//! Matrix struct and relevant implementations.
//!
//! Example usage - addition of two matrices:
//! ```
//! use matrix::Matrix;
//! use std::str::FromStr;
//! let m1 = Matrix::from_str("1,2\n3,4").expect("Expect parse correct");
//! let m2 = Matrix::from_str("1,1\n1,1").expect("Expect parse correct");
//! let m_add = &m1 + &m2;
//! println!("m1 + m2 =\n{}", m_add);
//! ```
//! TODO:: Create matrix multiplication method

use crate::error::{MatrixSetValueError, ParseMatrixError};
use std::{
    fmt::Display,
    ops::{Add, Mul, Sub},
    str::FromStr,
};
#[derive(Debug, PartialEq, Eq)]
pub struct Matrix {
    /// Number of rows in matrix.
    pub nrows: usize,

    /// Number of columns in matrix.
    pub ncols: usize,

    /// Data stored in the matrix, you should not access this directly
    data: Vec<Vec<i32>>,
}

pub trait MatrixMath {
    fn inverse(&self) -> Matrix {
        (1 / (self.determinant())) * &self.adjoint()
    }
    /// Finds the matrix of cofactors for any N-by-N matrix
    fn cofactor(&self) -> Matrix {
        todo!();
    }
    /// Finds the matrix of minors for any N-by-N matrix.
    fn minor(&self) -> Matrix {
        todo!();
    }
    /// Finds the determinant of any N-by-N matrix.
    fn determinant(&self) -> i32 {
        todo!();
    }
    /// Finds the transpose of any matrix.
    fn transpose(&self) -> Matrix {
        todo!();
    }
    /// Finds the adjoint matrix (transpose of cofactors) for any N-by-N matrix.
    fn adjoint(&self) -> Matrix {
        self.cofactor().transpose()
    }
}
impl MatrixMath for Matrix {
    /// Evaluates any N-by-N matrix.
    ///
    /// This function panics if the matrix is not square!
    fn determinant(&self) -> i32 {
        if !self.is_square() {
            panic!()
        };
        if self.nrows == 2 && self.ncols == 2 {
            return self.data[0][0] * self.data[1][1] - self.data[0][1] * self.data[1][0];
        }
        let mut tmp = 0;
        for (i, n) in self.data[0].iter().enumerate() {
            let mult = if i % 2 == 0 { -*n } else { *n };
            let eval = self.splice(i).determinant();
            tmp += mult * eval;
        }
        tmp
    }

    /// Evaluates the tranpose of the matrix.
    ///
    /// Each row becomes a column, each column becomes a row.
    fn transpose(&self) -> Matrix {
        let mut new_data = Vec::<Vec<i32>>::new();
        for i in 0..self.nrows {
            let mut new_row = Vec::<i32>::new();
            for j in 0..self.ncols {
                new_row.push(self.data[j][i]);
            }
            new_data.push(new_row);
        }
        Matrix {
            nrows: self.ncols,
            ncols: self.nrows,
            data: new_data,
        }
    }
}
impl Matrix {
    /// Matrix initialiser function.
    ///
    /// Accepts a new array of data as a list of rows.
    ///
    /// TODOs
    /// - Add row length check
    pub fn new(data: Vec<Vec<i32>>) -> Matrix {
        Matrix {
            nrows: data.len(),
            ncols: data[0].len(),
            data,
        }
    }
    /// Query one element at selected position.
    ///
    /// Returns `None` if index is out of bounds.
    pub fn get(&self, row_index: usize, column_index: usize) -> Option<i32> {
        let r = self.data.get(row_index)?;
        let n = r.get(column_index)?;
        Some(*n)
    }

    /// Update one element at selected position.
    ///
    /// Returns `Err()` if index is out of bounds.
    pub fn set(
        &mut self,
        row_index: usize,
        column_index: usize,
        new_data: i32,
    ) -> Result<(), MatrixSetValueError> {
        self.data[row_index][column_index] = new_data;
        Ok(())
    }

    /// Checks if this is a square matrix.
    pub fn is_square(&self) -> bool {
        self.nrows == self.ncols
    }
    pub fn splice(&self, at_index: usize) -> Matrix {
        let mut data: Vec<Vec<i32>> = Vec::new();
        for i in 0..self.data.len() {
            if i == 0 {
                continue;
            }
            let mut r: Vec<i32> = Vec::new();
            for j in 0..self.data[i].len() {
                if j == at_index {
                    continue;
                }
                r.push(self.data[i][j]);
            }
            data.push(r);
        }
        Matrix::new(data)
    }
}
impl FromStr for Matrix {
    type Err = ParseMatrixError;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut d: Vec<Vec<i32>> = Vec::new();
        let rows_iter = s.split('\n');
        for txt in rows_iter {
            let mut r: Vec<i32> = Vec::new();
            for ch in txt.split(',') {
                let parsed = match i32::from_str(ch) {
                    Ok(n) => Ok(n),
                    Err(_e) => Err(ParseMatrixError),
                };
                r.push(parsed?);
            }
            d.push(r);
        }
        Ok(Matrix::new(d))
    }
}

impl Display for Matrix {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut builder = String::new();
        for (i, r) in self.data.iter().enumerate() {
            let mut row_str = if i == 0 || i == self.nrows - 1 {
                "+".to_string()
            } else {
                "|".to_string()
            };
            for (j, n) in r.iter().enumerate() {
                row_str += &format!("{}{}", n, if j == self.ncols - 1 { "" } else { "," });
            }
            row_str += if i == 0 || i == self.nrows - 1 {
                "+\n"
            } else {
                "|\n"
            };
            builder += &row_str;
        }
        write!(f, "{}", builder)
    }
}
impl<'a, 'b> Add<&'b Matrix> for &'a Matrix {
    type Output = Matrix;
    fn add(self, rhs: &'b Matrix) -> Self::Output {
        if (self.nrows != rhs.nrows) || (self.ncols != rhs.ncols) {
            panic!("Cannot add two matrices with different dimensions");
        }
        let mut x = Matrix {
            nrows: self.nrows,
            ncols: self.ncols,
            data: self.data.clone(),
        };
        for (i, r) in rhs.data.iter().enumerate() {
            for (j, n) in r.iter().enumerate() {
                x.data[i][j] += n;
            }
        }
        x
    }
}
impl<'a, 'b> Sub<&'b Matrix> for &'a Matrix {
    type Output = Matrix;
    fn sub(self, rhs: &'b Matrix) -> Self::Output {
        todo!()
    }
}
impl<'a> Mul<&'a Matrix> for i32 {
    type Output = Matrix;
    fn mul(self, rhs: &'a Matrix) -> Self::Output {
        let mut d: Vec<Vec<i32>> = Vec::new();
        for r in &rhs.data {
            let mut nr: Vec<i32> = Vec::new();
            for v in r {
                nr.push(self * v);
            }
            d.push(nr);
        }
        Matrix::new(d)
    }
}
impl<'a, 'b> Mul<&'b Matrix> for &'a Matrix {
    type Output = Matrix;
    fn mul(self, rhs: &'b Matrix) -> Self::Output {
        fn reduce(lhs: &Matrix, rhs: &Matrix, at_r: usize, at_c: usize) -> i32 {
            let mut tmp = 0;
            for i in 0..lhs.ncols {
                tmp += lhs.get(at_r, i).unwrap() * rhs.get(i, at_c).unwrap();
            }
            tmp
        }
        let mut d: Vec<Vec<i32>> = Vec::new();
        if self.ncols != rhs.nrows {
            println!("LHS: \n{}RHS: \n{}", self, rhs);
            println!("LHS nrows: {} ;; RHS ncols: {}", self.nrows, rhs.ncols);
            panic!()
        }
        for i in 0..self.nrows {
            let mut r: Vec<i32> = Vec::new();
            for j in 0..rhs.ncols {
                r.push(reduce(self, rhs, i, j));
            }
            d.push(r);
        }
        Matrix::new(d)
    }
}

impl From<Vec<i32>> for Matrix {
    fn from(value: Vec<i32>) -> Self {
        Matrix {
            nrows: value.len(),
            ncols: 1,
            data: value.iter().map(|v| vec![*v]).collect(),
        }
    }
}