Added Vein Mining

src/main/java/wtf/hak/survivalfabric/veinminer/VeinMinerSession.java

@@ -0,0 +1,66 @@
+package wtf.hak.survivalfabric.veinminer;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Set;
+
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.math.BlockPos;
+
+public class VeinMinerSession {
+    private static ArrayList<VeinMinerSession> sessions = new ArrayList<>();
+
+    public ServerPlayerEntity player;
+    public ServerWorld world;
+    public Set<BlockPos> positions;
+    public BlockPos initialPos;
+
+    public static VeinMinerSession sessionForPlayer(ServerPlayerEntity player) {
+        for (var session: sessions) {
+            if (session.player == player) {
+                return session;
+            }
+        }
+        return null;
+    }
+
+    public static VeinMinerSession sessionForPosition(BlockPos position) {
+        for (var session: sessions) {
+            if (session.positions.contains(position)) {
+                return session;
+            }
+        }
+        return null;
+    }
+
+    public static VeinMinerSession start(ServerPlayerEntity player, ServerWorld world, BlockPos initialPos) {
+        var session = new VeinMinerSession(player, world, initialPos);
+        sessions.add(session);
+        return session;
+    }
+
+    private static void finish(VeinMinerSession session) {
+        sessions.remove(session);
+    }
+
+    private VeinMinerSession(ServerPlayerEntity player, ServerWorld world, BlockPos initialPos) {
+        this.player = player;
+        this.world = world;
+        this.initialPos = initialPos;
+        this.positions = new HashSet<>();
+        positions.add(initialPos);
+    }
+
+    public void addPosition(BlockPos pos) {
+        positions.add(pos);
+    }
+
+    public void removePosition(BlockPos pos) {
+        positions.remove(pos);
+    }
+
+    public void finish() {
+        finish(this);
+    }
+}