using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Headers;
using Microsoft.Extensions.Options;
using Microsoft.Net.Http.Headers;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Web.Commands;
using SixLabors.ImageSharp.Web.Middleware;
using SixLabors.ImageSharp.Web.Processors;
using Umbraco.Cms.Core.Configuration.Models;

namespace Umbraco.Cms.Web.Common.DependencyInjection
{
    /// <summary>
    /// Configures the ImageSharp middleware options.
    /// </summary>
    /// <seealso cref="IConfigureOptions{ImageSharpMiddlewareOptions}" />
    public sealed class ConfigureImageSharpMiddlewareOptions : IConfigureOptions<ImageSharpMiddlewareOptions>
    {
        private readonly Configuration _configuration;
        private readonly ImagingSettings _imagingSettings;

        /// <summary>
        /// Initializes a new instance of the <see cref="ConfigureImageSharpMiddlewareOptions" /> class.
        /// </summary>
        /// <param name="configuration">The ImageSharp configuration.</param>
        /// <param name="imagingSettings">The Umbraco imaging settings.</param>
        public ConfigureImageSharpMiddlewareOptions(Configuration configuration, IOptions<ImagingSettings> imagingSettings)
        {
            _configuration = configuration;
            _imagingSettings = imagingSettings.Value;
        }

        /// <inheritdoc />
        public void Configure(ImageSharpMiddlewareOptions options)
        {
            options.Configuration = _configuration;

            options.BrowserMaxAge = _imagingSettings.Cache.BrowserMaxAge;
            options.CacheMaxAge = _imagingSettings.Cache.CacheMaxAge;
            options.CacheHashLength = _imagingSettings.Cache.CacheHashLength;

            // Use configurable maximum width and height
            options.OnParseCommandsAsync = context =>
            {
                if (context.Commands.Count == 0)
                {
                    return Task.CompletedTask;
                }

                int width = context.Parser.ParseValue<int>(context.Commands.GetValueOrDefault(ResizeWebProcessor.Width), context.Culture);
                if (width <= 0 || width > _imagingSettings.Resize.MaxWidth)
                {
                    context.Commands.Remove(ResizeWebProcessor.Width);
                }

                int height = context.Parser.ParseValue<int>(context.Commands.GetValueOrDefault(ResizeWebProcessor.Height), context.Culture);
                if (height <= 0 || height > _imagingSettings.Resize.MaxHeight)
                {
                    context.Commands.Remove(ResizeWebProcessor.Height);
                }

                return Task.CompletedTask;
            };

            // Change Cache-Control header when cache buster value is present
            options.OnPrepareResponseAsync = context =>
            {
                if (context.Request.Query.ContainsKey("rnd") || context.Request.Query.ContainsKey("v"))
                {
                    ResponseHeaders headers = context.Response.GetTypedHeaders();

                    CacheControlHeaderValue cacheControl = headers.CacheControl ?? new CacheControlHeaderValue()
                    {
                        Public = true
                    };
                    cacheControl.MustRevalidate = false; // ImageSharp enables this by default
                    cacheControl.Extensions.Add(new NameValueHeaderValue("immutable"));

                    headers.CacheControl = cacheControl;
                }

                return Task.CompletedTask;
            };
        }
    }
}