// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.Globalization;

namespace Grand.Web.Common.TagHelpers.Admin.Extend
{
    internal static class ExpressionMetadataProvider
    {
        /// <summary>
        /// Gets <see cref="ModelExplorer"/> for named <paramref name="expression"/> in given
        /// <paramref name="viewData"/>.
        /// </summary>
        /// <param name="expression">Expression name, relative to <c>viewData.Model</c>.</param>
        /// <param name="viewData">
        /// The <see cref="ViewDataDictionary"/> that may contain the <paramref name="expression"/> value.
        /// </param>
        /// <param name="metadataProvider">The <see cref="IModelMetadataProvider"/>.</param>
        /// <returns>
        /// <see cref="ModelExplorer"/> for named <paramref name="expression"/> in given <paramref name="viewData"/>.
        /// </returns>
        public static ModelExplorer FromStringExpression(
            string expression,
            ViewDataDictionary viewData,
            IModelMetadataProvider metadataProvider)
        {
            ArgumentNullException.ThrowIfNull(viewData);

            var viewDataInfo = ViewDataEvaluator.Eval(viewData, expression);
            if (viewDataInfo == null)
            {
                // Try getting a property from ModelMetadata if we couldn't find an answer in ViewData
                var propertyExplorer = viewData.ModelExplorer.GetExplorerForProperty(expression);
                if (propertyExplorer != null)
                {
                    return propertyExplorer;
                }
            }

            if (viewDataInfo != null)
            {
                if (viewDataInfo.Container == viewData &&
                    viewDataInfo.Value == viewData.Model &&
                    string.IsNullOrEmpty(expression))
                {
                    // Nothing for empty expression in ViewData and ViewDataEvaluator just returned the model. Handle
                    // using FromModel() for its object special case.
                    return FromModel(viewData, metadataProvider);
                }

                ModelExplorer containerExplorer = viewData.ModelExplorer;
                if (viewDataInfo.Container != null)
                {
                    containerExplorer = metadataProvider.GetModelExplorerForType(
                        viewDataInfo.Container.GetType(),
                        viewDataInfo.Container);
                }

                if (viewDataInfo.PropertyInfo != null)
                {
                    // We've identified a property access, which provides us with accurate metadata.
                    var containerMetadata = metadataProvider.GetMetadataForType(viewDataInfo.Container.GetType());
                    var propertyMetadata = containerMetadata.Properties[viewDataInfo.PropertyInfo.Name];

                    Func<object, object> modelAccessor = (ignore) => viewDataInfo.Value;
                    return containerExplorer.GetExplorerForExpression(propertyMetadata, modelAccessor);
                }

                if (viewDataInfo.Value != null)
                {
                    // We have a value, even though we may not know where it came from.
                    var valueMetadata = metadataProvider.GetMetadataForType(viewDataInfo.Value.GetType());
                    return containerExplorer.GetExplorerForExpression(valueMetadata, viewDataInfo.Value);
                }
            }

            // Treat the expression as string if we don't find anything better.
            var stringMetadata = metadataProvider.GetMetadataForType(typeof(string));
            return viewData.ModelExplorer.GetExplorerForExpression(stringMetadata, modelAccessor: null);
        }

        private static ModelExplorer FromModel(
            ViewDataDictionary viewData,
            IModelMetadataProvider metadataProvider)
        {
            ArgumentNullException.ThrowIfNull(viewData);

            if (viewData.ModelMetadata.ModelType == typeof(object))
            {
                // Use common simple type rather than object so e.g. Editor() at least generates a TextBox.
                var model = viewData.Model == null ? null : Convert.ToString(viewData.Model, CultureInfo.CurrentCulture);
                return metadataProvider.GetModelExplorerForType(typeof(string), model);
            }

            return viewData.ModelExplorer;
        }
    }
}
