Overworld Movement (#9)

Co-authored-by: luckyturtledev <git@lukas1818.de>
Reviewed-on: #9
Co-authored-by: Dominic <git@msrd0.de>
Co-committed-by: Dominic <git@msrd0.de>

src/game.rs

@@ -2,22 +2,64 @@ use crate::{
 	activities::{house, overworld, Activity},
 	State
 };
-use comfy::EngineContext;
-use std::ops::Sub;
+use comfy::{EngineContext, Vec2};
+use std::{ops::Sub, time::Instant};
 
 #[derive(Debug)]
 pub struct Ghost {
-	/// current electric charge of the Ghost
+	/// Current electric charge of the Ghost.
 	pub charge: f32,
-	/// max electric charge of the Ghost
-	pub max_charge: f32
+	/// Max electric charge of the Ghost.
+	pub max_charge: f32,
+
+	/// The position of the ghost in the overworld. Expressed in tile coordinates, but
+	/// as a float as a ghost takes more than one tick to move.
+	pub overworld_pos: Vec2,
+	/// Pending movement of the ghost in the overworld.
+	pub overworld_movement_pending: Vec2,
+	/// The current movement speed of the ghost in tiles/sec.
+	pub overworld_movement_speed: f32,
+	/// The timestamp of the last overworld position update.
+	pub overworld_pos_last_update: Instant
+}
+
+impl Ghost {
+	pub fn update_overworld_pos(&mut self, now: Instant) {
+		// This calculation is extremely simplistic. It will not work properly if both
+		// x and y of movement_pending are non-zero. But we only move left,right,up,down
+		// so that should never happen!
+		let secs = now
+			.duration_since(self.overworld_pos_last_update)
+			.as_secs_f32();
+		let mut movement = self.overworld_movement_pending.signum()
+			* self.overworld_movement_speed
+			* secs;
+
+		// limit the movement to the remaining movement
+		if self.overworld_movement_pending.x.abs() < movement.x.abs() {
+			movement.x = self.overworld_movement_pending.x;
+		}
+		if self.overworld_movement_pending.y.abs() < movement.y.abs() {
+			movement.y = self.overworld_movement_pending.y;
+		}
+
+		// execute the movement
+		self.overworld_pos += movement;
+		self.overworld_movement_pending -= movement;
+		self.overworld_pos_last_update = now;
+	}
 }
 
 impl Default for Ghost {
 	fn default() -> Self {
 		Self {
 			charge: 1000.0,
-			max_charge: 1000.0
+			max_charge: 1000.0,
+
+			overworld_pos: Vec2::ZERO,
+			overworld_movement_pending: Vec2::ZERO,
+			overworld_movement_speed: 0.0,
+			overworld_pos_last_update: Instant::now()
 		}
 	}
 }