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//! contains system for archer enemy AI

use std::cmp;

use specs::{prelude::*, System};

use crate::{engine::components::UnitComponent, unit::UnitType};

/// This system acts as an enemy AI, attacking the player if an archer
/// exists and can attack the [`Warrior`](crate::warrior::Warrior).
/// The difference from the sludge is that the archer's arrows can reach
/// the warrior as long as there is no other enemy in the way.
pub struct ArcherSystem;

impl<'a> System<'a> for ArcherSystem {
    type SystemData = WriteStorage<'a, UnitComponent>;

    fn run(&mut self, mut units: Self::SystemData) {
        let mut units = (&mut units).join();
        let warrior_comp = units
            .by_ref()
            .find(|comp| match comp.unit.unit_type {
                UnitType::Warrior(_) => true,
                _ => false,
            })
            .unwrap();
        let enemy_comps: Vec<&mut UnitComponent> = units
            .by_ref()
            .filter(|comp| match comp.unit.unit_type {
                UnitType::Warrior(_) => false,
                _ => true,
            })
            .collect();
        for archer_comp in enemy_comps
            .iter()
            .filter(|comp| comp.unit.unit_type == UnitType::Archer)
        {
            let (wx, _) = warrior_comp.unit.position;
            let (sx, _) = archer_comp.unit.position;
            let (hp, _) = archer_comp.unit.hp;

            let obstructions: Vec<&&mut UnitComponent> = enemy_comps
                .iter()
                .filter(|comp| {
                    let (x, _) = comp.unit.position;
                    wx < x && x < sx
                })
                .collect();

            // if the Archer is killed and the entity is deleted, but `world.maintain()` hasn't
            // been called yet, then we need to see if the Archer is at 0 hp (dead) here.
            if hp > 0 && obstructions.is_empty() {
                println!(
                    "{archer:?} attacks {warrior:?}",
                    archer = archer_comp.unit.unit_type,
                    warrior = warrior_comp.unit.unit_type
                );
                let (current, max) = warrior_comp.unit.hp;
                let remaining = cmp::max(current - archer_comp.unit.atk, 0);
                println!(
                    "{warrior:?} takes {atk} damage, {remaining} HP left",
                    warrior = warrior_comp.unit.unit_type,
                    atk = archer_comp.unit.atk,
                    remaining = remaining
                );
                warrior_comp.unit.hp = (remaining, max);
            }
        }
    }
}