import 'package:eatvio_app/features/insights/models/insights_payload_model.dart';
import 'package:eatvio_app/features/insights/models/insights_period.dart';
import 'package:eatvio_app/features/profile/models/circumference_model.dart';
import 'package:eatvio_app/features/profile/models/weight_model.dart';
import 'package:eatvio_app/generated/l10n.dart';

/// Собирает [InsightsPayloadModel] из сырых точек мобильного API.
///
/// Зеркало веб-`UserInsightsService`: порог изменения [deltaEpsilon], минимум две
/// точки для дельты, те же категории ИМТ и формат подписей.
class InsightsTextBuilder {
  InsightsTextBuilder(this.s);

  final S s;

  static const double deltaEpsilon = 0.05;
  static const String _emptyHeadline = '—';

  InsightsPayloadModel build({
    required List<WeightModel> weights,
    required List<CircumferenceModel> circumferences,
    required BodyPeriod period,
    int? heightCm,
  }) {
    final sortedWeights = [...weights]
      ..sort((a, b) => a.createdAt.compareTo(b.createdAt));
    final sortedCircumferences = [...circumferences]
      ..sort((a, b) => a.createdAt.compareTo(b.createdAt));

    return InsightsPayloadModel(
      weight: buildWeight(sortedWeights, period),
      bmi: buildBmi(sortedWeights, period, heightCm),
      measure: buildMeasure(sortedCircumferences, period),
    );
  }

  WeightChartModel buildWeight(List<WeightModel> weights, BodyPeriod period) {
    final values = weights.map((e) => e.weight).toList();
    final last = values.isEmpty ? null : values.last;
    final delta = values.length < 2 ? null : _round(values.last - values.first);

    return WeightChartModel(
      labels: weights.map((e) => formatLabel(e.createdAt)).toList(),
      values: values,
      last: last,
      delta: delta,
      headline: last == null ? _emptyHeadline : last.toStringAsFixed(1),
      unit: s.insights_unit_kg,
      deltaText: _weightDeltaText(values, period),
    );
  }

  BmiChartModel buildBmi(
    List<WeightModel> weights,
    BodyPeriod period,
    int? heightCm,
  ) {
    final hasHeight = heightCm != null && heightCm > 0;
    if (!hasHeight) {
      return BmiChartModel(
        headline: _emptyHeadline,
        deltaText: s.insights_need_height,
        hint: s.insights_need_height,
      );
    }

    final points = weights.where((e) => e.bmi != null).toList();
    final values = points.map((e) => e.bmi!).toList();
    final last = values.isEmpty ? null : values.last;
    final delta = values.length < 2 ? null : _round(values.last - values.first);
    final category = last == null ? null : bmiCategory(last);

    return BmiChartModel(
      labels: points.map((e) => formatLabel(e.createdAt)).toList(),
      values: values,
      last: last,
      delta: delta,
      headline: last == null ? _emptyHeadline : last.toStringAsFixed(1),
      category: category,
      deltaText: _bmiDeltaText(values, period, category),
      hint: s.insights_bmi_hint(heightCm.toString()),
    );
  }

  MeasureChartModel buildMeasure(
    List<CircumferenceModel> circumferences,
    BodyPeriod period,
  ) {
    final waist = circumferences.map((e) => e.waistCircumference).toList();
    final chest = circumferences.map((e) => e.chestCircumference).toList();
    final hips = circumferences.map((e) => e.hipCircumference).toList();

    return MeasureChartModel(
      labels: circumferences.map((e) => formatLabel(e.createdAt)).toList(),
      waist: waist,
      chest: chest,
      hips: hips,
      headline: waist.isEmpty ? _emptyHeadline : waist.last.round().toString(),
      deltaText: _measureDeltaText(
        waist: waist,
        chest: chest,
        hips: hips,
        period: period,
      ),
    );
  }

  /// Категория по таблице ВОЗ из постановки #2120.
  String bmiCategory(double bmi) {
    if (bmi < 16) {
      return s.insights_bmi_severe_underweight;
    }
    if (bmi < 18.5) {
      return s.insights_bmi_underweight;
    }
    if (bmi < 25) {
      return s.insights_bmi_normal;
    }
    if (bmi < 30) {
      return s.insights_bmi_overweight;
    }
    if (bmi < 35) {
      return s.insights_bmi_obesity_1;
    }
    if (bmi < 40) {
      return s.insights_bmi_obesity_2;
    }
    return s.insights_bmi_obesity_3;
  }

  String periodLabel(BodyPeriod period) {
    switch (period) {
      case BodyPeriod.month:
        return s.insights_period_label_1;
      case BodyPeriod.threeMonths:
        return s.insights_period_label_3;
      case BodyPeriod.sixMonths:
        return s.insights_period_label_6;
      case BodyPeriod.year:
        return s.insights_period_label_12;
      case BodyPeriod.all:
        return s.insights_period_label_all;
    }
  }

  String formatLabel(DateTime date) {
    final local = date.toLocal();
    final day = local.day.toString().padLeft(2, '0');
    final month = local.month.toString().padLeft(2, '0');
    return '$day.$month';
  }

  /// Одна цифра после запятой без хвостового нуля: `3`, `3.5`.
  String formatNumber(double value) {
    final text = value.toStringAsFixed(1);
    return text.endsWith('.0') ? text.substring(0, text.length - 2) : text;
  }

  String _weightDeltaText(List<double> values, BodyPeriod period) {
    if (values.length < 2) {
      return s.insights_not_enough;
    }
    final diff = values.last - values.first;
    final periodText = periodLabel(period);
    if (diff.abs() < deltaEpsilon) {
      return s.insights_weight_same(periodText);
    }
    final value = formatNumber(diff.abs());
    return diff < 0
        ? s.insights_weight_lost(value, periodText)
        : s.insights_weight_gained(value, periodText);
  }

  String _bmiDeltaText(
    List<double> values,
    BodyPeriod period,
    String? category,
  ) {
    if (values.length < 2 || category == null) {
      return s.insights_not_enough;
    }
    final diff = values.last - values.first;
    final periodText = periodLabel(period);
    if (diff.abs() < deltaEpsilon) {
      return s.insights_bmi_same(periodText, category);
    }
    final value = formatNumber(diff.abs());
    return diff < 0
        ? s.insights_bmi_lower(value, periodText, category)
        : s.insights_bmi_higher(value, periodText, category);
  }

  String _measureDeltaText({
    required List<double> waist,
    required List<double> chest,
    required List<double> hips,
    required BodyPeriod period,
  }) {
    if (waist.length < 2) {
      return s.insights_not_enough;
    }
    final parts = [
      _measurePart(s.insights_series_waist, waist),
      _measurePart(s.insights_series_chest, chest),
      _measurePart(s.insights_series_hips, hips),
    ];
    return s.insights_measures_summary(parts.join(', '), periodLabel(period));
  }

  String _measurePart(String name, List<double> values) {
    final diff = values.last - values.first;
    if (diff.abs() < deltaEpsilon) {
      return s.insights_measure_same(name);
    }
    final value = formatNumber(diff.abs());
    return diff < 0
        ? s.insights_measure_less(name, value)
        : s.insights_measure_more(name, value);
  }

  double _round(double value) => (value * 10).round() / 10;
}