import 'package:flutter/material.dart';

class _FaqEntry {
  final String question;
  final String answer;
  const _FaqEntry(this.question, this.answer);
}

class _FaqSection {
  final String title;
  final List<_FaqEntry> entries;
  const _FaqSection(this.title, this.entries);
}

const _faqSections = <_FaqSection>[
  _FaqSection('Missouri Motor Fuel Tax Refund', [
    _FaqEntry(
      'What is the Missouri Motor Fuel Tax Refund?',
      'Missouri actually offers two separate fuel tax refunds — it\'s worth evaluating '
          'both to see how you could benefit:\n\n'
          '• Highway use — up to 12.5¢ per gallon.\n'
          '• Non-highway use — up to 29.5¢ per gallon.\n\n'
          "This app helps you collect and organize the receipts you'll need to claim "
          "either one. This isn't tax advice — for guidance on which refund(s) fit your "
          'situation, consult a tax professional. Rates and eligibility are set by '
          'Missouri law, which can change at any time, so always confirm current details '
          'with the Missouri Department of Revenue before filing.',
    ),
    _FaqEntry(
      'Is this app affiliated with the Missouri Department of Revenue?',
      "No. This is an independent tool for organizing your own receipts — it isn't run by, "
          "endorsed by, or connected to the State of Missouri. It doesn't file anything on "
          'your behalf.',
    ),
    _FaqEntry(
      'How do I generate a report for my refund claim?',
      "On the Reports tab, pick a date range to see your totals, then use Share or Print. "
          "There's also a link to Missouri's official Motor Fuel Refund Claim form once "
          "you're ready to file.",
    ),
  ]),
  _FaqSection('Usage', [
    _FaqEntry(
      'How do I log a fuel purchase?',
      "On the Receipts tab, tap the + button, snap a photo of the receipt, and the app "
          'reads the date, gallons, and price automatically. Review (and correct, if '
          'needed) the values before saving — every field stays editable both before and '
          'after saving.',
    ),
    _FaqEntry(
      'What if the app misreads my receipt?',
      'Automatic reading is usually accurate but not perfect — correct any field yourself '
          'before saving, or edit it afterward from the entry\'s detail page.',
    ),
    _FaqEntry(
      "Found a receipt, VIN, or error the app couldn't handle?",
      'Send it to ohbrer+ShowMeTheFuelRefund@gmail.com — example receipts or VINs that '
          "didn't scan correctly, screenshots of error screens, or anything else that "
          "didn't work as expected all help improve the app.",
    ),
    _FaqEntry(
      'Do I need to add a vehicle before logging a receipt?',
      'Yes — every fuel entry is linked to a vehicle. Add one on the Vehicles tab first '
          "(you'll need its VIN).",
    ),
  ]),
  _FaqSection('Data Safety', [
    _FaqEntry(
      'Is my data backed up?',
      'Not by default — everything you log lives only on this device until you connect a '
          'cloud storage account (Settings > Data). Once connected, a copy is kept there '
          'too, in storage you control.',
    ),
    _FaqEntry(
      'What cloud storage options are supported?',
      'Google Drive, Dropbox, OneDrive, or your own WebDAV server (Nextcloud, ownCloud, or '
          'any self-hosted WebDAV server).',
    ),
    _FaqEntry(
      "What happens if I lose my phone, or reinstall the app?",
      "If you never connected cloud storage, that data is gone — it only ever lived on "
          "that device. If you had connected one, reconnect the same account on the new "
          "device (or after reinstalling) and your vehicles, receipts, and photos sync back "
          'down automatically.',
    ),
    _FaqEntry(
      'How do I delete my data?',
      'Settings > Data > Advanced has options to purge everything, or just fuel entries in '
          "a specific date range. Both are permanent and can't be undone.",
    ),
  ]),
  _FaqSection('Advertisements', [
    _FaqEntry(
      'Why do I sometimes see an ad?',
      'Syncing your data to the cloud requires watching a short ad, to help support the '
          "app — at most once every 5 minutes, so it won't show again if you sync "
          'repeatedly in a short span.',
    ),
    _FaqEntry(
      'How do I remove ads?',
      '"Remove Ads for a Year" in Settings is a one-time purchase that disables ads for a '
          "year from when you buy it. It doesn't auto-renew or charge you again "
          "automatically — once the year's up, ads come back until you buy again.",
    ),
  ]),
];

/// A simple, static list of common questions grouped into sections —
/// reached from [SettingsScreen] (and every tab's AppBar via
/// [FaqActionButton]), the "back up your data" reminder, and the
/// first-launch user agreement screen.
class FaqScreen extends StatelessWidget {
  /// If given, that question's entry starts expanded (and the rest
  /// collapsed) instead of everything starting collapsed — used when a
  /// link elsewhere in the app points at one specific answer, e.g. the
  /// backup reminder dialog jumping straight to the backup question rather
  /// than making the user hunt for it.
  final String? initiallyExpandedQuestion;

  const FaqScreen({super.key, this.initiallyExpandedQuestion});

  @override
  Widget build(BuildContext context) {
    final textTheme = Theme.of(context).textTheme;

    return Scaffold(
      appBar: AppBar(title: const Text('FAQ')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          for (final section in _faqSections) ...[
            Padding(
              padding: const EdgeInsets.fromLTRB(4, 8, 4, 8),
              child: Text(
                section.title,
                style: textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w700),
              ),
            ),
            for (final entry in section.entries)
              Padding(
                padding: const EdgeInsets.only(bottom: 12),
                child: Card(
                  child: ExpansionTile(
                    title: Text(entry.question, style: textTheme.titleSmall),
                    initiallyExpanded: entry.question == initiallyExpandedQuestion,
                    childrenPadding: const EdgeInsets.fromLTRB(16, 0, 16, 16),
                    expandedCrossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(entry.answer, style: textTheme.bodyMedium),
                    ],
                  ),
                ),
              ),
            const SizedBox(height: 8),
          ],
        ],
      ),
    );
  }
}

/// A "?" AppBar action that jumps straight to [FaqScreen] — added to every
/// tab's AppBar (Receipts, Vehicles, Reports, Settings; see [MainShell])
/// so help is reachable the same way no matter which screen the user's on.
class FaqActionButton extends StatelessWidget {
  const FaqActionButton({super.key});

  @override
  Widget build(BuildContext context) {
    return IconButton(
      icon: const Icon(Icons.help_outline),
      tooltip: 'FAQ',
      onPressed: () => Navigator.of(context).push(
        MaterialPageRoute(builder: (_) => const FaqScreen()),
      ),
    );
  }
}