using System.Collections;
using System.Collections.Concurrent;
using System.Reflection;
using Umbraco.Cms.Core.Composing;

namespace Umbraco.Cms.Core.Models;

public static class DeepCloneHelper
{
    /// <summary>
    ///     Used to avoid constant reflection (perf)
    /// </summary>
    private static readonly ConcurrentDictionary<Type, ClonePropertyInfo[]> PropCache = new();

    /// <summary>
    ///     Used to deep clone any reference properties on the object (should be done after a MemberwiseClone for which the
    ///     outcome is 'output')
    /// </summary>
    /// <param name="input"></param>
    /// <param name="output"></param>
    /// <returns></returns>
    public static void DeepCloneRefProperties(IDeepCloneable input, IDeepCloneable output)
    {
        Type inputType = input.GetType();
        Type outputType = output.GetType();

        if (inputType != outputType)
        {
            throw new InvalidOperationException("Both the input and output types must be the same");
        }

        // get the property metadata from cache so we only have to figure this out once per type
        ClonePropertyInfo[] refProperties = PropCache.GetOrAdd(inputType, type =>
            inputType.GetProperties()
                .Select<PropertyInfo, ClonePropertyInfo?>(propertyInfo =>
                {
                    if (

                        // is not attributed with the ignore clone attribute
                        propertyInfo.GetCustomAttribute<DoNotCloneAttribute>() != null

                        // reference type but not string
                        || propertyInfo.PropertyType.IsValueType || propertyInfo.PropertyType == typeof(string)

                        // settable
                        || propertyInfo.CanWrite == false

                        // non-indexed
                        || propertyInfo.GetIndexParameters().Any())
                    {
                        return null;
                    }

                    if (TypeHelper.IsTypeAssignableFrom<IDeepCloneable>(propertyInfo.PropertyType))
                    {
                        return new ClonePropertyInfo(propertyInfo) { IsDeepCloneable = true };
                    }

                    if (TypeHelper.IsTypeAssignableFrom<IEnumerable>(propertyInfo.PropertyType)
                        && TypeHelper.IsTypeAssignableFrom<string>(propertyInfo.PropertyType) == false)
                    {
                        if (propertyInfo.PropertyType.IsGenericType
                            && (propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(IEnumerable<>)
                                || propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(ICollection<>)
                                || propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(IList<>)
                                || propertyInfo.PropertyType.GetGenericTypeDefinition() == typeof(IReadOnlyCollection<>)))
                        {
                            // if it is a IEnumerable<>, IReadOnlyCollection<T>, IList<T> or ICollection<> we'll use a List<> since it implements them all
                            Type genericType =
                                typeof(List<>).MakeGenericType(propertyInfo.PropertyType.GetGenericArguments());
                            return new ClonePropertyInfo(propertyInfo) { GenericListType = genericType };
                        }

                        if (propertyInfo.PropertyType.IsArray
                            || (propertyInfo.PropertyType.IsInterface &&
                                propertyInfo.PropertyType.IsGenericType == false))
                        {
                            // if its an array, we'll create a list to work with first and then convert to array later
                            // otherwise if its just a regular derivative of IEnumerable, we can use a list too
                            return new ClonePropertyInfo(propertyInfo) { GenericListType = typeof(List<object>) };
                        }

                        // skip instead of trying to create instance of abstract or interface
                        if (propertyInfo.PropertyType.IsAbstract || propertyInfo.PropertyType.IsInterface)
                        {
                            return null;
                        }

                        // its a custom IEnumerable, we'll try to create it
                        try
                        {
                            var custom = Activator.CreateInstance(propertyInfo.PropertyType);

                            // if it's an IList we can work with it, otherwise we cannot
                            if (custom is not IList)
                            {
                                return null;
                            }

                            return new ClonePropertyInfo(propertyInfo) { GenericListType = propertyInfo.PropertyType };
                        }
                        catch (Exception)
                        {
                            // could not create this type so we'll skip it
                            return null;
                        }
                    }

                    return new ClonePropertyInfo(propertyInfo);
                })
                .Where(x => x.HasValue)
                .Select(x => x!.Value)
                .ToArray());

        foreach (ClonePropertyInfo clonePropertyInfo in refProperties)
        {
            if (clonePropertyInfo.IsDeepCloneable)
            {
                // this ref property is also deep cloneable so clone it
                var result = (IDeepCloneable?)clonePropertyInfo.PropertyInfo.GetValue(input, null);

                if (result != null)
                {
                    // set the cloned value to the property
                    clonePropertyInfo.PropertyInfo.SetValue(output, result.DeepClone(), null);
                }
            }
            else if (clonePropertyInfo.IsList)
            {
                var enumerable = (IEnumerable?)clonePropertyInfo.PropertyInfo.GetValue(input, null);
                if (enumerable == null)
                {
                    continue;
                }

                IList? newList = clonePropertyInfo.GenericListType is not null
                    ? (IList?)Activator.CreateInstance(clonePropertyInfo.GenericListType)
                    : null;

                var isUsableType = true;

                // now clone each item
                foreach (var o in enumerable)
                {
                    // first check if the item is deep cloneable and copy that way
                    if (o is IDeepCloneable dc)
                    {
                        newList?.Add(dc.DeepClone());
                    }
                    else if (o is string || o.GetType().IsValueType)
                    {
                        // check if the item is a value type or a string, then we can just use it
                        newList?.Add(o);
                    }
                    else
                    {
                        // this will occur if the item is not a string or value type or IDeepCloneable, in this case we cannot
                        // clone each element, we'll need to skip this property, people will have to manually clone this list
                        isUsableType = false;
                        break;
                    }
                }

                // if this was not usable, skip this property
                if (isUsableType == false)
                {
                    continue;
                }

                if (clonePropertyInfo.PropertyInfo.PropertyType.IsArray)
                {
                    // need to convert to array
                    var arr = (object?[]?)Activator.CreateInstance(
                        clonePropertyInfo.PropertyInfo.PropertyType,
                        newList?.Count ?? 0);
                    for (var i = 0; i < newList?.Count; i++)
                    {
                        if (arr != null)
                        {
                            arr[i] = newList[i];
                        }
                    }

                    // set the cloned collection
                    clonePropertyInfo.PropertyInfo.SetValue(output, arr, null);
                }
                else
                {
                    // set the cloned collection
                    clonePropertyInfo.PropertyInfo.SetValue(output, newList, null);
                }
            }
        }
    }

    /// <summary>
    ///     Stores the metadata for the properties for a given type so we know how to create them
    /// </summary>
    private struct ClonePropertyInfo
    {
        public ClonePropertyInfo(PropertyInfo propertyInfo)
            : this()
        {
            PropertyInfo = propertyInfo ?? throw new ArgumentNullException("propertyInfo");
        }

        public PropertyInfo PropertyInfo { get; }

        public bool IsDeepCloneable { get; set; }

        public Type? GenericListType { get; set; }

        public bool IsList => GenericListType != null;
    }

    public static void CloneListItems<TList, TEntity>(TList source, TList target)
        where TList : ICollection<TEntity>
    {
        target.Clear();
        foreach (TEntity entity in source)
        {
            target.Add(entity is IDeepCloneable deepCloneableEntity
                ? (TEntity)deepCloneableEntity.DeepClone()
                : entity);
        }
    }
}