import React, { useEffect, useMemo, useRef, useState } from 'react';

import { ipcChannels } from '../../shared/ipc/contracts';
import { buildHelpLinkCatalog, splitHelpTextWithLinks } from '../editor/help/helpLinkify';
import {
  HELP_SECTION_IDS,
  helpSectionBodyKey,
  helpSectionTitleKey,
  parseHelpSectionId,
  type HelpSectionId,
} from '../editor/help/helpSections';
import { useEditorI18n } from '../editor/i18n/EditorI18nContext';
import { getDndApi } from '../shared/dndApi';

import styles from './InstructionsApp.module.css';

function InstructionsPanel({ initialSection }: { initialSection: HelpSectionId }) {
  const { t } = useEditorI18n();
  const [activeId, setActiveId] = useState<HelpSectionId>(initialSection);
  const contentRef = useRef<HTMLDivElement | null>(null);
  const navRef = useRef<HTMLElement | null>(null);

  useEffect(() => {
    setActiveId(initialSection);
  }, [initialSection]);

  useEffect(() => {
    contentRef.current?.scrollTo({ top: 0 });
    const activeNav = navRef.current?.querySelector<HTMLElement>('[aria-current="true"]');
    activeNav?.scrollIntoView({ block: 'nearest' });
  }, [activeId]);

  const linkCatalog = useMemo(
    () => buildHelpLinkCatalog((id) => t(helpSectionTitleKey(id))),
    [t],
  );

  const body = t(helpSectionBodyKey(activeId));
  const paragraphs = body.split('\n\n').filter((p) => p.trim() !== '');

  return (
    <div className={styles.page} data-testid="instructions-app">
      <div ref={contentRef} className={styles.content}>
        <div className={styles.contentTitle}>{t(helpSectionTitleKey(activeId))}</div>
        {paragraphs.map((p, i) => (
          <p key={i} className={styles.paragraph}>
            {splitHelpTextWithLinks(p, linkCatalog).map((part, j) =>
              part.type === 'text' ? (
                <React.Fragment key={j}>{part.value}</React.Fragment>
              ) : (
                <button
                  key={j}
                  type="button"
                  className={styles.inlineLink}
                  onClick={() => setActiveId(part.id)}
                >
                  {part.value}
                </button>
              ),
            )}
          </p>
        ))}
      </div>
      <nav ref={navRef} className={styles.nav} aria-label={t('help.navAria')}>
        {HELP_SECTION_IDS.map((id) => (
          <button
            key={id}
            type="button"
            className={[styles.navItem, id === activeId ? styles.navItemActive : '']
              .filter(Boolean)
              .join(' ')}
            aria-current={id === activeId ? 'true' : undefined}
            onClick={() => setActiveId(id)}
          >
            {t(helpSectionTitleKey(id))}
          </button>
        ))}
      </nav>
    </div>
  );
}

export function InstructionsApp() {
  const [section, setSection] = useState<HelpSectionId>('overview');

  useEffect(() => {
    const api = getDndApi();
    void api.invoke(ipcChannels.windows.getInstructionsSection, {}).then(({ section: next }) => {
      setSection(parseHelpSectionId(next));
    });
    return api.on(ipcChannels.windows.instructionsSection, ({ section: next }) => {
      setSection(parseHelpSectionId(next));
    });
  }, []);

  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      if (e.key === 'Escape') window.close();
    };
    window.addEventListener('keydown', onKey);
    return () => window.removeEventListener('keydown', onKey);
  }, []);

  return <InstructionsPanel initialSection={section} />;
}