using System;
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using System.Collections.Generic;
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using System.Collections.Immutable;
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using System.IO;
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using System.Linq;
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using System.Net;
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using System.Net.Http;
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using System.Threading.Tasks;
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namespace OpenTap
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{
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/// <summary>
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/// A mechanism for retrieving <see cref="IPicture"/> data with <see cref="PictureDataExtensions"/>
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/// </summary>
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internal interface IPictureDataProvider
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{
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/// <summary>
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/// The order in which IPictureDataProviders will be tested. Lowers numbers go first
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/// </summary>
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double Order { get; }
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/// <summary>
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/// Get a stream of the picture data
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/// </summary>
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/// <param name="picture"></param>
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/// <returns></returns>
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Task<Stream> GetStream(IPicture picture);
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/// <summary>
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/// Get a string specifying the picture format
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/// </summary>
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/// <param name="picture"></param>
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/// <returns></returns>
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Task<string> GetFormat(IPicture picture);
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}
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/// <summary>
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/// Picture data provider for URI sources.
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/// </summary>
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class DefaultPictureDataProvider : IPictureDataProvider
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{
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public double Order => 10;
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/// <summary>
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/// Relative URIs are poorly supported in dotnet core. Ensure we only use absolute URIs by normalizing path strings to absolute paths.
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/// </summary>
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/// <param name="source"></param>
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/// <returns></returns>
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private string normalizeSource(string source)
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{
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try
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{
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if (File.Exists(source))
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return Path.GetFullPath(source);
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}
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catch
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{
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// this is fine -- source is not a file
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}
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return source;
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}
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public async Task<Stream> GetStream(IPicture picture)
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{
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if (await GetFormat(picture) == null) return null;
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var source = normalizeSource(picture.Source);
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if (Uri.TryCreate(source, UriKind.Absolute, out var uri))
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{
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#pragma warning disable SYSLIB0014
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var req = WebRequest.Create(uri);
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#pragma warning restore SYSLIB0014
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var response = await req.GetResponseAsync();
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return response.GetResponseStream();
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}
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return null;
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}
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public Task<string> GetFormat(IPicture picture)
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{
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var source = normalizeSource(picture.Source);
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if (Uri.TryCreate(source, UriKind.Absolute, out var uri))
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{
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var name = uri.Segments.LastOrDefault();
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if (string.IsNullOrWhiteSpace(name) == false)
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{
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var ext = Path.GetExtension(name);
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if (ext.StartsWith(".") && ext.Length > 1) return Task.FromResult(ext.Substring(1));
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}
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}
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return Task.FromResult<string>(null);
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}
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}
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/// <summary>
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/// Provide <see cref="IPicture"/> data from <see cref="IPictureDataProvider"/> implementations.
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/// </summary>
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public static class PictureDataExtensions
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{
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private static IPictureDataProvider[] cache = Array.Empty<IPictureDataProvider>();
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private static ISet<ITypeData> cacheKey;
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private static IEnumerable<IPictureDataProvider> GetProviders()
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{
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var types = TypeData.GetDerivedTypes<IPictureDataProvider>()
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.Where(td => td.CanCreateInstance).ToImmutableHashSet();
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if (cacheKey == null || types.SetEquals(cacheKey) == false)
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{
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cache = types.TrySelect(td => td.CreateInstance(), ex => log.Debug("Unable to load IPictureDataProvider: {0}", ex.Message))
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.OfType<IPictureDataProvider>().OrderBy(p => p.Order)
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.ToArray();
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cacheKey = types;
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}
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return cache;
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}
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private static TraceSource log = Log.CreateSource(nameof(PictureDataExtensions));
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private static async Task<T> GetFirst<T>(IPicture picture, Func<IPicture, IPictureDataProvider, Task<T>> func) where T : class
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{
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foreach (var provider in GetProviders())
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{
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try
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{
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var res = await func(picture, provider);
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if (res != null)
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return res;
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}
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catch (Exception ex)
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{
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log.Debug($"Unexpected error in {nameof(IPictureDataProvider)} '{TypeData.GetTypeData(provider).AsTypeData().GetBestName()}'.");
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log.Debug(ex);
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}
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}
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return null;
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}
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/// <summary>
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/// Get a stream of the picture from the first <see cref="IPictureDataProvider"/> which returns a non-null.
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/// </summary>
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/// <param name="picture"></param>
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public static Task<Stream> GetStream(this IPicture picture) =>
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GetFirst(picture, (pic, provider) => provider.GetStream(pic));
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/// <summary>
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/// Get the format of the picture from the first <see cref="IPictureDataProvider"/> which returns a non-null.
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/// </summary>
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/// <param name="picture"></param>
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public static Task<string> GetFormat(this IPicture picture) => GetFirst(picture, (pic, provider) => provider.GetFormat(pic));
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}
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}
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