//  Stiletto
//  Copyright (C) 2020 Stiletto Authors
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU Affero General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Affero General Public License for more details.
//
//  You should have received a copy of the GNU Affero General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.

use std::vec::Vec;

use im::{vector, Vector};

use serde::de::{Deserializer, SeqAccess, Visitor};
use serde::ser::Serializer;
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, druid::Data)]
pub struct Path {
    pub kurbo_path: druid::kurbo::BezPath,
}

#[derive(Serialize, Deserialize)]
#[serde(remote = "druid::Color")]
enum ColorDef {
    Rgba32(u32),
}

struct Interval {
    start_pos: f64,
    end_pos: f64,
}

impl Interval {
    fn new(x1: f64, x2: f64) -> Interval {
        Interval {
            start_pos: x1.min(x2),
            end_pos: x1.max(x2),
        }
    }

    fn new_ordered(start: f64, end: f64) -> Interval {
        Interval {
            start_pos: start,
            end_pos: end,
        }
    }

    fn overlaps(&self, other: &Self) -> bool {
        self.start_pos < other.end_pos && other.start_pos < self.end_pos
    }
}

// O(1) complexity
// TODO(francesco): Implement this in a way that is not so flamboyant
// TODO(francesco): Implement intersection test for bezier curves
fn segment_intersects_rect(segment: &druid::kurbo::PathSeg, rect: druid::Rect) -> bool {
    match segment {
        druid::kurbo::PathSeg::Line(line) => {
            // A Segment intersects the rect
            // if their projections on the x and y line both overlap
            let line_x_proj = Interval::new(line.p0.x, line.p1.x);
            let line_y_proj = Interval::new(line.p0.y, line.p1.y);

            let rect_x_proj = Interval::new_ordered(rect.min_x(), rect.max_x());
            let rect_y_proj = Interval::new_ordered(rect.min_y(), rect.max_y());

            line_x_proj.overlaps(&rect_x_proj) && line_y_proj.overlaps(&rect_y_proj)
        }

        _ => {
            unimplemented!();
        }
    }
}

#[derive(Debug, Clone, druid::Data, Serialize, Deserialize)]
pub enum CanvasElement {
    Freehand {
        path: Path,
        thickness: f64,
        #[serde(with = "ColorDef")]
        stroke_color: druid::Color,
    },
}

impl CanvasElement {
    pub fn bounding_box(&self) -> druid::Rect {
        match self {
            CanvasElement::Freehand {
                path, thickness, ..
            } => {
                use druid::kurbo::Shape;
                path.kurbo_path
                    .bounding_box()
                    .inflate(*thickness, *thickness)
            }
        }
    }

    pub fn intersects_rect(&self, rect: druid::Rect) -> bool {
        match self {
            CanvasElement::Freehand { path, .. } => {
                // TODO(enrico) this doesn't handle thickness
                path.kurbo_path
                    .segments()
                    .any(|segment| segment_intersects_rect(&segment, rect))
            }
        }
    }

    pub fn draw(&self, ctx: &mut druid::PaintCtx) {
        match self {
            CanvasElement::Freehand {
                path,
                thickness,
                stroke_color,
            } => {
                use druid::RenderContext;
                ctx.stroke(&path.kurbo_path, &*stroke_color, *thickness);
            }
        }
    }

    pub fn draw_selected(&self, ctx: &mut druid::PaintCtx) {
        match self {
            CanvasElement::Freehand {
                path,
                thickness,
                ..
            } => {
                use druid::RenderContext;
                ctx.stroke(&path.kurbo_path, &druid::Color::rgb(10.0, 0.0, 255.0), *thickness * 1.4);
            }
        }
    }
}

#[derive(Clone, druid::Data)]
pub struct Canvas {
    elements: Vector<CanvasElement>,
    content_size: druid::Size,
    selected_elements: Vector<usize>,
}

impl Canvas {
    pub fn new() -> Self {
        Canvas {
            elements: vector![],
            content_size: druid::Size::new(0.0, 0.0),
            selected_elements: vector![],
        }
    }

    pub fn new_with_elements(elements: Vector<CanvasElement>) -> Self {
        let mut cv = Canvas::new();
        for e in elements {
            cv.add_element(e);
        }
        cv
    }

    pub fn add_element(&mut self, element: CanvasElement) {
        self.content_size = self
            .content_size
            .to_rect()
            .union(element.bounding_box())
            .size();
        self.elements.push_back(element);
    }

    pub fn elements(&self) -> &Vector<CanvasElement> {
        &self.elements
    }

    /// Find all CanvasElement that intersect with rect
    pub fn find_intersections(&self, rect: druid::Rect) -> Vec<usize> {
        let mut found_elements = Vec::<usize>::new();

        for (i, elem) in self.elements.iter().enumerate() {
            // Check if the element intersects the eraser rect
            if elem.bounding_box().intersect(rect).area() > 0.0 {
                if elem.intersects_rect(rect) {
                    found_elements.push(i);
                }
            }
        }

        found_elements
    }

    pub fn content_size(&self) -> druid::Size {
        self.content_size
    }

    pub fn selected_elements(&self) -> &Vector<usize> {
        &self.selected_elements
    }

    pub fn selected_elements_mut(&mut self) -> &mut Vector<usize> {
        &mut self.selected_elements
    }
}

impl Serialize for Path {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        use druid::kurbo::PathEl;

        serializer.collect_seq(self.kurbo_path.iter().filter_map(|path_el| match path_el {
            PathEl::MoveTo(pt) => Some(Into::<(f64, f64)>::into(pt)),
            PathEl::LineTo(pt) => Some(Into::<(f64, f64)>::into(pt)),
            _ => None,
        }).collect::<Vec<(f64, f64)>>())
    }
}

impl<'de> Deserialize<'de> for Path {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        struct PathVisitor;

        impl<'de> Visitor<'de> for PathVisitor {
            type Value = Path;

            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
                write!(formatter, "A sequence of 2D points")
            }

            fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
            where
                A: SeqAccess<'de>,
            {
                use druid::kurbo::BezPath;

                let mut kurbo_path = BezPath::new();
                let mut first_element = true;
                while let Some(point) = seq.next_element::<(f64, f64)>()? {
                    if first_element {
                        kurbo_path.move_to(point);
                        first_element = false;
                    } else {
                        kurbo_path.line_to(point);
                    }
                }

                Ok(Path { kurbo_path })
            }
        }

        deserializer.deserialize_seq(PathVisitor)
    }
}