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use crate::{WorldDuration, WorldInstant, CHUNK_HEIGHT, CHUNK_WIDTH};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

/// Contains the map tiles, spawn points (if any), and player characters for a
/// limited area in the game.
///
/// Chunks are the main level of granularity within the game: each Chunk can be
/// updated independently, and when players move between chunks, they get
/// removed from one and added to the other, so that players are always in one
/// specific chunk.
#[derive(Clone, Serialize, Deserialize)]
pub struct Chunk {
    /// The wall layer of this chunk. Walls block movement. The [Vec] contains
    /// [CHUNK_WIDTH] × [CHUNK_HEIGHT] elements. The tile for coordinates X and
    /// Y can be found at index `X + Y * CHUNK_WIDTH`. The value is [None] if
    /// there's no wall at the given position.
    pub walls: Vec<Option<TileIndex>>,
    /// The floor layer of this chunk. The [Vec] contains [CHUNK_WIDTH] ×
    /// [CHUNK_HEIGHT] elements. The tile for coordinates X and Y can be found
    /// at index `X + Y * CHUNK_WIDTH`. The value is [None] if there's just
    /// empty floor at the given position.
    pub floors: Vec<Option<TileIndex>>,
    /// The list of points in this Chunk where a player can be spawned when
    /// they're initially added into the world.
    pub spawns: Vec<Point>,
    /// The player characters in this chunk.
    pub pcs: HashMap<PcHandle, PlayerCharacter>,
}

impl Chunk {
    /// Returns true if there's a wall at the given coordinates.
    pub fn is_wall(&self, x: i32, y: i32) -> bool {
        if x >= 0 && x < CHUNK_WIDTH as i32 && y >= 0 && y < CHUNK_HEIGHT as i32 {
            self.walls[x as usize + y as usize * CHUNK_WIDTH].is_some()
        } else {
            false
        }
    }
}

/// An identifier for different looking tiles.
///
/// The inner value refers to the index of the sprite in the tileset, starting
/// from top-left, going row-by-row from left to right, up to down.
#[derive(Clone, Serialize, Deserialize)]
pub struct TileIndex(pub u32);

/// A randomly generated identifier that differentiates different player
/// characters.
///
/// One player character will retain the same PcHandle for their entire
/// lifetime.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct PcHandle(pub u64);

/// Player character information, relative to the chunk the player is in.
#[derive(Clone, Serialize, Deserialize)]
pub struct PlayerCharacter {
    /// The position of the player within the [Chunk] the player is in.
    pub position: Point,
    /// Information about the player's movement, [None] if they're not moving.
    pub current_move: Option<MoveStatus>,
}

/// Information about a character moving from point A to B.
#[derive(Clone, Serialize, Deserialize)]
pub struct MoveStatus {
    /// How many timesteps the move will take.
    pub duration: WorldDuration,
    /// The timestep during which the movement started.
    pub start_frame: WorldInstant,
    /// The point where the player was during the start of the move. May be
    /// outside the bounds of the chunks, if the move originated from a
    /// neighboring chunk.
    pub from: Point,
    /// The point where the player ends up as a result of the move.
    pub to: Point,
}

/// Coordinates.
///
/// The inner values represent the X and Y coordinates, in that order.
#[derive(Clone, Copy, Serialize, Deserialize)]
pub struct Point(pub i32, pub i32);