ControlFetcherMixin.cs

// Copyright (c) 2023 .NET Foundation and Contributors. All rights reserved.
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for full license information.

using System.Collections.Concurrent;
using System.Reflection;
using System.Runtime.CompilerServices;

using Android.App;
using Android.Views;

namespace ReactiveUI;

/// <summary>
/// Control Fetcher Mix-in helps you automatically wire-up Activities and
/// Fragments via property names, similar to Butter Knife, as well as allows
/// you to fetch controls manually.
/// </summary>
public static partial class ControlFetcherMixin
{
    private static readonly ConcurrentDictionary<Assembly, Dictionary<string, int>> _controlIds = new();

    private static readonly ConditionalWeakTable<object, Dictionary<string, View?>> _viewCache = [];

    /// <summary>
    /// Gets the control from an activity.
    /// </summary>
    /// <param name="activity">The activity.</param>
    /// <param name="propertyName">The property name.</param>
    /// <returns>The return view.</returns>
    public static View? GetControl(this Activity activity, [CallerMemberName] string? propertyName = null) // TODO: Create Test
        => GetCachedControl(propertyName, activity, () => activity.FindViewById(GetControlIdByName(activity.GetType().Assembly, propertyName)));

    /// <summary>
    /// Gets the control from a view.
    /// </summary>
    /// <param name="view">The view.</param>
    /// <param name="assembly">The assembly containing the user-defined view.</param>
    /// <param name="propertyName">The property.</param>
    /// <returns>The return view.</returns>
    public static View? GetControl(this View view, Assembly assembly, [CallerMemberName] string? propertyName = null) // TODO: Create Test
        => GetCachedControl(propertyName, view, () => view.FindViewById(GetControlIdByName(assembly, propertyName)));

    /// <summary>
    /// Wires a control to a property.
    /// </summary>
    /// <param name="layoutHost">The layout view host.</param>
    /// <param name="resolveMembers">The resolve members.</param>
    public static void WireUpControls(this ILayoutViewHost layoutHost, ResolveStrategy resolveMembers = ResolveStrategy.Implicit) // TODO: Create Test
    {
        if (layoutHost is null)
        {
            throw new ArgumentNullException(nameof(layoutHost));
        }

        var members = layoutHost.GetWireUpMembers(resolveMembers).ToList();
        foreach (var member in members)
        {
            try
            {
                var view = layoutHost.View?.GetControl(layoutHost.GetType().Assembly, member.GetResourceName());
                member.SetValue(layoutHost, view);
            }
            catch (Exception ex)
            {
                throw new
                    MissingFieldException("Failed to wire up the Property " + member.Name + " to a View in your layout with a corresponding identifier", ex);
            }
        }
    }

    /// <summary>
    /// Wires a control to a property.
    /// </summary>
    /// <param name="view">The view.</param>
    /// <param name="resolveMembers">The resolve members.</param>
    public static void WireUpControls(this View view, ResolveStrategy resolveMembers = ResolveStrategy.Implicit) // TODO: Create Test
    {
        if (view is null)
        {
            throw new ArgumentNullException(nameof(view));
        }

        var members = view.GetWireUpMembers(resolveMembers);

        foreach (var member in members)
        {
            try
            {
                // Find the android control with the same name
                var currentView = view.GetControl(view.GetType().Assembly, member.GetResourceName());

                // Set the activity field's value to the view with that identifier
                member.SetValue(view, currentView);
            }
            catch (Exception ex)
            {
                throw new
                    MissingFieldException("Failed to wire up the Property " + member.Name + " to a View in your layout with a corresponding identifier", ex);
            }
        }
    }

    /// <summary>
    /// Wires a control to a property.
    /// This should be called in the Fragment's OnCreateView, with the newly inflated layout.
    /// </summary>
    /// <param name="fragment">The fragment.</param>
    /// <param name="inflatedView">The inflated view.</param>
    /// <param name="resolveMembers">The resolve members.</param>
    [Obsolete("This class is obsoleted in this android platform")]
    public static void WireUpControls(this Fragment fragment, View inflatedView, ResolveStrategy resolveMembers = ResolveStrategy.Implicit) // TODO: Create Test
    {
        if (fragment is null)
        {
            throw new ArgumentNullException(nameof(fragment));
        }

        var members = fragment.GetWireUpMembers(resolveMembers);

        foreach (var member in members)
        {
            try
            {
                // Find the android control with the same name from the view
                var view = inflatedView.GetControl(fragment.GetType().Assembly, member.GetResourceName());

                // Set the activity field's value to the view with that identifier
                member.SetValue(fragment, view);
            }
            catch (Exception ex)
            {
                throw new
                    MissingFieldException("Failed to wire up the Property " + member.Name + " to a View in your layout with a corresponding identifier", ex);
            }
        }
    }

    /// <summary>
    /// Wires a control to a property.
    /// </summary>
    /// <param name="activity">The Activity.</param>
    /// <param name="resolveMembers">The resolve members.</param>
    public static void WireUpControls(this Activity activity, ResolveStrategy resolveMembers = ResolveStrategy.Implicit) // TODO: Create Test
    {
        if (activity is null)
        {
            throw new ArgumentNullException(nameof(activity));
        }

        var members = activity.GetWireUpMembers(resolveMembers);

        foreach (var member in members)
        {
            try
            {
                // Find the android control with the same name
                var view = activity.GetControl(member.GetResourceName());

                // Set the activity field's value to the view with that identifier
                member.SetValue(activity, view);
            }
            catch (Exception ex)
            {
                throw new
                    MissingFieldException("Failed to wire up the Property " + member.Name + " to a View in your layout with a corresponding identifier", ex);
            }
        }
    }

    internal static IEnumerable<PropertyInfo> GetWireUpMembers(this object @this, ResolveStrategy resolveStrategy)
    {
        var members = @this.GetType().GetRuntimeProperties();

        return resolveStrategy switch
        {
            ResolveStrategy.ExplicitOptIn =>
                members.Where(member => member.GetCustomAttribute<WireUpResourceAttribute>(true) is not null),
            ResolveStrategy.ExplicitOptOut =>
                members.Where(member => typeof(View).IsAssignableFrom(member.PropertyType) && member.GetCustomAttribute<IgnoreResourceAttribute>(true) is null),

            // Implicit matches the Default.
            _ => members.Where(member => member.PropertyType.IsSubclassOf(typeof(View)) || member.GetCustomAttribute<WireUpResourceAttribute>(true) is not null),
        };
    }

    internal static string GetResourceName(this PropertyInfo member)
    {
        var resourceNameOverride = member.GetCustomAttribute<WireUpResourceAttribute>()?.ResourceNameOverride;
        return resourceNameOverride ?? member.Name;
    }

    private static View? GetCachedControl(string? propertyName, object rootView, Func<View?> fetchControlFromView)
    {
        if (propertyName is null)
        {
            throw new ArgumentNullException(nameof(propertyName));
        }

        if (fetchControlFromView is null)
        {
            throw new ArgumentNullException(nameof(fetchControlFromView));
        }

        var ourViewCache = _viewCache.GetOrCreateValue(rootView);

        if (ourViewCache.TryGetValue(propertyName, out var ret))
        {
            return ret;
        }

        ret = fetchControlFromView();

        ourViewCache.Add(propertyName, ret);
        return ret;
    }

    private static int GetControlIdByName(Assembly assembly, string? name)
    {
        if (name is null)
        {
            throw new ArgumentNullException(nameof(name));
        }

        var ids = _controlIds.GetOrAdd(
                                       assembly,
                                       currentAssembly =>
                                       {
#if NET8_0_OR_GREATER
                                            var resources = Assembly.Load(currentAssembly
                                                            .GetReferencedAssemblies()
                                                            .First(an => an.FullName.StartsWith("_Microsoft.Android.Resource.Designer")).ToString())
                                                            .GetModules()
                                                            .SelectMany(x => x.GetTypes())
                                                            .First(x => x.Name == "ResourceConstant");
#else
                                            var resources = currentAssembly.GetModules().SelectMany(x => x.GetTypes()).First(x => x.Name == "Resource");
#endif

                                            var idType = resources.GetNestedType("Id") ?? throw new InvalidOperationException("Id is not a valid nested type in the resources.");
                                            return idType.GetFields()
                                                        .Where(x => x.FieldType == typeof(int))
                                                        .ToDictionary(k => k.Name, v => ((int?)v.GetRawConstantValue()) ?? 0, StringComparer.InvariantCultureIgnoreCase);
                                       });

        return ids[name];
    }
}