// ============================================
// Final-Projekt: Todo-App in C++
// Moderne C++17 Implementierung mit STL
// ============================================

#include <iostream>
#include <vector>
#include <string>
#include <ctime>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <algorithm>

// ============================================
// KLASSE: Todo
// ============================================
class Todo {
private:
    int id_;
    std::string title_;
    std::string description_;
    bool completed_;
    std::time_t created_at_;

public:
    // Konstruktor
    Todo(int id, std::string title, std::string description)
        : id_(id)
        , title_(std::move(title))
        , description_(std::move(description))
        , completed_(false)
        , created_at_(std::time(nullptr)) {}
    
    // Getter
    int id() const { return id_; }
    const std::string& title() const { return title_; }
    const std::string& description() const { return description_; }
    bool completed() const { return completed_; }
    std::time_t created_at() const { return created_at_; }
    
    // Setter
    void toggle_completed() { completed_ = !completed_; }
    void set_title(const std::string& title) { title_ = title; }
    void set_description(const std::string& desc) { description_ = desc; }
    
    // Formatierung für Ausgabe
    std::string to_string() const {
        std::stringstream ss;
        ss << "#" << id_ << " [" << (completed_ ? "✓" : " ") << "] " << title_;
        return ss.str();
    }
    
    // Serialisierung für Datei-Speicherung
    std::string serialize() const {
        std::stringstream ss;
        ss << id_ << "|" << title_ << "|" << description_ << "|" 
           << (completed_ ? "1" : "0") << "|" << created_at_;
        return ss.str();
    }
    
    static Todo deserialize(const std::string& line) {
        std::stringstream ss(line);
        std::string part;
        std::vector<std::string> parts;
        
        while (std::getline(ss, part, '|')) {
            parts.push_back(part);
        }
        
        Todo todo(std::stoi(parts[0]), parts[1], parts[2]);
        if (parts[3] == "1") todo.toggle_completed();
        return todo;
    }
};

// ============================================
// KLASSE: TodoManager
// ============================================
class TodoManager {
private:
    std::vector<Todo> todos_;
    int next_id_ = 1;
    const std::string filename_ = "todos_cpp.txt";

public:
    // CRUD Operationen
    void add(const std::string& title, const std::string& description) {
        todos_.emplace_back(next_id_++, title, description);
        std::cout << "✓ Todo hinzugefügt!\n";
    }
    
    void list() const {
        if (todos_.empty()) {
            std::cout << "Keine Todos vorhanden.\n";
            return;
        }
        
        std::cout << "\n=== DEINE TODOS ===\n";
        for (const auto& todo : todos_) {
            std::cout << todo.to_string() << "\n";
            if (!todo.description().empty()) {
                std::cout << "    " << todo.description() << "\n";
            }
        }
        std::cout << "\n";
    }
    
    void complete(int id) {
        auto it = find_by_id(id);
        if (it != todos_.end()) {
            it->toggle_completed();
            std::cout << "✓ Todo #" << id << (it->completed() ? " abgeschlossen" : " wieder geöffnet") << "\n";
        } else {
            std::cout << "✗ Todo #" << id << " nicht gefunden!\n";
        }
    }
    
    void remove(int id) {
        auto it = find_by_id(id);
        if (it != todos_.end()) {
            todos_.erase(it);
            // IDs neu zuweisen
            for (size_t i = 0; i < todos_.size(); ++i) {
                // Note: In echtem Code würde man IDs nicht ändern
            }
            std::cout << "✓ Todo #" << id << " gelöscht!\n";
        } else {
            std::cout << "✗ Todo #" << id << " nicht gefunden!\n";
        }
    }
    
    void edit(int id, const std::string& new_title) {
        auto it = find_by_id(id);
        if (it != todos_.end()) {
            it->set_title(new_title);
            std::cout << "✓ Todo #" << id << " aktualisiert!\n";
        } else {
            std::cout << "✗ Todo #" << id << " nicht gefunden!\n";
        }
    }
    
    // Filter-Funktionen
    void list_open() const {
        std::cout << "\n=== OFFENE TODOS ===\n";
        for (const auto& todo : todos_) {
            if (!todo.completed()) {
                std::cout << todo.to_string() << "\n";
            }
        }
        std::cout << "\n";
    }
    
    void list_completed() const {
        std::cout << "\n=== ABGESCHLOSSENE TODOS ===\n";
        for (const auto& todo : todos_) {
            if (todo.completed()) {
                std::cout << todo.to_string() << "\n";
            }
        }
        std::cout << "\n";
    }
    
    void search(const std::string& keyword) const {
        std::cout << "\n=== SUCHERGEBNISSE ===\n";
        for (const auto& todo : todos_) {
            if (todo.title().find(keyword) != std::string::npos ||
                todo.description().find(keyword) != std::string::npos) {
                std::cout << todo.to_string() << "\n";
            }
        }
        std::cout << "\n";
    }
    
    // Datei-Operationen
    void save() const {
        std::ofstream file(filename_);
        if (!file) {
            std::cout << "✗ Fehler beim Speichern!\n";
            return;
        }
        
        for (const auto& todo : todos_) {
            file << todo.serialize() << "\n";
        }
        
        std::cout << "✓ " << todos_.size() << " Todos gespeichert!\n";
    }
    
    void load() {
        std::ifstream file(filename_);
        if (!file) {
            std::cout << "Keine vorhandenen Daten. Starte neu...\n";
            return;
        }
        
        todos_.clear();
        std::string line;
        while (std::getline(file, line)) {
            if (!line.empty()) {
                todos_.push_back(Todo::deserialize(line));
            }
        }
        
        // next_id aktualisieren
        if (!todos_.empty()) {
            next_id_ = std::max_element(todos_.begin(), todos_.end(),
                [](const Todo& a, const Todo& b) { return a.id() < b.id(); })->id() + 1;
        }
        
        std::cout << "✓ " << todos_.size() << " Todos geladen!\n";
    }

private:
    std::vector<Todo>::iterator find_by_id(int id) {
        return std::find_if(todos_.begin(), todos_.end(),
            [id](const Todo& t) { return t.id() == id; });
    }
};

// ============================================
// UI-FUNKTIONEN
// ============================================
void print_menu() {
    std::cout << "\n=== TODO-APP (C++ Edition) ===\n";
    std::cout << "1. Todo hinzufügen\n";
    std::cout << "2. Alle Todos anzeigen\n";
    std::cout << "3. Offene Todos anzeigen\n";
    std::cout << "4. Abgeschlossene Todos anzeigen\n";
    std::cout << "5. Todo abschließen/öffnen\n";
    std::cout << "6. Todo bearbeiten\n";
    std::cout << "7. Todo löschen\n";
    std::cout << "8. Suchen\n";
    std::cout << "9. Speichern\n";
    std::cout << "0. Beenden\n";
    std::cout << "Wahl: ";
}

// ============================================
// HAUPTPROGRAMM
// ============================================
int main() {
    TodoManager manager;
    manager.load();
    
    std::cout << "\n📝 Willkommen zur Todo-App (C++17)!\n";
    
    int choice;
    std::string title, description, keyword;
    int id;
    
    while (true) {
        print_menu();
        
        if (!(std::cin >> choice)) {
            std::cin.clear();
            std::cin.ignore(10000, '\n');
            std::cout << "Ungültige Eingabe!\n";
            continue;
        }
        std::cin.ignore(10000, '\n');  // Rest der Zeile ignorieren
        
        switch (choice) {
            case 1:
                std::cout << "Titel: ";
                std::getline(std::cin, title);
                std::cout << "Beschreibung: ";
                std::getline(std::cin, description);
                manager.add(title, description);
                break;
                
            case 2:
                manager.list();
                break;
                
            case 3:
                manager.list_open();
                break;
                
            case 4:
                manager.list_completed();
                break;
                
            case 5:
                std::cout << "Todo-ID: ";
                std::cin >> id;
                manager.complete(id);
                break;
                
            case 6:
                std::cout << "Todo-ID: ";
                std::cin >> id;
                std::cin.ignore(10000, '\n');
                std::cout << "Neuer Titel: ";
                std::getline(std::cin, title);
                manager.edit(id, title);
                break;
                
            case 7:
                std::cout << "Todo-ID: ";
                std::cin >> id;
                manager.remove(id);
                break;
                
            case 8:
                std::cout << "Suchbegriff: ";
                std::getline(std::cin, keyword);
                manager.search(keyword);
                break;
                
            case 9:
                manager.save();
                break;
                
            case 0: {
                std::cout << "Speichern vor Beenden? (j/n): ";
                char save_choice;
                std::cin >> save_choice;
                if (save_choice == 'j' || save_choice == 'J') {
                    manager.save();
                }
                std::cout << "Auf Wiedersehen!\n";
                return 0;
            }
                
            default:
                std::cout << "Ungültige Wahl!\n";
        }
    }
    
    return 0;
}