add placeholderapi hook

src/main/java/me/youhavetrouble/preventstabby/hooks/PlacoholderApiHook.java

@@ -0,0 +1,53 @@
+package me.youhavetrouble.preventstabby.hooks;
+
+import me.clip.placeholderapi.expansion.PlaceholderExpansion;
+import me.youhavetrouble.preventstabby.PreventStabby;
+import me.youhavetrouble.preventstabby.util.PluginMessages;
+import org.bukkit.OfflinePlayer;
+import org.jetbrains.annotations.NotNull;
+
+import java.time.Instant;
+import java.util.UUID;
+
+public class PlacoholderApiHook extends PlaceholderExpansion {
+
+    private final PreventStabby plugin;
+
+    public PlacoholderApiHook(PreventStabby preventStabby) {
+        plugin = preventStabby;
+    }
+
+    @Override
+    public @NotNull String getIdentifier() {
+        return "preventstabby";
+    }
+
+    @Override
+    public @NotNull String getAuthor() {
+        return plugin.getDescription().getAuthors().get(0);
+    }
+
+    @Override
+    public @NotNull String getVersion() {
+        return plugin.getDescription().getVersion();
+    }
+
+    @Override
+    public String onRequest(OfflinePlayer player, String params) {
+        if (params.equalsIgnoreCase("combat_time")) {
+            return getCombatTimePlaceholder(player.getUniqueId());
+        }
+        return null;
+    }
+
+    private String getCombatTimePlaceholder(UUID uuid) {
+        long seconds = plugin.getPlayerManager().getPlayer(uuid).getCombattime() - Instant.now().getEpochSecond();
+        if (seconds > 0) {
+            String msg = plugin.getConfigCache().getPlaceholder_combat_time();
+            msg = msg.replaceAll("%time%", String.valueOf(seconds));
+            return PluginMessages.parseMessage(msg);
+        }
+        return PluginMessages.parseMessage(plugin.getConfigCache().getPlaceholder_not_in_combat());
+    }
+
+}