/// Transaction labels (built-in + user-created) and local annotations.
library;

import 'package:flutter/material.dart';

import 'bank.dart';

/// A spend/income label shown on transactions.
class TxLabel {
  const TxLabel({
    required this.id,
    required this.name,
    required this.color,
    this.icon = Icons.label_outline,
    this.custom = false,
    this.parentId,
  });

  final String id;
  final String name;
  final Color color;
  final IconData icon;
  final bool custom;

  /// Optional parent label id for nesting (sub-labels).
  final String? parentId;

  bool get isRoot => parentId == null || parentId!.isEmpty;

  TxLabel copyWith({
    String? name,
    Color? color,
    IconData? icon,
    String? parentId,
    bool clearParent = false,
  }) {
    return TxLabel(
      id: id,
      name: name ?? this.name,
      color: color ?? this.color,
      icon: icon ?? this.icon,
      custom: custom,
      parentId: clearParent ? null : (parentId ?? this.parentId),
    );
  }

  Map<String, dynamic> toJson() => {
        'id': id,
        'name': name,
        // ignore: deprecated_member_use — wide compatibility across Flutter versions
        'color': color.value,
        'custom': custom,
        if (parentId != null && parentId!.isNotEmpty) 'parentId': parentId,
      };

  factory TxLabel.fromJson(Map<String, dynamic> json) {
    final parent = json['parentId'] as String?;
    return TxLabel(
      id: json['id'] as String? ?? 'custom',
      name: json['name'] as String? ?? 'Label',
      color: Color(json['color'] as int? ?? 0xFF64748B),
      custom: json['custom'] as bool? ?? true,
      parentId: (parent != null && parent.isNotEmpty) ? parent : null,
    );
  }
}

/// One row in a depth-first label tree walk.
class LabelTreeEntry {
  const LabelTreeEntry({required this.label, required this.depth});

  final TxLabel label;
  final int depth;
}

/// Max nesting depth (root = 0).
const int kMaxLabelDepth = 3;

/// Depth-first tree order using each label's [TxLabel.parentId].
List<LabelTreeEntry> flattenLabelTree(
  Iterable<TxLabel> labels, {
  String? Function(String id)? parentOf,
}) {
  final byId = <String, TxLabel>{
    for (final label in labels) label.id: label,
  };
  String? resolveParent(String id) {
    if (parentOf != null) return parentOf(id);
    return byId[id]?.parentId;
  }

  final children = <String?, List<TxLabel>>{};
  for (final label in byId.values) {
    final parent = resolveParent(label.id);
    final key = (parent != null && byId.containsKey(parent)) ? parent : null;
    (children[key] ??= []).add(label);
  }
  for (final list in children.values) {
    list.sort((a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()));
  }

  final out = <LabelTreeEntry>[];
  void walk(String? parentId, int depth) {
    final kids = children[parentId];
    if (kids == null) return;
    for (final label in kids) {
      out.add(LabelTreeEntry(label: label, depth: depth));
      if (depth < kMaxLabelDepth) {
        walk(label.id, depth + 1);
      }
    }
  }

  walk(null, 0);
  return out;
}

/// Visible indent depth among [visibleIds] only (skip missing ancestors).
int labelVisibleDepth(
  String labelId,
  Set<String> visibleIds,
  String? Function(String id) parentOf,
) {
  var depth = 0;
  var parent = parentOf(labelId);
  final seen = <String>{labelId};
  while (parent != null && parent.isNotEmpty && seen.add(parent)) {
    if (visibleIds.contains(parent)) depth++;
    parent = parentOf(parent);
  }
  return depth;
}

/// Filter-only id for txs with no labels (not an assignable category).
const String kUncategorizedFilterId = '__uncategorized__';

/// Chip presentation for [kUncategorizedFilterId] refine filters.
const TxLabel kUncategorizedFilterLabel = TxLabel(
  id: kUncategorizedFilterId,
  name: 'Uncategorized',
  color: Color(0xFF64748B),
  icon: Icons.label_off_outlined,
);

/// Built-in presets (no "uncategorized" / "other" as assignable labels).
const List<TxLabel> kBuiltinLabels = [
  TxLabel(
    id: 'groceries',
    name: 'Groceries',
    color: Color(0xFF16A34A),
    icon: Icons.shopping_cart_outlined,
  ),
  TxLabel(
    id: 'energy',
    name: 'Energy',
    color: Color(0xFFEAB308),
    icon: Icons.bolt_outlined,
  ),
  TxLabel(
    id: 'salary',
    name: 'Salary',
    color: Color(0xFF0F766E),
    icon: Icons.payments_outlined,
  ),
  TxLabel(
    id: 'mortgage',
    name: 'Mortgage',
    color: Color(0xFF7C3AED),
    icon: Icons.home_work_outlined,
  ),
  TxLabel(
    id: 'transport',
    name: 'Transport',
    color: Color(0xFF2563EB),
    icon: Icons.directions_bus_outlined,
  ),
  TxLabel(
    id: 'dining',
    name: 'Dining',
    color: Color(0xFFEA580C),
    icon: Icons.restaurant_outlined,
  ),
  TxLabel(
    id: 'shopping',
    name: 'Shopping',
    color: Color(0xFFDB2777),
    icon: Icons.shopping_bag_outlined,
  ),
  TxLabel(
    id: 'health',
    name: 'Health',
    color: Color(0xFFDC2626),
    icon: Icons.local_hospital_outlined,
  ),
  TxLabel(
    id: 'transfer',
    name: 'Transfer',
    color: Color(0xFF0891B2),
    icon: Icons.swap_horiz,
  ),
];

/// Palette for newly created custom labels.
const List<Color> kCustomLabelColors = [
  Color(0xFF0F766E),
  Color(0xFF7C3AED),
  Color(0xFFEA580C),
  Color(0xFF2563EB),
  Color(0xFFDB2777),
  Color(0xFF16A34A),
  Color(0xFFDC2626),
  Color(0xFF57534E),
];

/// Local overlay for a bank transaction.
class TxMeta {
  const TxMeta({
    this.labelIds = const [],
    this.recurring = false,
    this.notes = '',
  });

  /// Zero or more label ids on this transaction.
  final List<String> labelIds;
  final bool recurring;
  final String notes;

  static const empty = TxMeta();

  bool get hasLabel => labelIds.isNotEmpty;
  bool get hasNotes => notes.trim().isNotEmpty;

  /// First label id, if any (for compact UI).
  String? get primaryLabelId => labelIds.isEmpty ? null : labelIds.first;

  bool hasLabelId(String id) => labelIds.contains(id);

  TxMeta copyWith({
    List<String>? labelIds,
    bool clearLabels = false,
    bool? recurring,
    String? notes,
  }) {
    return TxMeta(
      labelIds: clearLabels ? const [] : (labelIds ?? this.labelIds),
      recurring: recurring ?? this.recurring,
      notes: notes ?? this.notes,
    );
  }

  Map<String, dynamic> toJson() => {
        'labelIds': labelIds,
        // Legacy single-label keys for older builds.
        'labelId': primaryLabelId,
        'category': primaryLabelId,
        'recurring': recurring,
        'notes': notes,
      };

  factory TxMeta.fromJson(Map<String, dynamic> json) {
    return TxMeta(
      labelIds: _parseLabelIds(json),
      recurring: json['recurring'] as bool? ?? false,
      notes: json['notes'] as String? ?? '',
    );
  }
}

List<String> _parseLabelIds(Map<String, dynamic> json) {
  final raw = json['labelIds'];
  if (raw is List) {
    return [
      for (final item in raw)
        if (item is String &&
            item.isNotEmpty &&
            item != 'uncategorized' &&
            item != 'other')
          item,
    ];
  }
  final single = (json['labelId'] as String?) ??
      _migrateLegacyCategory(json['category'] as String?);
  if (single == null) return const [];
  return [single];
}

String? _migrateLegacyCategory(String? name) {
  if (name == null || name.isEmpty) return null;
  if (name == 'uncategorized' || name == 'other') return null;
  return name;
}

/// Notes / recurring template keyed by exact merchant+amount match.
class TxExactTemplate {
  const TxExactTemplate({this.notes = '', this.recurring = false});

  final String notes;
  final bool recurring;

  Map<String, dynamic> toJson() => {
        'notes': notes,
        'recurring': recurring,
      };

  factory TxExactTemplate.fromJson(Map<String, dynamic> json) {
    return TxExactTemplate(
      notes: json['notes'] as String? ?? '',
      recurring: json['recurring'] as bool? ?? false,
    );
  }
}

/// Strip bank noise so supermarket / POS lines group by merchant stem.
///
/// Example: `BCK*AH CAMPUS DIEMEN ZUID NLD Pasvolgnr:…` → `ah campus`
/// Example: `Albert Heijn 1562 Utrecht` → `albert heijn`
String merchantKeyFromDescription(String description) {
  var s = description
      .trim()
      .toLowerCase()
      .replaceAll('·', ' ')
      .replaceAll(RegExp(r'\s+'), ' ');
  if (s.startsWith('naam:')) {
    s = s.substring(5).trim();
    final om = s.indexOf(' omschrijving:');
    if (om > 0) s = s.substring(0, om);
  }

  const markers = [
    ' pasvolgnr',
    'kaartnr',
    ' datum:',
    ' tijd:',
    ' transactie:',
    ' term:',
    ' valutadatum',
    ' iban:',
    ' kenmerk:',
    ' machtiging',
    ' overige partij',
    ' retourpin',
  ];
  for (final marker in markers) {
    final index = s.indexOf(marker);
    if (index > 6) {
      s = s.substring(0, index);
    }
  }

  s = s
      .replaceAll(RegExp(r'^bck\*'), '')
      .replaceAll(RegExp(r'\s+'), ' ')
      .trim();

  // Drop trailing country / city noise and store / terminal numbers.
  s = s.replaceAll(
    RegExp(
      r'\s+(nld|nl|nederland|netherlands|bel|belgium|deu|germany|de)\s*$',
    ),
    '',
  );
  // Remove digit runs (store ids, amounts embedded in text, etc.).
  s = s.replaceAll(RegExp(r'\b\d+\b'), ' ');
  s = s.replaceAll(RegExp(r'\s+'), ' ').trim();

  // Keep a short stem so "ah campus diemen zuid" ≈ "ah campus".
  final words = [
    for (final w in s.split(' '))
      if (w.length > 1) w,
  ];
  if (words.isEmpty) return s;
  if (words.length <= 2) return words.join(' ');
  // Prefer first two tokens for long POS strings; three when the 2nd is tiny
  // ("de", "van") so "albert heijn" / "jumbo city" stay intact.
  if (words[1].length <= 2 && words.length >= 3) {
    return words.take(3).join(' ');
  }
  return words.take(2).join(' ');
}

/// Default “apply to similar” pattern — usually the merchant stem.
String defaultSimilarPattern(String description) =>
    merchantKeyFromDescription(description);

/// Income / expense / any — used by list filters and similar matching.
enum TxFlowFilter { all, income, expense }

/// Absolute-amount filter for transaction lists (exact and/or range).
class TxAmountRange {
  const TxAmountRange({this.exact, this.min, this.max});

  /// Exact absolute amount; when set, takes precedence over [min]/[max].
  final double? exact;

  /// Inclusive lower bound on absolute amount; null = no lower bound.
  final double? min;

  /// Inclusive upper bound on absolute amount; null = no upper bound.
  final double? max;

  bool get isActive => exact != null || min != null || max != null;
}

bool txMatchesAmountRange(BankTransaction tx, TxAmountRange range) {
  if (!range.isActive) return true;
  final abs = tx.amount.abs();
  if (range.exact != null) {
    // Match to the nearest cent.
    return (abs - range.exact!).abs() < 0.005;
  }
  if (range.min != null && abs < range.min!) return false;
  if (range.max != null && abs > range.max!) return false;
  return true;
}

/// Criteria for finding similar transactions (apply-to-similar).
class SimilarMatchCriteria {
  const SimilarMatchCriteria({
    required this.pattern,
    this.flow = TxFlowFilter.all,
  });

  /// Plain contains needle, or `/regex/`.
  final String pattern;

  /// Limit matches to income, expense, or either.
  final TxFlowFilter flow;

  SimilarMatchCriteria copyWith({
    String? pattern,
    TxFlowFilter? flow,
  }) {
    return SimilarMatchCriteria(
      pattern: pattern ?? this.pattern,
      flow: flow ?? this.flow,
    );
  }
}

bool txMatchesFlow(BankTransaction tx, TxFlowFilter flow) {
  switch (flow) {
    case TxFlowFilter.all:
      return true;
    case TxFlowFilter.income:
      return tx.amount > 0;
    case TxFlowFilter.expense:
      return tx.amount < 0;
  }
}

bool txMatchesSimilarCriteria(BankTransaction tx, SimilarMatchCriteria criteria) {
  if (!txMatchesFlow(tx, criteria.flow)) return false;
  return descriptionMatchesPattern(tx.description, criteria.pattern);
}

/// Match [description] against a simple contains needle or `/regex/`.
bool descriptionMatchesPattern(String description, String pattern) {
  final raw = pattern.trim();
  if (raw.isEmpty) return false;
  final hay = description.toLowerCase();

  if (raw.length >= 3 && raw.startsWith('/') && raw.endsWith('/')) {
    final body = raw.substring(1, raw.length - 1);
    if (body.isEmpty) return false;
    try {
      return RegExp(body, caseSensitive: false).hasMatch(description);
    } catch (_) {
      return hay.contains(raw.toLowerCase());
    }
  }

  final needle = raw.toLowerCase();
  if (needle.length < 2) return false;
  return hay.contains(needle);
}