SPIGOT-7396: Add PlayerSignOpenEvent

By: Miles Holder <mwholder2005@gmail.com>

paper-api/src/main/java/org/bukkit/event/player/PlayerSignOpenEvent.java

@@ -0,0 +1,101 @@
+package org.bukkit.event.player;
+
+import org.bukkit.block.Sign;
+import org.bukkit.block.sign.Side;
+import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is fired when a sign is opened by the player.
+ */
+@ApiStatus.Experimental
+public class PlayerSignOpenEvent extends PlayerEvent implements Cancellable {
+
+    private static final HandlerList handlers = new HandlerList();
+    private final Sign sign;
+    private final Side side;
+    private final Cause cause;
+    private boolean cancelled;
+
+    public PlayerSignOpenEvent(@NotNull final Player player, @NotNull final Sign sign, @NotNull final Side side, @NotNull final Cause cause) {
+        super(player);
+        this.sign = sign;
+        this.side = side;
+        this.cause = cause;
+    }
+
+    /**
+     * Gets the sign that was opened.
+     *
+     * @return opened sign
+     */
+    @NotNull
+    public Sign getSign() {
+        return this.sign;
+    }
+
+    /**
+     * Gets side of the sign opened.
+     *
+     * @return side of sign opened
+     */
+    @NotNull
+    public Side getSide() {
+        return this.side;
+    }
+
+    /**
+     * Gets the cause of the sign open.
+     *
+     * @return sign open cause
+     */
+    @NotNull
+    public Cause getCause() {
+        return this.cause;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return this.cancelled;
+    }
+
+    @Override
+    public void setCancelled(boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+
+    @ApiStatus.Experimental
+    public enum Cause {
+
+        /**
+         * Indicate the sign was opened because of an interaction.
+         */
+        INTERACT,
+        /**
+         * Indicate the sign was opened because the sign was placed.
+         */
+        PLACE,
+        /**
+         * Indicate the sign was opened because of a plugin.
+         */
+        PLUGIN,
+        /**
+         * Indicate the sign was opened for an unknown reason.
+         */
+        UNKNOWN;
+    }
+}