import 'package:flutter_riverpod/flutter_riverpod.dart';

class FriendExpense {
  final String name;
  final double spent;
  final String note;
  FriendExpense({required this.name, required this.spent, this.note = ""});
}

class SplitterState {
  final List<FriendExpense> friends;
  SplitterState({this.friends = const []});
}

class SplitterNotifier extends StateNotifier<SplitterState> {
  SplitterNotifier() : super(SplitterState());

  void addFriend(String name, double spent, String note) {
    state = SplitterState(friends: [...state.friends, FriendExpense(name: name, spent: spent, note: note)]);
  }

  void removeFriend(int index) {
    var newList = List<FriendExpense>.from(state.friends);
    newList.removeAt(index);
    state = SplitterState(friends: newList);
  }

  List<String> calculateSettlements(double userSpent) {
    List<FriendExpense> all = [
      FriendExpense(name: "Io (Tu)", spent: userSpent, note: "Mio anticipo"),
      ...state.friends
    ];

    if (all.length < 2) return ["Aggiungi almeno un amico per il calcolo"];

    double totalSpent = all.fold(0, (sum, f) => sum + f.spent);
    double share = totalSpent / all.length;

    List<String> results = [
      "TOTALE: ${totalSpent.toStringAsFixed(2)}€",
      "QUOTA: ${share.toStringAsFixed(2)}€",
      "--------------------------------"
    ];

    Map<String, double> balances = { for (var f in all) f.name: f.spent - share };
    var creditors = balances.entries.where((e) => e.value > 0.01).toList();
    var debtors = balances.entries.where((e) => e.value < -0.01).toList();

    int cIdx = 0, dIdx = 0;
    while (cIdx < creditors.length && dIdx < debtors.length) {
      double amount = (creditors[cIdx].value < -debtors[dIdx].value) ? creditors[cIdx].value : -debtors[dIdx].value;
      results.add("${debtors[dIdx].key} ➔ ${creditors[cIdx].key}: ${amount.toStringAsFixed(2)}€");
      if ((creditors[cIdx].value - amount).abs() < 0.01) cIdx++;
      if ((debtors[dIdx].value + amount).abs() < 0.01) dIdx++;
    }
    return results;
  }
}

final splitterProvider = StateNotifierProvider<SplitterNotifier, SplitterState>((ref) => SplitterNotifier());