dr2d 0.0.1-alpha.1

// SPDX-License-Identifier: Apache-2.0
// Copyright 2026 Krishnamoorthy Sankaran <krishnamoorthy.sankaran@sekrad.org>

//! Text rendering via embedded glyph atlas.
//!
//! Provides a [`GlyphAtlas`] with simple geometric glyph outlines for ASCII
//! characters (A-Z, a-z, 0-9, common punctuation). Glyphs are tessellated
//! into triangle vertices using lyon at render time.
//!
//! This module is gated behind the `text` feature flag.

use std::collections::HashMap;

use lyon::math::point;
use lyon::path::Path;
use lyon::tessellation::{
    BuffersBuilder, FillOptions, FillTessellator, FillVertex, VertexBuffers,
};

use crate::renderer::vertex::Vertex;

/// Error type for glyph operations.
#[derive(Debug, thiserror::Error)]
pub enum GlyphError {
    /// Tessellation failed for a specific character.
    #[error("Tessellation failed for character '{0}': {1}")]
    TessellationFailed(char, String),
}

/// Default glyph advance width in the unit coordinate system (0..1).
const GLYPH_ADVANCE: f32 = 0.7;

/// Embedded glyph atlas with simple geometric outlines for ASCII characters.
///
/// Each glyph is stored as a set of closed polygons (line-segment outlines)
/// that can be tessellated into triangles via lyon.
pub struct GlyphAtlas {
    /// Map from character to list of closed polygons.
    /// Each polygon is a `Vec<[f32; 2]>` of vertices in unit space (roughly 0..1).
    glyphs: HashMap<char, Vec<Vec<[f32; 2]>>>,
}

impl Default for GlyphAtlas {
    fn default() -> Self {
        Self::new()
    }
}

impl GlyphAtlas {
    /// Create a new atlas with embedded ASCII glyphs.
    ///
    /// Includes outlines for A-Z, a-z, 0-9, and common punctuation.
    /// Glyphs are simple geometric representations using line segments.
    pub fn new() -> Self {
        let mut glyphs: HashMap<char, Vec<Vec<[f32; 2]>>> = HashMap::new();

        // Helper: insert a single-polygon glyph
        macro_rules! glyph {
            ($ch:expr, $( [ $($pt:expr),+ ] ),+ $(,)?) => {
                glyphs.insert($ch, vec![ $( vec![ $($pt),+ ] ),+ ]);
            };
        }

        // --- Uppercase letters (unit space ~0.0..0.6 wide, 0.0..1.0 tall) ---

        // A - triangle shape
        glyph!('A',
            [[0.0, 1.0], [0.3, 0.0], [0.6, 1.0], [0.5, 1.0], [0.3, 0.2], [0.1, 1.0]],
            [[0.15, 0.65], [0.45, 0.65], [0.45, 0.55], [0.15, 0.55]]
        );
        // B - two bumps
        glyph!('B',
            [[0.0, 0.0], [0.4, 0.0], [0.55, 0.1], [0.55, 0.4], [0.4, 0.5],
             [0.55, 0.6], [0.55, 0.9], [0.4, 1.0], [0.0, 1.0], [0.0, 0.9],
             [0.1, 0.9], [0.1, 0.55], [0.4, 0.55], [0.45, 0.45], [0.45, 0.1],
             [0.1, 0.1], [0.1, 0.9], [0.0, 0.9]]
        );
        // C - open rectangle
        glyph!('C',
            [[0.55, 0.1], [0.1, 0.1], [0.1, 0.9], [0.55, 0.9], [0.55, 1.0],
             [0.0, 1.0], [0.0, 0.0], [0.55, 0.0]]
        );
        // D
        glyph!('D',
            [[0.0, 0.0], [0.35, 0.0], [0.55, 0.2], [0.55, 0.8], [0.35, 1.0],
             [0.0, 1.0], [0.0, 0.9], [0.1, 0.9], [0.1, 0.1], [0.35, 0.1],
             [0.45, 0.25], [0.45, 0.75], [0.35, 0.9], [0.1, 0.9], [0.0, 0.9]]
        );
        // E
        glyph!('E',
            [[0.0, 0.0], [0.5, 0.0], [0.5, 0.1], [0.1, 0.1], [0.1, 0.45],
             [0.4, 0.45], [0.4, 0.55], [0.1, 0.55], [0.1, 0.9], [0.5, 0.9],
             [0.5, 1.0], [0.0, 1.0]]
        );
        // F
        glyph!('F',
            [[0.0, 0.0], [0.5, 0.0], [0.5, 0.1], [0.1, 0.1], [0.1, 0.45],
             [0.4, 0.45], [0.4, 0.55], [0.1, 0.55], [0.1, 1.0], [0.0, 1.0]]
        );
        // G
        glyph!('G',
            [[0.55, 0.1], [0.1, 0.1], [0.1, 0.9], [0.55, 0.9], [0.55, 0.5],
             [0.3, 0.5], [0.3, 0.6], [0.45, 0.6], [0.45, 0.8], [0.55, 0.8],
             [0.55, 1.0], [0.0, 1.0], [0.0, 0.0], [0.55, 0.0]]
        );
        // H
        glyph!('H',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.45], [0.5, 0.45], [0.5, 0.0],
             [0.6, 0.0], [0.6, 1.0], [0.5, 1.0], [0.5, 0.55], [0.1, 0.55],
             [0.1, 1.0], [0.0, 1.0]]
        );
        // I
        glyph!('I',
            [[0.1, 0.0], [0.4, 0.0], [0.4, 0.1], [0.3, 0.1], [0.3, 0.9],
             [0.4, 0.9], [0.4, 1.0], [0.1, 1.0], [0.1, 0.9], [0.2, 0.9],
             [0.2, 0.1], [0.1, 0.1]]
        );
        // J
        glyph!('J',
            [[0.15, 0.0], [0.5, 0.0], [0.5, 0.1], [0.4, 0.1], [0.4, 0.85],
             [0.3, 0.95], [0.1, 0.95], [0.0, 0.85], [0.0, 0.7], [0.1, 0.7],
             [0.1, 0.8], [0.15, 0.85], [0.25, 0.85], [0.3, 0.8], [0.3, 0.1],
             [0.15, 0.1]]
        );
        // K
        glyph!('K',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.4], [0.4, 0.0], [0.55, 0.0],
             [0.2, 0.45], [0.55, 1.0], [0.4, 1.0], [0.1, 0.55], [0.1, 1.0],
             [0.0, 1.0]]
        );
        // L
        glyph!('L',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.9], [0.5, 0.9], [0.5, 1.0],
             [0.0, 1.0]]
        );
        // M
        glyph!('M',
            [[0.0, 0.0], [0.1, 0.0], [0.3, 0.4], [0.5, 0.0], [0.6, 0.0],
             [0.6, 1.0], [0.5, 1.0], [0.5, 0.25], [0.3, 0.6], [0.1, 0.25],
             [0.1, 1.0], [0.0, 1.0]]
        );
        // N
        glyph!('N',
            [[0.0, 0.0], [0.1, 0.0], [0.5, 0.75], [0.5, 0.0], [0.6, 0.0],
             [0.6, 1.0], [0.5, 1.0], [0.1, 0.25], [0.1, 1.0], [0.0, 1.0]]
        );
        // O
        glyph!('O',
            [[0.0, 0.1], [0.1, 0.0], [0.5, 0.0], [0.6, 0.1], [0.6, 0.9],
             [0.5, 1.0], [0.1, 1.0], [0.0, 0.9], [0.0, 0.1],
             [0.1, 0.15], [0.1, 0.85], [0.15, 0.9], [0.45, 0.9], [0.5, 0.85],
             [0.5, 0.15], [0.45, 0.1], [0.15, 0.1], [0.1, 0.15]]
        );

        // P
        glyph!('P',
            [[0.0, 0.0], [0.4, 0.0], [0.55, 0.1], [0.55, 0.4], [0.4, 0.5],
             [0.1, 0.5], [0.1, 1.0], [0.0, 1.0], [0.0, 0.0],
             [0.1, 0.1], [0.1, 0.4], [0.4, 0.4], [0.45, 0.35], [0.45, 0.15],
             [0.4, 0.1], [0.1, 0.1]]
        );
        // Q - O with a tail
        glyph!('Q',
            [[0.0, 0.1], [0.1, 0.0], [0.5, 0.0], [0.6, 0.1], [0.6, 0.9],
             [0.5, 1.0], [0.1, 1.0], [0.0, 0.9]],
            [[0.4, 0.75], [0.55, 1.0], [0.45, 1.0], [0.35, 0.8]]
        );
        // R
        glyph!('R',
            [[0.0, 0.0], [0.4, 0.0], [0.55, 0.1], [0.55, 0.4], [0.4, 0.5],
             [0.55, 1.0], [0.4, 1.0], [0.28, 0.55], [0.1, 0.55], [0.1, 1.0],
             [0.0, 1.0], [0.0, 0.0],
             [0.1, 0.1], [0.1, 0.45], [0.4, 0.45], [0.45, 0.35], [0.45, 0.15],
             [0.4, 0.1], [0.1, 0.1]]
        );
        // S
        glyph!('S',
            [[0.0, 0.85], [0.0, 0.55], [0.1, 0.55], [0.1, 0.8], [0.45, 0.8],
             [0.5, 0.75], [0.5, 0.6], [0.45, 0.55], [0.1, 0.45], [0.0, 0.35],
             [0.0, 0.1], [0.1, 0.0], [0.55, 0.0], [0.55, 0.3], [0.45, 0.3],
             [0.45, 0.15], [0.15, 0.15], [0.1, 0.2], [0.1, 0.35], [0.15, 0.4],
             [0.5, 0.5], [0.6, 0.6], [0.6, 0.85], [0.5, 0.95], [0.1, 0.95]]
        );
        // T
        glyph!('T',
            [[0.0, 0.0], [0.6, 0.0], [0.6, 0.1], [0.35, 0.1], [0.35, 1.0],
             [0.25, 1.0], [0.25, 0.1], [0.0, 0.1]]
        );
        // U
        glyph!('U',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.85], [0.15, 0.9], [0.45, 0.9],
             [0.5, 0.85], [0.5, 0.0], [0.6, 0.0], [0.6, 0.9], [0.5, 1.0],
             [0.1, 1.0], [0.0, 0.9]]
        );
        // V
        glyph!('V',
            [[0.0, 0.0], [0.1, 0.0], [0.3, 0.8], [0.5, 0.0], [0.6, 0.0],
             [0.35, 1.0], [0.25, 1.0]]
        );
        // W
        glyph!('W',
            [[0.0, 0.0], [0.1, 0.0], [0.2, 0.7], [0.3, 0.3], [0.4, 0.7],
             [0.5, 0.0], [0.6, 0.0], [0.45, 1.0], [0.35, 1.0], [0.3, 0.6],
             [0.25, 1.0], [0.15, 1.0]]
        );
        // X
        glyph!('X',
            [[0.0, 0.0], [0.15, 0.0], [0.3, 0.4], [0.45, 0.0], [0.6, 0.0],
             [0.38, 0.5], [0.6, 1.0], [0.45, 1.0], [0.3, 0.6], [0.15, 1.0],
             [0.0, 1.0], [0.22, 0.5]]
        );
        // Y
        glyph!('Y',
            [[0.0, 0.0], [0.15, 0.0], [0.3, 0.4], [0.45, 0.0], [0.6, 0.0],
             [0.35, 0.55], [0.35, 1.0], [0.25, 1.0], [0.25, 0.55]]
        );
        // Z
        glyph!('Z',
            [[0.0, 0.0], [0.6, 0.0], [0.6, 0.1], [0.15, 0.9], [0.6, 0.9],
             [0.6, 1.0], [0.0, 1.0], [0.0, 0.9], [0.45, 0.1], [0.0, 0.1]]
        );

        // --- Lowercase letters (smaller, offset down) ---
        // For simplicity, lowercase maps to scaled-down uppercase for many letters.
        // Some letters get distinct shapes.

        // a
        glyph!('a',
            [[0.05, 0.35], [0.4, 0.35], [0.5, 0.45], [0.5, 1.0], [0.4, 1.0],
             [0.4, 0.9], [0.15, 0.95], [0.05, 0.85], [0.05, 0.7], [0.15, 0.6],
             [0.4, 0.6], [0.4, 0.5], [0.15, 0.5], [0.05, 0.45]],
            [[0.15, 0.7], [0.4, 0.7], [0.4, 0.8], [0.15, 0.85]]
        );
        // b
        glyph!('b',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.4], [0.35, 0.35], [0.5, 0.45],
             [0.5, 0.9], [0.35, 1.0], [0.1, 1.0], [0.0, 1.0]],
            [[0.1, 0.5], [0.35, 0.5], [0.4, 0.55], [0.4, 0.85], [0.35, 0.9],
             [0.1, 0.9]]
        );
        // c
        glyph!('c',
            [[0.45, 0.45], [0.1, 0.45], [0.05, 0.5], [0.05, 0.9], [0.1, 0.95],
             [0.45, 0.95], [0.45, 1.0], [0.05, 1.0], [0.0, 0.9], [0.0, 0.45],
             [0.1, 0.35], [0.45, 0.35]]
        );
        // d
        glyph!('d',
            [[0.5, 0.0], [0.6, 0.0], [0.6, 1.0], [0.25, 1.0], [0.1, 0.9],
             [0.1, 0.45], [0.25, 0.35], [0.5, 0.35]],
            [[0.2, 0.5], [0.5, 0.5], [0.5, 0.9], [0.25, 0.9], [0.2, 0.85]]
        );
        // e
        glyph!('e',
            [[0.05, 0.65], [0.45, 0.65], [0.45, 0.5], [0.1, 0.5], [0.05, 0.55],
             [0.05, 0.45], [0.1, 0.35], [0.45, 0.35], [0.5, 0.45], [0.5, 0.7],
             [0.05, 0.7], [0.05, 0.9], [0.1, 0.95], [0.45, 0.95], [0.45, 1.0],
             [0.05, 1.0], [0.0, 0.9], [0.0, 0.45]]
        );
        // f
        glyph!('f',
            [[0.15, 0.35], [0.5, 0.35], [0.5, 0.45], [0.3, 0.45], [0.3, 1.0],
             [0.2, 1.0], [0.2, 0.45], [0.05, 0.45], [0.05, 0.35], [0.2, 0.35],
             [0.2, 0.15], [0.25, 0.05], [0.4, 0.0], [0.5, 0.0], [0.5, 0.1],
             [0.3, 0.1], [0.3, 0.35]]
        );

        // g
        glyph!('g',
            [[0.1, 0.35], [0.45, 0.35], [0.5, 0.45], [0.5, 1.1], [0.45, 1.2],
             [0.1, 1.2], [0.1, 1.1], [0.4, 1.1], [0.4, 0.95], [0.15, 1.0],
             [0.05, 0.9], [0.05, 0.45], [0.1, 0.35]],
            [[0.15, 0.5], [0.4, 0.5], [0.4, 0.85], [0.15, 0.9]]
        );
        // h
        glyph!('h',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.45], [0.35, 0.35], [0.45, 0.45],
             [0.45, 1.0], [0.35, 1.0], [0.35, 0.5], [0.1, 0.55], [0.1, 1.0],
             [0.0, 1.0]]
        );
        // i
        glyph!('i',
            [[0.2, 0.4], [0.3, 0.4], [0.3, 1.0], [0.2, 1.0]],
            [[0.2, 0.15], [0.3, 0.15], [0.3, 0.28], [0.2, 0.28]]
        );
        // j
        glyph!('j',
            [[0.3, 0.4], [0.4, 0.4], [0.4, 1.05], [0.35, 1.15], [0.15, 1.15],
             [0.1, 1.1], [0.2, 1.1], [0.3, 1.05], [0.3, 0.4]],
            [[0.3, 0.15], [0.4, 0.15], [0.4, 0.28], [0.3, 0.28]]
        );
        // k
        glyph!('k',
            [[0.0, 0.0], [0.1, 0.0], [0.1, 0.55], [0.35, 0.35], [0.5, 0.35],
             [0.2, 0.6], [0.5, 1.0], [0.35, 1.0], [0.1, 0.65], [0.1, 1.0],
             [0.0, 1.0]]
        );
        // l
        glyph!('l',
            [[0.2, 0.0], [0.3, 0.0], [0.3, 0.9], [0.4, 1.0], [0.4, 1.0],
             [0.3, 1.0], [0.2, 0.9]]
        );
        // m
        glyph!('m',
            [[0.0, 0.35], [0.1, 0.35], [0.1, 0.4], [0.2, 0.35], [0.3, 0.4],
             [0.4, 0.35], [0.5, 0.4], [0.5, 1.0], [0.4, 1.0], [0.4, 0.5],
             [0.3, 0.5], [0.3, 1.0], [0.2, 1.0], [0.2, 0.5], [0.1, 0.5],
             [0.1, 1.0], [0.0, 1.0]]
        );
        // n
        glyph!('n',
            [[0.0, 0.35], [0.1, 0.35], [0.1, 0.45], [0.35, 0.35], [0.45, 0.45],
             [0.45, 1.0], [0.35, 1.0], [0.35, 0.5], [0.1, 0.55], [0.1, 1.0],
             [0.0, 1.0]]
        );
        // o
        glyph!('o',
            [[0.05, 0.45], [0.15, 0.35], [0.45, 0.35], [0.55, 0.45], [0.55, 0.9],
             [0.45, 1.0], [0.15, 1.0], [0.05, 0.9]],
            [[0.15, 0.5], [0.45, 0.5], [0.45, 0.85], [0.15, 0.85]]
        );
        // p
        glyph!('p',
            [[0.0, 0.35], [0.1, 0.35], [0.1, 0.4], [0.35, 0.35], [0.5, 0.45],
             [0.5, 0.9], [0.35, 1.0], [0.1, 1.0], [0.1, 1.2], [0.0, 1.2]],
            [[0.1, 0.5], [0.35, 0.5], [0.4, 0.55], [0.4, 0.85], [0.35, 0.9],
             [0.1, 0.9]]
        );
        // q
        glyph!('q',
            [[0.5, 0.35], [0.6, 0.35], [0.6, 1.2], [0.5, 1.2], [0.5, 1.0],
             [0.25, 1.0], [0.1, 0.9], [0.1, 0.45], [0.25, 0.35]],
            [[0.2, 0.5], [0.5, 0.5], [0.5, 0.9], [0.25, 0.9], [0.2, 0.85]]
        );
        // r
        glyph!('r',
            [[0.0, 0.35], [0.1, 0.35], [0.1, 0.45], [0.25, 0.35], [0.45, 0.35],
             [0.45, 0.45], [0.2, 0.5], [0.1, 0.55], [0.1, 1.0], [0.0, 1.0]]
        );
        // s
        glyph!('s',
            [[0.05, 0.85], [0.05, 0.7], [0.15, 0.7], [0.15, 0.8], [0.4, 0.8],
             [0.45, 0.75], [0.45, 0.7], [0.1, 0.6], [0.05, 0.5], [0.05, 0.45],
             [0.1, 0.35], [0.5, 0.35], [0.5, 0.5], [0.4, 0.5], [0.4, 0.45],
             [0.15, 0.45], [0.1, 0.5], [0.1, 0.55], [0.45, 0.65], [0.5, 0.75],
             [0.5, 0.9], [0.4, 1.0], [0.1, 1.0]]
        );
        // t
        glyph!('t',
            [[0.15, 0.1], [0.25, 0.1], [0.25, 0.35], [0.45, 0.35], [0.45, 0.45],
             [0.25, 0.45], [0.25, 0.9], [0.35, 0.95], [0.45, 0.95], [0.45, 1.0],
             [0.3, 1.0], [0.15, 0.9]]
        );
        // u
        glyph!('u',
            [[0.0, 0.35], [0.1, 0.35], [0.1, 0.85], [0.15, 0.9], [0.35, 0.9],
             [0.4, 0.85], [0.4, 0.35], [0.5, 0.35], [0.5, 0.9], [0.4, 1.0],
             [0.1, 1.0], [0.0, 0.9]]
        );
        // v
        glyph!('v',
            [[0.0, 0.35], [0.1, 0.35], [0.25, 0.85], [0.4, 0.35], [0.5, 0.35],
             [0.3, 1.0], [0.2, 1.0]]
        );
        // w
        glyph!('w',
            [[0.0, 0.35], [0.1, 0.35], [0.15, 0.75], [0.25, 0.5], [0.35, 0.75],
             [0.4, 0.35], [0.5, 0.35], [0.4, 1.0], [0.3, 1.0], [0.25, 0.7],
             [0.2, 1.0], [0.1, 1.0]]
        );
        // x
        glyph!('x',
            [[0.0, 0.35], [0.15, 0.35], [0.25, 0.55], [0.35, 0.35], [0.5, 0.35],
             [0.32, 0.65], [0.5, 1.0], [0.35, 1.0], [0.25, 0.75], [0.15, 1.0],
             [0.0, 1.0], [0.18, 0.65]]
        );
        // y
        glyph!('y',
            [[0.0, 0.35], [0.1, 0.35], [0.25, 0.75], [0.4, 0.35], [0.5, 0.35],
             [0.3, 0.85], [0.2, 1.15], [0.05, 1.2], [0.05, 1.1], [0.15, 1.1]]
        );
        // z
        glyph!('z',
            [[0.05, 0.35], [0.5, 0.35], [0.5, 0.45], [0.15, 0.9], [0.5, 0.9],
             [0.5, 1.0], [0.05, 1.0], [0.05, 0.9], [0.4, 0.45], [0.05, 0.45]]
        );

        // --- Digits ---
        // 0
        glyph!('0',
            [[0.05, 0.1], [0.15, 0.0], [0.45, 0.0], [0.55, 0.1], [0.55, 0.9],
             [0.45, 1.0], [0.15, 1.0], [0.05, 0.9]],
            [[0.15, 0.15], [0.45, 0.15], [0.45, 0.85], [0.15, 0.85]]
        );
        // 1
        glyph!('1',
            [[0.15, 0.15], [0.3, 0.0], [0.4, 0.0], [0.4, 0.9], [0.5, 0.9],
             [0.5, 1.0], [0.15, 1.0], [0.15, 0.9], [0.3, 0.9], [0.3, 0.2],
             [0.15, 0.3]]
        );
        // 2
        glyph!('2',
            [[0.05, 0.1], [0.15, 0.0], [0.45, 0.0], [0.55, 0.1], [0.55, 0.4],
             [0.45, 0.5], [0.15, 0.5], [0.1, 0.55], [0.55, 0.9], [0.55, 1.0],
             [0.05, 1.0], [0.05, 0.9], [0.4, 0.55], [0.05, 0.45], [0.05, 0.1]]
        );
        // 3
        glyph!('3',
            [[0.05, 0.1], [0.15, 0.0], [0.45, 0.0], [0.55, 0.1], [0.55, 0.4],
             [0.45, 0.5], [0.55, 0.6], [0.55, 0.9], [0.45, 1.0], [0.15, 1.0],
             [0.05, 0.9], [0.05, 0.8], [0.15, 0.8], [0.15, 0.9], [0.4, 0.9],
             [0.45, 0.85], [0.45, 0.6], [0.35, 0.55], [0.35, 0.45], [0.45, 0.4],
             [0.45, 0.15], [0.4, 0.1], [0.15, 0.1], [0.15, 0.2], [0.05, 0.2]]
        );
        // 4
        glyph!('4',
            [[0.35, 0.0], [0.45, 0.0], [0.45, 0.55], [0.55, 0.55], [0.55, 0.65],
             [0.45, 0.65], [0.45, 1.0], [0.35, 1.0], [0.35, 0.65], [0.05, 0.65],
             [0.05, 0.55], [0.35, 0.0]],
            [[0.15, 0.55], [0.35, 0.55], [0.35, 0.2]]
        );
        // 5
        glyph!('5',
            [[0.05, 0.0], [0.55, 0.0], [0.55, 0.1], [0.15, 0.1], [0.15, 0.4],
             [0.45, 0.4], [0.55, 0.5], [0.55, 0.9], [0.45, 1.0], [0.15, 1.0],
             [0.05, 0.9], [0.05, 0.8], [0.15, 0.8], [0.15, 0.9], [0.4, 0.9],
             [0.45, 0.85], [0.45, 0.55], [0.4, 0.5], [0.05, 0.5]]
        );
        // 6
        glyph!('6',
            [[0.15, 0.0], [0.45, 0.0], [0.55, 0.1], [0.55, 0.15], [0.45, 0.15],
             [0.45, 0.1], [0.15, 0.1], [0.1, 0.15], [0.1, 0.45], [0.45, 0.45],
             [0.55, 0.55], [0.55, 0.9], [0.45, 1.0], [0.15, 1.0], [0.05, 0.9],
             [0.05, 0.1]],
            [[0.15, 0.55], [0.45, 0.55], [0.45, 0.85], [0.15, 0.85]]
        );
        // 7
        glyph!('7',
            [[0.05, 0.0], [0.55, 0.0], [0.55, 0.15], [0.3, 1.0], [0.2, 1.0],
             [0.45, 0.1], [0.05, 0.1]]
        );
        // 8
        glyph!('8',
            [[0.1, 0.0], [0.5, 0.0], [0.55, 0.1], [0.55, 0.4], [0.5, 0.5],
             [0.55, 0.6], [0.55, 0.9], [0.5, 1.0], [0.1, 1.0], [0.05, 0.9],
             [0.05, 0.6], [0.1, 0.5], [0.05, 0.4], [0.05, 0.1]],
            [[0.15, 0.1], [0.45, 0.1], [0.45, 0.4], [0.15, 0.4]],
            [[0.15, 0.6], [0.45, 0.6], [0.45, 0.9], [0.15, 0.9]]
        );
        // 9
        glyph!('9',
            [[0.1, 0.0], [0.5, 0.0], [0.55, 0.1], [0.55, 0.9], [0.45, 1.0],
             [0.15, 1.0], [0.05, 0.9], [0.05, 0.85], [0.15, 0.85], [0.15, 0.9],
             [0.45, 0.9], [0.5, 0.85], [0.5, 0.55], [0.15, 0.55], [0.05, 0.45],
             [0.05, 0.1]],
            [[0.15, 0.15], [0.45, 0.15], [0.45, 0.45], [0.15, 0.45]]
        );

        // --- Common punctuation ---
        // Period
        glyph!('.',
            [[0.1, 0.85], [0.2, 0.85], [0.2, 1.0], [0.1, 1.0]]
        );
        // Comma
        glyph!(',',
            [[0.1, 0.85], [0.2, 0.85], [0.2, 1.0], [0.05, 1.15], [0.0, 1.1],
             [0.1, 1.0]]
        );
        // Exclamation
        glyph!('!',
            [[0.1, 0.0], [0.2, 0.0], [0.2, 0.7], [0.1, 0.7]],
            [[0.1, 0.85], [0.2, 0.85], [0.2, 1.0], [0.1, 1.0]]
        );
        // Question mark
        glyph!('?',
            [[0.0, 0.1], [0.1, 0.0], [0.4, 0.0], [0.5, 0.1], [0.5, 0.35],
             [0.35, 0.5], [0.3, 0.5], [0.3, 0.65], [0.2, 0.65], [0.2, 0.45],
             [0.4, 0.3], [0.4, 0.15], [0.35, 0.1], [0.15, 0.1], [0.1, 0.15],
             [0.0, 0.15]],
            [[0.2, 0.8], [0.3, 0.8], [0.3, 0.95], [0.2, 0.95]]
        );
        // Colon
        glyph!(':',
            [[0.15, 0.3], [0.25, 0.3], [0.25, 0.45], [0.15, 0.45]],
            [[0.15, 0.7], [0.25, 0.7], [0.25, 0.85], [0.15, 0.85]]
        );
        // Semicolon
        glyph!(';',
            [[0.15, 0.3], [0.25, 0.3], [0.25, 0.45], [0.15, 0.45]],
            [[0.15, 0.7], [0.25, 0.7], [0.25, 0.85], [0.1, 1.0], [0.05, 0.95],
             [0.15, 0.85]]
        );
        // Hyphen/minus
        glyph!('-',
            [[0.1, 0.45], [0.4, 0.45], [0.4, 0.55], [0.1, 0.55]]
        );
        // Underscore
        glyph!('_',
            [[0.0, 0.95], [0.5, 0.95], [0.5, 1.0], [0.0, 1.0]]
        );
        // Space — no polygons, just advance
        glyphs.insert(' ', vec![]);
        // Plus
        glyph!('+',
            [[0.2, 0.25], [0.3, 0.25], [0.3, 0.45], [0.5, 0.45], [0.5, 0.55],
             [0.3, 0.55], [0.3, 0.75], [0.2, 0.75], [0.2, 0.55], [0.0, 0.55],
             [0.0, 0.45], [0.2, 0.45]]
        );
        // Equals
        glyph!('=',
            [[0.05, 0.35], [0.45, 0.35], [0.45, 0.45], [0.05, 0.45]],
            [[0.05, 0.55], [0.45, 0.55], [0.45, 0.65], [0.05, 0.65]]
        );
        // Open paren
        glyph!('(',
            [[0.3, 0.0], [0.35, 0.0], [0.2, 0.3], [0.2, 0.7], [0.35, 1.0],
             [0.3, 1.0], [0.1, 0.7], [0.1, 0.3]]
        );
        // Close paren
        glyph!(')',
            [[0.15, 0.0], [0.2, 0.0], [0.4, 0.3], [0.4, 0.7], [0.2, 1.0],
             [0.15, 1.0], [0.3, 0.7], [0.3, 0.3]]
        );
        // Slash
        glyph!('/',
            [[0.4, 0.0], [0.5, 0.0], [0.1, 1.0], [0.0, 1.0]]
        );
        // At sign @
        glyph!('@',
            [[0.55, 0.6], [0.55, 0.1], [0.5, 0.0], [0.1, 0.0], [0.0, 0.1],
             [0.0, 0.9], [0.1, 1.0], [0.55, 1.0], [0.55, 0.85], [0.6, 0.85],
             [0.6, 1.0], [0.5, 1.1], [0.1, 1.1], [0.0, 1.0], [0.0, 0.0],
             [0.1, 0.0], [0.55, 0.0], [0.6, 0.1], [0.6, 0.6]],
            [[0.2, 0.3], [0.4, 0.3], [0.45, 0.4], [0.45, 0.7], [0.4, 0.8],
             [0.2, 0.8], [0.15, 0.7], [0.15, 0.4]]
        );
        // Hash #
        glyph!('#',
            [[0.15, 0.0], [0.25, 0.0], [0.22, 0.3], [0.42, 0.3], [0.45, 0.0],
             [0.55, 0.0], [0.52, 0.3], [0.6, 0.3], [0.6, 0.4], [0.5, 0.4],
             [0.48, 0.6], [0.6, 0.6], [0.6, 0.7], [0.46, 0.7], [0.43, 1.0],
             [0.33, 1.0], [0.36, 0.7], [0.16, 0.7], [0.13, 1.0], [0.03, 1.0],
             [0.06, 0.7], [0.0, 0.7], [0.0, 0.6], [0.08, 0.6], [0.1, 0.4],
             [0.0, 0.4], [0.0, 0.3], [0.12, 0.3]],
            [[0.2, 0.4], [0.18, 0.6], [0.38, 0.6], [0.4, 0.4]]
        );
        // Double quote
        glyph!('"',
            [[0.1, 0.0], [0.2, 0.0], [0.2, 0.3], [0.1, 0.3]],
            [[0.3, 0.0], [0.4, 0.0], [0.4, 0.3], [0.3, 0.3]]
        );
        // Single quote / apostrophe
        glyph!('\'',
            [[0.15, 0.0], [0.25, 0.0], [0.25, 0.3], [0.15, 0.3]]
        );

        Self { glyphs }
    }

    /// Tessellate a string into triangle vertices.
    ///
    /// Each character is looked up in the atlas and tessellated into triangles
    /// positioned at the appropriate cursor location. The `font_size` parameter
    /// scales the unit-space glyphs.
    ///
    /// Returns an empty `Vec` for an empty string. Unknown characters are
    /// skipped, but the cursor still advances by the default glyph width.
    pub fn tessellate_string(
        &self,
        text: &str,
        x: f32,
        y: f32,
        font_size: f32,
    ) -> Vec<Vertex> {
        if text.is_empty() {
            return Vec::new();
        }

        let mut vertices = Vec::new();
        let mut cursor_x = x;
        let advance = GLYPH_ADVANCE * font_size;
        let default_color = [1.0_f32, 1.0, 1.0, 1.0]; // white

        for ch in text.chars() {
            if let Some(polygons) = self.glyphs.get(&ch) {
                for polygon in polygons {
                    let tess_verts = tessellate_glyph_polygon(
                        polygon, cursor_x, y, font_size, default_color,
                    );
                    vertices.extend_from_slice(&tess_verts);
                }
            }
            // Always advance cursor, even for unknown characters
            cursor_x += advance;
        }

        vertices
    }
}

/// Tessellate a single closed polygon (glyph outline) into filled triangles.
///
/// Scales and translates the unit-space polygon by `font_size` and `(ox, oy)`.
fn tessellate_glyph_polygon(
    polygon: &[[f32; 2]],
    ox: f32,
    oy: f32,
    font_size: f32,
    color: [f32; 4],
) -> Vec<Vertex> {
    if polygon.len() < 3 {
        return Vec::new();
    }

    let mut builder = Path::builder();
    builder.begin(point(
        polygon[0][0] * font_size + ox,
        polygon[0][1] * font_size + oy,
    ));
    for pt in &polygon[1..] {
        builder.line_to(point(pt[0] * font_size + ox, pt[1] * font_size + oy));
    }
    builder.close();
    let path = builder.build();

    let mut geometry: VertexBuffers<Vertex, u32> = VertexBuffers::new();
    let mut fill_tess = FillTessellator::new();
    let result = fill_tess.tessellate_path(
        &path,
        &FillOptions::default(),
        &mut BuffersBuilder::new(&mut geometry, |vertex: FillVertex| Vertex {
            position: vertex.position().to_array(),
            color,
        }),
    );

    match result {
        Ok(_) => {
            // Convert indexed geometry to flat triangle list
            geometry
                .indices
                .iter()
                .map(|&i| geometry.vertices[i as usize])
                .collect()
        }
        Err(e) => {
            log::warn!("Glyph tessellation failed: {e}");
            Vec::new()
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn empty_string_returns_empty_vec() {
        let atlas = GlyphAtlas::new();
        let verts = atlas.tessellate_string("", 0.0, 0.0, 16.0);
        assert!(verts.is_empty());
    }

    #[test]
    fn ascii_letter_produces_vertices() {
        let atlas = GlyphAtlas::new();
        let verts = atlas.tessellate_string("A", 0.0, 0.0, 16.0);
        assert!(!verts.is_empty(), "Expected vertices for 'A'");
    }

    #[test]
    fn unknown_char_skipped_but_cursor_advances() {
        let atlas = GlyphAtlas::new();
        // '★' is not in the atlas
        let with_unknown = atlas.tessellate_string("A★B", 0.0, 0.0, 16.0);
        let without_unknown = atlas.tessellate_string("AB", 0.0, 0.0, 16.0);
        // Both should produce vertices for A and B, but positions differ
        // because the unknown char still advances the cursor
        assert!(!with_unknown.is_empty());
        assert!(!without_unknown.is_empty());
    }

    #[test]
    fn space_produces_no_vertices() {
        let atlas = GlyphAtlas::new();
        let verts = atlas.tessellate_string(" ", 0.0, 0.0, 16.0);
        assert!(verts.is_empty(), "Space should produce no vertices");
    }

    #[test]
    fn digits_produce_vertices() {
        let atlas = GlyphAtlas::new();
        let verts = atlas.tessellate_string("0123456789", 0.0, 0.0, 16.0);
        assert!(!verts.is_empty(), "Expected vertices for digits");
    }

    #[test]
    fn punctuation_produces_vertices() {
        let atlas = GlyphAtlas::new();
        let verts = atlas.tessellate_string(".,!?:-_+=()/", 0.0, 0.0, 16.0);
        assert!(!verts.is_empty(), "Expected vertices for punctuation");
    }

    #[test]
    fn all_uppercase_produce_vertices() {
        let atlas = GlyphAtlas::new();
        for ch in 'A'..='Z' {
            let s = String::from(ch);
            let verts = atlas.tessellate_string(&s, 0.0, 0.0, 16.0);
            assert!(!verts.is_empty(), "Expected vertices for '{ch}'");
        }
    }

    #[test]
    fn all_lowercase_produce_vertices() {
        let atlas = GlyphAtlas::new();
        for ch in 'a'..='z' {
            let s = String::from(ch);
            let verts = atlas.tessellate_string(&s, 0.0, 0.0, 16.0);
            assert!(!verts.is_empty(), "Expected vertices for '{ch}'");
        }
    }
}