Added detailed plugin information to the plugins page (#1013)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/PluginSystem/PluginLinks.cs

@@ -0,0 +1,83 @@
+using System.Diagnostics.CodeAnalysis;
+
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tools.PluginSystem;
+
+/// <summary>
+/// Recognizes the links in the metadata of plugins.
+/// </summary>
+/// <remarks>
+/// The source URL of a plugin has to be such a link, and its support contact may be one. A plugin may
+/// only link to a website or to a mail address: another scheme, such as file: or javascript:, would let a
+/// plugin open anything on the computer of the user with a single click. Loading a plugin and showing its
+/// links both decide with this class, so that AI Studio never offers a link which loading would refuse.
+/// </remarks>
+public static class PluginLinks
+{
+    /// <summary>
+    /// Tries to read a text as a link which a plugin may offer.
+    /// </summary>
+    /// <param name="text">The text to read. Whitespace around it does not count.</param>
+    /// <param name="uri">The link, when the text is one.</param>
+    /// <returns>True, when the text is an absolute http, https, or mailto link, and a mailto link names a recipient.</returns>
+    public static bool TryParse(string text, [NotNullWhen(true)] out Uri? uri)
+    {
+        if (Uri.TryCreate(text.Trim(), UriKind.Absolute, out uri) && IsAllowed(uri))
+            return true;
+
+        uri = null;
+        return false;
+    }
+
+    /// <summary>
+    /// Checks whether a link writes a mail instead of opening a website.
+    /// </summary>
+    /// <param name="uri">The link to check.</param>
+    /// <returns>True, when the link is a mailto link.</returns>
+    public static bool IsMail(Uri uri) => uri.Scheme.Equals(Uri.UriSchemeMailto, StringComparison.OrdinalIgnoreCase);
+
+    /// <summary>
+    /// Checks whether a text is one of the links which the Assistant Builder writes into the plugins it
+    /// generates.
+    /// </summary>
+    /// <remarks>
+    /// Every plugin has to state a support contact and a source URL, so the Assistant Builder fills in
+    /// links to MindWork AI. They tell nothing about the plugin itself, so AI Studio treats them as not
+    /// stated: it neither shows them nor offers a button for them. The check goes by the text alone, so
+    /// these links count as not stated in any other plugin as well.
+    /// </remarks>
+    /// <param name="text">The text to check. Whitespace around it does not count.</param>
+    /// <returns>True, when the text is one of these placeholders.</returns>
+    public static bool IsPlaceholder(string text) => text.Trim() is AssistantPluginGenerationService.DEFAULT_SUPPORT_CONTACT or AssistantPluginGenerationService.DEFAULT_SOURCE_URL;
+
+    /// <summary>
+    /// Gets the text by which the user recognizes a link.
+    /// </summary>
+    /// <param name="uri">The link.</param>
+    /// <returns>For a mailto link its recipient, without the scheme and without a subject. For a website the link as the plugin states it.</returns>
+    public static string GetDisplayText(Uri uri) => IsMail(uri) ? Uri.UnescapeDataString(GetRecipient(uri).Trim().ToString()) : uri.OriginalString;
+
+    private static bool IsAllowed(Uri uri)
+    {
+        // Without a recipient, the mail program would open a mail to nobody:
+        if (IsMail(uri))
+            return !GetRecipient(uri).IsWhiteSpace();
+
+        return uri.Scheme.Equals(Uri.UriSchemeHttp, StringComparison.OrdinalIgnoreCase) || uri.Scheme.Equals(Uri.UriSchemeHttps, StringComparison.OrdinalIgnoreCase);
+    }
+
+    /// <summary>
+    /// Gets the recipient of a mailto link, which is everything between the colon and the first
+    /// question mark.
+    /// </summary>
+    /// <param name="mailUri">The mailto link.</param>
+    /// <returns>The recipient as the link states it, which may be empty.</returns>
+    private static ReadOnlySpan<char> GetRecipient(Uri mailUri)
+    {
+        var text = mailUri.OriginalString.AsSpan();
+        var recipient = text[(text.IndexOf(':') + 1)..];
+        var queryStart = recipient.IndexOf('?');
+        return queryStart >= 0 ? recipient[..queryStart] : recipient;
+    }
+}