XAML-Map-Control/MapControl/Shared/ImageLoader.cs

using Microsoft.Extensions.Logging;
using System;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;
#if WPF
using System.Windows.Media;
#elif UWP
using Windows.UI.Xaml.Media;
#elif WINUI
using Microsoft.UI.Xaml.Media;
#elif AVALONIA
using ImageSource = Avalonia.Media.IImage;
#endif

namespace MapControl
{
    public static partial class ImageLoader
    {
        private static ILogger logger;
        private static ILogger Logger => logger ??= ImageLoader.LoggerFactory?.CreateLogger(typeof(ImageLoader));

        public static ILoggerFactory LoggerFactory { get; set; }

        /// <summary>
        /// The System.Net.Http.HttpClient instance used to download images via a http or https Uri.
        /// </summary>
        public static HttpClient HttpClient { get; set; }

        static ImageLoader()
        {
            HttpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(10) };
            HttpClient.DefaultRequestHeaders.Add("User-Agent", $"XAML-Map-Control/{typeof(ImageLoader).Assembly.GetName().Version}");
        }

        public static async Task<ImageSource> LoadImageAsync(byte[] buffer)
        {
            using var stream = new MemoryStream(buffer);

            return await LoadImageAsync(stream);
        }

        public static async Task<ImageSource> LoadImageAsync(Uri uri, IProgress<double> progress = null)
        {
            ImageSource image = null;

            progress?.Report(0d);

            try
            {
                if (!uri.IsAbsoluteUri)
                {
                    image = await LoadImageAsync(uri.OriginalString);
                }
                else if (uri.Scheme == Uri.UriSchemeHttp || uri.Scheme == Uri.UriSchemeHttps)
                {
                    (var buffer, var _) = await GetHttpResponseAsync(uri, progress);

                    if (buffer != null)
                    {
                        image = await LoadImageAsync(buffer);
                    }
                }
                else if (uri.IsFile)
                {
                    image = await LoadImageAsync(uri.LocalPath);
                }
                else
                {
                    image = LoadImage(uri);
                }
            }
            catch (Exception ex)
            {
                Logger?.LogError(ex, "Failed loading {uri}", uri);
            }

            progress?.Report(1d);

            return image;
        }

        internal static async Task<(byte[], TimeSpan?)> GetHttpResponseAsync(Uri uri, IProgress<double> progress = null)
        {
            byte[] buffer = null;
            TimeSpan? maxAge = null;

            try
            {
                var completionOptions = progress != null ? HttpCompletionOption.ResponseHeadersRead : HttpCompletionOption.ResponseContentRead;

                using var responseMessage = await HttpClient.GetAsync(uri, completionOptions).ConfigureAwait(false);

                if (responseMessage.IsSuccessStatusCode)
                {
                    if (progress != null && responseMessage.Content.Headers.ContentLength.HasValue)
                    {
                        buffer = await ReadAsByteArray(responseMessage.Content, progress).ConfigureAwait(false);
                    }
                    else
                    {
                        buffer = await responseMessage.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
                    }

                    maxAge = responseMessage.Headers.CacheControl?.MaxAge;
                }
                else
                {
                    Logger?.LogWarning("{status} ({reason}) from {uri}", (int)responseMessage.StatusCode, responseMessage.ReasonPhrase, uri);
                }
            }
            catch (TaskCanceledException)
            {
                Logger?.LogWarning("Timeout while loading {uri}", uri);
            }
            catch (Exception ex)
            {
                Logger?.LogError(ex, "Failed loading {uri}", uri);
            }

            return (buffer, maxAge);
        }

        private static async Task<byte[]> ReadAsByteArray(HttpContent content, IProgress<double> progress)
        {
            var length = (int)content.Headers.ContentLength.Value;
            var buffer = new byte[length];

            using (var stream = await content.ReadAsStreamAsync().ConfigureAwait(false))
            {
                int offset = 0;
                int read;

                while (offset < length &&
                    (read = await stream.ReadAsync(buffer, offset, length - offset).ConfigureAwait(false)) > 0)
                {
                    offset += read;

                    if (offset < length) // 1.0 reported by caller
                    {
                        progress.Report((double)offset / length);
                    }
                }
            }

            return buffer;
        }
    }
}