//! SVG builders for the floating tab bar's action icons.
//!
//! The touch tab bar (`hud_plugin::tab_bar`) is icon-first, but the bundled
//! FiraMono face has no icon glyphs (and the Geometric Shapes block U+25xx
//! is missing on Android entirely), so the icons are authored here as tiny
//! stroke-based SVGs and rasterised through the same `usvg`/`resvg` pipeline
//! as the card themes (`assets::rasterize_svg`).
//!
//! Icons are drawn in **white** on a transparent background inside a
//! 24-unit logical box; the spawn site tints them to the theme colour via
//! `ImageNode::color` (a per-node multiply), so one texture serves every
//! button state.

use bevy::image::Image;
use bevy::math::UVec2;

use super::svg_loader::{SvgLoaderError, rasterize_svg};

/// Rasterisation size for one tab-bar icon texture. Icons display at
/// 24 logical px; 96 px texels keep them crisp at the Fold's 1.2 scale
/// factor (and any future 3× phone) while staying trivially small.
pub const HUD_ICON_TEXTURE_PX: u32 = 96;

/// The five actions the floating touch tab bar can show.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum HudIcon {
    /// Counter-clockwise "take back" arrow.
    Undo,
    /// Two offset card outlines — draw from the stock.
    Draw,
    /// Lightbulb — highlight a suggested move.
    Hint,
    /// Two vertical bars.
    Pause,
    /// Three-line hamburger — the floating menu button.
    Menu,
}

impl HudIcon {
    /// Build the icon's SVG document. All icons share one visual language:
    /// 2-unit white strokes, round caps, transparent fill, 24-unit box.
    pub fn svg(self) -> String {
        let body = match self {
            // Arrow head pointing left into a half-circle sweeping back
            // over the top — the conventional undo mark.
            HudIcon::Undo => concat!(
                r##"<path d="M 8 5 L 4 9 L 8 13"/>"##,
                r##"<path d="M 4 9 H 14 A 5.5 5.5 0 0 1 14 20 H 8"/>"##,
            ),
            // Back card peeks out behind the front card; the front card is
            // drawn second so its stroke reads on top.
            HudIcon::Draw => concat!(
                r##"<rect x="8.5" y="3" width="11" height="15" rx="2"/>"##,
                r##"<rect x="4" y="6.5" width="11" height="15" rx="2"/>"##,
            ),
            // Bulb dome with a flat lamp base beneath.
            HudIcon::Hint => concat!(
                r##"<path d="M 9 15.5 A 6.5 6.5 0 1 1 15 15.5 V 18 H 9 Z"/>"##,
                r##"<path d="M 10 21 H 14"/>"##,
            ),
            HudIcon::Pause => concat!(
                r##"<path d="M 9 6 V 18"/>"##,
                r##"<path d="M 15 6 V 18"/>"##,
            ),
            HudIcon::Menu => concat!(
                r##"<path d="M 4 6.5 H 20"/>"##,
                r##"<path d="M 4 12 H 20"/>"##,
                r##"<path d="M 4 17.5 H 20"/>"##,
            ),
        };
        format!(
            concat!(
                r##"<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">"##,
                r##"<g fill="none" stroke="#ffffff" stroke-width="2" "##,
                r##"stroke-linecap="round" stroke-linejoin="round">{body}</g>"##,
                r##"</svg>"##,
            ),
            body = body
        )
    }

    /// Rasterise this icon into a Bevy [`Image`] at
    /// [`HUD_ICON_TEXTURE_PX`] square.
    pub fn rasterize(self) -> Result<Image, SvgLoaderError> {
        rasterize_svg(self.svg().as_bytes(), UVec2::splat(HUD_ICON_TEXTURE_PX))
    }
}

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

    const ALL: [HudIcon; 5] = [
        HudIcon::Undo,
        HudIcon::Draw,
        HudIcon::Hint,
        HudIcon::Pause,
        HudIcon::Menu,
    ];

    /// Every icon must survive the real usvg/resvg pipeline at the real
    /// texture size — a malformed path here would otherwise only surface
    /// as a blank button on device.
    #[test]
    fn every_icon_rasterizes_at_texture_size() {
        for icon in ALL {
            let img = icon.rasterize().expect("icon SVG must rasterise");
            assert_eq!(img.width(), HUD_ICON_TEXTURE_PX, "{icon:?} width");
            assert_eq!(img.height(), HUD_ICON_TEXTURE_PX, "{icon:?} height");
        }
    }

    /// Rasterised icons must contain visible (non-transparent) pixels —
    /// guards against a stroke accidentally drawn outside the viewBox.
    #[test]
    fn every_icon_has_visible_pixels() {
        for icon in ALL {
            let img = icon.rasterize().expect("icon SVG must rasterise");
            let data = img.data.as_ref().expect("rasterised image has data");
            let opaque = data.chunks_exact(4).filter(|px| px[3] > 0).count();
            assert!(
                opaque > 100,
                "{icon:?} renders only {opaque} visible pixels"
            );
        }
    }
}