ditto/src/utils/note.ts

import 'linkify-plugin-hashtag';
import linkifyStr from 'linkify-string';
import linkify from 'linkifyjs';
import { nip19, nip27 } from 'nostr-tools';

import { Conf } from '@/config.ts';
import { MastodonMention } from '@/entities/MastodonMention.ts';
import { html } from '@/utils/html.ts';
import { getUrlMediaType, isPermittedMediaType } from '@/utils/media.ts';

linkify.registerCustomProtocol('nostr', true);
linkify.registerCustomProtocol('wss');

type Link = ReturnType<typeof linkify.find>[0];

interface ParsedNoteContent {
  html: string;
  links: Link[];
  /** First non-media URL - eligible for a preview card. */
  firstUrl: string | undefined;
}

/** Convert Nostr content to Mastodon API HTML. Also return parsed data. */
function parseNoteContent(content: string, mentions: MastodonMention[]): ParsedNoteContent {
  const links = linkify.find(content).filter(isLinkURL);
  const firstUrl = links.find(isNonMediaLink)?.href;

  const result = linkifyStr(content, {
    render: {
      hashtag: ({ content }) => {
        const tag = content.replace(/^#/, '');
        const href = Conf.local(`/tags/${tag}`);
        return html`<a class="mention hashtag" href="${href}" rel="tag"><span>#</span>${tag}</a>`;
      },
      url: ({ attributes, content }) => {
        try {
          const { protocol, pathname } = new URL(content);

          if (protocol === 'nostr:') {
            const match = pathname.match(new RegExp(`^${nip19.BECH32_REGEX.source}`));
            if (match) {
              const bech32 = match[0];
              const extra = pathname.slice(bech32.length);
              const decoded = nip19.decode(bech32);
              const pubkey = getDecodedPubkey(decoded);
              if (pubkey) {
                const mention = mentions.find((m) => m.id === pubkey);
                const npub = nip19.npubEncode(pubkey);
                const acct = mention?.acct ?? npub;
                const name = mention?.acct ?? npub.substring(0, 8);
                const href = mention?.url ?? Conf.local(`/@${acct}`);
                return html`<span class="h-card"><a class="u-url mention" href="${href}" rel="ugc">@<span>${name}</span></a></span>${extra}`;
              } else {
                return '';
              }
            } else {
              return content;
            }
          }
        } catch {
          // fallthrough
        }

        const attr = Object.entries(attributes)
          .map(([name, value]) => `${name}="${value}"`)
          .join(' ');

        return `<a ${attr}>${content}</a>`;
      },
    },
  }).replace(/\n+$/, '');

  return {
    html: result,
    links,
    firstUrl,
  };
}

/** Remove imeta links. */
function stripimeta(content: string, tags: string[][]): string {
  const imeta = tags.filter(([name]) => name === 'imeta');

  if (!imeta.length) {
    return content;
  }

  const urls = new Set(
    imeta.map(([, ...values]) => values.map((v) => v.split(' ')).find(([name]) => name === 'url')?.[1]),
  );

  const lines = content.split('\n').reverse();

  for (const line of [...lines]) {
    if (line === '' || urls.has(line)) {
      lines.splice(0, 1);
    } else {
      break;
    }
  }

  return lines.reverse().join('\n');
}

/** Returns a matrix of tags. Each item is a list of NIP-94 tags representing a file. */
function getMediaLinks(links: Pick<Link, 'href'>[]): string[][][] {
  return links.reduce<string[][][]>((acc, link) => {
    const mediaType = getUrlMediaType(link.href);
    if (!mediaType) return acc;

    if (isPermittedMediaType(mediaType, ['audio', 'image', 'video'])) {
      acc.push([
        ['url', link.href],
        ['m', mediaType],
      ]);
    }

    return acc;
  }, []);
}

function isNonMediaLink({ href }: Link): boolean {
  return /^https?:\/\//.test(href) && !getUrlMediaType(href);
}

/** Ensures the Link is a URL so it can be parsed. */
function isLinkURL(link: Link): boolean {
  return link.type === 'url';
}

/** Get pubkey from decoded bech32 entity, or undefined if not applicable. */
function getDecodedPubkey(decoded: nip19.DecodeResult): string | undefined {
  switch (decoded.type) {
    case 'npub':
      return decoded.data;
    case 'nprofile':
      return decoded.data.pubkey;
  }
}

/** Find a quote in the content. */
function findQuoteInContent(content: string): string | undefined {
  try {
    for (const { decoded } of nip27.matchAll(content)) {
      switch (decoded.type) {
        case 'note':
          return decoded.data;
        case 'nevent':
          return decoded.data.id;
      }
    }
  } catch (_) {
    // do nothing
  }
}

export { findQuoteInContent, getMediaLinks, parseNoteContent, stripimeta };