47 lines
2.0 KiB
C#
47 lines
2.0 KiB
C#
 
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using System.Net;
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using System.Text.RegularExpressions;
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using decePubClient.Models.Mastodon;
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using Microsoft.AspNetCore.Components;
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namespace decePubClient.Helpers
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{
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/// <summary>
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/// A post's or an account's custom emoji (`:shortcode:` among its <c>emojis</c>) shown as their pictures. The shortcode
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/// stays as the picture's alt text, so it is what a screen reader reads and what is copied. Only shortcodes the
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/// server listed for that post or account are replaced, and only with an http(s) picture.
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/// </summary>
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public static partial class CustomEmojis
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{
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[GeneratedRegex(@":([A-Za-z0-9_+-]{1,64}):")]
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private static partial Regex Shortcode();
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[GeneratedRegex(@"(<[^>]*>)")]
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private static partial Regex Tag();
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/// <summary>Plain text (a name, a content warning): escaped, then its shortcodes as pictures.</summary>
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public static MarkupString Text(string text, IReadOnlyCollection<CustomEmoji> emojis) =>
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new(Replace(WebUtility.HtmlEncode(text ?? string.Empty), emojis));
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/// <summary>HTML the server sanitized: the shortcodes in its text, never inside a tag.</summary>
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public static string Html(string html, IReadOnlyCollection<CustomEmoji> emojis) =>
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emojis.Count == 0 || string.IsNullOrEmpty(html)
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? html
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: string.Concat(Tag().Split(html).Select(part => part.StartsWith('<') ? part : Replace(part, emojis)));
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static string Replace(string text, IReadOnlyCollection<CustomEmoji> emojis)
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{
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if (emojis.Count == 0 || !text.Contains(':'))
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return text;
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var known = new Dictionary<string, string>(StringComparer.Ordinal);
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foreach (var emoji in emojis)
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if (!string.IsNullOrEmpty(emoji.Shortcode) && Uri.TryCreate(emoji.Url, UriKind.Absolute, out var url)
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&& url.Scheme is "https" or "http")
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known.TryAdd(emoji.Shortcode, url.AbsoluteUri);
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return Shortcode().Replace(text, match => known.TryGetValue(match.Groups[1].Value, out var url)
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? $"<img class=\"custom-emoji\" src=\"{WebUtility.HtmlEncode(url)}\" alt=\"{match.Value}\" title=\"{match.Value}\" draggable=\"false\" />"
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: match.Value);
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}
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}
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}
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