sizes test...");

        // Test various vector sizes
        let sizes = vec![16, 32, 64, 128, 256, 512, 1024, 2048, 4096];

        for _ in 0..1_000 {
            for size in &sizes {
                println!("Testing size: {}", size);
                let v1 = generate_random_vector(*size);
                let v2 = generate_random_vector(*size);
                test_distance_functions(&v1, &v2);
            }
        }
    }

    #[test]
    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "sse"
    ))]
    fn test_sse_edge_cases() {
        if !is_x86_feature_detected!("sse") {
            println!("sse edge cases test skipped");
            return;
        }

        println!("Running SSE edge cases test...");

        // Test edge cases with non-multiple-of-16 sizes
        let edge_sizes = vec![1, 4, 8, 15, 17, 31, 33, 63, 65, 127, 129];

        for size in edge_sizes {
            println!("Testing edge case size: {}", size);
            let v1 = generate_random_vector(size);
            let v2 = generate_random_vector(size);
            test_distance_functions(&v1, &v2);
        }
    }

    #[test]
    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "sse"
    ))]
    fn test_sse_special_values() {
        if !is_x86_feature_detected!("sse") {
            println!("sse special values test skipped");
            return;
        }

        println!("Running SSE special values test...");

        // Test with special values
        let size = 128;

        // Test with zeros
        let v1 = vec![0.0; size];
        let v2 = vec![0.0; size];
        test_distance_functions(&v1, &v2);

        // Test with ones
        let v1 = vec![1.0; size];
        let v2 = vec![1.0; size];
        test_distance_functions(&v1, &v2);

        // Test with alternating values
        let v1: Vec<f32> = (0..size)
            .map(|i| if i % 2 == 0 { 1.0 } else { -1.0 })
            .collect();
        let v2: Vec<f32> = (0..size)
            .map(|i| if i % 2 == 0 { -1.0 } else { 1.0 })
            .collect();
        test_distance_functions(&v1, &v2);

        // Test with very small values
        let v1: Vec<f32> = (0..size).map(|_| 1e-6).collect();
        let v2: Vec<f32> = (0..size).map(|_| 2e-6).collect();
        test_distance_functions(&v1, &v2);

        // Test with very large values
        let v1: Vec<f32> = (0..size).map(|_| 1e6).collect();
        let v2: Vec<f32> = (0..size).map(|_| 2e6).collect();
        test_distance_functions(&v1, &v2);
    }
}
