From 76c33a8178db40d6ca5f0a72f3cb2d943296f8fc Mon Sep 17 00:00:00 2001
From: Bryson Zimmerman <brzimmer@nmu.edu>
Date: Tue, 12 Nov 2024 19:10:51 -0500
Subject: [PATCH] Initial setup for converting from HashMap to
 TileNavigatedArray

---
 ...PathFinder.kt => ArrayBackedPathfinder.kt} |  6 +-
 src/main/kotlin/Main.kt                       |  2 +-
 src/main/kotlin/MapBackedPathfinder.kt        | 76 +++++++++++++++++++
 src/test/kotlin/TileNavigatedArrayTest.kt     | 16 ++++
 4 files changed, 95 insertions(+), 5 deletions(-)
 rename src/main/kotlin/{PathFinder.kt => ArrayBackedPathfinder.kt} (96%)
 create mode 100644 src/main/kotlin/MapBackedPathfinder.kt
 create mode 100644 src/test/kotlin/TileNavigatedArrayTest.kt

diff --git a/src/main/kotlin/PathFinder.kt b/src/main/kotlin/ArrayBackedPathfinder.kt
similarity index 96%
rename from src/main/kotlin/PathFinder.kt
rename to src/main/kotlin/ArrayBackedPathfinder.kt
index 4653e24..3263fc0 100644
--- a/src/main/kotlin/PathFinder.kt
+++ b/src/main/kotlin/ArrayBackedPathfinder.kt
@@ -4,12 +4,12 @@ import technology.zim.data.Directions
 import technology.zim.data.Tile
 import technology.zim.data.TileHeap
 
-//A* to be upgraded with hierarchies
+//A* pathfinder backed by an array to improve efficiency
 
 //Needs https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/PriorityQueue.html
 //and https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html
 
-object PathFinder {
+object ArrayBackedPathfinder {
     //TODO: Replace with array for coordinate lookups for speed, do it in a separate pathfinder class to demonstrate the difference
     val gVals = HashMap<Tile, Int>()
     //work along the path, marking tiles with VISITED along the way
@@ -53,8 +53,6 @@ object PathFinder {
 
         //At this point, a path is found
         println("Path found!")
-
-
     }
 
     fun markPath(start: Tile, end:Tile) {
diff --git a/src/main/kotlin/Main.kt b/src/main/kotlin/Main.kt
index 7a73a36..2df9037 100644
--- a/src/main/kotlin/Main.kt
+++ b/src/main/kotlin/Main.kt
@@ -13,7 +13,7 @@ class HierarchicalPathfinding {
 
             println("Pathfinding")
             var startTime = System.currentTimeMillis()
-            PathFinder.generatePath(Tile(0, 0), Tile(n-1, (n-1)))
+            MapBackedPathfinder.generatePath(Tile(0, 0), Tile(n-1, (n-1)))
             var endTime = System.currentTimeMillis()
             val aStarMs = endTime - startTime
 
diff --git a/src/main/kotlin/MapBackedPathfinder.kt b/src/main/kotlin/MapBackedPathfinder.kt
new file mode 100644
index 0000000..a953b37
--- /dev/null
+++ b/src/main/kotlin/MapBackedPathfinder.kt
@@ -0,0 +1,76 @@
+package technology.zim
+
+import technology.zim.data.Directions
+import technology.zim.data.Tile
+import technology.zim.data.TileHeap
+
+//A* to be upgraded with hierarchies
+
+//Needs https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/PriorityQueue.html
+//and https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Comparator.html
+
+object MapBackedPathfinder {
+    val gVals = HashMap<Tile, Int>()
+    //work along the path, marking tiles with VISITED along the way
+    //if marking with visited is too expensive, just make the path and finalize it
+    fun generatePath(start: Tile, end: Tile) {
+        if(!start.isInBounds() || !end.isInBounds()) {
+            throw IndexOutOfBoundsException("Cannot generate a path to or from an out of bounds tile")
+        }
+
+        if(start == end) {
+            println("Ouroboros detected")
+            return
+        }
+
+        val frontier = TileHeap(end, gVals)
+
+        //Prime the things
+        gVals.put(start, 0)
+        frontier.insert(start)
+
+        var current: Tile
+        var currentG: Int
+
+        do {
+            current = frontier.popMin()
+            currentG = gVals.get(current) ?: 0.also { println("Failed to get gVal that must exist") }
+
+
+            current.getConnections().forEach { candidateTile ->
+                val candidateG = gVals.get(candidateTile)?:-1
+                //Ensure that the tile is within bounds
+                if(candidateTile.isInBounds() && candidateG == -1)
+                {
+                    //Otherwise, the tile has been reached and this path is not better, so carry on
+                    gVals.put(candidateTile, currentG + 1)
+                    frontier.insert(candidateTile)
+                    World.update(candidateTile, candidateTile.getProperties() +Directions.FRONTIER)
+                }
+            }
+        } while( current != end)
+
+        //At this point, a path is found
+        println("Path found!")
+    }
+
+    fun markPath(start: Tile, end:Tile) {
+        //Step through the path from end until start
+        var current = end
+        var lowestG = Int.MAX_VALUE
+        var lowestCost = end
+        while(current != start) {
+            World.update(current, current.getProperties() + Directions.INPATH)
+            current.getConnections().forEach { candidateTile ->
+                val candidateG = gVals.get(candidateTile) ?: -1
+                if(candidateTile.isInBounds() && candidateG != -1 && candidateG < lowestG ) {
+                    lowestG = candidateG
+                    lowestCost = candidateTile
+                }
+            }
+            current = lowestCost
+        }
+        World.update(start, start.getProperties() + Directions.INPATH)
+    }
+
+}
\ No newline at end of file
diff --git a/src/test/kotlin/TileNavigatedArrayTest.kt b/src/test/kotlin/TileNavigatedArrayTest.kt
new file mode 100644
index 0000000..28e2e32
--- /dev/null
+++ b/src/test/kotlin/TileNavigatedArrayTest.kt
@@ -0,0 +1,16 @@
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+
+class TileNavigatedArrayTest {
+
+    @BeforeTest
+    fun setUp() {
+
+    }
+
+
+    @Test
+    fun addAndAccessTest() {
+
+    }
+}
\ No newline at end of file