// SPDX-License-Identifier: LGPL-2.1-only
// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>

use web_sys::Element;

use crate::app::App;
use crate::event_loop::AppData;
use crate::event_loop::surface::Insets;

/// The main surface's browser half.
#[ derive( Default ) ]
pub( crate ) struct WebSurfaceState
{
	/// The software renderer's frame, unpremultiplied for `putImageData`.
	pub pixels: Vec<u8>,
}

/// The safe-area insets `probe` is padded by, in CSS pixels; none without a probe.
fn safe_area( probe: Option<&Element> ) -> Insets
{
	let ( Some( probe ), Some( window ) ) = ( probe, web_sys::window() ) else { return Insets::default() };
	let Ok( Some( style ) ) = window.get_computed_style( probe ) else { return Insets::default() };
	let side = |name: &str| style.get_property_value( name ).ok()
		.and_then( |value| value.trim().trim_end_matches( "px" ).parse::<f32>().ok() )
		.unwrap_or( 0.0 );
	Insets { top: side( "padding-top" ), right: side( "padding-right" ), bottom: side( "padding-bottom" ), left: side( "padding-left" ) }
}

impl<A: App> AppData<A>
{
	/// Size the main surface to the canvas, whose CSS pixels are the surface's logical ones at the page's `devicePixelRatio`, so the canvas holds the display's own pixels, and keep the view out of what a phone's notch and bars cover.
	pub( super ) fn fit_canvas_element( &mut self )
	{
		let insets = safe_area( self.platform.inset_probe.as_ref() );
		if insets != self.main.insets
		{
			self.main.insets = insets;
			self.main.request_redraw();
		}

		let canvas   = &self.platform.canvas;
		let ( w, h ) = ( canvas.client_width().max( 1 ) as u32, canvas.client_height().max( 1 ) as u32 );
		let scale    = web_sys::window().map_or( 1.0, |w| w.device_pixel_ratio() ) as f32;
		if self.main.configured && ( w, h ) == ( self.main.width, self.main.height ) && scale == self.main.scale_factor { return; }

		if scale != self.main.scale_factor
		{
			self.main.scale_factor = scale;
			if let Some( ref mut canvas ) = self.main.canvas { canvas.set_dpi_scale( scale ); }
		}
		self.main.set_size( w, h );
		self.on_main_resized( w, h );
	}
}