// use std::fmt;
use strum::EnumIter;
use strum::IntoEnumIterator;
// use strum_macros::EnumIter;

#[derive(Debug, EnumIter, PartialEq, Copy, Clone)]
pub enum Groups {
    Row,
    Column,
    Cell,
}

#[derive(Debug, Clone)]
pub struct AnyGroup {
    pub size: u8,
    pub width: u8,
    pub max_index: usize,
    pub groups: [Vec<usize>; 3],
    pub row_cell: Vec<usize>,
    pub col_cell: Vec<usize>,
}

/// Find the number of digits needed to display given number.
fn find_number_width(mut number: usize) -> usize {
    let mut size: usize = 1;
    number /= 10;
    while number > 0 {
        size += 1;
        number /= 10;
    }
    size
}

impl AnyGroup {
    pub fn new(board_size: u8) -> Self {
        let b_width = board_size as usize * board_size as usize;
        let size = b_width * b_width;
        let mut g = AnyGroup {
            size: board_size,
            width: board_size * board_size,
            max_index: size,
            groups: [vec![0; size], vec![0; size], vec![0; size]],
            row_cell: vec![0; size],
            col_cell: vec![0; size],
            /*
            row: vec![0; b_width * b_width],
            column: vec![0; size],
            cell: vec![0; size],
            */
        };
        g.calculate();
        g
    }

    fn calculate(&mut self) {
        let size = self.size;
        for y in 0..self.width {
            self.row_cell[y as usize] = y as usize / size as usize;
            self.col_cell[y as usize] = (y as usize/ size as usize) * size as usize;

            for x in 0..self.width {
                let index = self.pos(x,y);
                // x as usize + y as usize * self.width as usize;
                
                self.groups[Groups::Row as usize][index] = self.pos(x, y);
                self.groups[Groups::Column as usize][index] = self.pos(y, x);

                // self.row[index] = self.pos(x, y);
                // self.column[index] = self.pos(y, x);

                let x_off = x / size;
                let y_off = y / size;
                let x_mod = x % size;
                let y_mod = y % size;
                // x is correct:
                //    x_mod + y_mod * self.size;
                // y is correct:
                //    x_off + y_off * self.size
                self.groups[Groups::Cell as usize][index] =
                    self.pos(x_mod + y_mod * size, x_off + y_off * size);

            }
        }
    }

    #[must_use]
    #[inline]
    /// Convert (X,Y) to index.
    pub fn pos(&self, x: u8, y: u8) -> usize {
        x as usize + y as usize * self.width as usize
    }

    #[must_use]
    #[inline]
    /// Convert index to (X,Y).
    pub fn xy(&self, index: usize) -> (u8, u8) {
        let width = self.width as usize;
        ((index % width) as u8, (index / width) as u8)
    }

    /// Indexes for that Group (Row,Column,Cell)
    pub fn group(&self, g: Groups, row: u8) -> &[usize] {
        let width = self.width as usize;
        let start = row as usize * width;
        &self.groups[g as usize][start..start + width]
    }

    /// Indexes for that row
    pub fn row(&self, row: u8) -> &[usize] {
        // return slice of row:
        let width = self.width as usize;
        let start = row as usize * width;
        &self.groups[Groups::Row as usize][start..start + width]
    }

    /// Indexes for that column
    pub fn column(&self, column: u8) -> &[usize] {
        // return slice of row:
        let width = self.width as usize;
        let start = column as usize * width;
        &self.groups[Groups::Column as usize][start..start + width]
    }

    // Indexes for that cell.
    pub fn cell(&self, cell: u8) -> &[usize] {
        // return slice of cell:
        let width = self.width as usize;
        let start = cell as usize * width;
        &self.groups[Groups::Cell as usize][start..start + width]
    }

    #[must_use]
    /// Which cell contains (x,y)?
    pub fn which_cell(&self, x: u8, y: u8) -> u8 {
        (x / self.size) + (y / self.size) * self.size
    }

    /*
    #[deprecated="Use xy() instead"]
    #[must_use]
    /// Convert index to x,y offsets.
    pub fn cell_offset(&self, idx:u8) -> (u8,u8) {
        (idx % self.size, idx / self.size)
    }
    */
    
    #[must_use]
    /// Which index for given cell and (x,y)?
    pub fn which_cell_index(&self, cell_index:u8, x:u8, y:u8) -> usize {
        let (sx,sy) = self.cell_start(cell_index);
        self.pos(sx + x, sy+y)
    }

    #[must_use]
    /// Where does a given cell index start?
    pub fn cell_start(&self, cell_index:u8) -> (u8,u8) {
        ((cell_index % self.size) * self.size, (cell_index/self.size) * self.size)
    }

    #[must_use]
    /// Return index of cell (x,y)
    /// - This uses the groups to locate the index of the group.
    pub fn cell_index(&self, index: u8, x: u8, y: u8) -> usize {
        debug_assert!( x < self.size);
        debug_assert!( y < self.size);
        
        let result: usize =
            self.groups[Groups::Cell as usize][index as usize * self.width as usize];
        result + (y * self.width + x) as usize
    }

    // Possibly update this so it shows +1 on x and y
    // to match actual positions (rather then starting at 0).
    /// display Group
    pub fn display(&self) {
        let max_index_size = find_number_width(self.width as usize * self.width as usize);
        let max_pos_size = find_number_width(self.width as usize);

        let printer = |row: u8, data: &[usize]| {
            print!("[{:2}: ", row);
            for j in data {
                let xy = self.xy(*j);
                print!(
                    "{0:1$}({3:2$},{4:2$}) ",
                    j,
                    max_index_size,
                    max_pos_size,
                    xy.0 + 1,
                    xy.1 + 1
                );
            }
            println!("");
        };

        for g in Groups::iter() {
            println!("{:?}:", g);

            for i in 0..self.width {
                let r = self.group(g, i);
                /*
                print!("[{:2}]: ", i);
                for j in r {
                    let xy = self.xy(*j);
                    print!("{0:1$}({2:2},{3:2}) ", j, max_index_size, xy.0, xy.1);
                }
                println!("");
                */
                printer(i, r);
            }
        }
    }
}

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

    #[test]
    /// Verify that each index (0..max_index) is defined in each group.
    /// - Verify that it is used, and only once.
    fn check_dynamic() {
        for size in 3..=5 {
            let g = AnyGroup::new(size);
            // g.display();
            let mut all = vec![0 as u8; g.max_index];

            // Verify the X,Y values are in the correct cell.
            for gr in Groups::iter() {
                all.fill(0);

                for idx in 0..g.width {
                    let grp = g.group(gr, idx); // cell(idx);
                                                // g.display();
                    for indexes in grp {
                        let (x, y) = g.xy(*indexes);
                        assert!(
                            all[*indexes] == 0,
                            "{:?} Size {} Index [{}]({},{}) already seen",
                            gr,
                            size,
                            *indexes,
                            x + 1,
                            y + 1
                        );
                        all[*indexes] = 1;
                        if gr == Groups::Cell {
                            assert_eq!(
                                g.which_cell(x, y),
                                idx,
                                "Verify {:?} [{}]({},{}) in cell {}",
                                gr,
                                *indexes,
                                x,
                                y,
                                idx
                            );
                        }
                    }
                }
                for indexes in 0..g.max_index {
                    let (x, y) = g.xy(indexes);
                    assert!(
                        all[indexes] == 1,
                        "{:?} Size {} Index [{}]({},{}) not seen",
                        gr,
                        size,
                        indexes,
                        x + 1,
                        y + 1
                    );
                }
            }

            /*
            all.fill(0);
            for idx in 0..g.width {
                let grp = g.row(idx);

                for indexes in grp {
                    let (x, y) = g.xy(*indexes);
                    assert_eq!(y, idx, "Expected row Y {} == {}", y, idx);
                    assert!(
                        all[*indexes] == 0,
                        "Size {} row Index [{}]({},{}) already seen",
                        size,
                        *indexes,
                        x + 1,
                        y + 1
                    );
                    all[*indexes] = 1;
                }
            }
            for indexes in 0..g.max_index {
                let (x, y) = g.xy(indexes);
                assert!(
                    all[indexes] == 1,
                    "Size {} row Index [{}]({},{}) not seen",
                    size,
                    indexes,
                    x + 1,
                    y + 1
                );
            }

            all.fill(0);
            for idx in 0..g.width {
                let grp = g.column(idx);

                for indexes in grp {
                    let (x, y) = g.xy(*indexes);
                    assert_eq!(x, idx, "Expected column X {} == {}", x, idx);

                    assert!(
                        all[*indexes] == 0,
                        "Size {} col Index [{}]({},{}) already seen",
                        size,
                        *indexes,
                        x + 1,
                        y + 1
                    );
                    all[*indexes] = 1;
                }
            }
            for indexes in 0..g.max_index {
                let (x, y) = g.xy(indexes);
                assert!(
                    all[indexes] == 1,
                    "Size {} col Index [{}]({},{}) not seen",
                    size,
                    indexes,
                    x + 1,
                    y + 1
                );
            }
            */
        }
    }
    #[test]
    fn check_cells() {
        let size = 3;
        let g = AnyGroup::new(size);
        assert_eq!(g.cell_index(0, 0, 0), 0);
    }
}