Remember the last node extraction after a restart

pom.xml

@@ -85,6 +85,12 @@
                 </exclusion>
             </exclusions>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.14.0</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>net.tfminecraft</groupId>
             <artifactId>magic</artifactId>
@@ -130,6 +136,11 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.14.1</version>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.5.4</version>
+            </plugin>
         </plugins>
     </build>
 </project>

src/main/java/net/tfminecraft/dowsing/utils/Database.java

@@ -140,6 +140,9 @@ public void loadNodes() {
     				}
     				setSlots(currentType, activePMs);
     				Node n = new Node(id, b, loc, g, isActive, level, cycleTime, currentType, timeLeft, inputCounter, efficiency);
+    				if(json.containsKey(LastCycleResult.KEY)) {
+    					n.setLastResult(LastCycleResult.fromJson(json.get(LastCycleResult.KEY)));
+    				}
     				NodeManager.nodes.add(n);
     			} catch (Exception ex) {
     				ex.printStackTrace();
@@ -261,6 +264,7 @@ public void saveNode(Node n) {
         	}
         	defaults.put("active pms", pmArray);
 			defaults.put("efficiency", n.getEfficiency());
+			defaults.put(LastCycleResult.KEY, LastCycleResult.toJson(n.getLastResult()));
         	save(file, defaults);
         } catch (Throwable ex) {
 			ex.printStackTrace();

src/main/java/net/tfminecraft/dowsing/utils/LastCycleResult.java

@@ -0,0 +1,59 @@
+package net.tfminecraft.dowsing.utils;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.json.simple.JSONObject;
+
+public final class LastCycleResult {
+
+	public static final String KEY = "last result";
+
+	private LastCycleResult() {}
+
+	@SuppressWarnings("unchecked")
+	public static JSONObject toJson(Map<String, Integer> result) {
+		JSONObject object = new JSONObject();
+		if(result == null) {
+			return object;
+		}
+		for(Map.Entry<String, Integer> entry : result.entrySet()) {
+			if(entry.getKey() == null || entry.getKey().isBlank() || entry.getValue() == null || entry.getValue() <= 0) {
+				continue;
+			}
+			object.put(entry.getKey(), entry.getValue());
+		}
+		return object;
+	}
+
+	public static Map<String, Integer> fromJson(Object raw) {
+		Map<String, Integer> result = new HashMap<>();
+		if(!(raw instanceof JSONObject object)) {
+			return result;
+		}
+		for(Object key : object.keySet()) {
+			if(key == null) {
+				continue;
+			}
+			int amount = amountOf(object.get(key));
+			if(amount > 0) {
+				result.put(String.valueOf(key), amount);
+			}
+		}
+		return result;
+	}
+
+	static int amountOf(Object value) {
+		if(value instanceof Number number) {
+			return number.intValue();
+		}
+		if(value == null) {
+			return 0;
+		}
+		try {
+			return (int) Math.round(Double.parseDouble(value.toString()));
+		} catch (NumberFormatException ex) {
+			return 0;
+		}
+	}
+}

src/test/java/net/tfminecraft/dowsing/utils/LastCycleResultTest.java

@@ -0,0 +1,45 @@
+package net.tfminecraft.dowsing.utils;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.json.simple.JSONObject;
+import org.junit.jupiter.api.Test;
+
+class LastCycleResultTest {
+
+	@Test
+	void roundTripsExtractedItems() {
+		Map<String, Integer> extracted = new LinkedHashMap<>();
+		extracted.put("m.materials.niter", 1);
+		extracted.put("m.materials.arcane_crystal", 3);
+
+		JSONObject stored = LastCycleResult.toJson(extracted);
+		Map<String, Integer> loaded = LastCycleResult.fromJson(stored);
+
+		assertEquals(extracted, loaded);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Test
+	void readsNumericAmountsWrittenByTheJsonParser() {
+		JSONObject stored = new JSONObject();
+		stored.put("m.materials.niter", 1L);
+		stored.put("m.materials.arcane_crystal", 3.0d);
+
+		Map<String, Integer> loaded = LastCycleResult.fromJson(stored);
+
+		assertEquals(1, loaded.get("m.materials.niter"));
+		assertEquals(3, loaded.get("m.materials.arcane_crystal"));
+	}
+
+	@Test
+	void missingOrEmptyResultsStayEmpty() {
+		assertTrue(LastCycleResult.fromJson(null).isEmpty());
+		assertTrue(LastCycleResult.toJson(Map.of()).isEmpty());
+		assertTrue(LastCycleResult.toJson(null).isEmpty());
+	}
+}