Grovewright/core/src/command.rs

//! Everything a player can ask the world to do.

use crate::codec::{DecodeError, Reader, Writer};
use crate::map::Pos;
use crate::player::{clamp_name, PlayerId, PlayerKey, MAX_NAME_BYTES};

/// A request that changes the world. Commands are the only way to change it.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Command {
    /// A player enters the world, new or returning.
    Join { key: PlayerKey, name: String },
    /// A player leaves the world. Their inventory stays.
    Leave { player: PlayerId },
    /// A player hits the tile at `pos` with their pickaxe.
    Dig { player: PlayerId, pos: Pos },
}

const TAG_JOIN: u8 = 1;
const TAG_LEAVE: u8 = 2;
const TAG_DIG: u8 = 3;

impl Command {
    pub fn encode(&self, w: &mut Writer) {
        match self {
            Command::Join { key, name } => {
                w.u8(TAG_JOIN);
                w.raw(key);
                w.str(&clamp_name(name));
            }
            Command::Leave { player } => {
                w.u8(TAG_LEAVE);
                w.u8(player.0);
            }
            Command::Dig { player, pos } => {
                w.u8(TAG_DIG);
                w.u8(player.0);
                w.i32(pos.x);
                w.i32(pos.y);
            }
        }
    }

    pub fn decode(r: &mut Reader<'_>) -> Result<Self, DecodeError> {
        match r.u8()? {
            TAG_JOIN => {
                let mut key = [0u8; 16];
                key.copy_from_slice(r.raw(16)?);
                let name = r.string()?;
                if name.len() > MAX_NAME_BYTES {
                    return Err(DecodeError::InvalidValue("player name"));
                }
                Ok(Command::Join { key, name })
            }
            TAG_LEAVE => Ok(Command::Leave {
                player: PlayerId(r.u8()?),
            }),
            TAG_DIG => {
                let player = PlayerId(r.u8()?);
                let x = r.i32()?;
                let y = r.i32()?;
                Ok(Command::Dig {
                    player,
                    pos: Pos::new(x, y),
                })
            }
            _ => Err(DecodeError::InvalidValue("command tag")),
        }
    }
}