Add ActionManager and PendingAction

plugin/src/main/java/de/epiceric/shopchest/action/ActionManager.java

@@ -0,0 +1,44 @@
+package de.epiceric.shopchest.action;
+
+import java.util.*;
+
+public class ActionManager {
+
+    private final Map<UUID, PendingAction> playerActions;
+
+    public ActionManager() {
+        playerActions = new HashMap<>();
+    }
+
+    /**
+     * Submit a {@link PendingAction} for a {@link org.bukkit.entity.Player}
+     *
+     * @param playerId the {@link org.bukkit.entity.Player}'s {@link UUID}
+     * @param action   The {@link PendingAction} that he will do
+     * @return An {@link Optional} {@link PendingAction} which is :
+     * - empty if the action was correctly submitted
+     * - filled by the current action that has not been executed (mean that the submitted action is rejected)
+     */
+    public Optional<PendingAction> submitAction(UUID playerId, PendingAction action) {
+        Objects.requireNonNull(playerId);
+        Objects.requireNonNull(action);
+        final PendingAction registeredAction = playerActions.compute(
+                playerId,
+                (k, v) -> (v == null || v.hasExpired() ? action : v)
+        );
+        return registeredAction == action ? Optional.empty() : Optional.of(registeredAction);
+    }
+
+    /**
+     * Get the current action of a {@link org.bukkit.entity.Player}
+     *
+     * @param uuid {@link org.bukkit.entity.Player}'s {@link UUID}
+     * @return An {@link Optional} {@link PendingAction} which is :
+     * - empty if there is no pending action for this player
+     * - filled by the current valid pending action if there is one
+     */
+    public Optional<PendingAction> getAction(UUID uuid) {
+        return Optional.ofNullable(playerActions.computeIfPresent(uuid, (k, v) -> v.hasExpired() ? null : v));
+    }
+
+}

plugin/src/main/java/de/epiceric/shopchest/action/PendingAction.java

@@ -0,0 +1,42 @@
+package de.epiceric.shopchest.action;
+
+import org.bukkit.block.Block;
+
+import java.util.concurrent.CompletableFuture;
+
+public abstract class PendingAction {
+
+    protected final Block block;
+    protected final long endTime;
+
+    public PendingAction(Block block, long duration) {
+        this.block = block;
+        this.endTime = System.currentTimeMillis() + duration;
+    }
+
+    /**
+     * Check if the action is applicable to a specific {@link Block}
+     *
+     * @param block The block to check
+     * @return {@code true} if this action is applicable to this {@link Block}, {@code false} otherwise
+     */
+    public abstract boolean canApply(Block block);
+
+    /**
+     * Check if this action is still valid
+     *
+     * @return {@code true} if this action is valid, {@code false} otherwise
+     */
+    public boolean hasExpired() {
+        return System.currentTimeMillis() > endTime;
+    }
+
+    /**
+     * Execute the action
+     *
+     * @param block The targeted block by this action
+     * @return A {@link CompletableFuture} that symbolize the execute action
+     */
+    public abstract CompletableFuture<Void> execute(Block block);
+
+}