#![feature(const_generics)]
#![feature(const_evaluatable_checked)]
#![allow(incomplete_features)]
#[macro_use]
extern crate approx;

use structs::Tuple;

use std::ops::Index;

#[derive(Debug)]
pub struct Matrix<const H: usize, const W: usize> {
    matrix: [[f32; W]; H],
}

impl<const H: usize, const W: usize> Matrix<H, W> {

    pub fn default() -> Self {
        Matrix {
            matrix: [[0f32; W]; H],
        }
    }

    pub fn from_array(matrix: [[f32; W]; H]) -> Matrix<H, W> {
        Matrix {
            matrix,
        }
    }

    pub fn identity() -> Matrix<H, W> {
        // I can't figure out how to assign a 2d array to matrix inside the generic
        // so I instead create the new and then assign 1.0 to the necessary values
        let mut m = Self::default();
        for i in 0..m.matrix.len() {
            m.matrix[i][i] = 1.0;
        }
        m
    }

    pub fn transpose(&mut self) {
        for i in 0..self.matrix.len() {
            for j in i..self.matrix[0].len() {
                let v = self.matrix[i][j];
                self.matrix[i][j] = self.matrix[j][i];
                self.matrix[j][i] = v;
            }
        }
    }

    pub fn determinant(&self) -> f32 {
        self.matrix[0][0] * self.matrix[1][1] - self.matrix[0][1] * self.matrix[1][0]
    }

    fn zero_skip(&self, val: usize) -> usize {
        if val == 0 {
            1
        } else {
            0
        }
    }

    fn bound_skip(&self, val: usize, bound: usize) -> usize {
        if val < bound {
            bound
        } else {
            bound - 1
        }
    }

    pub fn minor(&self, row: usize, col: usize) -> f32
    {
        let t = self.zero_skip(row);
        let b = self.bound_skip(row, H - 1);
        let l = self.zero_skip(col);
        let r = self.bound_skip(col, W - 1);

        let tl = self.matrix[t][l];
        let br = self.matrix[b][r];
        let tr = self.matrix[t][r];
        let bl = self.matrix[b][l];

        tl * br - tr * bl
    }

    pub fn cofactor(&self, row: usize, col: usize) -> f32 {
        self.minor(row, col) * if row + col % 1 == 0 {
            1.0
        }
        else {
            -1.0
        }
    }

    pub fn sub_matrix(&self, skip_row: usize, skip_col: usize) -> Matrix<{H - 1}, {W - 1}>
    {
        let mut idx_row: usize = 0;

        let mut arr = [[0f32; W - 1]; H - 1];
        for (i, row) in self.matrix.iter().enumerate().take(H) {
            if i == skip_row { continue; }
            let mut idx_col: usize = 0;
            for (j, col) in row.iter().enumerate().take(W) {
                if j == skip_col { continue; }
                arr[idx_row][idx_col] = *col;
                idx_col += 1;
            }
            idx_row += 1;
        }
        Matrix::from_array(arr)
    }
}

impl<const H: usize, const W: usize> Index<usize> for Matrix<H, W> {
    type Output = [f32; W];
    fn index(&self, index: usize) -> &Self::Output {
        &self.matrix[index]
    }
}

impl<const H: usize, const W: usize> PartialEq for Matrix<H, W> {
    fn eq(&self, _rhs: &Self) -> bool {
        if self.matrix.len() != _rhs.matrix.len() {
            return false;
        }
        
        for row_idx in 0..self.matrix.len() {
            if self.matrix[row_idx].len() != _rhs.matrix[row_idx].len() {
                return false;
            }
            for col_idx in 0..self.matrix[row_idx].len() {
                if !relative_eq!(self.matrix[row_idx][col_idx], _rhs.matrix[row_idx][col_idx]) {
                    return false;
                }
            }
        }
        true
    }
}

impl<const H: usize, const W: usize> Matrix<H, W> {
    fn calc_val_for_mul(&self, row: usize, rhs: &Matrix<H, W>, col: usize) -> f32 {
        let mut sum = 0.0;
        for i in 0..W {
            sum += self.matrix[row][i] * rhs.matrix[i][col];
        }
        sum
    }

    fn calc_val_for_mul_tuple(&self, row: usize, tuple: &Tuple) -> f32 {
        (self.matrix[row][0] * tuple.x()) +
        (self.matrix[row][1] * tuple.y()) +
        (self.matrix[row][2] * tuple.z()) +
        (self.matrix[row][3] * tuple.w())
    }
}

impl<const H: usize, const W: usize> std::ops::Mul<Matrix<H, W>> for Matrix<H, W> {
    type Output = Matrix<H, W>;

    fn mul(self, _rhs: Matrix<H, W>) -> Matrix<H, W> {
        let mut result = [[0f32; W]; H];
        for (row, val) in result.iter_mut().enumerate().take(H) {
            for (col, v) in val.iter_mut().enumerate().take(W) {
                *v = self.calc_val_for_mul(row, &_rhs, col);
            }
        }
        Matrix::from_array(result)
    }

}

impl<const H: usize, const W: usize> std::ops::Mul<Tuple> for Matrix<H, W> {
    type Output = Tuple;

    fn mul(self, _rhs: Tuple) -> Tuple {
        Tuple::new(
            self.calc_val_for_mul_tuple(0, &_rhs),
            self.calc_val_for_mul_tuple(1, &_rhs),
            self.calc_val_for_mul_tuple(2, &_rhs),
            self.calc_val_for_mul_tuple(3, &_rhs),
        )
    }

}

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

    #[test]
    fn matrix_4x4() {
        let m = [
            [1.0, 2.0, 3.0, 4.0],
            [5.5, 6.5, 7.5, 8.5],
            [9.0, 10.0, 11.0, 12.0],
            [13.5, 14.5, 15.5, 16.5],
        ];

        let matrix = Matrix::from_array(m);
        assert_eq!(1.0, matrix[0][0]);
        assert_eq!(4.0, matrix[0][3]);
        assert_eq!(5.5, matrix[1][0]);
        assert_eq!(7.5, matrix[1][2]);
        assert_eq!(11.0, matrix[2][2]);
        assert_eq!(13.5,  matrix[3][0]);
        assert_eq!(15.5,  matrix[3][2]);
    }

    #[test]
    fn matrix_4x4_array() {
        let m = [
            [1.0, 2.0, 3.0, 4.0],
            [5.5, 6.5, 7.5, 8.5],
            [9.0, 10.0, 11.0, 12.0],
            [13.5, 14.5, 15.5, 16.5],
        ];

        let matrix = Matrix::from_array(m);
        assert_eq!(1.0, matrix[0][0]);
        assert_eq!(4.0, matrix[0][3]);
        assert_eq!(5.5, matrix[1][0]);
        assert_eq!(7.5, matrix[1][2]);
        assert_eq!(11.0, matrix[2][2]);
        assert_eq!(13.5,  matrix[3][0]);
        assert_eq!(15.5,  matrix[3][2]);
    }

    #[test]
    fn matrix_2x2() {
        let m = [
            [-3.0, 5.0,],
            [1.0, 2.0,],
        ];
        let matrix = Matrix::from_array(m);
        assert_eq!(-3.0, matrix[0][0]);
        assert_eq!(5.0, matrix[0][1]);
        assert_eq!(1.0, matrix[1][0]);
        assert_eq!(2.0, matrix[1][1]);
    }

    #[test]
    fn matrix_3x3() {
        let m = [
            [-3.0, 5.0, 0.0],
            [1.0, -2.0, -7.0],
            [0.0, 1.0, 1.0],
        ];

        let matrix = Matrix::from_array(m);
        assert_eq!(-3.0, matrix[0][0]);
        assert_eq!(-2.0, matrix[1][1]);
        assert_eq!(1.0, matrix[2][2]);
    }

    #[test]
    fn matrix_equality_a() {
        let a = [
            [1.0, 2.0, 3.0, 4.0],
            [5.0, 6.0, 7.0, 8.0],
            [9.0, 8.0, 7.0, 6.0],
            [5.0, 4.0, 3.0, 2.0],
        ];
        let m_a = Matrix::from_array(a);
            
        let b = [
            [1.0, 2.0, 3.0, 4.0],
            [5.0, 6.0, 7.0, 8.0],
            [9.0, 8.0, 7.0, 6.0],
            [5.0, 4.0, 3.0, 2.0],
        ];

        let m_b = Matrix::from_array(b);

        assert_eq!(m_a, m_b);
    }

    #[test]
    fn matrix_equality_b() {
        let a = [
            [1.0, 2.0, 3.0, 4.0],
            [5.0, 6.0, 7.0, 8.0],
            [9.0, 8.0, 7.0, 6.0],
            [5.0, 4.0, 3.0, 2.0],
        ];
        let m_a = Matrix::from_array(a);
            
        let b = [
            [2.0, 3.0, 4.0, 5.0],
            [6.0, 7.0, 8.0, 9.0],
            [8.0, 7.0, 6.0, 5.0],
            [4.0, 3.0, 2.0, 1.0],
        ];

        let m_b = Matrix::from_array(b);

        assert_ne!(m_a, m_b);
    }

    #[test]
    fn multiply() {
        let matrix_a = Matrix::from_array([
            [1.0, 2.0, 3.0, 4.0,],
            [5.0, 6.0, 7.0, 8.0,],
            [9.0, 8.0, 7.0, 6.0,],
            [5.0, 4.0, 3.0, 2.0,],
        ]);
        let matrix_b = Matrix::from_array([
            [-2.0, 1.0, 2.0, 3.0,],
            [3.0, 2.0, 1.0, -1.0,],
            [4.0, 3.0, 6.0, 5.0,],
            [1.0, 2.0, 7.0, 8.0,],
        ]);

        let expected = Matrix::from_array([
            [20.0, 22.0, 50.0, 48.0],
            [44.0, 54.0, 114.0, 108.0],
            [40.0, 58.0, 110.0, 102.0,],
            [16.0, 26.0, 46.0, 42.0],
        ]);

        assert_eq!(matrix_a * matrix_b, expected);
    }

    #[test]
    fn multiply_by_tuple() {
        let matrix = Matrix::from_array([
            [1.0, 2.0, 3.0, 4.0],
            [2.0, 4.0, 4.0, 2.0],
            [8.0, 6.0, 4.0, 1.0],
            [0.0, 0.0, 0.0, 1.0],
        ]);

        let tuple = Tuple::new(1.0, 2.0, 3.0, 1.0);
        let expected = Tuple::new(18.0, 24.0, 33.0, 1.0);

        assert_eq!(matrix * tuple, expected);
    }

    #[test]
    fn matrix_by_identity() {
        let matrix = Matrix::from_array([
            [0.0, 1.0, 2.0, 4.0,],
            [1.0, 2.0, 4.0, 8.0,],
            [2.0, 4.0, 8.0, 16.0],
            [4.0, 8.0, 16.0, 32.0,]
        ]);

        let expected = Matrix::from_array([
            [0.0, 1.0, 2.0, 4.0,],
            [1.0, 2.0, 4.0, 8.0,],
            [2.0, 4.0, 8.0, 16.0],
            [4.0, 8.0, 16.0, 32.0,]
        ]);

        assert_eq!(matrix * Matrix::identity(), expected);
    }

    #[test]
    fn tuple_by_identity() {
        let t = Tuple::new(1.0, 2.0, 3.0, 4.0);
        let expected = Tuple::new(1.0, 2.0, 3.0, 4.0);

        assert_eq!(Matrix::<4, 4>::identity() * t, expected);
    }

    #[test]
    fn transposition() {
        let mut m = Matrix::from_array([
            [0.0, 9.0, 3.0, 0.0],
            [9.0, 8.0, 0.0, 8.0],
            [1.0, 8.0, 5.0, 3.0],
            [0.0, 0.0, 5.0, 8.0],
        ]);

        let expected = Matrix::from_array([
            [0.0, 9.0, 1.0, 0.0],
            [9.0, 8.0, 8.0, 0.0],
            [3.0, 0.0, 5.0, 5.0],
            [0.0, 8.0, 3.0, 8.0],
        ]);
        m.transpose();
        assert_eq!(m, expected);
    }

    #[test]
    fn transpose_identity() {
        let mut m = Matrix::identity();
        m.transpose();
        assert_eq!(m, Matrix::<4, 4>::identity());
    }

    #[test]
    fn determinant_2x2() {
        let m = Matrix::from_array([
            [1.0, 5.0],
            [-3.0, 2.0],
        ]);

        assert_eq!(17.0, m.determinant());
    }

    #[test]
    fn submatrix_3x3() {
        let start = Matrix::from_array([
            [1.0, 5.0, 0.0],
            [-3.0, 2.0, 7.0],
            [0.0, 6.0, -3.0],
        ]);

        let expected = Matrix::from_array([
            [-3.0, 2.0],
            [0.0, 6.0],
        ]);

        assert_eq!(expected, start.sub_matrix(0, 2));
    }

    #[test]
    fn submatrix_4x4() {
        let start = Matrix::from_array([
            [-6.0, 1.0, 1.0, 6.0],
            [-8.0, 5.0, 8.0, 6.0],
            [-1.0, 0.0, 8.0, 2.0],
            [-7.0, 1.0, -1.0, 1.0],
        ]);
        let expected = Matrix::from_array([
            [-6.0, 1.0, 6.0],
            [-8.0, 8.0, 6.0],
            [-7.0, -1.0, 1.0],
        ]);

        assert_eq!(expected, start.sub_matrix(2, 1));
    }

    #[test]
    fn minor_3x3() {
        let m = Matrix::from_array([
            [3.0, 5.0, 0.0],
            [2.0, -1.0, -7.0],
            [6.0, -1.0, 5.0],
        ]);

        let s = m.sub_matrix(1, 0);

        assert_eq!(25.0, s.determinant());
        assert_eq!(25.0, m.minor(1, 0));
    }

    #[test]
    fn cofactor_3x3() {
        let m = Matrix::from_array([
            [3.0, 5.0, 0.0],
            [2.0, -1.0, -7.0],
            [6.0, -1.0, 5.0],
        ]);
        assert_eq!(-12.0, m.minor(0, 0));
        assert_eq!(-12.0, m.cofactor(0, 0));
        assert_eq!(25.0, m.minor(1, 0));
        assert_eq!(-25.0, m.cofactor(1, 0));

    }
}