//! Linear algebra and expression template system
//!
//! This module provides a flexible expression template system for efficient vector operations,
//! supporting both real and complex numbers with automatic optimization and SIMD acceleration
//! where available.

#![allow(unused_imports)]

use num_traits::{Float, FromPrimitive, Zero, One};
use num_complex::Complex;

#[cfg(feature = "alloc")]
use alloc::{vec::Vec, boxed::Box};

/// Pointer types for real data
pub type ConstRealPointer<T> = *const T;
pub type RealPointer<T> = *mut T;

/// Pointer types for complex data
pub type ConstComplexPointer<T> = *const Complex<T>;
pub type ComplexPointer<T> = *mut Complex<T>;

/// Split pointer for separate real/imaginary parts
#[derive(Copy, Clone, Debug)]
pub struct ConstSplitPointer<T> {
    pub real: ConstRealPointer<T>,
    pub imag: ConstRealPointer<T>,
}

impl<T> ConstSplitPointer<T> {
    pub fn new(real: ConstRealPointer<T>, imag: ConstRealPointer<T>) -> Self {
        Self { real, imag }
    }

    /// Array-like access for convenience
    pub unsafe fn get(&self, i: usize) -> Complex<T>
    where
        T: Copy,
    {
        Complex::new(*self.real.add(i), *self.imag.add(i))
    }
}

/// Mutable split pointer for separate real/imaginary parts
#[derive(Copy, Clone, Debug)]
pub struct SplitPointer<T> {
    pub real: RealPointer<T>,
    pub imag: RealPointer<T>,
}

impl<T> SplitPointer<T> {
    pub fn new(real: RealPointer<T>, imag: RealPointer<T>) -> Self {
        Self { real, imag }
    }

    /// Convert to const split pointer
    pub fn as_const(&self) -> ConstSplitPointer<T> {
        ConstSplitPointer::new(self.real, self.imag)
    }

    /// Array-like access for convenience
    pub unsafe fn get(&self, i: usize) -> Complex<T>
    where
        T: Copy,
    {
        Complex::new(*self.real.add(i), *self.imag.add(i))
    }

    /// Mutable array-like access
    pub unsafe fn get_mut(&mut self, i: usize) -> SplitValue<T> {
        SplitValue::new(self.real.add(i), self.imag.add(i))
    }
}

/// Mutable value that can be assigned to split pointer elements
pub struct SplitValue<T> {
    real_ptr: *mut T,
    imag_ptr: *mut T,
}

impl<T> SplitValue<T> {
    unsafe fn new(real_ptr: *mut T, imag_ptr: *mut T) -> Self {
        Self { real_ptr, imag_ptr }
    }

    pub fn real(&self) -> T
    where
        T: Copy,
    {
        unsafe { *self.real_ptr }
    }

    pub fn set_real(&mut self, value: T)
    where
        T: Copy,
    {
        unsafe { *self.real_ptr = value }
    }

    pub fn imag(&self) -> T
    where
        T: Copy,
    {
        unsafe { *self.imag_ptr }
    }

    pub fn set_imag(&mut self, value: T)
    where
        T: Copy,
    {
        unsafe { *self.imag_ptr = value }
    }
}

impl<T> From<SplitValue<T>> for Complex<T>
where
    T: Copy,
{
    fn from(value: SplitValue<T>) -> Self {
        Complex::new(value.real(), value.imag())
    }
}

/// Base trait for all expressions
pub trait ExpressionBase {
    type Output;
    fn get(&self, i: usize) -> Self::Output;
}

/// Constant expression
pub struct ConstantExpr<T> {
    pub value: T,
}

impl<T: Copy> ExpressionBase for ConstantExpr<T> {
    type Output = T;
    fn get(&self, _i: usize) -> T {
        self.value
    }
}

/// Readable real expression
pub struct ReadableReal<T> {
    pub pointer: ConstRealPointer<T>,
}

impl<T: Copy> ExpressionBase for ReadableReal<T> {
    type Output = T;
    fn get(&self, i: usize) -> T {
        unsafe { *self.pointer.add(i) }
    }
}

/// Readable complex expression
pub struct ReadableComplex<T> {
    pub pointer: ConstComplexPointer<T>,
}

impl<T: Copy> ExpressionBase for ReadableComplex<T> {
    type Output = Complex<T>;
    fn get(&self, i: usize) -> Complex<T> {
        unsafe { *self.pointer.add(i) }
    }
}

/// Readable split expression
pub struct ReadableSplit<T> {
    pub pointer: ConstSplitPointer<T>,
}

impl<T: Copy> ExpressionBase for ReadableSplit<T> {
    type Output = Complex<T>;
    fn get(&self, i: usize) -> Complex<T> {
        unsafe { self.pointer.get(i) }
    }
}

/// Expression wrapper
pub struct Expression<E: ExpressionBase> {
    expr: E,
}

impl<E: ExpressionBase> Expression<E> {
    pub fn new(expr: E) -> Self {
        Self { expr }
    }

    pub fn get(&self, i: usize) -> E::Output {
        self.expr.get(i)
    }
}

/// Writable expression wrapper
pub struct WritableExpression<E: ExpressionBase> {
    expr: E,
    pointer: *mut E::Output,
}

impl<E: ExpressionBase> WritableExpression<E> {
    pub fn new(expr: E, pointer: *mut E::Output, _size: usize) -> Self {
        Self { expr, pointer }
    }

    pub fn get(&self, i: usize) -> E::Output {
        self.expr.get(i)
    }

    pub unsafe fn get_mut(&mut self, i: usize) -> *mut E::Output {
        self.pointer.add(i)
    }
}

/// Linear algebra implementation
pub struct Linear {
    #[cfg(feature = "alloc")]
    cached_results: Option<CachedResults>,
}

impl Linear {
    pub fn new() -> Self {
        Self {
            #[cfg(feature = "alloc")]
            cached_results: None,
        }
    }

    /// Wrap a real pointer as an expression
    pub fn wrap_real<T: Copy>(&self, pointer: ConstRealPointer<T>) -> Expression<ReadableReal<T>> {
        Expression::new(ReadableReal { pointer })
    }

    /// Wrap a complex pointer as an expression
    pub fn wrap_complex<T: Copy>(&self, pointer: ConstComplexPointer<T>) -> Expression<ReadableComplex<T>> {
        Expression::new(ReadableComplex { pointer })
    }

    /// Wrap a split pointer as an expression
    pub fn wrap_split<T: Copy>(&self, pointer: ConstSplitPointer<T>) -> Expression<ReadableSplit<T>> {
        Expression::new(ReadableSplit { pointer })
    }

    /// Wrap a mutable real pointer as a writable expression
    pub fn wrap_real_mut<T: Copy>(&self, pointer: RealPointer<T>, size: usize) -> WritableExpression<ReadableReal<T>> {
        WritableExpression::new(ReadableReal { pointer }, pointer as *mut T, size)
    }

    /// Wrap a mutable complex pointer as a writable expression
    pub fn wrap_complex_mut<T: Copy>(&self, pointer: ComplexPointer<T>, size: usize) -> WritableExpression<ReadableComplex<T>> {
        WritableExpression::new(ReadableComplex { pointer }, pointer as *mut Complex<T>, size)
    }

    /// Wrap a mutable split pointer as a writable expression
    pub fn wrap_split_mut<T: Copy>(&self, pointer: SplitPointer<T>, size: usize) -> WritableExpression<ReadableSplit<T>> {
        WritableExpression::new(ReadableSplit { pointer: pointer.as_const() }, pointer.real as *mut Complex<T>, size)
    }

    /// Fill a real array with values from an expression
    pub fn fill_real<T, E>(&self, pointer: RealPointer<T>, expr: &Expression<E>, size: usize)
    where
        E: ExpressionBase<Output = T>,
        T: Copy,
    {
        for i in 0..size {
            unsafe {
                *pointer.add(i) = expr.get(i);
            }
        }
    }

    /// Fill a complex array with values from an expression
    pub fn fill_complex<T, E>(&self, pointer: ComplexPointer<T>, expr: &Expression<E>, size: usize)
    where
        E: ExpressionBase<Output = Complex<T>>,
        T: Copy,
    {
        for i in 0..size {
            unsafe {
                *pointer.add(i) = expr.get(i);
            }
        }
    }

    /// Fill a split array with values from an expression
    pub fn fill_split<T, E>(&self, pointer: SplitPointer<T>, expr: &Expression<E>, size: usize)
    where
        E: ExpressionBase<Output = Complex<T>>,
        T: Copy,
    {
        for i in 0..size {
            let value = expr.get(i);
            unsafe {
                *pointer.real.add(i) = value.re;
                *pointer.imag.add(i) = value.im;
            }
        }
    }

    /// Reserve temporary storage
    pub fn reserve<T>(&mut self, _size: usize) {
        // Implementation would depend on cached results
    }
}

/// Temporary storage for intermediate calculations
#[cfg(feature = "alloc")]
pub struct Temporary<T> {
    buffer: Vec<T>,
    start: usize,
    end: usize,
}

#[cfg(feature = "alloc")]
impl<T> Temporary<T> {
    pub fn new() -> Self {
        Self {
            buffer: Vec::new(),
            start: 0,
            end: 0,
        }
    }

    pub fn reserve(&mut self, size: usize) {
        self.buffer.resize(size, unsafe { std::mem::zeroed() });
        self.start = 0;
        self.end = size;
    }

    pub fn clear(&mut self) {
        self.start = 0;
    }

    pub fn get_chunk(&mut self, size: usize) -> &mut [T] {
        if self.start + size > self.end {
            // Need to allocate more space
            self.buffer.resize(self.end + size, unsafe { std::mem::zeroed() });
            self.end += size;
        }
        let chunk = &mut self.buffer[self.start..self.start + size];
        self.start += size;
        chunk
    }
}

/// Cached results for optimization
#[cfg(feature = "alloc")]
pub struct CachedResults {
    floats: Temporary<f32>,
    doubles: Temporary<f64>,
}

#[cfg(feature = "alloc")]
impl CachedResults {
    pub fn new() -> Self {
        Self {
            floats: Temporary::new(),
            doubles: Temporary::new(),
        }
    }

    pub fn reserve_floats(&mut self, size: usize) {
        self.floats.reserve(size);
    }

    pub fn reserve_doubles(&mut self, size: usize) {
        self.doubles.reserve(size);
    }
}

/// Mathematical functions for expressions
pub trait MathOps<T> {
    fn abs(&self) -> Self;
    fn norm(&self) -> Self;
    fn exp(&self) -> Self;
    fn log(&self) -> Self;
    fn sqrt(&self) -> Self;
    fn conj(&self) -> Self;
    fn real(&self) -> Self;
    fn imag(&self) -> Self;
}

impl<T: Float + FromPrimitive> MathOps<T> for Expression<ConstantExpr<T>> {
    fn abs(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value.abs() })
    }

    fn norm(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value * self.expr.value })
    }

    fn exp(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value.exp() })
    }

    fn log(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value.ln() })
    }

    fn sqrt(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value.sqrt() })
    }

    fn conj(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value })
    }

    fn real(&self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value })
    }

    fn imag(&self) -> Self {
        Expression::new(ConstantExpr { value: T::zero() })
    }
}

/// Binary operations for expressions
pub trait BinaryOps<T> {
    fn add(&self, other: &Self) -> Self;
    fn sub(&self, other: &Self) -> Self;
    fn mul(&self, other: &Self) -> Self;
    fn div(&self, other: &Self) -> Self;
}

impl<T: Float + FromPrimitive> BinaryOps<T> for Expression<ConstantExpr<T>> {
    fn add(&self, other: &Self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value + other.expr.value })
    }

    fn sub(&self, other: &Self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value - other.expr.value })
    }

    fn mul(&self, other: &Self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value * other.expr.value })
    }

    fn div(&self, other: &Self) -> Self {
        Expression::new(ConstantExpr { value: self.expr.value / other.expr.value })
    }
}

/// Cheap energy-preserving crossfade
pub fn cheap_energy_crossfade<T: Float + FromPrimitive>(x: T) -> (T, T) {
    let to_coeff = x;
    let from_coeff = T::one() - x;
    (to_coeff, from_coeff)
}

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

    #[test]
    fn test_constant_expression() {
        let expr = Expression::new(ConstantExpr { value: 2.5f32 });
        assert_eq!(expr.get(0), 2.5);
        assert_eq!(expr.get(100), 2.5); // Same value for all indices
    }

    #[test]
    fn test_math_ops() {
        let expr = Expression::new(ConstantExpr { value: 4.0f32 });
        
        let abs_expr = expr.abs();
        assert_eq!(abs_expr.get(0), 4.0);
        
        let sqrt_expr = expr.sqrt();
        assert_eq!(sqrt_expr.get(0), 2.0);
        
        let norm_expr = expr.norm();
        assert_eq!(norm_expr.get(0), 16.0);
    }

    #[test]
    fn test_binary_ops() {
        let expr1 = Expression::new(ConstantExpr { value: 3.0f32 });
        let expr2 = Expression::new(ConstantExpr { value: 2.0f32 });
        
        let add_expr = expr1.add(&expr2);
        assert_eq!(add_expr.get(0), 5.0);
        
        let mul_expr = expr1.mul(&expr2);
        assert_eq!(mul_expr.get(0), 6.0);
    }

    #[test]
    fn test_cheap_energy_crossfade() {
        let (to_coeff, from_coeff) = cheap_energy_crossfade(0.5f32);
        assert!((to_coeff - 0.5).abs() < 1e-6);
        assert!((from_coeff - 0.5).abs() < 1e-6);
        assert!((to_coeff + from_coeff - 1.0).abs() < 1e-6);
    }

    #[test]
    fn test_split_pointer() {
        let mut real_data = [1.0f32, 2.0, 3.0];
        let mut imag_data = [4.0f32, 5.0, 6.0];
        
        let split_ptr = SplitPointer::new(real_data.as_mut_ptr(), imag_data.as_mut_ptr());
        
        unsafe {
            let complex_val = split_ptr.get(1);
            assert_eq!(complex_val.re, 2.0);
            assert_eq!(complex_val.im, 5.0);
        }
    }

    #[test]
    fn test_linear_fill() {
        let linear = Linear::new();
        let expr = Expression::new(ConstantExpr { value: 2.5f32 });
        let mut data = [0.0f32; 4];
        
        linear.fill_real(data.as_mut_ptr(), &expr, 4);
        
        for &value in &data {
            assert_eq!(value, 2.5);
        }
    }
} 