From b652bd512d7359152608d485fba9d6131e25814e Mon Sep 17 00:00:00 2001
From: Michael Smith <m@michaelsmith.be>
Date: Wed, 27 Oct 2021 00:02:09 +0200
Subject: [PATCH] Sword-fighting

---
 src/main.rs | 89 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 83 insertions(+), 6 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index f725d40..e8b794e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -54,6 +54,8 @@ struct Object {
   name: String,
   blocks: bool,
   alive: bool,
+  fighter: Option<Fighter>,
+  ai: Option<Ai>,
 }
 
 impl Object {
@@ -66,6 +68,8 @@ impl Object {
       name: name.into(),
       blocks: blocks,
       alive: false,
+      fighter: None,
+      ai: None,
     }
   }
 
@@ -83,6 +87,12 @@ impl Object {
     self.x = x;
     self.y = y;
   }
+
+  pub fn distance_to(&self, other: &Object) -> f32 {
+    let dx = other.x - self.x;
+    let dy = other.y - self.y;
+    ((dx.pow(2) + dy.pow(2)) as f32).sqrt()
+  }
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -146,6 +156,15 @@ impl Rect {
   }
 }
 
+// Combat related properties and methods (monster, player, NPC).
+#[derive(Clone, Copy, Debug, PartialEq)]
+struct Fighter {
+  max_hp: i32,
+  hp: i32,
+  defense: i32,
+  power: i32,
+}
+
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum PlayerAction {
   TookTurn,
@@ -153,6 +172,11 @@ enum PlayerAction {
   Exit,
 }
 
+#[derive(Clone, Debug, PartialEq)]
+enum Ai {
+  Basic,
+}
+
 fn handle_keys(tcod: &mut Tcod, game: &Game, objects: &mut Vec<Object>) -> PlayerAction {
   use tcod::input::Key;
   use tcod::input::KeyCode::*;
@@ -275,10 +299,26 @@ fn place_objects(room: Rect, map: &Map, objects: &mut Vec<Object>) {
     if !is_blocked(x, y, map, objects) {
       let mut monster = if rand::random::<f32>() < 0.8 {
         // 80% chance of spawning an orc
-        Object::new(x, y, 'o', "orc", DESATURATED_GREEN, true)
+        let mut orc = Object::new(x, y, 'o', "orc", DESATURATED_GREEN, true);
+        orc.fighter = Some(Fighter {
+          max_hp: 10,
+          hp: 10,
+          defense: 0,
+          power: 3,
+        });
+        orc.ai = Some(Ai::Basic);
+        orc
       } else {
         // 20% chance of spawning a troll
-        Object::new(x, y, 'T', "troll", DARKER_GREEN, true)
+        let mut troll = Object::new(x, y, 'T', "troll", DARKER_GREEN, true);
+        troll.fighter = Some(Fighter {
+          max_hp: 16,
+          hp: 16,
+          defense: 1,
+          power: 4,
+        });
+        troll.ai = Some(Ai::Basic);
+        troll
       };
 
       monster.alive = true;
@@ -327,6 +367,38 @@ fn player_move_or_attack(dx: i32, dy: i32, game: &Game, objects: &mut [Object])
   }
 }
 
+fn move_towards(id: usize, target_x: i32, target_y: i32, map: &Map, objects: &mut [Object]) {
+  // Vector from this object to the target, and distance
+  let dx = target_x - objects[id].x;
+  let dy = target_y - objects[id].y;
+  let distance = ((dx.pow(2) + dy.pow(2)) as f32).sqrt();
+
+  // Normalize it to length 1 (preserving direction), then round it and
+  // convert it to integer so the movement is restricted to the map grid
+  let dx = (dx as f32 / distance).round() as i32;
+  let dy = (dy as f32 / distance).round() as i32;
+  move_by(id, dx, dy, map, objects);
+}
+
+fn ai_take_turn(monster_id: usize, tcod: &Tcod, game: &Game, objects: &mut [Object]) {
+  // A basic monster takes its turn. If you can see it, it can see you.
+  let (monster_x, monster_y) = objects[monster_id].pos();
+  if tcod.fov.is_in_fov(monster_x, monster_y) {
+    if objects[monster_id].distance_to(&objects[PLAYER]) >= 2.0 {
+      // Move towards player if far away
+      let (player_x, player_y) = objects[PLAYER].pos();
+      move_towards(monster_id, player_x, player_y, &game.map, objects);
+    } else if objects[PLAYER].fighter.map_or(false, |f| f.hp > 0) {
+      // Close enough, attach! (if the player is still alive.)
+      let monster = &objects[monster_id];
+      println!(
+        "The attack of the {} bounces off your shiny metal armor!",
+        monster.name
+      );
+    }
+  }
+}
+
 fn render_all(tcod: &mut Tcod, game: &mut Game, objects: &[Object], fov_recompute: bool) {
   if fov_recompute {
     let player = &objects[PLAYER];
@@ -398,6 +470,12 @@ fn main() {
   // Create player object
   let mut player = Object::new(0, 0, '@', "player", WHITE, true);
   player.alive = true;
+  player.fighter = Some(Fighter {
+    max_hp: 30,
+    hp: 30,
+    defense: 2,
+    power: 5,
+  });
 
   // List of objects in the world
   let mut objects = vec![player];
@@ -437,10 +515,9 @@ fn main() {
 
     // Let monsters take their turn
     if objects[PLAYER].alive && player_action != PlayerAction::DidntTakeTurn {
-      for object in &objects {
-        // ONly if object is not player
-        if (object as *const _) != (&objects[PLAYER] as *const _) {
-          println!("The {} growls!", object.name);
+      for id in 0..objects.len() {
+        if objects[id].ai.is_some() {
+          ai_take_turn(id, &tcod, &game, &mut objects);
         }
       }
     }