import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../l10n/app_localizations.dart';
import 'radar_timeline.dart';

/// Renders [age] at a scale a reader can take in at a glance.
///
/// Minutes alone stop being informative quickly: data three days old reads as
/// "Aggiornato 4320 minuti fa", which is a number nobody converts in their
/// head. The unit steps up so the magnitude is obvious even when the exact
/// figure is not.
String formatDataAge(AppLocalizations l10n, Duration age) {
  final clamped = age.isNegative ? Duration.zero : age;
  if (clamped.inHours < 1) return l10n.dataAgeMinutes(clamped.inMinutes);
  if (clamped.inDays < 1) return l10n.dataAgeHours(clamped.inHours);
  return l10n.dataAgeDays(clamped.inDays);
}

/// States the age of the radar data, and says so loudly when it is stale.
///
/// Radar shown without its age is radar the reader will assume is current. That
/// is the failure mode that matters for a weather app: someone deciding whether
/// to leave the house based on a picture of the sky from an hour ago. So the
/// age is always on screen, not only when something has gone wrong.
class DataAgeBanner extends ConsumerWidget {
  const DataAgeBanner({super.key, this.now});

  /// Injectable clock for tests.
  final DateTime? now;

  /// Beyond this the data stops being "the current picture".
  ///
  /// Frames arrive every five minutes, so a gap this size means several
  /// publishes were missed, not that one is slightly late.
  static const Duration staleAfter = Duration(minutes: 20);

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    final state = ref.watch(radarTimelineProvider);
    final manifest = state.manifest;

    if (manifest == null || manifest.isEmpty) {
      // Nothing to date. Whether that is a failure or a first load is the
      // timeline bar's business, not this widget's.
      return const SizedBox.shrink();
    }

    final age = manifest.ageAt(now ?? DateTime.now());
    final ageText = formatDataAge(l10n, age);
    final isStale = age >= staleAfter || state.error != null;

    if (!isStale) {
      // Full width and left aligned, matching the stale variant below, so the
      // text does not jump across the screen when the state flips.
      return SizedBox(
        width: double.infinity,
        child: Padding(
          padding: const EdgeInsets.fromLTRB(16, 0, 16, 4),
          child: Text(
            ageText,
            style: theme.textTheme.bodySmall?.copyWith(
              color: theme.colorScheme.outline,
            ),
          ),
        ),
      );
    }

    return Container(
      width: double.infinity,
      color: theme.colorScheme.errorContainer,
      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
      child: Row(
        children: [
          Icon(
            Icons.warning_amber_rounded,
            size: 18,
            color: theme.colorScheme.onErrorContainer,
          ),
          const SizedBox(width: 8),
          Expanded(
            child: Text(
              // The age goes inside the warning rather than replacing it: "not
              // updated" alone leaves the reader guessing how far off it is.
              state.error != null
                  ? '${l10n.dataUnavailable} · $ageText'
                  : l10n.radarStaleWithAge(ageText),
              style: theme.textTheme.bodySmall?.copyWith(
                color: theme.colorScheme.onErrorContainer,
              ),
            ),
          ),
        ],
      ),
    );
  }
}