/// <summary>
/// Creates an <see cref="IAvatarProvider"/> based on the given
/// <see cref="AvatarProvider"/> and <see cref="AvatarFallbackType"/> enum options.
/// </summary>
/// <returns>Returns an avatar provider that can be used to resolve user avatars.</returns>
public static IAvatarProvider CreateAvatarProvider(
AvatarProvider provider,
AvatarFallbackType?fallbackType,
IAvatarDownloader downloader = null)
{
// initialize download only if needed (some options, like local providers, don't need a downloader)
// and use the downloader provided as parameter if possible.
var lazyDownloader = new Lazy <IAvatarDownloader>(() => downloader ?? new AvatarDownloader());
// build collection of (non-null) providers
var providers = new[]
{
BuildMainProvider(),
BuildFallbackProvider()
}
.Where(p => p != null)
.ToArray();
// only create chained avatar overhead if really needed
return(providers.Length switch
{
0 => null,
1 => providers[0],
_ => new ChainedAvatarProvider(providers),
});
public GravatarProvider(
IAvatarDownloader downloader,
AvatarFallbackType?fallback,
bool forceFallback = false)
{
_downloader = downloader ?? throw new ArgumentNullException(nameof(downloader));
_fallback = fallback;
_forceFallback = forceFallback;
}
/// <summary>
/// Parses a single template segment.
/// </summary>
private static IAvatarProvider?FromTemplateSegment(IAvatarDownloader downloader, string providerTemplate)
{
// if the segment is a tag like "<Demo>", we extract the name
// and try to parse it as an AvatarProvider enum.
if (providerTemplate.StartsWith("<") && providerTemplate.EndsWith(">"))
{
var providerName = providerTemplate.Substring(1, providerTemplate.Length - 2);
if (Enum.TryParse <AvatarProvider>(providerName, true, out var provider) &&
provider != AvatarProvider.Custom)
{
return(AvatarService.CreateAvatarProvider(provider, null, downloader));
}
return(null);
}
// in all other cases assume it's an UriTemplate
return(new UriTemplateResolver(providerTemplate));
}
/// <summary>
/// Parses a custom avatar template string and creates an <see cref="IAvatarProvider"/> from it.
/// </summary>
/// <param name="customProviderTemplates">The custom avatar provider template.</param>
/// <param name="downloader">The downloader that is used to download avatar images.</param>
/// <returns>Returns the <see cref="IAvatarProvider"/> described by the template.</returns>
public static IAvatarProvider ParseTemplateString(string customProviderTemplates, IAvatarDownloader downloader)
{
if (downloader is null)
{
throw new ArgumentNullException(nameof(downloader));
}
var providerParts = customProviderTemplates
.Split(';')
.Select(p => p.Trim())
.Select(p => FromTemplateSegment(downloader, p))
.WhereNotNull()
.ToArray();
// We can't use the chain provider here, because some returned providers (namely UriTemplateResolvers)
// don't actually fulfill the interface contract of IAvatarProvider. UriTemplateResolver is a special
// case that exists to prevent variables like hashes from being evaluated/calculated multiple times.
return(new CustomAvatarProvider(downloader, providerParts));
}
private CustomAvatarProvider(IAvatarDownloader downloader, IAvatarProvider[] subProvider)
{
_downloader = downloader ?? throw new ArgumentNullException(nameof(downloader));
_subProvider = subProvider ?? throw new ArgumentNullException(nameof(subProvider));
}
public GithubAvatarProvider([NotNull] IAvatarDownloader downloader, bool onlySupplyNoReply = false)
{
_downloader = downloader ?? throw new ArgumentNullException(nameof(downloader));
_onlySupplyNoReply = onlySupplyNoReply;
}