//! Module for drawing SVG files to the screen or maybe a texture etc.

pub mod style;

use crate::math::Vec2;
use raylib::drawing::RaylibDraw;
use std::fs::File;
use std::io::{self, Read};
use std::ops::Deref;
use std::path::Path;
use std::str::FromStr;
use style::Style;
use svgtypes::{Path as SVGPath, PathSegment};
use xmltree::{Element, XMLNode};

/// Find the first XML-Node with the given name. With depth, the maximum depth the
/// algorithm will search to can be set. If it is set to `None`, the algorithm will search the
/// entire sub-tree. Returns `None` if no such child can be found. Returns itself, in case the root
/// node is already of the name given.
pub fn find_first_node(root: Element, name: &str, depth: Option<usize>) -> Option<Element> {
    // The abort condition of this recursive function. If the element itself is of the required
    // name, return it.
    if root.name == name {
        return Some(root);
    }
    // Also abort, if the depth is reached.
    if depth == Some(0) {
        return None;
    }

    // Decrease the depth by one for all calls on the children, if it is set.
    let depth = match depth {
        Some(depth) => Some(depth - 1),
        None => None,
    };

    // Recursively look for the element in this node's children.
    for child in root.children {
        // We only care for the elements, not for comments, cdata etc.
        if let XMLNode::Element(element) = child {
            if let Some(element) = find_first_node(element, name, depth) {
                return Some(element);
            }
        }
    }

    None
}

/// Read an svg file from the given path. On success, return the first graphics data that is read
/// from this file. This can be used to draw an SVG.
pub fn read_svg_file<P: AsRef<Path>>(file: P) -> io::Result<Element> {
    let mut file = File::open(file)?;
    let mut data = String::new();
    file.read_to_string(&mut data)?;

    let root: Element = match Element::parse(data.as_bytes()) {
        Ok(root) => root,
        Err(err) => return Err(io::Error::new(io::ErrorKind::InvalidData, err)),
    };

    match find_first_node(root, "g", None) {
        Some(graphics) => Ok(graphics),
        None => Err(io::Error::new(
            io::ErrorKind::InvalidData,
            "No graphics element in the file",
        )),
    }
}

/// Trait that indicates a struct is capable of drawing SVG-elements.
pub trait DrawSVG {
    /// Draw the elements given by `svg_data` and all its children to the implementor, with the
    /// specified scale and translated by `position_px`.
    fn draw_svg(&mut self, svg_data: &Element, pixels_per_m: f32, position_px: Vec2<f32>);
}

impl<D> DrawSVG for D
where
    D: RaylibDraw,
{
    fn draw_svg(&mut self, svg_data: &Element, pixels_per_m: f32, position_px: Vec2<f32>) {
        assert_eq!(&svg_data.name, "g");

        // Go through all the graphics children and draw them one by one
        for child in &svg_data.children {
            if let XMLNode::Element(child) = child {
                match child.name.as_str() {
                    "path" => draw_path(self, child, pixels_per_m, position_px),
                    other => warn!("Unsupported SVG-Element {}", other),
                }
            }
        }
    }
}

// Helper functions to draw specific parts of the SVG file --------------------

fn draw_path(
    d: &mut impl RaylibDraw,
    path_data: &Element,
    pixels_per_m: f32,
    position_px: Vec2<f32>,
) {
    let style = if let Some(style_data) = path_data.attributes.get("style") {
        match Style::from_str(style_data) {
            Ok(style) => style,
            Err(err) => {
                warn!("Could not parse path style: {}", err);
                warn!("Using default style instead");
                Style::default()
            }
        }
    } else {
        Style::default()
    };

    let move_data = match path_data.attributes.get("d") {
        Some(d) => d,
        None => {
            error!("Unable to draw path, no move data found");
            return;
        }
    };

    let mut path: SVGPath = match move_data.parse() {
        Ok(mv) => mv,
        Err(err) => {
            error!(
                "Unable to draw path, move data not correctly formatted: {}",
                err
            );
            return;
        }
    };

    path.conv_to_absolute();

    let mut current_pos: Vec2<f32> = Vec2::new(0., 0.);
    for segment in path.deref() {
        match segment {
            PathSegment::MoveTo { x, y, .. } => {
                current_pos.x = *x as f32;
                current_pos.y = *y as f32;
            }
            PathSegment::LineTo { x, y, .. } => {
                d.draw_line_ex(
                    current_pos * pixels_per_m / 1000. + position_px,
                    Vec2::new(*x as f32, *y as f32) * pixels_per_m / 1000. + position_px,
                    pixels_per_m * style.stroke_width / 1000.,
                    style.stroke,
                );
                current_pos.x = *x as f32;
                current_pos.y = *y as f32;
            }
            PathSegment::HorizontalLineTo { x, .. } => {
                d.draw_line_ex(
                    current_pos * pixels_per_m / 1000. + position_px,
                    Vec2::new(*x as f32, current_pos.y) * pixels_per_m / 1000. + position_px,
                    pixels_per_m * style.stroke_width / 1000.,
                    style.stroke,
                );
                current_pos.x = *x as f32;
            }
            PathSegment::VerticalLineTo { y, .. } => {
                d.draw_line_ex(
                    current_pos * pixels_per_m / 1000. + position_px,
                    Vec2::new(current_pos.x, *y as f32) * pixels_per_m / 1000. + position_px,
                    pixels_per_m * style.stroke_width / 1000.,
                    style.stroke,
                );
                current_pos.y = *y as f32;
            }
            PathSegment::ClosePath { .. } => return,
            other => warn!("Ignoring unsupported {:?}", other),
        }
    }
}