Use Dijkstra algorithm to describe monster paths

dungeonbattle/entities/player.py

@@ -1,4 +1,5 @@
 from random import randint
+from typing import Dict, Tuple
 
 from ..interfaces import FightingEntity
 
@@ -14,6 +15,7 @@ class Player(FightingEntity):
     level: int = 1
     current_xp: int = 0
     max_xp: int = 10
+    paths: Dict[Tuple[int, int], Tuple[int, int]]
 
     def move(self, y: int, x: int) -> None:
         """
@@ -22,6 +24,7 @@ class Player(FightingEntity):
         super().move(y, x)
         self.map.currenty = y
         self.map.currentx = x
+        self.recalculate_paths()
 
     def level_up(self) -> None:
         """
@@ -61,3 +64,26 @@ class Player(FightingEntity):
                     self.add_xp(randint(3, 7))
                 return True
         return super().check_move(y, x, move_if_possible)
+
+    def recalculate_paths(self) -> None:
+        """
+        Use Dijkstra algorithm to calculate best paths
+        for monsters to go to the player.
+        """
+        queue = [(self.y, self.x)]
+        visited = []
+        predecessors = {}
+        while queue:
+            y, x = queue.pop(0)
+            visited.append((y, x))
+            for diff_y, diff_x in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
+                new_y, new_x = y + diff_y, x + diff_x
+                if not 0 <= new_y < self.map.height or \
+                        not 0 <= new_x < self.map.width or \
+                        not self.map.tiles[y][x].can_walk() or \
+                        (new_y, new_x) in visited or \
+                        (new_y, new_x) in queue:
+                    continue
+                predecessors[(new_y, new_x)] = (y, x)
+                queue.append((new_y, new_x))
+        self.paths = predecessors