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

//! A 3×3 unlock-pattern grid. The widget is stateless: the app owns the
//! visited node list and passes it back in for drawing. A press or a drag
//! that reaches a node fires `on_node( index )` with the node's index,
//! 0 to 8 row-major; the app decides whether to append it. Release fires
//! `on_release`.

use std::sync::Arc;
use crate::types::{ Color, Length, Point, Rect };
use crate::render::Canvas;
use super::Element;

mod theme;
#[ cfg( test ) ]
mod tests;

pub const NODES: u8 = 9;

pub struct PatternGrid<Msg: Clone>
{
	pub( crate ) path:        Vec<u8>,
	pub( crate ) on_node:     Option<Arc<dyn Fn( u8 ) -> Msg>>,
	pub( crate ) on_release:  Option<Msg>,
	pub( crate ) hide_stroke: bool,
	pub( crate ) error:       bool,
	pub( crate ) size:        Option<Length>,
}

impl<Msg: Clone> PatternGrid<Msg>
{
	pub fn new( path: Vec<u8> ) -> Self
	{
		Self { path, on_node: None, on_release: None, hide_stroke: false, error: false, size: None }
	}

	/// Side of the square grid; without it the theme's fluid default applies.
	pub fn size( mut self, s: impl Into<Length> ) -> Self
	{
		self.size = Some( s.into() );
		self
	}

	pub fn on_node( mut self, f: impl Fn( u8 ) -> Msg + 'static ) -> Self
	{
		self.on_node = Some( Arc::new( f ) );
		self
	}

	pub fn on_release( mut self, msg: Msg ) -> Self
	{
		self.on_release = Some( msg );
		self
	}

	/// Draw only the nodes, never the stroke: against shoulder surfing.
	pub fn hide_stroke( mut self, hide: bool ) -> Self
	{
		self.hide_stroke = hide;
		self
	}

	/// Paint the current path in the danger colour.
	pub fn error( mut self, error: bool ) -> Self
	{
		self.error = error;
		self
	}

	pub( crate ) fn map_msg<U>( self, f: &super::MapFn<Msg, U> ) -> PatternGrid<U>
	where
		U: Clone + 'static,
		Msg: 'static,
	{
		let on_node = self.on_node.map( |old| -> Arc<dyn Fn( u8 ) -> U>
		{
			let mapper = Arc::clone( f );
			Arc::new( move |n| ( *mapper )( ( *old )( n ) ) )
		} );
		PatternGrid
		{
			path:        self.path,
			on_node,
			on_release:  self.on_release.map( |m| ( *f )( m ) ),
			hide_stroke: self.hide_stroke,
			error:       self.error,
			size:        self.size,
		}
	}

	pub fn preferred_size( &self, max_width: f32, canvas: &Canvas ) -> ( f32, f32 )
	{
		let size = match self.size
		{
			Some( l ) => canvas.resolve_geom( l ),
			None      => canvas.geom_px( theme::SIZE ),
		};
		let size = size.min( max_width );
		( size, size )
	}

	pub fn draw( &self, canvas: &mut Canvas, rect: Rect, _focused: bool )
	{
		let palette  = crate::theme::palette();
		let active   = if self.error { palette.danger } else { palette.accent };
		let node_r   = canvas.geom_px( theme::NODE_RADIUS );
		let dot_r    = canvas.geom_px( theme::DOT_RADIUS );
		let stroke_w = canvas.geom_px( theme::STROKE_W );

		if !self.hide_stroke
		{
			for pair in self.path.windows( 2 )
			{
				let a = node_center( rect, pair[ 0 ] );
				let b = node_center( rect, pair[ 1 ] );
				canvas.draw_line( a.x, a.y, b.x, b.y, active, stroke_w );
			}
		}

		for node in 0..NODES
		{
			let c       = node_center( rect, node );
			let visited = self.path.contains( &node );
			if visited
			{
				let ring = Color { a: active.a * theme::RING_ALPHA, ..active };
				circle( canvas, c, node_r, ring );
			}
			circle( canvas, c, dot_r, if visited { active } else { palette.text_secondary } );
		}
	}
}

fn circle( canvas: &mut Canvas, center: Point, radius: f32, color: Color )
{
	let rect = Rect { x: center.x - radius, y: center.y - radius, width: radius * 2.0, height: radius * 2.0 };
	canvas.fill_rect( rect, color, radius );
}

/// Centre of node `index` (0 to 8, row-major) inside `rect`.
pub fn node_center( rect: Rect, index: u8 ) -> Point
{
	let col  = ( index % 3 ) as f32;
	let row  = ( index / 3 ) as f32;
	let side = rect.width.min( rect.height );
	let ox   = rect.x + ( rect.width  - side ) / 2.0;
	let oy   = rect.y + ( rect.height - side ) / 2.0;
	let cell = side / 3.0;
	Point { x: ox + cell * ( col + 0.5 ), y: oy + cell * ( row + 0.5 ) }
}

/// The node under `pos`, if within the snap radius of one.
pub fn node_at( rect: Rect, pos: Point, snap_radius: f32 ) -> Option<u8>
{
	( 0..NODES ).find( |&node|
	{
		let c = node_center( rect, node );
		( pos.x - c.x ).hypot( pos.y - c.y ) <= snap_radius
	} )
}

/// Snap radius in design pixels, resolved by the input path through the canvas density.
pub fn snap_design_px() -> f32
{
	theme::SNAP_RADIUS
}

pub fn pattern_grid<Msg: Clone>( path: Vec<u8> ) -> PatternGrid<Msg>
{
	PatternGrid::new( path )
}

impl<Msg: Clone + 'static> From<PatternGrid<Msg>> for Element<Msg>
{
	fn from( g: PatternGrid<Msg> ) -> Self
	{
		Element::PatternGrid( g )
	}
}