[Feature] Parameter precondition attribute for simplifying performing…

… hierarchical operations within a guild (#2906)

* Support interaction framework and update bundled preconditions docs

* Support text commands and update bundled preconditions docs

* Fix example

* Move hierarchy util to `PermissionUtils`

* Refactoring

docs/guides/int_framework/preconditions.md

@@ -30,6 +30,7 @@ to use.
 * @Discord.Interactions.RequireNsfwAttribute
 * @Discord.Interactions.RequireRoleAttribute
 * @Discord.Interactions.RequireTeamAttribute
+* @Discord.Interactions.DoHierarchyCheckAttribute
 
 ## Using Preconditions
 

docs/guides/text_commands/preconditions.md

@@ -29,6 +29,7 @@ to use.
 * @Discord.Commands.RequireBotPermissionAttribute
 * @Discord.Commands.RequireUserPermissionAttribute
 * @Discord.Commands.RequireNsfwAttribute
+* @Discord.Commands.DoHierarchyCheckAttribute
 
 ## Using Preconditions
 

src/Discord.Net.Commands/Attributes/Preconditions/DoHierarchyCheckAttribute.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Discord.Commands
+{
+    /// <summary>
+    ///     Ensures that command parameters are passed within a correct hierarchical context.
+    /// </summary>
+    /// <remarks>
+    ///     Useful for performing hierarchical operations within a guild, such as managing roles or users.
+    ///     <note type="warning">
+    ///         This supports <see cref="IRole"/>, <see cref="IGuildUser"/>, and <see cref="IUser"/> parameter types.
+    ///     </note>
+    /// </remarks>
+    /// <exception cref="ArgumentOutOfRangeException">
+    ///     Thrown when the parameter type is not supported by this precondition attribute.
+    /// </exception>
+    /// <seealso cref="RequireBotPermissionAttribute"/>
+    /// <seealso cref="RequireUserPermissionAttribute"/>
+    public class DoHierarchyCheckAttribute : ParameterPreconditionAttribute
+    {
+        /// <summary>
+        ///     Gets or sets the error message displayed when the command is used outside of a guild.
+        /// </summary>
+        public string NotAGuildErrorMessage { get; set; } = "This command cannot be used outside of a guild.";
+
+        /// <summary>
+        ///     Gets the error message to be returned if execution context doesn't pass the precondition check.
+        /// </summary>
+        public string ErrorMessage { get; set; } = "You cannot target anyone who is higher or equal in the hierarchy to you or the bot.";
+
+        /// <inheritdoc />
+        /// <exception cref="ArgumentOutOfRangeException">
+        ///     Thrown when the parameter type is not supported by this precondition attribute.
+        /// </exception>
+        public override async Task<PreconditionResult> CheckPermissionsAsync(ICommandContext context, ParameterInfo parameterInfo, object value, IServiceProvider services)
+        {
+            if (context.User is not IGuildUser guildUser)
+                return PreconditionResult.FromError(NotAGuildErrorMessage);
+
+            var hieararchy = PermissionUtils.GetHieararchy(value);
+            if (hieararchy >= guildUser.Hierarchy ||
+                hieararchy >= (await context.Guild.GetCurrentUserAsync().ConfigureAwait(false)).Hierarchy)
+                return PreconditionResult.FromError(ErrorMessage);
+
+            return PreconditionResult.FromSuccess();
+        }
+    }
+}

src/Discord.Net.Core/Utils/PermissionUtils.cs

@@ -0,0 +1,31 @@
+using System;
+
+namespace Discord
+{
+    /// <summary>
+    ///     Provides a series of helper methods for permissions.
+    /// </summary>
+    public static class PermissionUtils
+    {
+        /// <summary>
+        ///     Determines the hierarchy of a target object based on its type.
+        /// </summary>
+        /// <param name="target">
+        ///     The target object: <see cref="IRole"/>, <see cref="IGuildUser"/>, or <see cref="IUser"/>.
+        /// </param>
+        /// <returns>
+        ///     An integer representing the hierarchy of the target.
+        /// </returns>
+        /// <exception cref="ArgumentOutOfRangeException">
+        ///     Thrown when the parameter type is not supported by this precondition attribute.
+        /// </exception>
+        public static int GetHieararchy(object target) => target switch
+        {
+            // The order of cases here is important to determine the correct hierarchy value.
+            IRole role => role.Position,
+            IGuildUser guildUser => guildUser.Hierarchy,
+            IUser => int.MinValue,
+            _ => throw new ArgumentOutOfRangeException(nameof(target), "Cannot determine hierarchy for the provided target.")
+        };
+    }
+}

src/Discord.Net.Interactions/Attributes/Preconditions/DoHierarchyCheckAttribute.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Discord.Interactions
+{
+    /// <summary>
+    ///     Ensures that command parameters are passed within a correct hierarchical context.
+    /// </summary>
+    /// <remarks>
+    ///     Useful for performing hierarchical operations within a guild, such as managing roles or users.
+    ///     <note type="warning">
+    ///         This supports <see cref="IRole"/>, <see cref="IGuildUser"/>, and <see cref="IUser"/> parameter types.
+    ///     </note>
+    /// </remarks>
+    /// <exception cref="ArgumentOutOfRangeException">
+    ///     Thrown when the parameter type is not supported by this precondition attribute.
+    /// </exception>
+    /// <seealso cref="RequireRoleAttribute"/>
+    /// <seealso cref="RequireBotPermissionAttribute"/>
+    /// <seealso cref="RequireUserPermissionAttribute"/>
+    public class DoHierarchyCheckAttribute : ParameterPreconditionAttribute
+    {
+        /// <summary>
+        ///     Gets or sets the error message displayed when the command is used outside of a guild.
+        /// </summary>
+        public string NotAGuildErrorMessage { get; set; } = "This command cannot be used outside of a guild.";
+
+        /// <inheritdoc />
+        public override string ErrorMessage => "You cannot target anyone who is higher or equal in the hierarchy to you or the bot.";
+
+        /// <inheritdoc />
+        /// <exception cref="ArgumentOutOfRangeException">
+        ///     Thrown when the parameter type is not supported by this precondition attribute.
+        /// </exception>
+        public override async Task<PreconditionResult> CheckRequirementsAsync(IInteractionContext context, IParameterInfo parameterInfo, object value, IServiceProvider services)
+        {
+            if (context.User is not IGuildUser guildUser)
+                return PreconditionResult.FromError(NotAGuildErrorMessage);
+
+            var hieararchy = PermissionUtils.GetHieararchy(value);
+            if (hieararchy >= guildUser.Hierarchy ||
+                hieararchy >= (await context.Guild.GetCurrentUserAsync().ConfigureAwait(false)).Hierarchy)
+                return PreconditionResult.FromError(ErrorMessage);
+
+            return PreconditionResult.FromSuccess();
+        }
+    }
+}