malice

import type { Mention } from './mentions';

import { linkSpans } from './urls';

export type InlineSegment =

  | { kind: 'text'; text: string }

  | { kind: 'mention'; text: string; user_id: string }

  | { kind: 'link'; text: string; href: string };

interface Span {

  start: number;

  end: number;

  segment: InlineSegment;

}

const WORD_CHAR = /[\p{L}\p{N}_]/u;

function escapeRegExp(text: string): string {

  return text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');

}

function mentionSpans(text: string, mentions: Mention[], taken: Span[]): Span[] {

  const byText = new Map(mentions.filter((m) => m.text).map((m) => [m.text, m.user_id]));

  if (byText.size === 0) return [];

  const names = [...byText.keys()].sort((a, b) => b.length - a.length);

  const out: Span[] = [];

  for (const m of text.matchAll(new RegExp(names.map(escapeRegExp).join('|'), 'g'))) {

    const start = m.index;

    const end = start + m[0].length;

    if (WORD_CHAR.test(text[start - 1] ?? '') || WORD_CHAR.test(text[end] ?? '')) continue;

    if (taken.some((s) => start < s.end && end > s.start)) continue;

    out.push({ start, end, segment: { kind: 'mention', text: m[0], user_id: byText.get(m[0])! } });

  }

  return out;

}

export function segmentInline(text: string, mentions: Mention[]): InlineSegment[] {

  const links: Span[] = linkSpans(text).map((l) => ({

    start: l.start,

    end: l.end,

    segment: { kind: 'link', text: text.slice(l.start, l.end), href: l.href }

  }));

  const spans = [...links, ...mentionSpans(text, mentions, links)].sort((a, b) => a.start - b.start);

  const out: InlineSegment[] = [];

  let last = 0;

  for (const s of spans) {

    if (s.start > last) out.push({ kind: 'text', text: text.slice(last, s.start) });

    out.push(s.segment);

    last = s.end;

  }

  if (last < text.length) out.push({ kind: 'text', text: text.slice(last) });

  return out;

}