Add Coal Cents economy

CoalGov/src/main/java/com/librewiki/coalgov/service/BuildProtectionService.java

@@ -0,0 +1,43 @@
+package com.librewiki.coalgov.service;
+
+import com.librewiki.coalgov.CoalGovPlugin;
+import com.librewiki.coalgov.model.Claim;
+import org.bukkit.Location;
+import org.bukkit.entity.Player;
+
+import java.sql.SQLException;
+import java.util.Optional;
+
+public final class BuildProtectionService {
+    private final CoalGovPlugin plugin;
+    private final ClaimService claimService;
+
+    public BuildProtectionService(CoalGovPlugin plugin, ClaimService claimService) {
+        this.plugin = plugin;
+        this.claimService = claimService;
+    }
+
+    public BuildDecision canModify(Player player, Location location) throws SQLException {
+        if (plugin.hasAdminBypass(player)) {
+            return BuildDecision.allow();
+        }
+        Optional<Claim> claim = claimService.claimAt(location);
+        if (claim.isEmpty()) {
+            return BuildDecision.deny("This land is unclaimed and protected by the Ministry.");
+        }
+        if (!claim.get().ownerUuid().equals(player.getUniqueId())) {
+            return BuildDecision.deny("This claim belongs to another citizen.");
+        }
+        return BuildDecision.allow();
+    }
+
+    public record BuildDecision(boolean allowed, String message) {
+        public static BuildDecision allow() {
+            return new BuildDecision(true, "");
+        }
+
+        public static BuildDecision deny(String message) {
+            return new BuildDecision(false, message);
+        }
+    }
+}