// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.

//! Defines basic arithmetic kernels for `PrimitiveArrays`.
//!
//! These kernels can leverage SIMD if available on your system.  Currently no runtime
//! detection is provided, you should enable the specific SIMD intrinsics using
//! `RUSTFLAGS="-C target-feature=+avx2"` for example.  See the documentation
//! [here] (https://doc.rust-lang.org/stable/std/arch/) for more information.

use std::mem;
use std::ops::{Add, Div, Mul, Sub};
use std::slice::from_raw_parts_mut;
use std::sync::Arc;

use num::Zero;

use crate::array::*;
use crate::array_data::ArrayData;
use crate::buffer::MutableBuffer;
use crate::builder::PrimitiveBuilder;
use crate::compute::util::apply_bin_op_to_option_bitmap;
use crate::datatypes;
use crate::error::{ArrowError, Result};

/// Helper function to perform math lambda function on values from two arrays. If either
/// left or right value is null then the output value is also null, so `1 + null` is
/// `null`.
pub fn math_op<T, F>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
    op: F,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    F: Fn(T::Native, T::Native) -> Result<T::Native>,
{
    if left.len() != right.len() {
        return Err(ArrowError::ComputeError(
            "Cannot perform math operation on arrays of different length".to_string(),
        ));
    }
    let mut b = PrimitiveBuilder::<T>::new(left.len());
    for i in 0..left.len() {
        let index = i;
        if left.is_null(i) || right.is_null(i) {
            b.append_null()?;
        } else {
            b.append_value(op(left.value(index), right.value(index))?)?;
        }
    }
    Ok(b.finish())
}

/// SIMD vectorized version of `math_op` above.
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
fn simd_math_op<T, F>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
    op: F,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    T::Simd: Add<Output = T::Simd>
        + Sub<Output = T::Simd>
        + Mul<Output = T::Simd>
        + Div<Output = T::Simd>,
    F: Fn(T::Simd, T::Simd) -> T::Simd,
{
    if left.len() != right.len() {
        return Err(ArrowError::ComputeError(
            "Cannot perform math operation on arrays of different length".to_string(),
        ));
    }

    let null_bit_buffer = apply_bin_op_to_option_bitmap(
        left.data().null_bitmap(),
        right.data().null_bitmap(),
        |a, b| a & b,
    )?;

    let lanes = T::lanes();
    let buffer_size = left.len() * mem::size_of::<T::Native>();
    let mut result = MutableBuffer::new(buffer_size).with_bitset(buffer_size, false);

    for i in (0..left.len()).step_by(lanes) {
        let simd_left = T::load(left.value_slice(i, lanes));
        let simd_right = T::load(right.value_slice(i, lanes));
        let simd_result = T::bin_op(simd_left, simd_right, &op);

        let result_slice: &mut [T::Native] = unsafe {
            from_raw_parts_mut(
                (result.data_mut().as_mut_ptr() as *mut T::Native).offset(i as isize),
                lanes,
            )
        };
        T::write(simd_result, result_slice);
    }

    let data = ArrayData::new(
        T::get_data_type(),
        left.len(),
        None,
        null_bit_buffer,
        left.offset(),
        vec![result.freeze()],
        vec![],
    );
    Ok(PrimitiveArray::<T>::from(Arc::new(data)))
}

/// Perform `left + right` operation on two arrays. If either left or right value is null
/// then the result is also null.
pub fn add<T>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    T::Native: Add<Output = T::Native>
        + Sub<Output = T::Native>
        + Mul<Output = T::Native>
        + Div<Output = T::Native>
        + Zero,
{
    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    return simd_math_op(&left, &right, |a, b| a + b);

    #[allow(unreachable_code)]
    math_op(left, right, |a, b| Ok(a + b))
}

/// Perform `left - right` operation on two arrays. If either left or right value is null
/// then the result is also null.
pub fn subtract<T>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    T::Native: Add<Output = T::Native>
        + Sub<Output = T::Native>
        + Mul<Output = T::Native>
        + Div<Output = T::Native>
        + Zero,
{
    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    return simd_math_op(&left, &right, |a, b| a - b);

    #[allow(unreachable_code)]
    math_op(left, right, |a, b| Ok(a - b))
}

/// Perform `left * right` operation on two arrays. If either left or right value is null
/// then the result is also null.
pub fn multiply<T>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    T::Native: Add<Output = T::Native>
        + Sub<Output = T::Native>
        + Mul<Output = T::Native>
        + Div<Output = T::Native>
        + Zero,
{
    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    return simd_math_op(&left, &right, |a, b| a * b);

    #[allow(unreachable_code)]
    math_op(left, right, |a, b| Ok(a * b))
}

/// Perform `left / right` operation on two arrays. If either left or right value is null
/// then the result is also null. If any right hand value is zero then the result of this
/// operation will be `Err(ArrowError::DivideByZero)`.
pub fn divide<T>(
    left: &PrimitiveArray<T>,
    right: &PrimitiveArray<T>,
) -> Result<PrimitiveArray<T>>
where
    T: datatypes::ArrowNumericType,
    T::Native: Add<Output = T::Native>
        + Sub<Output = T::Native>
        + Mul<Output = T::Native>
        + Div<Output = T::Native>
        + Zero,
{
    math_op(left, right, |a, b| {
        if b.is_zero() {
            Err(ArrowError::DivideByZero)
        } else {
            Ok(a / b)
        }
    })
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::array::Int32Array;

    #[test]
    fn test_primitive_array_add() {
        let a = Int32Array::from(vec![5, 6, 7, 8, 9]);
        let b = Int32Array::from(vec![6, 7, 8, 9, 8]);
        let c = add(&a, &b).unwrap();
        assert_eq!(11, c.value(0));
        assert_eq!(13, c.value(1));
        assert_eq!(15, c.value(2));
        assert_eq!(17, c.value(3));
        assert_eq!(17, c.value(4));
    }

    #[test]
    fn test_primitive_array_add_mismatched_length() {
        let a = Int32Array::from(vec![5, 6, 7, 8, 9]);
        let b = Int32Array::from(vec![6, 7, 8]);
        let e = add(&a, &b)
            .err()
            .expect("should have failed due to different lengths");
        assert_eq!(
            "ComputeError(\"Cannot perform math operation on arrays of different length\")",
            format!("{:?}", e)
        );
    }

    #[test]
    fn test_primitive_array_subtract() {
        let a = Int32Array::from(vec![1, 2, 3, 4, 5]);
        let b = Int32Array::from(vec![5, 4, 3, 2, 1]);
        let c = subtract(&a, &b).unwrap();
        assert_eq!(-4, c.value(0));
        assert_eq!(-2, c.value(1));
        assert_eq!(0, c.value(2));
        assert_eq!(2, c.value(3));
        assert_eq!(4, c.value(4));
    }

    #[test]
    fn test_primitive_array_multiply() {
        let a = Int32Array::from(vec![5, 6, 7, 8, 9]);
        let b = Int32Array::from(vec![6, 7, 8, 9, 8]);
        let c = multiply(&a, &b).unwrap();
        assert_eq!(30, c.value(0));
        assert_eq!(42, c.value(1));
        assert_eq!(56, c.value(2));
        assert_eq!(72, c.value(3));
        assert_eq!(72, c.value(4));
    }

    #[test]
    fn test_primitive_array_divide() {
        let a = Int32Array::from(vec![15, 15, 8, 1, 9]);
        let b = Int32Array::from(vec![5, 6, 8, 9, 1]);
        let c = divide(&a, &b).unwrap();
        assert_eq!(3, c.value(0));
        assert_eq!(2, c.value(1));
        assert_eq!(1, c.value(2));
        assert_eq!(0, c.value(3));
        assert_eq!(9, c.value(4));
    }

    #[test]
    fn test_primitive_array_divide_by_zero() {
        let a = Int32Array::from(vec![15]);
        let b = Int32Array::from(vec![0]);
        assert_eq!(
            ArrowError::DivideByZero,
            divide(&a, &b).err().expect("divide by zero should fail")
        );
    }

    #[test]
    fn test_primitive_array_divide_f64() {
        let a = Float64Array::from(vec![15.0, 15.0, 8.0]);
        let b = Float64Array::from(vec![5.0, 6.0, 8.0]);
        let c = divide(&a, &b).unwrap();
        assert_eq!(3.0, c.value(0));
        assert_eq!(2.5, c.value(1));
        assert_eq!(1.0, c.value(2));
    }

    #[test]
    fn test_primitive_array_add_with_nulls() {
        let a = Int32Array::from(vec![Some(5), None, Some(7), None]);
        let b = Int32Array::from(vec![None, None, Some(6), Some(7)]);
        let c = add(&a, &b).unwrap();
        assert_eq!(true, c.is_null(0));
        assert_eq!(true, c.is_null(1));
        assert_eq!(false, c.is_null(2));
        assert_eq!(true, c.is_null(3));
        assert_eq!(13, c.value(2));
    }

}