turtlegame/src/activities/overworld/worldgen.rs

use comfy::{IVec2, UVec2};
use std::collections::HashMap;

enum MovementCost {
	/// No movement possible - cost infinitely high.
	Infinite,
	/// There is a path for this movement - movement is cheap.
	Path,
	/// There is no path and no obstacle.
	Default,
	/// There is an obstacle (i.e. fence) - movement is expensive.
	Obstacle
}

#[derive(Debug)]
struct Tile;

impl Tile {
	pub fn can_stand_inside(&self) -> bool {
		unimplemented!()
	}
	pub fn movement_cost_left(&self) -> MovementCost {
		unimplemented!()
	}
	pub fn movement_cost_right(&self) -> MovementCost {
		unimplemented!()
	}
	pub fn movement_cost_up(&self) -> MovementCost {
		unimplemented!()
	}
	pub fn movement_cost_down(&self) -> MovementCost {
		unimplemented!()
	}
	pub fn can_enter_house(&self) -> bool {
		unimplemented!()
	}
}

/// The size of a chunk (both width and height). This value squared gives the amount of
/// tiles in the chunk.
const CHUNK_SIZE: u32 = 100;

/// Chunks
#[derive(Debug)]
pub struct Chunk {
	/// All tiles within this chunk.
	tiles: [Tile; (CHUNK_SIZE * CHUNK_SIZE) as usize],
	/// All paths that leave this chunk on the left hand side.
	paths_left: Vec<u32>,
	/// All paths that leave this chunk on the right hand side.
	paths_right: Vec<u32>,
	/// All paths that leave this chunk on the bottom side.
	paths_bottom: Vec<u32>,
	/// All paths that leave this chunk on the top side.
	paths_top: Vec<u32>
}

impl Chunk {
	pub fn get_tile(&self, local_chunk_coords: UVec2) -> Option<&Tile> {
		self.tiles
			.get((local_chunk_coords.y * CHUNK_SIZE + local_chunk_coords.x) as usize)
	}

	/// iterate over all tiles and its local chunk coords
	pub fn iter_tiles(&self) -> impl Iterator<Item = (UVec2, &Tile)> {
		self.tiles.iter().enumerate().map(|(i, tile)| {
			let i = i as u32;
			(UVec2::new(i % CHUNK_SIZE, i / CHUNK_SIZE), tile)
		})
	}
}

#[derive(Debug, Default)]
pub struct Overworld {
	chunks: HashMap<IVec2, Chunk>
}

impl Overworld {
	/// Return a [`Tile`] at the given world coordinates, or `None` if that tile has not
	/// been generated yet.
	pub fn get_tile(&self, world_coords: IVec2) -> Option<&Tile> {
		let tile_coords = IVec2 {
			x: world_coords.x.div_euclid(CHUNK_SIZE as _),
			y: world_coords.y.div_euclid(CHUNK_SIZE as _)
		};
		let local_coords = UVec2 {
			x: world_coords.x.rem_euclid(CHUNK_SIZE as _) as _,
			y: world_coords.y.rem_euclid(CHUNK_SIZE as _) as _
		};

		let chunk = self.chunks.get(&tile_coords)?;
		chunk.get_tile(local_coords)
	}

	fn get_or_generate_tile(&self, world_coords: IVec2) -> &Tile {
		unimplemented!()
	}

	/// iterate over all tiles and its global coords
	pub fn iter_tiles(&self) -> impl Iterator<Item = (IVec2, &Tile)> {
		self.chunks.iter().flat_map(|(chunk_coords, chunk)| {
			chunk.iter_tiles().map(|(local_coords, tile)| {
				// never fail because chunksize fits alswas into i32
				let local_coords: IVec2 = local_coords.try_into().unwrap();
				(local_coords + (*chunk_coords * CHUNK_SIZE as i32), tile)
			})
		})
	}
}