// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE-APACHE file or at:
//     https://www.apache.org/licenses/LICENSE-2.0

//! Text drawing API for `kas_wgpu`

use wgpu_glyph::{ab_glyph, Extra, SectionGlyph};

use super::{CustomWindow, DrawWindow};
use kas::draw::{Colour, Draw, DrawText, Pass};
use kas::geom::{Quad, Vec2};
use kas::text::fonts::{fonts, FontId};
use kas::text::{Effect, Glyph, TextDisplay};

fn to_point(Vec2(x, y): Vec2) -> ab_glyph::Point {
    ab_glyph::Point { x, y }
}

fn ktv_to_point(kas::text::Vec2(x, y): kas::text::Vec2) -> ab_glyph::Point {
    ab_glyph::Point { x, y }
}

impl<CW: CustomWindow + 'static> DrawText for DrawWindow<CW> {
    fn prepare_fonts(&mut self) {
        let fonts = fonts();
        let n1 = self.glyph_brush.fonts().len();
        let n2 = fonts.num_fonts();
        if n2 > n1 {
            // TODO: use extra caching so we don't load font for each window
            let font_data = kas::text::fonts::fonts().font_data();
            for i in n1..n2 {
                let (data, index) = font_data.get_data(i);
                let font = ab_glyph::FontRef::try_from_slice_and_index(data, index).unwrap();
                let id = self.glyph_brush.add_font(font);
                assert_eq!(id.0, i);
            }
        }
    }

    fn text(
        &mut self,
        pass: Pass,
        pos: Vec2,
        bounds: Vec2,
        offset: Vec2,
        text: &TextDisplay,
        col: Colour,
    ) {
        let time = std::time::Instant::now();
        let ab_pos = to_point(pos);
        let ab_offset = ab_pos - to_point(offset);

        let mut glyphs = Vec::with_capacity(text.num_glyphs());
        let for_glyph = |font_id: FontId, _, height: f32, glyph: Glyph| {
            glyphs.push(SectionGlyph {
                section_index: 0,
                byte_index: 0, // not used
                glyph: ab_glyph::Glyph {
                    id: ab_glyph::GlyphId(glyph.id.0),
                    scale: height.into(),
                    position: ab_offset + ktv_to_point(glyph.position),
                },
                font_id: wgpu_glyph::FontId(font_id.get()),
            });
        };
        text.glyphs(for_glyph);

        let min = ab_pos;
        let max = ab_pos + to_point(bounds);
        let bounds = ab_glyph::Rect { min, max };

        let extra = vec![Extra {
            color: col.into(),
            z: pass.depth(),
        }];
        self.glyph_brush.queue_pre_positioned(glyphs, extra, bounds);
        self.dur_text += time.elapsed();
    }

    fn text_col_effects(
        &mut self,
        pass: Pass,
        pos: Vec2,
        bounds: Vec2,
        offset: Vec2,
        text: &TextDisplay,
        col: Colour,
        effects: &[Effect<()>],
    ) {
        // Optimisation: use cheaper TextDisplay::glyphs method
        if effects.len() <= 1
            && effects
                .get(0)
                .map(|e| e.flags == Default::default())
                .unwrap_or(true)
        {
            return self.text(pass, pos, bounds, offset, text, col);
        }

        let time = std::time::Instant::now();
        let ab_pos = to_point(pos);
        let ab_offset = ab_pos - to_point(offset);

        let mut glyphs = Vec::with_capacity(text.num_glyphs());
        if effects.len() > 1
            || effects
                .get(0)
                .map(|e| *e != Default::default())
                .unwrap_or(false)
        {
            let for_glyph = |font_id: FontId, _, height: f32, glyph: Glyph, _, _| {
                glyphs.push(SectionGlyph {
                    section_index: 0,
                    byte_index: 0, // not used
                    glyph: ab_glyph::Glyph {
                        id: ab_glyph::GlyphId(glyph.id.0),
                        scale: height.into(),
                        position: ab_offset + ktv_to_point(glyph.position),
                    },
                    font_id: wgpu_glyph::FontId(font_id.get()),
                });
            };
            let for_rect = |x1, x2, mut y, h: f32, _, _| {
                let y2 = y + h;
                if h < 1.0 {
                    // h too small can make the line invisible due to rounding
                    // In this case we prefer to push the line up (nearer text).
                    y = y2 - 1.0;
                }
                let quad = Quad::with_coords(pos + Vec2(x1, y), pos + Vec2(x2, y2));
                self.rect(pass, quad, col);
            };
            text.glyphs_with_effects(effects, for_glyph, for_rect);
        } else {
            let for_glyph = |font_id: FontId, _, height: f32, glyph: Glyph| {
                glyphs.push(SectionGlyph {
                    section_index: 0,
                    byte_index: 0, // not used
                    glyph: ab_glyph::Glyph {
                        id: ab_glyph::GlyphId(glyph.id.0),
                        scale: height.into(),
                        position: ab_offset + ktv_to_point(glyph.position),
                    },
                    font_id: wgpu_glyph::FontId(font_id.get()),
                });
            };
            text.glyphs(for_glyph);
        }

        let min = ab_pos;
        let max = ab_pos + to_point(bounds);
        let bounds = ab_glyph::Rect { min, max };

        let extra = vec![Extra {
            color: col.into(),
            z: pass.depth(),
        }];
        self.glyph_brush.queue_pre_positioned(glyphs, extra, bounds);
        self.dur_text += time.elapsed();
    }

    fn text_effects(
        &mut self,
        pass: Pass,
        pos: Vec2,
        bounds: Vec2,
        offset: Vec2,
        text: &TextDisplay,
        effects: &[Effect<Colour>],
    ) {
        // Optimisation: use cheaper TextDisplay::glyphs method
        if effects.len() <= 1
            && effects
                .get(0)
                .map(|e| e.flags == Default::default())
                .unwrap_or(true)
        {
            let col = effects.get(0).map(|e| e.aux).unwrap_or(Colour::default());
            return self.text(pass, pos, bounds, offset, text, col);
        }

        let time = std::time::Instant::now();
        let ab_pos = to_point(pos);
        let ab_offset = ab_pos - to_point(offset);

        let mut glyphs = Vec::with_capacity(text.num_glyphs());
        let mut extra = Vec::with_capacity(effects.len() + 1);
        {
            let mut index_incr = 0;
            if effects.get(1).map(|e| e.start > 0).unwrap_or(true) {
                index_incr = 1;
                extra.push(Extra {
                    color: Colour::default().into(),
                    z: pass.depth(),
                });
            }
            for e in effects {
                extra.push(Extra {
                    color: e.aux.into(),
                    z: pass.depth(),
                });
            }

            let for_glyph = |font_id: FontId, _, height: f32, glyph: Glyph, i: usize, _| {
                glyphs.push(SectionGlyph {
                    section_index: i.wrapping_add(index_incr),
                    byte_index: 0, // not used
                    glyph: ab_glyph::Glyph {
                        id: ab_glyph::GlyphId(glyph.id.0),
                        scale: height.into(),
                        position: ab_offset + ktv_to_point(glyph.position),
                    },
                    font_id: wgpu_glyph::FontId(font_id.get()),
                });
            };
            let for_rect = |x1, x2, mut y, h: f32, i: usize, _| {
                let y2 = y + h;
                if h < 1.0 {
                    // h too small can make the line invisible due to rounding
                    // In this case we prefer to push the line up (nearer text).
                    y = y2 - 1.0;
                }
                let quad = Quad::with_coords(pos + Vec2(x1, y), pos + Vec2(x2, y2));
                self.rect(pass, quad, effects[i].aux);
            };
            text.glyphs_with_effects(effects, for_glyph, for_rect);
        }

        let min = ab_pos;
        let max = ab_pos + to_point(bounds);
        let bounds = ab_glyph::Rect { min, max };

        self.glyph_brush.queue_pre_positioned(glyphs, extra, bounds);
        self.dur_text += time.elapsed();
    }
}