//! `cargo run --example scroll`
//!
//! Demonstrates the two main scroll use cases:
//!
//! - **List mode** — a long vertical list inside a `scroll(column(...))`.
//! - **Grid mode** — a grid of buttons inside a `scroll(grid(4))` (app-drawer style).
//!
//! Press the "List" / "Grid" toggle at the top to switch between modes.
//! Drag the content area to scroll. Esc exits.
//!
//! NOTE: ltk is a Wayland layer-shell toolkit. This example requires a running
//! Wayland compositor (e.g. sway, labwc, or a full desktop session).

use ltk::{
	App, Element, Keysym, ButtonVariant,
	button, column, row, text, scroll, grid, spacer,
};

// ── Messages ──────────────────────────────────────────────────────────────────

#[ derive( Clone ) ]
enum Message
{
	ShowList,
	ShowGrid,
	ItemPressed( usize ),
}

// ── App state ─────────────────────────────────────────────────────────────────

#[ derive( PartialEq ) ]
enum Mode { List, Grid }

struct ScrollApp
{
	mode:         Mode,
	last_pressed: Option<usize>,
}

impl ScrollApp
{
	fn new() -> Self
	{
		Self { mode: Mode::List, last_pressed: None }
	}
}

// ── App trait ─────────────────────────────────────────────────────────────────

const ITEM_COUNT: usize = 64;

impl App for ScrollApp
{
	type Message = Message;

	fn view( &self ) -> Element<Message>
	{
		let palette   = ltk::theme_palette();
		let primary   = palette.text_primary;
		let secondary = palette.text_secondary;

		let status = match self.last_pressed
		{
			Some( i ) => format!( "Pressed item {}", i + 1 ),
			None      => String::from( "Drag to scroll  ·  click an item" ),
		};

		// Top bar: toggle buttons + status
		let toggle_list = button::<Message>( "List" )
			.variant( if self.mode == Mode::List { ButtonVariant::Primary } else { ButtonVariant::Secondary } )
			.on_press( Message::ShowList );

		let toggle_grid = button::<Message>( "Grid" )
			.variant( if self.mode == Mode::Grid { ButtonVariant::Primary } else { ButtonVariant::Secondary } )
			.on_press( Message::ShowGrid );

		let top_bar = row::<Message>()
			.spacing( 8.0 )
			.push( toggle_list )
			.push( toggle_grid )
			.push( spacer() )
			.push( text( &status ).size( 14.0 ).color( secondary ) );

		// Scrollable content area
		let content: Element<Message> = match self.mode
		{
			Mode::List =>
			{
				// A long list of labeled buttons in a scrollable column
				let mut col = column::<Message>().padding( 8.0 ).spacing( 6.0 );
				for i in 0..ITEM_COUNT
				{
					col = col.push(
						button::<Message>( format!( "List item {}  —  click me", i + 1 ) )
							.variant( ButtonVariant::Secondary )
							.on_press( Message::ItemPressed( i ) ),
					);
				}
				scroll( col ).into()
			}
			Mode::Grid =>
			{
				// A grid of labeled buttons in a scrollable 4-column grid
				let mut g = grid::<Message>( 4 ).padding( 8.0 ).spacing( 6.0 );
				for i in 0..ITEM_COUNT
				{
					g = g.push(
						button::<Message>( format!( "Item {}", i + 1 ) )
							.variant( ButtonVariant::Secondary )
							.on_press( Message::ItemPressed( i ) ),
					);
				}
				scroll( g ).into()
			}
		};

		column::<Message>()
			.padding( 16.0 )
			.spacing( 12.0 )
			.push( text( "ltk — scroll showcase" ).size( 22.0 ).color( primary ).align_center() )
			.push( top_bar )
			.push( content )
			.push(
				text( "Drag = scroll  ·  Esc = quit" )
					.size( 12.0 )
					.color( secondary )
					.align_center(),
			)
			.into()
	}

	fn update( &mut self, msg: Message )
	{
		match msg
		{
			Message::ShowList          => self.mode = Mode::List,
			Message::ShowGrid          => self.mode = Mode::Grid,
			Message::ItemPressed( i )  => self.last_pressed = Some( i ),
		}
	}

	fn on_key( &mut self, keysym: Keysym ) -> Option<Message>
	{
		if keysym == Keysym::Escape { std::process::exit( 0 ); }
		None
	}
}

// ── Entry point ───────────────────────────────────────────────────────────────

fn main()
{
	ltk::run( ScrollApp::new() );
}