Initial commit for InventoryGui

.gitignore

@@ -0,0 +1,43 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+.kotlin
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/gradle.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="GradleSettings">
+    <option name="linkedExternalProjectsSettings">
+      <GradleProjectSettings>
+        <option name="externalProjectPath" value="$PROJECT_DIR$" />
+        <option name="gradleHome" value="" />
+        <option name="modules">
+          <set>
+            <option value="$PROJECT_DIR$" />
+          </set>
+        </option>
+      </GradleProjectSettings>
+    </option>
+  </component>
+</project>

.idea/misc.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="FrameworkDetectionExcludesConfiguration">
+    <file type="web" url="file://$PROJECT_DIR$" />
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="corretto-21" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>

build.gradle.kts

@@ -0,0 +1,53 @@
+import org.gradle.api.publish.maven.MavenPublication
+
+plugins {
+    `java-library`
+    `maven-publish`
+}
+
+val nexusUser = providers.gradleProperty("alttdSnapshotUsername").orNull ?: System.getenv("NEXUS_USERNAME")
+val nexusPass = providers.gradleProperty("alttdSnapshotPassword").orNull ?: System.getenv("NEXUS_PASSWORD")
+
+group = "com.alttd.inventory_gui"
+version = "1.1.0-SNAPSHOT"
+
+repositories {
+    mavenCentral()
+    maven("https://repo.papermc.io/repository/maven-public/")
+}
+
+dependencies {
+    compileOnly("org.projectlombok:lombok:1.18.30")
+    annotationProcessor("org.projectlombok:lombok:1.18.30")
+    compileOnly("io.papermc.paper:paper-api:1.21.11-R0.1-SNAPSHOT")
+}
+
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+    withSourcesJar()
+    withJavadocJar()
+}
+
+tasks.withType<JavaCompile>().configureEach {
+    options.encoding = "UTF-8"
+    options.release.set(21)
+}
+
+publishing {
+    repositories {
+        maven {
+            url = uri("https://repo.alttd.com/repository/alttd-snapshot/")
+            credentials {
+                username = nexusUser
+                password = nexusPass
+            }
+        }
+    }
+    publications {
+        create<MavenPublication>("mavenJava") {
+            from(components["java"])
+        }
+    }
+}

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Mon Jan 19 20:48:34 CET 2026
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

@@ -0,0 +1 @@
+rootProject.name = "InventoryGUI"

src/main/java/com/alttd/inventory_gui/click/GuiClickHandler.java

@@ -0,0 +1,27 @@
+package com.alttd.inventory_gui.click;
+
+import org.bukkit.event.inventory.InventoryClickEvent;
+
+/**
+ * Represents a functional interface for handling click events in a graphical user interface (GUI).
+ * This interface defines a single abstract method, allowing custom behavior to be implemented
+ * when a user interacts with a clickable GUI element.
+ * <p>
+ * The method {@link #onClick(InventoryClickEvent)} is triggered when an {@code InventoryClickEvent}
+ * occurs, enabling developers to implement specific actions based on the nature of the event.
+ * <p>
+ * It is typically used in conjunction with classes that represent GUI components, such as
+ * {@code GuiItem}, where this interface is employed to define the click behavior of a component.
+ */
+@FunctionalInterface
+public interface GuiClickHandler {
+    /**
+     * Handles an inventory click event, allowing custom actions to be performed when a user interacts
+     * with a graphical user interface (GUI) element.
+     *
+     * @param event the {@code InventoryClickEvent} representing the details of the user's interaction,
+     *              including the clicked slot, the item involved, and the action performed.
+     */
+    void onClick(InventoryClickEvent event);
+}
+

src/main/java/com/alttd/inventory_gui/click/GuiItem.java

@@ -0,0 +1,55 @@
+package com.alttd.inventory_gui.click;
+
+import lombok.Getter;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.inventory.ItemStack;
+
+/**
+ * Represents an item in a (inventory) graphical user interface (GUI).
+ * This class encapsulates an {@code ItemStack} with optional click handling behavior,
+ * allowing for the creation of both clickable and non-clickable GUI elements.
+ * Instances of this class are immutable and thread-safe.
+ */
+@SuppressWarnings("ClassCanBeRecord")
+public final class GuiItem {
+    @Getter
+    private final ItemStack stack;
+    @Getter
+    private final boolean clickable;
+    private final GuiClickHandler handler;
+
+    private GuiItem(ItemStack stack, boolean clickable, GuiClickHandler handler) {
+        this.stack = stack;
+        this.clickable = clickable;
+        this.handler = handler;
+    }
+
+    /**
+     * Creates a new {@code GuiItem} with the given {@code ItemStack} and click handling behavior.
+     * @param stack the {@code ItemStack} to represent in the GUI
+     * @param handler the {@code GuiClickHandler} to handle click events for this item, or {@code null} for non-clickable items
+     * @return a new {@code GuiItem} instance
+     */
+    public static GuiItem clickable(ItemStack stack, GuiClickHandler handler) {
+        return new GuiItem(stack, true, handler);
+    }
+
+    /**
+     * Creates a new non-clickable {@code GuiItem} with the given {@code ItemStack}.
+     * @param stack the {@code ItemStack} to represent in the GUI
+     * @return a new non-clickable {@code GuiItem} instance
+     */
+    public static GuiItem nonClickable(ItemStack stack) {
+        return new GuiItem(stack, false, null);
+    }
+
+    /**
+     * Handles a click event for this item if a click handler has been specified.
+     * @param event the {@code InventoryClickEvent} representing the details of the user's interaction
+     */
+    public void handle(InventoryClickEvent event) {
+        if (handler != null) {
+            handler.onClick(event);
+        }
+    }
+}

src/main/java/com/alttd/inventory_gui/gui/GuiClosePolicy.java

@@ -0,0 +1,24 @@
+package com.alttd.inventory_gui.gui;
+
+/**
+ * Enum representing the policies for handling the closing of GUI inventory interfaces.
+ * The close policy determines whether players are allowed to close the GUI or if the
+ * GUI should attempt to prevent closure.
+ * <p>
+ * This enum is primarily used in conjunction with the {@code InventoryGui} class to
+ * define the behavior of GUI sessions when a player attempts to close the inventory.
+ * <p>
+ * The available policies are:
+ * - {@code ALLOW_CLOSE}: Allows players to close the GUI without intervention.
+ * - {@code BLOCK_CLOSE}: Attempts to prevent players from closing the GUI by reopening it.
+ */
+public enum GuiClosePolicy {
+    /**
+     * Allows players to close the GUI without intervention.
+     */
+    ALLOW_CLOSE,
+    /**
+     * Attempts to prevent players from closing the GUI by reopening it.
+     */
+    BLOCK_CLOSE
+}

src/main/java/com/alttd/inventory_gui/gui/GuiListener.java

@@ -0,0 +1,92 @@
+package com.alttd.inventory_gui.gui;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.inventory.*;
+import org.bukkit.inventory.Inventory;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * The {@code GuiListener} class implements the {@code Listener} interface to handle
+ * inventory click and close events for GUI interactions in a Bukkit/Spigot plugin context.
+ * It ensures that proper event handling is delegated to the appropriate GUI session
+ * associated with a player.
+ * <p>
+ * This class relies on the {@code GuiSession} system to keep track of players' active
+ * GUI sessions and routes events to the corresponding {@code InventoryGui} instance.
+ * <p>
+ * The {@code GuiListener} is associated with a specific plugin by its name to ensure
+ * that event handling is scoped to the appropriate plugin's GUI instances.
+ */
+@SuppressWarnings("ClassCanBeRecord")
+public final class GuiListener implements Listener {
+
+    private final String ownerPluginName;
+
+    /**
+     * Constructs a new {@code GuiListener} instance.
+     * @param ownerPluginName the name of the plugin that owns the GUI instances to which this listener should be attached
+     */
+    public GuiListener(String ownerPluginName) {
+        this.ownerPluginName = ownerPluginName;
+    }
+
+    /**
+     * Handles interactions with inventories in the context of GUI sessions. This method ensures
+     * that the interaction is processed only if the player is part of an active GUI session.
+     * The method cancels the interaction event by default and delegates specific event handling
+     * to the associated GUI instance when applicable.
+     *
+     * @param event the {@code InventoryInteractEvent} triggered when a player interacts with an inventory
+     */
+    @EventHandler
+    public void onInventoryInteract(InventoryInteractEvent event) {
+        if (!(event.getWhoClicked() instanceof Player player)) {
+            return;
+        }
+
+        GuiSession.Entry entry = getEntry(player, event.getInventory());
+        if (entry == null) {
+            return;
+        }
+
+        event.setCancelled(true);
+        if (event instanceof InventoryClickEvent inventoryClickEvent) {
+            entry.gui().handleClick(inventoryClickEvent);
+        }
+    }
+
+    /**
+     * Handles inventory close events for GUI interactions.
+     * @param event the {@code InventoryCloseEvent} representing the details of the user's interaction
+     */
+    @EventHandler
+    public void onClose(InventoryCloseEvent event) {
+        if (!(event.getPlayer() instanceof Player player)) {
+            return;
+        }
+
+        GuiSession.Entry entry = getEntry(player, event.getInventory());
+        if (entry == null) {
+            return;
+        }
+
+        entry.gui().handleClose(player);
+        GuiSession.clear(player.getUniqueId());
+    }
+
+    private GuiSession.@Nullable Entry getEntry(Player player, Inventory event) {
+        GuiSession.Entry entry = GuiSession.get(player.getUniqueId());
+        if (entry == null) {
+            return null;
+        }
+        if (!entry.ownerPluginName().equals(ownerPluginName)) {
+            return null;
+        }
+        if (event != entry.inv()) {
+            return null;
+        }
+        return entry;
+    }
+}

src/main/java/com/alttd/inventory_gui/gui/GuiSession.java

@@ -0,0 +1,47 @@
+package com.alttd.inventory_gui.gui;
+
+import org.bukkit.inventory.Inventory;
+
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * The {@code GuiSession} class provides a static utility for managing GUI sessions in a Bukkit/Spigot plugin.
+ * It holds associations between players, their open GUIs, and the owning plugin for the GUI.
+ * This class ensures that GUIs are properly maintained and can be cleared when no longer needed.
+ * <p>
+ * Key responsibilities:
+ * - Binding a GUI session to a player's UUID.
+ * - Retrieving the active GUI session for a specific player.
+ * - Clearing an individual player's GUI session.
+ * - Clearing all GUI sessions associated with a specific plugin.
+ * <p>
+ * This class operates using a thread-safe {@code ConcurrentHashMap} to manage GUI sessions.
+ */
+public final class GuiSession {
+
+    private GuiSession() {
+
+    }
+
+    private static final Map<UUID, Entry> SESSIONS = new ConcurrentHashMap<>();
+
+    static void bind(UUID playerId, String ownerPluginName, InventoryGui gui, Inventory inv) {
+        SESSIONS.put(playerId, new Entry(ownerPluginName, gui, inv));
+    }
+
+    static Entry get(UUID playerId) {
+        return SESSIONS.get(playerId);
+    }
+
+    static void clear(UUID playerId) {
+        SESSIONS.remove(playerId);
+    }
+
+    static void clearAllForOwner(String ownerPluginName) {
+        SESSIONS.entrySet().removeIf(e -> e.getValue().ownerPluginName().equals(ownerPluginName));
+    }
+
+    record Entry(String ownerPluginName, InventoryGui gui, Inventory inv) {}
+}

src/main/java/com/alttd/inventory_gui/gui/InventoryGui.java

@@ -0,0 +1,125 @@
+package com.alttd.inventory_gui.gui;
+
+import com.alttd.inventory_gui.click.GuiItem;
+import com.alttd.inventory_gui.pane.GuiPane;
+import com.alttd.inventory_gui.pane.SimplePane;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NonNull;
+import net.kyori.adventure.text.Component;
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.plugin.Plugin;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * The InventoryGui class represents a dynamic GUI system for Bukkit/Spigot plugins,
+ * using inventories to create interactive user experiences. It allows developers
+ * to define and manage custom GUI layouts and behaviors, enabling players to interact
+ * with plugin elements directly in Minecraft.
+ * <p>
+ * This class is built with flexibility and ease of use in mind, supporting various
+ * customization options, event handling, and row validation to maintain consistency.
+ */
+@Builder
+public class InventoryGui {
+
+    @NonNull
+    @Getter
+    private final Plugin plugin;
+    @NonNull
+    private final Component title;
+    @NonNull
+    private final Integer rows;
+    @Getter
+    @Builder.Default
+    private final GuiClosePolicy closePolicy = GuiClosePolicy.ALLOW_CLOSE;
+    @Getter
+    private final GuiPane root;
+
+    private InventoryGui(@NotNull Plugin plugin, @NotNull Component title, int rows, GuiClosePolicy closePolicy, GuiPane root) {
+        validateRows(rows);
+
+        this.plugin = plugin;
+        this.title = title;
+        this.rows = rows;
+        this.closePolicy = closePolicy;
+        this.root = root != null ? root : new SimplePane(rows * 9);
+    }
+
+    private static void validateRows(int rows) {
+        if (rows < 1 || rows > 6) {
+            throw new IllegalArgumentException("Rows must be between 1 and 6");
+        }
+    }
+
+    /**
+     * Creates a new inventory for the specified player.
+     * @param player the player for whom to create the inventory
+     * @return a new inventory instance
+     */
+    public Inventory createInventory(Player player) {
+        return Bukkit.createInventory(player, rows * 9, title);
+    }
+
+    /**
+     * Renders the GUI's contents into the specified inventory.
+     * @param inv the inventory into which to render the GUI's contents
+     */
+    public void render(Inventory inv) {
+        inv.clear();
+        root.render(inv);
+    }
+
+    /**
+     * Opens the GUI for the specified player.
+     * @param player the player for whom to open the GUI
+     */
+    public void open(Player player) {
+        InventoryGuiLib.ensureInit(plugin);
+
+        Inventory inv = createInventory(player);
+        render(inv);
+        GuiSession.bind(player.getUniqueId(), plugin.getName(), this, inv);
+        player.openInventory(inv);
+    }
+
+    /**
+     * Handles inventory click events for GUI interactions.
+     * @param event the {@code InventoryClickEvent} representing the details of the user's interaction
+     */
+    public void handleClick(InventoryClickEvent event) {
+        event.setCancelled(true);
+
+        int raw = event.getRawSlot();
+        if (raw < 0 || raw >= event.getInventory().getSize()) {
+            return;
+        }
+
+        GuiItem item = root.getItem(raw);
+        if (item == null) {
+            return;
+        }
+
+        if (!item.isClickable()) {
+            event.setCancelled(true);
+            return;
+        }
+        item.handle(event);
+    }
+
+    /**
+     * Handles inventory close events for GUI interactions.
+     * @param player the player whose inventory was closed
+     */
+    public void handleClose(Player player) {
+        if (closePolicy == GuiClosePolicy.ALLOW_CLOSE) {
+            return;
+        }
+        if (closePolicy == GuiClosePolicy.BLOCK_CLOSE) {
+            plugin.getServer().getScheduler().runTask(plugin, () -> open(player));
+        }
+    }
+}

src/main/java/com/alttd/inventory_gui/gui/InventoryGuiLib.java

@@ -0,0 +1,69 @@
+package com.alttd.inventory_gui.gui;
+
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.Listener;
+import org.bukkit.plugin.Plugin;
+
+import java.util.Objects;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Utility class providing dynamic GUI management for Bukkit/Spigot-based plugins.
+ * Uses event registration and session handling to manage inventory-based GUIs.
+ * <p>
+ * This class is designed to simplify the management of plugin-specific inventory GUIs,
+ * ensuring that events are handled appropriately and associated entities are cleaned up
+ * on plugin unregistration.
+ * <p>
+ * Thread-safety is achieved via {@link ConcurrentHashMap} for storing plugin-specific
+ * registrations. Utility methods include initialization, registration of listeners, and
+ * cleanup of resources.
+ */
+public final class InventoryGuiLib {
+    private InventoryGuiLib() {}
+
+    private static final ConcurrentHashMap<String, Registration> REGISTRATIONS = new ConcurrentHashMap<>();
+
+    static void ensureInit(Plugin plugin) {
+        Objects.requireNonNull(plugin, "plugin cannot be null");
+
+        REGISTRATIONS.computeIfAbsent(plugin.getName(), name -> {
+            Listener listener = new GuiListener(name);
+            plugin.getServer().getPluginManager().registerEvents(listener, plugin);
+            return new Registration(plugin, listener);
+        });
+    }
+
+    /**
+     * Initializes the library for the specified plugin. This method ensures that the plugin
+     * is properly registered in the library, including the setup of necessary listeners for
+     * managing inventory GUI events.
+     *
+     * @param plugin the plugin for which the library is being initialized; must not be null
+     */
+    public static void init(Plugin plugin) {
+        Objects.requireNonNull(plugin, "plugin cannot be null");
+        ensureInit(plugin);
+    }
+
+    /**
+     * Unregisters the given plugin from the inventory GUI library, removing its associated
+     * event listeners and clearing all GUI sessions linked to the plugin.
+     *
+     * @param plugin the plugin to unregister; must not be null
+     */
+    public static void unregister(Plugin plugin) {
+        Objects.requireNonNull(plugin, "plugin cannot be null");
+
+        Registration reg = REGISTRATIONS.remove(plugin.getName());
+        if (reg == null) return;
+
+        HandlerList.unregisterAll(reg.listener());
+        GuiSession.clearAllForOwner(reg.ownerName());
+    }
+
+    private record Registration(Plugin owner, Listener listener) {
+        String ownerName() { return owner.getName(); }
+    }
+}
+

src/main/java/com/alttd/inventory_gui/pane/GuiPane.java

@@ -0,0 +1,36 @@
+package com.alttd.inventory_gui.pane;
+
+import com.alttd.inventory_gui.click.GuiItem;
+import org.bukkit.inventory.Inventory;
+
+/**
+ * Represents a pane in a (inventory) graphical user interface (GUI) inventory layout.
+ * A {@code GuiPane} acts as a container or layout for GUI items,
+ * enabling easier management of items in a specific section of an inventory.
+ * <p>
+ * Responsibilities:
+ * - Adding or removing items at specific slots within the pane.
+ * - Retrieving items from a specific slot in the pane.
+ * - Rendering the pane's contents into a provided inventory.
+ */
+public interface GuiPane {
+    /**
+     * Sets the item at the specified slot in the pane.
+     * @param slot the slot index at which to set the item
+     * @param item the item to set at the specified slot
+     */
+    void setItem(int slot, GuiItem item);
+
+    /**
+     * Retrieves the item at the specified slot in the pane.
+     * @param slot the slot index from which to retrieve the item
+     * @return the item at the specified slot, or {@code null} if no item is present at that slot
+     */
+    GuiItem getItem(int slot);
+
+    /**
+     * Renders the pane's contents into the provided inventory.
+     * @param inv the inventory into which to render the pane's contents
+     */
+    void render(Inventory inv);
+}

src/main/java/com/alttd/inventory_gui/pane/SimplePane.java

@@ -0,0 +1,57 @@
+package com.alttd.inventory_gui.pane;
+
+import com.alttd.inventory_gui.click.GuiItem;
+import org.bukkit.inventory.Inventory;
+
+/**
+ * The {@code SimplePane} class is an implementation of the {@code GuiPane} interface,
+ * designed to represent a simple container for GUI items within an inventory.
+ * <p>
+ * This class provides:
+ * - Management of a fixed-size array of {@code GuiItem} objects.
+ * - Methods to add, retrieve, and render items into an inventory.
+ * <p>
+ * Key Responsibilities:
+ * - Storing a collection of {@code GuiItem} objects in a fixed-sized pane.
+ * - Validating slot boundaries when setting or retrieving items.
+ * - Rendering the pane's items into a provided {@code Inventory}, ensuring item positions
+ *   from the pane correspond to positions in the inventory.
+ */
+@SuppressWarnings("ClassCanBeRecord")
+public final class SimplePane implements GuiPane {
+    private final GuiItem[] items;
+
+    /**
+     * Constructs a new {@code SimplePane} instance with the specified number of slots.
+     * @param size the number of slots in the pane
+     */
+    public SimplePane(int size) {
+        this.items = new GuiItem[size];
+    }
+
+    @Override
+    public void setItem(int slot, GuiItem item) {
+        if (slot < 0 || slot >= items.length) {
+            throw new IndexOutOfBoundsException();
+        }
+        items[slot] = item;
+    }
+
+    @Override
+    public GuiItem getItem(int slot) {
+        if (slot < 0 || slot >= items.length) {
+            return null;
+        }
+        return items[slot];
+    }
+
+    @Override
+    public void render(Inventory inv) {
+        for (int i = 0; i < items.length && i < inv.getSize(); i++) {
+            GuiItem guiItem = items[i];
+            if (guiItem != null) {
+                inv.setItem(i, guiItem.getStack());
+            }
+        }
+    }
+}