//! This module exports types related to rendering glyphs.

use bevy_asset::Handle;
use bevy_image::Image;
use bevy_math::{IVec2, Vec2};
use bevy_reflect::Reflect;
use bevy_sprite::TextureAtlasLayout;

/// A glyph of a font, typically representing a single character, positioned in screen space.
///
/// Contains information about how and where to render a glyph.
///
/// Used in [`TextPipeline::queue_text`](crate::TextPipeline::queue_text) and [`crate::TextLayoutInfo`] for rendering glyphs.
#[derive(Debug, Clone, Reflect)]
pub struct PositionedGlyph {
    /// The position of the glyph in the text block's bounding box.
    pub position: Vec2,
    /// The width and height of the glyph in logical pixels.
    pub size: Vec2,
    /// Information about the glyph's atlas.
    pub atlas_info: GlyphAtlasInfo,
    /// The index of the glyph in the [`ComputedTextBlock`](crate::ComputedTextBlock)'s tracked spans.
    pub span_index: usize,
    /// TODO: In order to do text editing, we need access to the size of glyphs and their index in the associated String.
    /// For example, to figure out where to place the cursor in an input box from the mouse's position.
    /// Without this, it's only possible in texts where each glyph is one byte. Cosmic text has methods for this
    /// cosmic-texts [hit detection](https://pop-os.github.io/cosmic-text/cosmic_text/struct.Buffer.html#method.hit)
    byte_index: usize,
}

impl PositionedGlyph {
    /// Creates a new [`PositionedGlyph`]
    pub fn new(position: Vec2, size: Vec2, atlas_info: GlyphAtlasInfo, span_index: usize) -> Self {
        Self {
            position,
            size,
            atlas_info,
            span_index,
            byte_index: 0,
        }
    }
}

/// Information about a glyph in an atlas.
///
/// Rasterized glyphs are stored as rectangles
/// in one or more [`FontAtlas`](crate::FontAtlas)es.
///
/// Used in [`PositionedGlyph`] and [`FontAtlasSet`](crate::FontAtlasSet).
#[derive(Debug, Clone, Reflect)]
pub struct GlyphAtlasInfo {
    /// A handle to the [`Image`] data for the texture atlas this glyph was placed in.
    ///
    /// A (weak) clone of the handle held by the [`FontAtlas`](crate::FontAtlas).
    pub texture: Handle<Image>,
    /// A handle to the [`TextureAtlasLayout`] map for the texture atlas this glyph was placed in.
    ///
    /// A (weak) clone of the handle held by the [`FontAtlas`](crate::FontAtlas).
    pub texture_atlas: Handle<TextureAtlasLayout>,
    /// Location and offset of a glyph within the texture atlas.
    pub location: GlyphAtlasLocation,
}

/// The location of a glyph in an atlas,
/// and how it should be positioned when placed.
///
/// Used in [`GlyphAtlasInfo`] and [`FontAtlas`](crate::FontAtlas).
#[derive(Debug, Clone, Copy, Reflect)]
pub struct GlyphAtlasLocation {
    /// The index of the glyph in the atlas
    pub glyph_index: usize,
    /// The required offset (relative positioning) when placed
    pub offset: IVec2,
}