PluralKit/PluralKit.Bot/Proxy/ProxyTagParser.cs

90 lines
3.6 KiB
C#

#nullable enable
using System.Collections.Generic;
using System.Linq;
using PluralKit.Core;
namespace PluralKit.Bot
{
public class ProxyTagParser
{
public bool TryMatch(IEnumerable<ProxyMember> members, string? input, out ProxyMatch result)
{
result = default;
// Null input is valid and is equivalent to empty string
if (input == null) return false;
// If the message starts with a @mention, and then proceeds to have proxy tags,
// extract the mention and place it inside the inner message
// eg. @Ske [text] => [@Ske text]
var leadingMention = ExtractLeadingMention(ref input);
// "Flatten" list of members to a list of tag-member pairs
// Then order them by "tag specificity"
// (prefix+suffix length desc = inner message asc = more specific proxy first)
var tags = members
.SelectMany(member => member.ProxyTags.Select(tag => (tag, member)))
.OrderByDescending(p => p.tag.ProxyString.Length);
// Iterate now-ordered list of tags and try matching each one
foreach (var (tag, member) in tags)
{
result.ProxyTags = tag;
result.Member = member;
// Skip blank tags (shouldn't ever happen in practice)
if (tag.Prefix == null && tag.Suffix == null) continue;
// Can we match with these tags?
if (TryMatchTagsInner(input, tag, out result.Content))
{
// If we extracted a leading mention before, add that back now
if (leadingMention != null) result.Content = $"{leadingMention} {result.Content}";
return true;
}
// (if not, keep going)
}
// We couldn't match anything :(
return false;
}
private bool TryMatchTagsInner(string input, ProxyTag tag, out string inner)
{
inner = "";
// Normalize null tags to empty strings
var prefix = tag.Prefix ?? "";
var suffix = tag.Suffix ?? "";
// Check if our input starts/ends with the tags
var isMatch = input.Length >= prefix.Length + suffix.Length
&& input.StartsWith(prefix) && input.EndsWith(suffix);
// Special case: image-only proxies + proxy tags with spaces
// Trim everything, then see if we have a "contentless tag pair" (normally disallowed, but OK if we have an attachment)
// Note `input` is still "", even if there are spaces between
if (!isMatch && input.Trim() == prefix.TrimEnd() + suffix.TrimStart())
return true;
if (!isMatch) return false;
// We got a match, extract inner text
inner = input.Substring(prefix.Length, input.Length - prefix.Length - suffix.Length);
// (see https://github.com/xSke/PluralKit/pull/181)
return inner.Trim() != "\U0000fe0f";
}
private string? ExtractLeadingMention(ref string input)
{
var mentionPos = 0;
if (!StringUtils.HasMentionPrefix(input, ref mentionPos, out _)) return null;
var leadingMention = input.Substring(0, mentionPos);
input = input.Substring(mentionPos);
return leadingMention;
}
}
}