pneuma/src/main.rs

#![feature(proc_macro_hygiene, decl_macro)]

#[macro_use]
extern crate rocket;

use rocket::State;
use rocket_contrib::json::Json;
use std::collections::HashMap;
use std::sync::Mutex;

mod battlesnake;

type Cache = Mutex<HashMap<String, GameState>>;

#[derive(Debug, Clone)]
pub struct GameState {
    path: Option<Vec<battlesnake::Coord>>,
    target: battlesnake::Coord,
}

#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}

#[get("/ping")]
fn ping() -> &'static str {
    "OK - Pneuma online"
}

#[post("/start", format = "json", data = "<msg>")]
fn start(
    cache: State<Cache>,
    msg: Json<battlesnake::SnakeRequest>,
) -> Json<battlesnake::StartResponse> {
    let head = msg.you.body[0];
    let target = find_target(&msg);
    let path = find_path(&msg, &head, &target);
    let gs = GameState {
        target: *target,
        path: path,
    };

    cache
        .lock()
        .expect("wanted to lock cache")
        .insert(msg.game.id.clone(), gs);

    Json(battlesnake::StartResponse {
        color: "#5ce8c3".to_string(),
        head_type: "beluga".to_string(),
        tail_type: "skinny".to_string(),
    })
}

fn find_path(
    msg: &battlesnake::SnakeRequest,
    head: &battlesnake::Coord,
    target: &battlesnake::Coord,
) -> Option<Vec<battlesnake::Coord>> {
    let path = pathfinding::directed::astar::astar(
        head,
        |n| msg.board.safe_neighbors(n).into_iter(),
        |n| (battlesnake::manhattan(n, &target) as usize),
        |n| n == target,
    );

    match path {
        None => return None,
        Some(x) => {
            return Some(x.0.iter().rev().cloned().collect());
        }
    }
}

#[post("/end", format = "json", data = "<msg>")]
fn end(cache_state: State<Cache>, msg: Json<battlesnake::SnakeRequest>) -> String {
    cache_state
        .lock()
        .expect("wanted cache to be lockable")
        .remove(&msg.game.id);

    "OK".to_string()
}

#[post("/move", format = "json", data = "<msg>")]
fn make_move(
    cache_state: State<Cache>,
    msg: Json<battlesnake::SnakeRequest>,
) -> Json<battlesnake::MoveResponse> {
    let head = msg.you.body[0];

    let mut cache = cache_state.lock().expect("wanted cache to be unlockable");
    let gs = cache.get_mut(&msg.game.id).unwrap();
    if gs.path.is_none() {
        println!("recalculating path");
        gs.target = *find_target(&msg);
        gs.path = find_path(&msg, &head, &gs.target);
    }

    match gs.path.as_mut().unwrap().pop() {
        None => {
            gs.path = None;
            let target = msg.board.safe_neighbors(&head)[0].0;
            let next_move = battlesnake::Line {
                start: &head,
                end: &target,
            }
            .direction()
            .to_string();
            println!("moving to {}, target: {:?}", next_move, target);
            Json(battlesnake::MoveResponse {
                move_field: next_move,
            })
        }
        Some(next) => {
            let next_move = battlesnake::Line {
                start: &head,
                end: &next,
            }
            .direction()
            .to_string();
            println!(
                "moving to {} {:?}, target: {:?}",
                next_move, next, gs.target
            );
            Json(battlesnake::MoveResponse {
                move_field: next_move,
            })
        }
    }
}

fn find_target<'a>(gs: &'a battlesnake::SnakeRequest) -> &'a battlesnake::Coord {
    let head = &gs.you.body[0];
    if gs.you.health > 30 {
        let mut lowest_score: u32 = 99999;
        let mut coord: &battlesnake::Coord = &gs.you.body.last().unwrap();

        for food in &gs.board.food {
            let score = battlesnake::manhattan(&head, &food);
            if score < lowest_score {
                lowest_score = score;
                coord = food;
            }
        }

        return coord;
    }

    return gs.you.body.last().unwrap();
}

fn main() {
    let map = HashMap::<String, GameState>::new();
    let mutex_map = Mutex::from(map);
    let prometheus = rocket_prometheus::PrometheusMetrics::new();
    rocket::ignite()
        .attach(prometheus.clone())
        .mount("/metrics", prometheus)
        .mount("/", routes![index, start, ping, make_move, end,])
        .manage(mutex_map)
        .launch();
}