From b0cf4cb8818c8440462e24c7b553bc4b90b3a8a2 Mon Sep 17 00:00:00 2001
From: Steph Enders <smenders@gmail.com>
Date: Sat, 10 Dec 2022 23:42:30 -0500
Subject: Move enemies that have no path

If there is no path to the player, the enemy will move in best effort
---
 dnglib/algs.lua   | 39 ++++++++++++++++++++++++++++++++++++++-
 maps/lvl2/dng.map | 12 ++++++------
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/dnglib/algs.lua b/dnglib/algs.lua
index 9bb2542..0b66604 100644
--- a/dnglib/algs.lua
+++ b/dnglib/algs.lua
@@ -113,6 +113,41 @@ local function push_moves(x, y, origin, map, queue, target_pos)
     return false
 end
 
+---
+---@param start_pos table [x, y]
+---@param target_pos table [x, y]
+---@param map table 2D map array
+---@return table best move to target [x, y]
+---
+local function best_effort_move(start_pos, target_pos, map)
+  local diff_x = target_pos.x - start_pos.x
+  local diff_y = target_pos.y - start_pos.y
+
+  local move = { dx = 0, dy = 0 }
+
+  if (math.abs(diff_x) > math.abs(diff_y)) then
+    -- do x moves first
+    if diff_x > 0 and can_move(start_pos.x + 1, start_pos.y, map) then
+      move.dx = 1
+      return move
+    elseif diff_x < 0 and can_move(start_pos.x - 1, start_pos.y, map) then
+      move.dx = -1
+      return move
+    end
+  else -- y moves
+    if diff_y > 0 and can_move(start_pos.x, start_pos.y + 1, map) then
+      move.dy = 1
+      return move
+    elseif diff_y < 0 and can_move(start_pos.y, start_pos.y - 1, map) then
+      move.dy = -1
+      return move
+    end
+  end
+  -- return 0, 0 move
+  return move
+end
+
+
 ---
 ---@param start_pos table [x, y]
 ---@param target_pos table [x, y]
@@ -142,7 +177,9 @@ local function pathfind(start_pos, target_pos, map)
             return { dx = origin.x - start_pos.x, dy = origin.y - start_pos.y }
         end
     end
-    return { dx = 0, dy = 0 }
+
+    --- cannot find path - just move "towards" player
+    return best_effort_move(start_pos, target_pos, map)
 end
 
 return {
diff --git a/maps/lvl2/dng.map b/maps/lvl2/dng.map
index 26467e0..7c5ff80 100644
--- a/maps/lvl2/dng.map
+++ b/maps/lvl2/dng.map
@@ -4,15 +4,15 @@ w e 0 0 0 t 0 0 0 0 0 0 w 0 0 0 w
 w 0 0 0 0 0 0 0 0 0 0 0 w t 0 0 w
 w 0 w w w w w w w w 0 w w w w 0 w
 w 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 w
-w 0 w w w w w w w w 0 w w 0 0 0 w
-w e 0 0 0 0 0 0 0 0 0 w 0 0 0 0 w
-w w 0 w w w w w w w 0 w w w w w w
-w t 0 w 0 0 w 0 0 0 0 w w w w 0 w
-w 0 w w 0 0 0 0 0 0 0 w e w w 0 w
+w 0 w w w w w w w w 0 w w w w w w
+w e 0 0 0 0 0 0 0 0 0 w 0 e 0 0 w
+w w 0 w w w w w w w 0 w 0 w 0 w w
+w t 0 w 0 0 w 0 0 0 0 w 0 0 w 0 w
+w 0 w w 0 0 0 0 0 0 0 w 0 0 w 0 w
 w 0 0 0 0 w w w w 0 w w w w w 0 w
 w t w w w 0 0 0 0 0 0 0 0 0 0 0 w
 w w w w w 0 w 0 0 0 0 0 w 0 w w w
 w 0 0 0 0 0 0 0 0 0 0 0 w 0 0 0 w
 w p w w w w w w w w w w w w w 0 w
 w 0 0 0 0 0 0 0 t 0 0 0 0 0 0 0 w
-w w w w w w w w w w w w w w w w w
\ No newline at end of file
+w w w w w w w w w w w w w w w w w
-- 
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