use itertools::Itertools;

use std::cmp::min;

use integral_geometry::{Line, Ray, Point, Polygon, Rect, Size};

use land2d::Land2D;

use outline_template::OutlineTemplate;

pub struct OutlinePoints {

    pub islands: Vec<Polygon>,

    pub fill_points: Vec<Point>,

    pub size: Size,

    pub play_box: Rect,

    intersections_box: Rect,

}

impl OutlinePoints {

    pub fn from_outline_template<I: Iterator<Item = u32>>(

        outline_template: &OutlineTemplate,

        play_box: Rect,

        size: Size,

        random_numbers: &mut I,

    ) -> Self {

        Self {

            play_box,

            size,

            islands: outline_template

                .islands

                .iter()

                .map(|i| {

                    i.iter()

                        .zip(random_numbers.tuples())

                        .map(|(rect, (rnd_a, rnd_b))| {

                            play_box.top_left() + rect.quotient(rnd_a as usize, rnd_b as usize)

                        })

                        .collect::<Vec<_>>()

                        .into()

                })

                .collect(),

            fill_points: outline_template.fill_points.clone(),

            intersections_box: Rect::at_origin(size)

                .with_margin(size.to_square().width as i32 * -2),

        }

    }

    pub fn total_len(&self) -> usize {

        self.islands.iter().map(|i| i.edges_count()).sum::<usize>() + self.fill_points.len()

    }

    pub fn iter(&self) -> impl Iterator<Item = &Point> {

        self.islands

            .iter()

            .flat_map(|p| p.iter())

            .chain(self.fill_points.iter())

    }

    pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut Point> {

        self.islands

            .iter_mut()

            .flat_map(|i| i.iter_mut())

            .chain(self.fill_points.iter_mut())

    }

    fn divide_edge<I: Iterator<Item = u32>>(

        &self,

        segment: Line,

        distance_divisor: u32,

        random_numbers: &mut I,

    ) -> Option<Point> {

        #[inline]

        fn intersects(ray: &Ray, edge: &Line) -> bool {

            ray.orientation(edge.start) != ray.orientation(edge.end)

        }

        #[inline]

        fn solve_intersection(

            intersections_box: &Rect,

            ray: &Ray,

            edge: &Line

        ) -> Option<(i32, u32)>

        {

            let edge_dir = edge.scaled_direction();

            let aqpb = ray.direction.cross(edge_dir) as i64;

            if aqpb != 0 {

                let mut iy =

                    ((((edge.start.x - ray.start.x) as i64 * ray.direction.y as i64

                        + ray.start.y as i64 * ray.direction.x as i64)

                    * edge_dir.y as i64

                    - edge.start.y as i64 * edge_dir.x as i64 * ray.direction.y as i64)

                    / aqpb) as i32;

                // is there better way to do it?

                if iy < intersections_box.top() {

                    iy = intersections_box.top();

                } else if iy > intersections_box.bottom() {

                    iy = intersections_box.bottom();

                }

                let ix = if ray.direction.y.abs() > edge_dir.y.abs() {

                    (iy - ray.start.y) * ray.direction.cotangent() + ray.start.x

                } else {

                    (iy - edge.start.y) * edge_dir.cotangent() + edge.start.x

                };

                let intersection_point = Point::new(ix, iy).clamp(intersections_box);

                let diff_point = ray.start - intersection_point;

                let t = ray.direction.dot(diff_point);

                if diff_point.max_norm() >= std::i16::MAX as i32 {

                    Some((t, std::i32::MAX as u32))

                } else {

                    let d = diff_point.integral_norm();

                    Some((t, d))

                }

            } else {

                None

            }

        }

        let min_distance = 40;

        // new point should fall inside this box

        let map_box = self.play_box.with_margin(min_distance);

        let normal = segment.scaled_normal();

        let normal_len = normal.integral_norm();

        let mid_point = segment.center();

        if (normal_len < min_distance as u32 * 3) || !map_box.contains_inside(mid_point) {

            return None;

        }

        let normal_ray = Ray::new(mid_point, normal);

        let mut dist_left = (self.size.width + self.size.height) as u32;

        let mut dist_right = dist_left;

        // find distances to map borders

        if normal.x != 0 {

            // where the normal line intersects the left map border

            let left_intersection = Point::new(

                map_box.left(),

                (map_box.left() - mid_point.x) * normal.tangent() + mid_point.y,

            );

            dist_left = (mid_point - left_intersection).integral_norm();

            // same for the right border

            let right_intersection = Point::new(

                map_box.right(),

                (map_box.right() - mid_point.x) * normal.tangent() + mid_point.y,

            );

            dist_right = (mid_point - right_intersection).integral_norm();

            if normal.x > 0 {

                std::mem::swap(&mut dist_left, &mut dist_right);

            }

        }

        if normal.y != 0 {

            // where the normal line intersects the top map border

            let top_intersection = Point::new(

                (map_box.top() - mid_point.y) * normal.cotangent() + mid_point.x,

                map_box.top(),

            );

            let dl = (mid_point - top_intersection).integral_norm();

            // same for the bottom border

            let bottom_intersection = Point::new(

                (map_box.bottom() - mid_point.y) * normal.cotangent() + mid_point.x,

                map_box.bottom(),

            );

            let dr = (mid_point - bottom_intersection).integral_norm();

            if normal.y < 0 {

                dist_left = min(dist_left, dl);

                dist_right = min(dist_right, dr);

            } else {

                dist_left = min(dist_left, dr);

                dist_right = min(dist_right, dl);

            }

        }

        // now go through all other segments

        for s in self.segments_iter() {

            if s != segment {

                if intersects(&normal_ray, &s) {

                    if let Some((t, d)) =

                        solve_intersection(&self.intersections_box, &normal_ray, &s)

                    {

                        if t > 0 {

                            dist_right = min(dist_right, d);

                        } else {

                            dist_left = min(dist_left, d);

                        }

                    }

                }

            }

        }

        // go through all points, including fill points

        for pi in self.iter().cloned() {

            if pi != segment.start && pi != segment.end {

                if intersects(&pi.ray_to(normal), &segment) {

                    // ray from segment.start

                    if let Some((t, d)) = solve_intersection(

                        &self.intersections_box, &normal_ray, &segment.start.line_to(pi),

                    ) {

                        if t > 0 {

                            dist_right = min(dist_right, d);

                        } else {

                            dist_left = min(dist_left, d);

                        }

                    }

                    // ray from segment.end

                    if let Some((t, d)) = solve_intersection(

                        &self.intersections_box, &normal_ray, &segment.end.line_to(pi)

                    ) {

                        if t > 0 {

                            dist_right = min(dist_right, d);

                        } else {

                            dist_left = min(dist_left, d);

                        }

                    }

                }

            }

        }

        let max_dist = normal_len * 100 / distance_divisor;

        dist_left = min(dist_left, max_dist);

        dist_right = min(dist_right, max_dist);

        if dist_right + dist_left < min_distance as u32 * 2 + 10 {

            // limits are too narrow, just divide

            Some(mid_point)

        } else {

            // select distance within [-dist_right; dist_left], keeping min_distance in mind

            let d = -(dist_right as i32)

                + min_distance

                + random_numbers.next().unwrap() as i32

                    % (dist_right as i32 + dist_left as i32 - min_distance * 2);

            Some(mid_point + normal * d / normal_len as i32)

        }

    }

    fn divide_edges<I: Iterator<Item = u32>>(

        &mut self,

        distance_divisor: u32,

        random_numbers: &mut I,

    ) {

        for is in 0..self.islands.len() {

            let mut i = 0;

            while i < self.islands[is].edges_count() {

                let segment = self.islands[is].get_edge(i);

                if let Some(new_point) = self.divide_edge(segment, distance_divisor, random_numbers)

                {

                    self.islands[is].split_edge(i, new_point);

                    i += 2;

                } else {

                    i += 1;

                }

            }

        }

    }

    pub fn distort<I: Iterator<Item = u32>>(

        &mut self,

        distance_divisor: u32,

        random_numbers: &mut I,

    ) {

        loop {

            let old_len = self.total_len();

            self.divide_edges(distance_divisor, random_numbers);

            if self.total_len() == old_len {

                break;

            }

        }

    }

    pub fn draw<T: Copy + PartialEq>(&self, land: &mut Land2D<T>, value: T) {

        for segment in self.segments_iter() {

            land.draw_line(segment, value);

        }

    }

    fn segments_iter<'a>(&'a self) -> impl Iterator<Item = Line> + 'a {

        self.islands.iter().flat_map(|p| p.iter_edges())

    }

    pub fn mirror(&mut self) {

        let r = self.size.width as i32 - 1;

        self.iter_mut().for_each(|p| p.x = r - p.x);

    }

    pub fn flip(&mut self) {

        let t = self.size.height as i32 - 1;

        self.iter_mut().for_each(|p| p.y = t - p.y);

    }

}

#[test()]

fn points_test() {

    let size = Size::square(100);

    let mut points = OutlinePoints {

        islands: vec![

            Polygon::new(&[Point::new(0, 0), Point::new(20, 0), Point::new(30, 30)]),

            Polygon::new(&[Point::new(10, 15), Point::new(15, 20), Point::new(20, 15)]),

        ],

        fill_points: vec![Point::new(1, 1)],

        play_box: Rect::at_origin(size).with_margin(10),

        size: Size::square(100),

        intersections_box: Rect::at_origin(size),

    };

    let segments: Vec<Line> = points.segments_iter().collect();

    assert_eq!(

        segments.first(),

        Some(&Line::new(Point::new(0, 0), Point::new(20, 0)))

    );

    assert_eq!(

        segments.last(),

        Some(&Line::new(Point::new(20, 15), Point::new(10, 15)))

    );

    points.iter_mut().for_each(|p| p.x = 2);

    assert_eq!(points.fill_points[0].x, 2);

    assert_eq!(points.islands[0].get_edge(0).start.x, 2);

}