From 45ab89f795ce5ef93ec496565c43d6fc762c3a1e Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Fri, 29 Oct 2021 10:30:17 -0400
Subject: [PATCH] Add initial monster chase mechanism

---
 src/map.rs               | 41 +++++++++++++++++++++++++++++++++++++++-
 src/monster_ai_system.rs | 28 ++++++++++++++++++++++-----
 2 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/src/map.rs b/src/map.rs
index 67ca173..f4b0127 100644
--- a/src/map.rs
+++ b/src/map.rs
@@ -1,5 +1,5 @@
 use super::Rect;
-use rltk::{Algorithm2D, BaseMap, Point, RandomNumberGenerator, Rltk, RGB};
+use rltk::{Algorithm2D, BaseMap, Point, RandomNumberGenerator, Rltk, SmallVec, RGB};
 use specs::prelude::*;
 use std::cmp::{max, min};
 
@@ -107,6 +107,15 @@ impl Map {
 
         map
     }
+
+    fn is_exit_valid(&self, x: i32, y: i32) -> bool {
+        if x < 1 || x > self.width - 1 || y < 1 || y > self.height - 1 {
+            return false;
+        }
+
+        let idx = self.xy_idx(x, y);
+        self.tiles[idx as usize] != TileType::Wall
+    }
 }
 
 impl Algorithm2D for Map {
@@ -119,6 +128,36 @@ impl BaseMap for Map {
     fn is_opaque(&self, idx: usize) -> bool {
         self.tiles[idx as usize] == TileType::Wall
     }
+
+    fn get_available_exits(&self, idx: usize) -> SmallVec<[(usize, f32); 10]> {
+        let mut exits = rltk::SmallVec::new();
+        let x = idx as i32 % self.width;
+        let y = idx as i32 / self.width;
+        let w = self.width as usize;
+
+        if self.is_exit_valid(x - 1, y) {
+            exits.push((idx - 1, 1.0))
+        };
+        if self.is_exit_valid(x + 1, y) {
+            exits.push((idx + 1, 1.0))
+        };
+        if self.is_exit_valid(x, y - 1) {
+            exits.push((idx - w, 1.0))
+        };
+        if self.is_exit_valid(x, y + 1) {
+            exits.push((idx + w, 1.0))
+        };
+
+        exits
+    }
+
+    fn get_pathing_distance(&self, idx1: usize, idx2: usize) -> f32 {
+        let w = self.width as usize;
+        let p1 = Point::new(idx1 % w, idx1 / w);
+        let p2 = Point::new(idx2 % w, idx2 / w);
+
+        rltk::DistanceAlg::Pythagoras.distance2d(p1, p2)
+    }
 }
 
 pub fn draw_map(ecs: &World, ctx: &mut Rltk) {
diff --git a/src/monster_ai_system.rs b/src/monster_ai_system.rs
index 2491fb7..eb136e9 100644
--- a/src/monster_ai_system.rs
+++ b/src/monster_ai_system.rs
@@ -1,23 +1,41 @@
-use super::{Monster, Name, Viewshed};
+use super::{Map, Monster, Name, Position, Viewshed};
 use rltk::{console, Point};
 use specs::prelude::*;
 
 pub struct MonsterAI {}
 
 impl<'a> System<'a> for MonsterAI {
+    #[allow(clippy::type_complexity)]
     type SystemData = (
+        WriteExpect<'a, Map>,
         ReadExpect<'a, Point>,
-        ReadStorage<'a, Viewshed>,
+        WriteStorage<'a, Viewshed>,
         ReadStorage<'a, Monster>,
         ReadStorage<'a, Name>,
+        WriteStorage<'a, Position>,
     );
 
     fn run(&mut self, data: Self::SystemData) {
-        let (player_pos, viewshed, monster, name) = data;
+        let (mut map, player_pos, mut viewshed, monster, name, mut position) = data;
 
-        for (viewshed, _monster, name) in (&viewshed, &monster, &name).join() {
+        for (mut viewshed, _monster, name, mut pos) in
+            (&mut viewshed, &monster, &name, &mut position).join()
+        {
             if viewshed.visible_tiles.contains(&*player_pos) {
-                console::log(format!("{} shouts insults", name.name));
+                console::log(&format!("{} shouts insults", name.name));
+
+                let path = rltk::a_star_search(
+                    map.xy_idx(pos.x, pos.y) as i32,
+                    map.xy_idx(player_pos.x, player_pos.y) as i32,
+                    &mut *map,
+                );
+
+                if path.success && path.steps.len() > 1 {
+                    pos.x = path.steps[1] as i32 % map.width;
+                    pos.y = path.steps[1] as i32 / map.width;
+
+                    viewshed.dirty = true;
+                }
             }
         }
     }