import 'dart:typed_data';

import 'package:flutter/services.dart' show rootBundle;
import 'package:http/http.dart' as http;
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

/// Rapport de fréquentation, généré côté client à partir des agrégats déjà
/// chargés par l'écran. L'envoi mensuel automatique, lui, devra être fait côté
/// backend (QuestPDF + Hangfire) — voir `plan-import-ia-stats-subsides.md §1`.

class ReportKpi {
  const ReportKpi(this.label, this.value, this.trend);

  final String label;
  final String value;
  final String? trend;
}

class ReportBar {
  const ReportBar(this.label, this.value, this.fraction);

  final String label;
  final String value;
  final double fraction;
}

class ReportBarGroup {
  const ReportBarGroup(this.title, this.subtitle, this.bars);

  final String title;
  final String subtitle;
  final List<ReportBar> bars;
}

class ReportTable {
  const ReportTable(this.title, this.headers, this.rows);

  final String title;
  final List<String> headers;
  final List<List<String>> rows;
}

class ReportDayPoint {
  const ReportDayPoint(this.label, this.visits);

  final String label;
  final int visits;
}

class StatisticsReportData {
  const StatisticsReportData({
    required this.instanceName,
    required this.title,
    required this.periodLabel,
    required this.takeaways,
    required this.kpis,
    required this.chartTitle,
    required this.chartSubtitle,
    required this.series,
    required this.axisLabels,
    required this.peakLabel,
    required this.barGroups,
    required this.tables,
    required this.generatedLabel,
    required this.brandArgb,
    required this.logo,
  });

  final String instanceName;
  final String title;
  final String periodLabel;
  final List<String> takeaways;
  final List<ReportKpi> kpis;
  final String chartTitle;
  final String chartSubtitle;
  final List<ReportDayPoint> series;

  /// Index des points de la série qui portent une étiquette sur l'axe des X.
  final List<int> axisLabels;
  final String? peakLabel;
  final List<ReportBarGroup> barGroups;
  final List<ReportTable> tables;
  final String generatedLabel;

  /// Couleur principale du canal de référence, en ARGB — l'écran n'a pas à
  /// connaître les types du paquet `pdf`.
  final int brandArgb;
  final Uint8List? logo;

  PdfColor get brandColor => PdfColor.fromInt(brandArgb);
}

const _ink = PdfColor.fromInt(0xFF14202B);
const _ink2 = PdfColor.fromInt(0xFF4A5A6B);
const _ink3 = PdfColor.fromInt(0xFF7C8B9A);
const _line = PdfColor.fromInt(0xFFD6DDE5);
const _track = PdfColor.fromInt(0xFFE7EBF1);
const _muted = PdfColor.fromInt(0xFFF3F5F8);

/// Le logo du client vit sur Firebase Storage. Sans en-tête CORS sur le bucket,
/// le navigateur refuse la lecture des octets : on retombe alors sur une page de
/// garde au seul nom de l'instance plutôt que de faire échouer le rapport.
Future<Uint8List?> fetchReportLogo(String? url) async {
  if (url == null || url.isEmpty) return null;
  try {
    final response = await http.get(Uri.parse(url));
    if (response.statusCode != 200) return null;
    return response.bodyBytes;
  } catch (_) {
    return null;
  }
}

Future<Uint8List> buildStatisticsReport(StatisticsReportData data) async {
  final fontData = await rootBundle.load('assets/fonts/OpenSans-Medium.ttf');
  final font = pw.Font.ttf(fontData);

  final document = pw.Document(
    theme: pw.ThemeData.withFont(base: font, bold: font, italic: font),
  );

  document.addPage(
    pw.MultiPage(
      pageFormat: PdfPageFormat.a4,
      margin: const pw.EdgeInsets.fromLTRB(38, 34, 38, 34),
      header: (context) =>
          context.pageNumber == 1 ? pw.SizedBox() : _runningHeader(data),
      footer: (context) => _footer(data, context),
      build: (context) => [
        _cover(data),
        if (data.takeaways.isNotEmpty) ...[
          pw.SizedBox(height: 22),
          _takeaways(data),
        ],
        pw.SizedBox(height: 18),
        _kpiRow(data),
        // Sous deux points il n'y a pas de courbe à tracer, et l'axe des X
        // dégénère en division par zéro.
        if (data.series.length >= 2) ...[
          pw.SizedBox(height: 22),
          _chart(data),
        ],
        for (final group in data.barGroups) ...[
          pw.SizedBox(height: 22),
          _barGroup(data, group),
        ],
        for (final table in data.tables) ...[
          pw.SizedBox(height: 22),
          _table(data, table),
        ],
      ],
    ),
  );

  return document.save();
}

pw.Widget _cover(StatisticsReportData data) {
  return pw.Column(
    crossAxisAlignment: pw.CrossAxisAlignment.start,
    children: [
      pw.Row(
        crossAxisAlignment: pw.CrossAxisAlignment.start,
        children: [
          pw.Expanded(
            child: pw.Column(
              crossAxisAlignment: pw.CrossAxisAlignment.start,
              children: [
                pw.Text(
                  data.instanceName,
                  style: pw.TextStyle(
                      fontSize: 11, color: data.brandColor, letterSpacing: 1.2),
                ),
                pw.SizedBox(height: 6),
                pw.Text(data.title,
                    style: const pw.TextStyle(fontSize: 25, color: _ink)),
                pw.SizedBox(height: 5),
                pw.Text(data.periodLabel,
                    style: const pw.TextStyle(fontSize: 12, color: _ink3)),
              ],
            ),
          ),
          if (data.logo != null)
            pw.Container(
              height: 52,
              constraints: const pw.BoxConstraints(maxWidth: 130),
              child:
                  pw.Image(pw.MemoryImage(data.logo!), fit: pw.BoxFit.contain),
            ),
        ],
      ),
      pw.SizedBox(height: 14),
      pw.Container(height: 2, color: data.brandColor),
    ],
  );
}

pw.Widget _runningHeader(StatisticsReportData data) {
  return pw.Container(
    margin: const pw.EdgeInsets.only(bottom: 16),
    padding: const pw.EdgeInsets.only(bottom: 6),
    decoration: const pw.BoxDecoration(
      border: pw.Border(bottom: pw.BorderSide(color: _line)),
    ),
    child: pw.Row(
      mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
      children: [
        pw.Text(data.instanceName,
            style: const pw.TextStyle(fontSize: 9, color: _ink3)),
        pw.Text(data.periodLabel,
            style: const pw.TextStyle(fontSize: 9, color: _ink3)),
      ],
    ),
  );
}

pw.Widget _footer(StatisticsReportData data, pw.Context context) {
  return pw.Container(
    margin: const pw.EdgeInsets.only(top: 14),
    child: pw.Row(
      mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
      children: [
        pw.Text(data.generatedLabel,
            style: const pw.TextStyle(fontSize: 8.5, color: _ink3)),
        pw.Text('${context.pageNumber} / ${context.pagesCount}',
            style: const pw.TextStyle(fontSize: 8.5, color: _ink3)),
      ],
    ),
  );
}

pw.Widget _takeaways(StatisticsReportData data) {
  return pw.Container(
    width: double.infinity,
    padding: const pw.EdgeInsets.symmetric(horizontal: 15, vertical: 13),
    decoration: pw.BoxDecoration(
      color: _muted,
      border: pw.Border.all(color: _line),
      borderRadius: pw.BorderRadius.circular(5),
    ),
    child: pw.Column(
      crossAxisAlignment: pw.CrossAxisAlignment.start,
      children: [
        for (final sentence in data.takeaways)
          pw.Padding(
            padding: pw.EdgeInsets.only(
                top: sentence == data.takeaways.first ? 0 : 5),
            child: pw.Text(sentence,
                style: const pw.TextStyle(
                    fontSize: 11, color: _ink, lineSpacing: 2.5)),
          ),
      ],
    ),
  );
}

/// Hauteur fixe assumée : `MultiPage` pose ses enfants sans contrainte
/// verticale, et `CrossAxisAlignment.stretch` y donnerait une hauteur infinie.
/// Le paquet `pdf` n'a pas d'`IntrinsicHeight` pour égaliser autrement.
pw.Widget _kpiRow(StatisticsReportData data) {
  return pw.SizedBox(
    height: 84,
    child: pw.Row(
      crossAxisAlignment: pw.CrossAxisAlignment.stretch,
      children: [
        for (final kpi in data.kpis) ...[
          pw.Expanded(
            child: pw.Container(
              padding: const pw.EdgeInsets.fromLTRB(12, 11, 12, 12),
              decoration: pw.BoxDecoration(border: pw.Border.all(color: _line)),
              child: pw.Column(
                crossAxisAlignment: pw.CrossAxisAlignment.start,
                children: [
                  pw.Text(kpi.label.toUpperCase(),
                      maxLines: 2,
                      style: const pw.TextStyle(
                          fontSize: 7.5, color: _ink3, letterSpacing: 0.4)),
                  pw.SizedBox(height: 6),
                  pw.Text(kpi.value,
                      maxLines: 1,
                      style:
                          pw.TextStyle(fontSize: 18, color: data.brandColor)),
                  if (kpi.trend != null) ...[
                    pw.SizedBox(height: 4),
                    pw.Text(kpi.trend!,
                        maxLines: 1,
                        style: const pw.TextStyle(fontSize: 8, color: _ink2)),
                  ],
                ],
              ),
            ),
          ),
          if (kpi != data.kpis.last) pw.SizedBox(width: 8),
        ],
      ],
    ),
  );
}

pw.Widget _chart(StatisticsReportData data) {
  final peak =
      data.series.map((point) => point.visits).reduce((a, b) => a > b ? a : b);
  final axisMax = _roundedAxisMax(peak);

  return _card(
    data,
    title: data.chartTitle,
    subtitle: data.chartSubtitle,
    child: pw.Column(
      crossAxisAlignment: pw.CrossAxisAlignment.start,
      children: [
        pw.SizedBox(
          height: 150,
          child: pw.Chart(
            grid: pw.CartesianGrid(
              xAxis: pw.FixedAxis<int>(
                data.axisLabels,
                format: (value) => data.series[value as int].label,
                textStyle: const pw.TextStyle(fontSize: 7.5, color: _ink3),
                color: _line,
              ),
              yAxis: pw.FixedAxis<int>(
                [0, (axisMax / 2).round(), axisMax.round()],
                divisions: true,
                divisionsColor: _line,
                textStyle: const pw.TextStyle(fontSize: 7.5, color: _ink3),
                color: _line,
              ),
            ),
            datasets: [
              pw.LineDataSet(
                data: [
                  for (var i = 0; i < data.series.length; i++)
                    pw.PointChartValue(
                        i.toDouble(), data.series[i].visits.toDouble()),
                ],
                color: data.brandColor,
                lineWidth: 1.4,
                drawPoints: false,
                drawSurface: true,
                surfaceColor: data.brandColor,
                surfaceOpacity: 0.16,
              ),
            ],
          ),
        ),
        if (data.peakLabel != null) ...[
          pw.SizedBox(height: 8),
          pw.Text(data.peakLabel!,
              style: const pw.TextStyle(fontSize: 9, color: _ink3)),
        ],
      ],
    ),
  );
}

pw.Widget _barGroup(StatisticsReportData data, ReportBarGroup group) {
  return _card(
    data,
    title: group.title,
    subtitle: group.subtitle,
    child: pw.Column(
      crossAxisAlignment: pw.CrossAxisAlignment.stretch,
      children: [
        for (final bar in group.bars)
          pw.Padding(
            padding: pw.EdgeInsets.only(bottom: bar == group.bars.last ? 0 : 9),
            child: pw.Column(
              crossAxisAlignment: pw.CrossAxisAlignment.stretch,
              children: [
                pw.Row(
                  children: [
                    pw.Expanded(
                      child: pw.Text(bar.label,
                          maxLines: 1,
                          style: const pw.TextStyle(fontSize: 10, color: _ink)),
                    ),
                    pw.SizedBox(width: 10),
                    pw.Text(bar.value,
                        style: const pw.TextStyle(fontSize: 9.5, color: _ink2)),
                  ],
                ),
                pw.SizedBox(height: 4),
                _barTrack(bar.fraction, data.brandColor),
              ],
            ),
          ),
      ],
    ),
  );
}

pw.Widget _table(StatisticsReportData data, ReportTable table) {
  return _card(
    data,
    title: table.title,
    subtitle: null,
    child: pw.TableHelper.fromTextArray(
      headers: table.headers,
      data: table.rows,
      border: null,
      headerStyle: const pw.TextStyle(fontSize: 9, color: _ink3),
      headerDecoration: const pw.BoxDecoration(
        border: pw.Border(bottom: pw.BorderSide(color: _line)),
      ),
      cellStyle: const pw.TextStyle(fontSize: 10, color: _ink),
      cellAlignment: pw.Alignment.centerLeft,
      cellHeight: 20,
      headerPadding: const pw.EdgeInsets.only(bottom: 6),
      cellPadding: const pw.EdgeInsets.symmetric(vertical: 3),
    ),
  );
}

pw.Widget _card(
  StatisticsReportData data, {
  required String title,
  required String? subtitle,
  required pw.Widget child,
}) {
  return pw.Container(
    width: double.infinity,
    padding: const pw.EdgeInsets.fromLTRB(15, 13, 15, 15),
    decoration: pw.BoxDecoration(border: pw.Border.all(color: _line)),
    child: pw.Column(
      crossAxisAlignment: pw.CrossAxisAlignment.start,
      children: [
        pw.Text(title,
            style: pw.TextStyle(fontSize: 12, color: data.brandColor)),
        if (subtitle != null) ...[
          pw.SizedBox(height: 2),
          pw.Text(subtitle,
              style: const pw.TextStyle(fontSize: 9, color: _ink3)),
        ],
        pw.SizedBox(height: 12),
        child,
      ],
    ),
  );
}

/// Le paquet `pdf` n'a pas d'équivalent de `FractionallySizedBox` : la
/// proportion se rend avec deux `Expanded` sur un millième près.
pw.Widget _barTrack(double fraction, PdfColor color) {
  const steps = 1000;
  final filled = (fraction.clamp(0.0, 1.0) * steps).round();
  if (filled >= steps) return pw.Container(height: 7, color: color);

  return pw.Container(
    height: 7,
    color: _track,
    child: pw.Row(
      children: [
        if (filled > 0)
          pw.Expanded(flex: filled, child: pw.Container(color: color)),
        pw.Expanded(flex: steps - filled, child: pw.SizedBox()),
      ],
    ),
  );
}

double _roundedAxisMax(int peak) {
  if (peak <= 4) return 4;
  var magnitude = 1.0;
  while (magnitude * 10 <= peak) {
    magnitude *= 10;
  }
  for (final step in const [1.0, 2.0, 4.0, 10.0]) {
    final candidate = magnitude * step;
    if (candidate >= peak) return candidate;
  }
  return magnitude * 10;
}