using System;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Mvc.Filters;

namespace StardewModdingAPI.Web.Framework
{
    /// <summary>A filter which increases the maximum request size for an endpoint.</summary>
    /// <remarks>Derived from <a href="https://stackoverflow.com/a/38360093/262123"/>.</remarks>
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
    public class AllowLargePostsAttribute : Attribute, IAuthorizationFilter, IOrderedFilter
    {
        /*********
        ** Fields
        *********/
        /// <summary>The underlying form options.</summary>
        private readonly FormOptions FormOptions;


        /*********
        ** Accessors
        *********/
        /// <summary>The attribute order.</summary>
        public int Order { get; set; }


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        public AllowLargePostsAttribute()
        {
            this.FormOptions = new FormOptions
            {
                ValueLengthLimit = 200 * 1024 * 1024 // 200MB
            };
        }

        /// <summary>Called early in the filter pipeline to confirm request is authorized.</summary>
        /// <param name="context">The authorisation filter context.</param>
        public void OnAuthorization(AuthorizationFilterContext context)
        {
            IFeatureCollection features = context.HttpContext.Features;
            IFormFeature formFeature = features.Get<IFormFeature>();

            if (formFeature?.Form == null)
            {
                // Request form has not been read yet, so set the limits
                features.Set<IFormFeature>(new FormFeature(context.HttpContext.Request, this.FormOptions));
            }
        }
    }
}