Implement BossBar API

By: Thinkofdeath <thinkofdeath@spigotmc.org>

paper-api/src/main/java/org/bukkit/boss/BossBar.java

@@ -0,0 +1,126 @@
+package org.bukkit.boss;
+
+import org.bukkit.entity.Player;
+
+import java.util.List;
+
+public interface BossBar {
+
+    /**
+     * Returns the title of this boss bar
+     *
+     * @return the title of the bar
+     */
+    String getTitle();
+
+    /**
+     * Sets the title of this boss bar
+     *
+     * @param title the title of the bar
+     */
+    void setTitle(String title);
+
+    /**
+     * Returns the color of this boss bar
+     *
+     * @return the color of the bar
+     */
+    BarColor getColor();
+
+    /**
+     * Sets the color of this boss bar.
+     *
+     * @param color the color of the bar
+     */
+    void setColor(BarColor color);
+
+    /**
+     * Returns the style of this boss bar
+     *
+     * @return the style of the bar
+     */
+    BarStyle getStyle();
+
+    /**
+     * Sets the bar style of this boss bar
+     *
+     * @param style the style of the bar
+     */
+    void setStyle(BarStyle style);
+
+    /**
+     * Remove an existing flag on this boss bar
+     *
+     * @param flag the existing flag to remove
+     */
+    void removeFlag(BarFlag flag);
+
+    /**
+     * Add an optional flag to this boss bar
+     *
+     * @param flag an optional flag to set on the boss bar
+     */
+    void addFlag(BarFlag flag);
+
+    /**
+     * Returns whether this boss bar as the passed flag set
+     *
+     * @param flag the flag to check
+     * @return whether it has the flag
+     */
+    boolean hasFlag(BarFlag flag);
+
+    /**
+     * Sets the progress of the bar. Values should be between 0.0 (empty) and
+     * 1.0 (full)
+     *
+     * @param progress the progress of the bar
+     */
+    void setProgress(double progress);
+
+    /**
+     * Returns the progress of the bar between 0.0 and 1.0
+     *
+     * @return the progress of the bar
+     */
+    double getProgress();
+
+    /**
+     * Adds the player to this boss bar causing it to display on their screen.
+     *
+     * @param player the player to add
+     */
+    void addPlayer(Player player);
+
+    /**
+     * Removes the player from this boss bar causing it to be removed from their
+     * screen.
+     *
+     * @param player the player to remove
+     */
+    void removePlayer(Player player);
+
+    /**
+     * Removes all players from this boss bar
+     *
+     * @see #removePlayer(Player)
+     */
+    void removeAll();
+
+    /**
+     * Returns all players viewing this boss bar
+     *
+     * @return a immutable list of players
+     */
+    List<Player> getPlayers();
+
+    /**
+     * Shows the previously hidden boss bar to all attached players
+     */
+    void show();
+
+    /**
+     * Hides this boss bar from all attached players
+     */
+    void hide();
+}