extern crate vec2d;

use std::cmp;

use std::ops;

pub struct Land2D<T> {

    pixels: vec2d::Vec2D<T>,

    width_mask: usize,

    height_mask: usize,

}

impl<T: Copy + PartialEq> Land2D<T> {

    pub fn new(width: usize, height: usize, fill_value: T) -> Self {

        assert!(width.is_power_of_two());

        assert!(height.is_power_of_two());

        Self {

            pixels: vec2d::Vec2D::new(width, height, fill_value),

            width_mask: !(width - 1),

            height_mask: !(height - 1),

        }

    }

    #[inline]

    pub fn width(&self) -> usize {

        self.pixels.width()

    }

    #[inline]

    pub fn height(&self) -> usize {

        self.pixels.height()

    }

    #[inline]

    pub fn is_valid_x(&self, x: i32) -> bool {

        (x as usize & self.width_mask) == 0

    }

    #[inline]

    pub fn is_valid_y(&self, y: i32) -> bool {

        (y as usize & self.height_mask) == 0

    }

    #[inline]

    pub fn is_valid_coordinate(&self, x: i32, y: i32) -> bool {

        self.is_valid_x(x) && self.is_valid_y(y)

    }

    #[inline]

    pub fn map<U: Default, F: FnOnce(&mut T) -> U>(&mut self, y: i32, x: i32, f: F) -> U {

        if self.is_valid_coordinate(x, y) {

            unsafe {

                // hey, I just checked that coordinates are valid!

                f(self.pixels.get_unchecked_mut(y as usize, x as usize))

            }

        } else {

            U::default()

        }

    }

    fn apply_along_line<U: Default + ops::AddAssign, F: FnMut(i32, i32) -> U>(

        x1: i32,

        y1: i32,

        x2: i32,

        y2: i32,

        f: &mut F,

    ) -> U {

        let mut result = U::default();

        let mut e_x: i32 = 0;

        let mut e_y: i32 = 0;

        let mut d_x: i32 = x2 - x1;

        let mut d_y: i32 = y2 - y1;

        let s_x: i32;

        let s_y: i32;

        if d_x > 0 {

            s_x = 1;

        } else if d_x < 0 {

            s_x = -1;

            d_x = -d_x;

        } else {

            s_x = d_x;

        }

        if d_y > 0 {

            s_y = 1;

        } else if d_y < 0 {

            s_y = -1;

            d_y = -d_y;

        } else {

            s_y = d_y;

        }

        let d = cmp::max(d_x, d_y);

        let mut x = x1;

        let mut y = y1;

        for _i in 0..=d {

            e_x += d_x;

            e_y += d_y;

            if e_x > d {

                e_x -= d;

                x += s_x;

            }

            if e_y > d {

                e_y -= d;

                y += s_y;

            }

            result += f(x, y);

        }

        result

    }

    fn apply_around_circle<U: Default + ops::AddAssign, F: FnMut(i32, i32) -> U>(

        radius: i32,

        f: &mut F,

    ) -> U {

        let mut dx: i32 = 0;

        let mut dy: i32 = radius;

        let mut d = 3 - 2 * radius;

        let mut result = U::default();

        while dx < dy {

            result += f(dx, dy);

            if d < 0 {

                d += 4 * dx + 6;

            } else {

                d += 4 * (dx - dy) + 10;

                dy -= 1;

            }

            dx += 1;

        }

        if dx == dy {

            result += f(dx, dy);

        }

        result

    }

    pub fn draw_line(&mut self, x1: i32, y1: i32, x2: i32, y2: i32, value: T) -> usize {

    }

    pub fn fill(&mut self, start_x: i32, start_y: i32, border_value: T, fill_value: T) {

        debug_assert!(self.is_valid_coordinate(start_x - 1, start_y));

        debug_assert!(self.is_valid_coordinate(start_x, start_y));

        let mut stack: Vec<(usize, usize, usize, isize)> = Vec::new();

        fn push<T: Copy + PartialEq>(

            land: &Land2D<T>,

            stack: &mut Vec<(usize, usize, usize, isize)>,

            xl: usize,

            xr: usize,

            y: usize,

            dir: isize,

        ) {

            let yd = y as isize + dir;

            if land.is_valid_coordinate(0, yd as i32) {

                stack.push((xl, xr, yd as usize, dir));

            }

        };

        let start_x_l = (start_x - 1) as usize;

        let start_x_r = start_x as usize;

        push(self, &mut stack, start_x_l, start_x_r, start_y as usize, -1);

        push(self, &mut stack, start_x_l, start_x_r, start_y as usize, 1);

        loop {

            let a = stack.pop();

            match a {

                None => return,

                Some(a) => {

                    let (mut xl, mut xr, y, mut dir) = a;

                    while xl > 0 && self

                        .pixels

                        .get(y, xl)

                        .map_or(false, |v| *v != border_value && *v != fill_value)

                    {

                        xl -= 1;

                    }

                    while xr < self.width() - 1 && self

                        .pixels

                        .get(y, xr)

                        .map_or(false, |v| *v != border_value && *v != fill_value)

                    {

                        xr += 1;

                    }

                    while xl < xr {

                        while xl <= xr

                            && (self.pixels[y][xl] == border_value

                                || self.pixels[y][xl] == fill_value)

                        {

                            xl += 1;

                        }

                        let mut x = xl;

                        while xl <= xr

                            && (self.pixels[y][xl] != border_value

                                && self.pixels[y][xl] != fill_value)

                        {

                            self.pixels[y][xl] = fill_value;

                            xl += 1;

                        }

                        if x < xl {

                            push(self, &mut stack, x, xl - 1, y, dir);

                            push(self, &mut stack, x, xl - 1, y, -dir);

                        }

                    }

                }

            }

        }

    }

    #[inline]

    fn fill_circle_line<F: Fn(&mut T) -> usize>(

        &mut self,

        y: i32,

        x_from: i32,

        x_to: i32,

        f: &F,

    ) -> usize {

        let mut result = 0;

        if self.is_valid_y(y) {

            for i in cmp::min(x_from, 0) as usize..cmp::max(x_to as usize, self.width() - 1) {

                unsafe {

                    // coordinates are valid at this point

                    result += f(self.pixels.get_unchecked_mut(y as usize, i));

                }

            }

        }

        result

    }

    #[inline]

    fn fill_circle_lines<F: Fn(&mut T) -> usize>(

        &mut self,

        x: i32,

        y: i32,

        dx: i32,

        dy: i32,

        f: &F,

    ) -> usize {

        self.fill_circle_line(y + dy, x - dx, x + dx, f)

            + self.fill_circle_line(y - dy, x - dx, x + dx, f)

            + self.fill_circle_line(y + dx, x - dy, x + dy, f)

            + self.fill_circle_line(y - dx, x - dy, x + dy, f)

    }

    pub fn change_round<F: Fn(&mut T) -> usize>(

        &mut self,

        x: i32,

        y: i32,

        radius: i32,

        f: F,

    ) -> usize {

        <Land2D<T>>::apply_around_circle(radius, &mut |dx, dy| {

            self.fill_circle_lines(x, y, dx, dy, &f)

        })

    }

    #[inline]

    fn change_dots_around<U: Default + ops::AddAssign, F: FnMut(i32, i32) -> U>(

        x: i32,

        y: i32,

        xx: i32,

        yy: i32,

        f: &mut F,

    ) -> U {

        let mut result = U::default();

        result += f(y + yy, x + xx);

        result += f(y - yy, x + xx);

        result += f(y + yy, x - xx);

        result += f(y - yy, x - xx);

        result += f(y + xx, x + yy);

        result += f(y - xx, x + yy);

        result += f(y + xx, x - yy);

        result += f(y - xx, x - yy);

        result

    }

    pub fn draw_thick_line(

        &mut self,

        x1: i32,

        y1: i32,

        x2: i32,

        y2: i32,

        radius: i32,

        value: T,

    ) -> usize {

        <Land2D<T>>::apply_around_circle(radius, &mut |dx, dy| {

            <Land2D<T>>::apply_along_line(x1, y1, x2, y2, &mut |x, y| {

                <Land2D<T>>::change_dots_around(x, y, dx, dy, &mut |x, y| {

                    self.map(x, y, |p| {

                        if *p != value {

                            *p = value;

                            1

                        } else {

                            0

                        }

                    })

                })

            })

        })

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn basics() {

        let l: Land2D<u8> = Land2D::new(32, 64, 0);

        assert!(l.is_valid_coordinate(0, 0));

        assert!(!l.is_valid_coordinate(-1, -1));

        assert!(l.is_valid_coordinate(31, 63));

        assert!(!l.is_valid_coordinate(32, 63));

        assert!(!l.is_valid_coordinate(31, 64));

    }

    #[test]

    fn fill() {

        let mut l: Land2D<u8> = Land2D::new(128, 128, 0);

        l.draw_line(0, 0, 32, 96, 1);

        l.draw_line(32, 96, 64, 32, 1);

        l.draw_line(64, 32, 96, 80, 1);

        l.draw_line(96, 80, 128, 0, 1);

        l.draw_line(0, 128, 64, 96, 1);

        l.draw_line(128, 128, 64, 96, 1);

        l.fill(32, 32, 1, 2);

        l.fill(16, 96, 1, 3);

        l.fill(60, 100, 1, 4);

        assert_eq!(l.pixels[0][0], 1);

        assert_eq!(l.pixels[96][64], 1);

        assert_eq!(l.pixels[40][32], 2);

        assert_eq!(l.pixels[40][96], 2);

        assert_eq!(l.pixels[5][0], 3);

        assert_eq!(l.pixels[120][0], 3);

        assert_eq!(l.pixels[5][127], 3);

        assert_eq!(l.pixels[120][127], 3);

        assert_eq!(l.pixels[35][64], 3);

        assert_eq!(l.pixels[120][20], 4);

        assert_eq!(l.pixels[120][100], 4);

        assert_eq!(l.pixels[100][64], 4);

    }

}