use crate::input::ContextMenu;
use crate::{
    text, Canvas, Color, HorizontalAlignment, Key, ScreenDims, ScreenPt, Text, VerticalAlignment,
};
use geom::{Bounds, Circle, Distance, Line, Polygon, Pt2D};
use glium::uniforms::{SamplerBehavior, SamplerWrapFunction, UniformValue};
use glium::Surface;
use std::cell::Cell;

const MAPSPACE: f32 = 0.0;
const SCREENSPACE: f32 = 1.0;

struct Uniforms<'a> {
    // (cam_x, cam_y, cam_zoom)
    transform: [f32; 3],
    // (window_width, window_height, 0.0 for mapspace or 1.0 for screenspace)
    window: [f32; 3],
    canvas: &'a Canvas,
}

impl<'a> Uniforms<'a> {
    fn new(canvas: &'a Canvas) -> Uniforms<'a> {
        Uniforms {
            transform: [
                canvas.cam_x as f32,
                canvas.cam_y as f32,
                canvas.cam_zoom as f32,
            ],
            window: [
                canvas.window_width as f32,
                canvas.window_height as f32,
                MAPSPACE,
            ],
            canvas,
        }
    }
}

impl<'b> glium::uniforms::Uniforms for Uniforms<'b> {
    fn visit_values<'a, F: FnMut(&str, UniformValue<'a>)>(&'a self, mut output: F) {
        output("transform", UniformValue::Vec3(self.transform));
        output("window", UniformValue::Vec3(self.window));

        let tile = SamplerBehavior {
            wrap_function: (
                SamplerWrapFunction::Repeat,
                SamplerWrapFunction::Repeat,
                SamplerWrapFunction::Repeat,
            ),
            ..Default::default()
        };
        for (idx, (_, tex)) in self.canvas.textures.iter().enumerate() {
            output(
                &format!("tex{}", idx),
                UniformValue::Texture2d(tex, Some(tile)),
            );
        }
    }
}

pub struct GfxCtx<'a> {
    pub(crate) target: &'a mut glium::Frame,
    program: &'a glium::Program,
    uniforms: Uniforms<'a>,
    params: glium::DrawParameters<'a>,

    screencap_mode: bool,
    pub(crate) naming_hint: Option<String>,

    // TODO Don't be pub. Delegate everything.
    pub canvas: &'a Canvas,
    pub prerender: &'a Prerender<'a>,
    context_menu: &'a ContextMenu,

    pub num_draw_calls: usize,
}

impl<'a> GfxCtx<'a> {
    pub(crate) fn new(
        canvas: &'a Canvas,
        prerender: &'a Prerender<'a>,
        target: &'a mut glium::Frame,
        program: &'a glium::Program,
        context_menu: &'a ContextMenu,
        screencap_mode: bool,
    ) -> GfxCtx<'a> {
        let params = glium::DrawParameters {
            blend: glium::Blend::alpha_blending(),
            depth: glium::Depth {
                test: glium::DepthTest::IfLessOrEqual,
                write: true,
                ..Default::default()
            },
            ..Default::default()
        };

        let uniforms = Uniforms::new(&canvas);

        GfxCtx {
            canvas,
            prerender,
            target,
            program,
            uniforms,
            params,
            num_draw_calls: 0,
            screencap_mode,
            naming_hint: None,
            context_menu,
        }
    }

    // Up to the caller to call unfork()!
    // TODO Canvas doesn't understand this change, so things like text drawing that use
    // map_to_screen will just be confusing.
    pub fn fork(&mut self, top_left_map: Pt2D, top_left_screen: ScreenPt, zoom: f64) {
        // map_to_screen of top_left_map should be top_left_screen
        let cam_x = (top_left_map.x() * zoom) - top_left_screen.x;
        let cam_y = (top_left_map.y() * zoom) - top_left_screen.y;

        self.uniforms.transform = [cam_x as f32, cam_y as f32, zoom as f32];
        self.uniforms.window = [
            self.canvas.window_width as f32,
            self.canvas.window_height as f32,
            SCREENSPACE,
        ];
    }

    pub fn fork_screenspace(&mut self) {
        self.uniforms.transform = [0.0, 0.0, 1.0];
        self.uniforms.window = [
            self.canvas.window_width as f32,
            self.canvas.window_height as f32,
            SCREENSPACE,
        ];
    }

    pub fn unfork(&mut self) {
        self.uniforms = Uniforms::new(&self.canvas);
    }

    pub fn clear(&mut self, color: Color) {
        match color {
            Color::RGBA(r, g, b, a) => {
                // Without this, SRGB gets enabled and post-processes the color from the fragment
                // shader.
                self.target.clear_color_srgb_and_depth((r, g, b, a), 1.0);
            }
            _ => unreachable!(),
        }
    }

    pub fn draw_line(&mut self, color: Color, thickness: Distance, line: &Line) {
        self.draw_polygon(color, &line.make_polygons(thickness));
    }

    pub fn draw_rounded_line(&mut self, color: Color, thickness: Distance, line: &Line) {
        self.draw_polygons(
            color,
            &vec![
                line.make_polygons(thickness),
                Circle::new(line.pt1(), thickness / 2.0).to_polygon(),
                Circle::new(line.pt2(), thickness / 2.0).to_polygon(),
            ],
        );
    }

    pub fn draw_arrow(&mut self, color: Color, thickness: Distance, line: &Line) {
        self.draw_polygon(color, &line.to_polyline().make_arrow(thickness).unwrap());
    }

    pub fn draw_circle(&mut self, color: Color, circle: &Circle) {
        self.draw_polygon(color, &circle.to_polygon());
    }

    pub fn draw_polygon(&mut self, color: Color, poly: &Polygon) {
        let obj = self.prerender.upload_temporary(vec![(color, poly)]);
        self.redraw(&obj);
    }

    pub fn draw_polygons(&mut self, color: Color, polygons: &Vec<Polygon>) {
        let obj = self
            .prerender
            .upload_temporary(polygons.iter().map(|p| (color, p)).collect());
        self.redraw(&obj);
    }

    pub fn redraw(&mut self, obj: &Drawable) {
        self.target
            .draw(
                &obj.vertex_buffer,
                &obj.index_buffer,
                &self.program,
                &self.uniforms,
                &self.params,
            )
            .unwrap();
        self.num_draw_calls += 1;

        // println!("{:?}", backtrace::Backtrace::new());
    }

    // Canvas stuff.

    // The text box covers up what's beneath and eats the cursor (for get_cursor_in_map_space).
    pub fn draw_blocking_text(
        &mut self,
        txt: &Text,
        (horiz, vert): (HorizontalAlignment, VerticalAlignment),
    ) {
        if txt.is_empty() {
            return;
        }
        let (mut width, height) = self.text_dims(&txt);
        let x1 = match horiz {
            HorizontalAlignment::Left => 0.0,
            HorizontalAlignment::Center => (self.canvas.window_width - width) / 2.0,
            HorizontalAlignment::Right => self.canvas.window_width - width,
            HorizontalAlignment::FillScreen => {
                width = self.canvas.window_width;
                0.0
            }
        };
        let y1 = match vert {
            VerticalAlignment::Top => 0.0,
            VerticalAlignment::Center => (self.canvas.window_height - height) / 2.0,
            VerticalAlignment::Bottom => self.canvas.window_height - height,
        };
        self.canvas.mark_covered_area(text::draw_text_bubble(
            self,
            ScreenPt::new(x1, y1),
            txt,
            (width, height),
        ));
    }

    pub fn get_screen_bounds(&self) -> Bounds {
        self.canvas.get_screen_bounds()
    }

    // TODO Rename these draw_nonblocking_text_*
    pub fn draw_text_at(&mut self, txt: &Text, map_pt: Pt2D) {
        let (width, height) = self.text_dims(&txt);
        let pt = self.canvas.map_to_screen(map_pt);
        text::draw_text_bubble(
            self,
            ScreenPt::new(pt.x - (width / 2.0), pt.y - (height / 2.0)),
            txt,
            (width, height),
        );
    }

    pub fn draw_text_at_mapspace(&mut self, txt: &Text, map_pt: Pt2D) {
        let (width, height) = self.text_dims(&txt);
        text::draw_text_bubble_mapspace(
            self,
            Pt2D::new(
                map_pt.x() - (width / (2.0 * text::SCALE_DOWN)),
                map_pt.y() - (height / (2.0 * text::SCALE_DOWN)),
            ),
            txt,
            (width, height),
        );
    }

    pub fn text_dims(&self, txt: &Text) -> (f64, f64) {
        self.canvas.text_dims(txt)
    }

    pub fn draw_text_at_screenspace_topleft(&mut self, txt: &Text, pt: ScreenPt) {
        let dims = self.text_dims(&txt);
        self.canvas
            .mark_covered_area(text::draw_text_bubble(self, pt, txt, dims));
    }

    pub fn draw_mouse_tooltip(&mut self, txt: &Text) {
        let (width, height) = self.text_dims(&txt);
        // TODO Maybe also consider the cursor as a valid center. After context menus go away, this
        // makes even more sense.
        let pt = ScreenDims::new(width, height).top_left_for_corner(
            ScreenPt::new(self.canvas.cursor_x, self.canvas.cursor_y),
            &self.canvas,
        );
        // No need to cover the tooltip; this tooltip follows the mouse anyway.
        text::draw_text_bubble(self, pt, txt, (width, height));
    }

    pub fn screen_to_map(&self, pt: ScreenPt) -> Pt2D {
        self.canvas.screen_to_map(pt)
    }

    pub fn get_cursor_in_map_space(&self) -> Option<Pt2D> {
        self.canvas.get_cursor_in_map_space()
    }

    pub fn get_num_uploads(&self) -> usize {
        self.prerender.num_uploads.get()
    }

    pub fn is_screencap(&self) -> bool {
        self.screencap_mode
    }

    pub fn set_screencap_naming_hint(&mut self, hint: String) {
        assert!(self.screencap_mode);
        assert!(self.naming_hint.is_none());
        self.naming_hint = Some(hint);
    }

    pub fn get_active_context_menu_keys(&self) -> Vec<Key> {
        match self.context_menu {
            ContextMenu::Inactive(ref keys) => keys.iter().cloned().collect(),
            ContextMenu::Displaying(ref menu) => {
                menu.active_choices().into_iter().cloned().collect()
            }
            _ => Vec::new(),
        }
    }

    pub fn upload(&mut self, batch: GeomBatch) -> Drawable {
        self.prerender.upload(batch)
    }
}

pub struct GeomBatch {
    list: Vec<(Color, Polygon)>,
}

impl GeomBatch {
    pub fn new() -> GeomBatch {
        GeomBatch { list: Vec::new() }
    }

    pub fn from(list: Vec<(Color, Polygon)>) -> GeomBatch {
        GeomBatch { list }
    }

    pub fn push(&mut self, color: Color, p: Polygon) {
        self.list.push((color, p));
    }

    pub fn extend(&mut self, color: Color, polys: Vec<Polygon>) {
        for p in polys {
            self.list.push((color, p));
        }
    }

    pub fn append(&mut self, other: &GeomBatch) {
        self.list.extend(other.list.clone());
    }

    pub fn draw(self, g: &mut GfxCtx) {
        let refs = self.list.iter().map(|(color, p)| (*color, p)).collect();
        let obj = g.prerender.upload_temporary(refs);
        g.redraw(&obj);
    }
}

// Something that's been sent to the GPU already.
pub struct Drawable {
    vertex_buffer: glium::VertexBuffer<Vertex>,
    index_buffer: glium::IndexBuffer<u32>,
}

#[derive(Copy, Clone)]
pub(crate) struct Vertex {
    position: [f32; 2],
    // If the last component is non-zero, then this is an RGBA value.
    // When the last component is 0, then this is (texture ID, tex coord X, text coord Y, 0)
    // And one more case -- (10, 0, 0, 0) means to just draw hatching.
    // TODO Make this u8?
    style: [f32; 4],
}

glium::implement_vertex!(Vertex, position, style);

// TODO Don't expose this directly
pub struct Prerender<'a> {
    pub(crate) display: &'a glium::Display,
    pub(crate) num_uploads: Cell<usize>,
    // TODO Prerender doesn't know what things are temporary and permanent. Could make the API more
    // detailed (and use the corresponding persistent glium types).
    pub(crate) total_bytes_uploaded: Cell<usize>,
}

impl<'a> Prerender<'a> {
    pub fn upload_borrowed(&self, list: Vec<(Color, &Polygon)>) -> Drawable {
        self.actually_upload(true, list)
    }

    pub fn upload(&self, batch: GeomBatch) -> Drawable {
        let borrows = batch.list.iter().map(|(c, p)| (*c, p)).collect();
        self.actually_upload(true, borrows)
    }

    pub fn get_total_bytes_uploaded(&self) -> usize {
        self.total_bytes_uploaded.get()
    }

    pub(crate) fn upload_temporary(&self, list: Vec<(Color, &Polygon)>) -> Drawable {
        self.actually_upload(false, list)
    }

    fn actually_upload(&self, permanent: bool, list: Vec<(Color, &Polygon)>) -> Drawable {
        self.num_uploads.set(self.num_uploads.get() + 1);

        let mut vertices: Vec<Vertex> = Vec::new();
        let mut indices: Vec<u32> = Vec::new();

        for (color, poly) in list {
            let idx_offset = vertices.len();
            let (pts, raw_indices) = poly.raw_for_rendering();
            for pt in pts {
                let style = match color {
                    Color::RGBA(r, g, b, a) => [r, g, b, a],
                    Color::Texture(id, (tex_width, tex_height)) => {
                        // The texture uses SamplerWrapFunction::Repeat, so don't clamp to [0, 1].
                        // Also don't offset based on the polygon's bounds -- even if there are
                        // separate but adjacent polygons, we want seamless tiling.
                        let tx = pt.x() / tex_width;
                        let ty = pt.y() / tex_height;
                        [id, tx as f32, ty as f32, 0.0]
                    }
                    Color::Hatching => [10.0, 0.0, 0.0, 0.0],
                };
                vertices.push(Vertex {
                    position: [pt.x() as f32, pt.y() as f32],
                    style,
                });
            }
            for idx in raw_indices {
                indices.push((idx_offset + *idx) as u32);
            }
        }

        let vertex_buffer = if permanent {
            glium::VertexBuffer::immutable(self.display, &vertices).unwrap()
        } else {
            glium::VertexBuffer::new(self.display, &vertices).unwrap()
        };
        let index_buffer = if permanent {
            glium::IndexBuffer::immutable(
                self.display,
                glium::index::PrimitiveType::TrianglesList,
                &indices,
            )
            .unwrap()
        } else {
            glium::IndexBuffer::new(
                self.display,
                glium::index::PrimitiveType::TrianglesList,
                &indices,
            )
            .unwrap()
        };

        if permanent {
            self.total_bytes_uploaded.set(
                self.total_bytes_uploaded.get()
                    + vertex_buffer.get_size()
                    + index_buffer.get_size(),
            );
        }

        Drawable {
            vertex_buffer,
            index_buffer,
        }
    }
}

pub struct MultiText {
    list: Vec<(Text, ScreenPt)>,
}

impl MultiText {
    pub fn new() -> MultiText {
        MultiText { list: Vec::new() }
    }

    pub fn add(&mut self, txt: Text, pt: ScreenPt) {
        self.list.push((txt, pt));
    }

    pub fn draw(&self, g: &mut GfxCtx) {
        for (txt, pt) in &self.list {
            g.draw_text_at_screenspace_topleft(txt, *pt);
        }
    }
}