From e6fcbd8dcf89c3dfb76ac42f9c06e8dbfc588199 Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Thu, 12 Mar 2026 00:54:34 -0400
Subject: [PATCH] Maze gen can now more efficiently produce an interesting map
 that is fully pathable.

---
 src/algos/maze.cpp | 65 +++++++++++++++++++++++++++++++++++++++++++---
 src/algos/maze.hpp |  2 ++
 tests/mazes.cpp    | 16 +++++++++---
 3 files changed, 75 insertions(+), 8 deletions(-)

diff --git a/src/algos/maze.cpp b/src/algos/maze.cpp
index 143e862..923e517 100644
--- a/src/algos/maze.cpp
+++ b/src/algos/maze.cpp
@@ -215,12 +215,11 @@ namespace maze {
 
   void Builder::remove_dead_ends() {
     dbc::check($dead_ends.size() > 0, "you have to run an algo first, no dead_ends to remove");
+
     for(auto at : $dead_ends) {
       for(matrix::compass it{$walls, at.x, at.y}; it.next();) {
-        if($walls[it.y][it.x] == 0) {
-          int diff_x = at.x - it.x;
-          int diff_y = at.y - it.y;
-          $walls[at.y + diff_y][at.x + diff_x] = 0;
+        if($walls[it.y][it.x] == SPACE_VALUE) {
+          punch_dead_end(at.x, at.y, it.x, it.y);
           break;
         }
       }
@@ -404,4 +403,62 @@ namespace maze {
 
     return true;
   }
+
+  void Builder::punch_dead_end(size_t at_x, size_t at_y, size_t x, size_t y) {
+    int diff_x = at_x - x;
+    int diff_y = at_y - y;
+    $walls[at_y + diff_y][at_x + diff_x] = SPACE_VALUE;
+  }
+
+  bool Builder::repair() {
+    // possible fixes
+    // go through each dead end and remove until it works
+    // go through each room and add a door until it works
+    // only find rooms that are unpathable and fix them
+    // walk the path deleting dead ends at the end of the path
+    std::vector<Point> removed_ends;
+    bool now_valid = false;
+
+    for(auto& at : $dead_ends) {
+      // punch a hole for this dead end
+      for(matrix::compass it{$walls, at.x, at.y}; it.next();) {
+        if($walls[it.y][it.x] == SPACE_VALUE) {
+          punch_dead_end(at.x, at.y, it.x, it.y);
+          removed_ends.push_back({it.x, it.y});
+          break;
+        }
+      }
+
+      // if that validates it then done
+      if(validate()) {
+        now_valid = true;
+        fmt::println("MID dead_end removed={}, total={}, %={}",
+          removed_ends.size(), $dead_ends.size(),
+          float(removed_ends.size()) / float($dead_ends.size()));
+        break;
+      }
+    }
+
+    // now go back and see if we can add any back
+    int added_back = 0;
+    for(auto& at : removed_ends) {
+      $walls[at.y][at.x] = WALL_VALUE;
+
+      if(!validate()) {
+        $walls[at.y][at.x] = SPACE_VALUE;
+      } else {
+        added_back++;
+      }
+    }
+
+    enclose();
+    now_valid = validate();
+
+    fmt::println("FINAL now_valid={} added_back={} removed={}, total={}, %={}",
+        now_valid, added_back, removed_ends.size() - added_back, $dead_ends.size(),
+        float(removed_ends.size() - added_back) / float($dead_ends.size()));
+
+    // didn't find a way to make it valid
+    return now_valid;
+  }
 }
diff --git a/src/algos/maze.hpp b/src/algos/maze.hpp
index a2e6259..717fad8 100644
--- a/src/algos/maze.hpp
+++ b/src/algos/maze.hpp
@@ -40,5 +40,7 @@ namespace maze {
     bool room_should_exist(Room& room, bool allow_dupes=false);
     void make_doors();
     bool validate();
+    bool repair();
+    void punch_dead_end(size_t at_x, size_t at_y, size_t x, size_t y);
   };
 }
diff --git a/tests/mazes.cpp b/tests/mazes.cpp
index 85304f6..57b1943 100644
--- a/tests/mazes.cpp
+++ b/tests/mazes.cpp
@@ -7,7 +7,7 @@
 #include "algos/maze.hpp"
 #include "algos/stats.hpp"
 
-#define DUMP 1
+#define DUMP 0
 
 using std::string;
 using matrix::Matrix;
@@ -106,7 +106,7 @@ TEST_CASE("hunt-and-kill validator", "[mazes]") {
   bool valid = true;
   Stats mofm;
 
-  for(int i = 0; i < 100; i++) {
+  for(int i = 0; i < 10; i++) {
     Stats door_prob;
 
     do {
@@ -123,16 +123,24 @@ TEST_CASE("hunt-and-kill validator", "[mazes]") {
       maze.enclose();
 
       valid = maze.validate();
-      if(valid && i == 99) {
-        maze.dump("VALIDATED");
+      if(!valid) valid = maze.repair();
+
+      if(i == 9) {
+        if(valid) {
+          maze.dump("VALIDATED");
+        } else {
+          matrix::dump("PATHING", maze.$paths.$paths);
+        }
       }
 
       door_prob.sample(valid);
     } while(!valid);
 
+    door_prob.dump();
     mofm.sample(door_prob.mean());
   }
 
+  fmt::println("FINAL m-of-m");
   mofm.dump();
   REQUIRE(mofm.mean() > 0.20);
 }