Rust Structs and Methods Challenges

use std::collections::HashMap;

#[derive(Debug, Clone)]
struct Cryptocurrency {
    symbol: String,
    name: String,
    current_price: f64, // Price in USD
}

#[derive(Debug, Clone)]
struct Transaction {
    id: String,
    crypto_symbol: String,
    transaction_type: TransactionType,
    amount: f64,
    price_at_time: f64,
    timestamp: u64,
    fee: f64,
}

#[derive(Debug, Clone)]
enum TransactionType {
    Buy,
    Sell,
    Transfer { to: String },
    Receive { from: String },
}

#[derive(Debug)]
struct Portfolio {
    holdings: HashMap<String, f64>, // symbol -> amount
    transactions: Vec<Transaction>,
}

#[derive(Debug)]
struct CryptoWallet {
    owner: String,
    portfolio: Portfolio,
    is_locked: bool,
    pin: String,
}

impl Cryptocurrency {
    fn new(symbol: String, name: String, current_price: f64) -> Self {
        // TODO: Implement constructor
        Cryptocurrency {
            symbol,
            name,
            current_price,
        }
    }
    
    fn update_price(&mut self, new_price: f64) {
        // TODO: Update the current price
    }
    
    fn market_cap(&self, circulating_supply: f64) -> f64 {
        // TODO: Calculate market cap (price * supply)
        0.0
    }
}

impl Transaction {
    fn new(
        crypto_symbol: String,
        transaction_type: TransactionType,
        amount: f64,
        price_at_time: f64,
        fee: f64,
    ) -> Self {
        // TODO: Generate unique ID and current timestamp
        Transaction {
            id: String::new(),
            crypto_symbol,
            transaction_type,
            amount,
            price_at_time,
            timestamp: 0,
            fee,
        }
    }
    
    fn total_cost(&self) -> f64 {
        // TODO: Calculate total cost including fees
        // For buy: (amount * price) + fee
        // For sell: (amount * price) - fee
        0.0
    }
    
    fn profit_loss(&self, current_price: f64) -> f64 {
        // TODO: Calculate P&L compared to current price
        0.0
    }
}

impl Portfolio {
    fn new() -> Self {
        // TODO: Create empty portfolio
        Portfolio {
            holdings: HashMap::new(),
            transactions: Vec::new(),
        }
    }
    
    fn add_transaction(&mut self, transaction: Transaction) {
        // TODO: Add transaction and update holdings
        // Update the holdings HashMap based on transaction type
    }
    
    fn get_balance(&self, symbol: &str) -> f64 {
        // TODO: Return balance for given cryptocurrency
        0.0
    }
    
    fn total_value(&self, crypto_prices: &HashMap<String, f64>) -> f64 {
        // TODO: Calculate total portfolio value in USD
        0.0
    }
    
    fn get_transaction_history(&self) -> &[Transaction] {
        // TODO: Return reference to transaction history
        &self.transactions
    }
}

impl CryptoWallet {
    fn new(owner: String, pin: String) -> Self {
        // TODO: Create new wallet with empty portfolio
        CryptoWallet {
            owner,
            portfolio: Portfolio::new(),
            is_locked: false,
            pin,
        }
    }
    
    fn unlock(&mut self, pin: &str) -> Result<(), String> {
        // TODO: Unlock wallet if PIN is correct
        Ok(())
    }
    
    fn lock(&mut self) {
        // TODO: Lock the wallet
    }
    
    fn buy_crypto(&mut self, symbol: String, amount: f64, price: f64) -> Result<String, String> {
        // TODO: Execute buy transaction if wallet is unlocked
        // Return transaction ID or error
        Ok(String::new())
    }
    
    fn sell_crypto(&mut self, symbol: String, amount: f64, price: f64) -> Result<String, String> {
        // TODO: Execute sell transaction if sufficient balance
        // Return transaction ID or error
        Ok(String::new())
    }
    
    fn get_portfolio_summary(&self) -> String {
        // TODO: Return formatted portfolio summary
        String::new()
    }
}

fn main() {
    println!("=== Crypto Wallet Simulator ===");
    
    // Create wallet
    let mut wallet = CryptoWallet::new(
        String::from("Alice"),
        String::from("1234")
    );
    
    // Unlock wallet
    wallet.unlock("1234").unwrap();
    
    // Buy some cryptocurrencies
    wallet.buy_crypto(String::from("BTC"), 0.1, 45000.0).unwrap();
    wallet.buy_crypto(String::from("ETH"), 2.0, 3000.0).unwrap();
    wallet.buy_crypto(String::from("SOL"), 100.0, 150.0).unwrap();
    
    // Sell some
    wallet.sell_crypto(String::from("SOL"), 25.0, 160.0).unwrap();
    
    // Display portfolio
    println!("{}", wallet.get_portfolio_summary());
    
    // Lock wallet
    wallet.lock();
    
    // Try to buy while locked (should fail)
    match wallet.buy_crypto(String::from("ADA"), 1000.0, 0.5) {
        Ok(_) => println!("Buy successful"),
        Err(e) => println!("Buy failed: {}", e),
    }
}

// Helper functions you might need:
fn generate_transaction_id() -> String {
    // Generate a unique transaction ID
    format!("tx_{}", get_current_timestamp())
}

fn get_current_timestamp() -> u64 {
    // Return current timestamp (simplified)
    1640995200
}

use std::collections::HashMap;

#[derive(Debug, Clone)]
struct PriceHistory {
    symbol: String,
    prices: Vec<(u64, f64)>, // (timestamp, price)
}

#[derive(Debug)]
struct PortfolioAnalytics {
    total_invested: f64,
    total_value: f64,
    unrealized_pnl: f64,
    realized_pnl: f64,
    best_performing_crypto: Option<String>,
    worst_performing_crypto: Option<String>,
    portfolio_diversity_score: f64,
}

#[derive(Debug)]
struct WalletSettings {
    default_fee_percentage: f64,
    auto_lock_timeout: u64,
    notification_preferences: Vec<String>,
    preferred_currency: String,
}

impl PriceHistory {
    fn new(symbol: String) -> Self {
        // TODO: Create new price history
        PriceHistory {
            symbol,
            prices: Vec::new(),
        }
    }
    
    fn add_price_point(&mut self, timestamp: u64, price: f64) {
        // TODO: Add price point and maintain chronological order
    }
    
    fn get_price_at_time(&self, timestamp: u64) -> Option<f64> {
        // TODO: Find closest price to given timestamp
        None
    }
    
    fn calculate_volatility(&self) -> f64 {
        // TODO: Calculate price volatility (standard deviation)
        0.0
    }
    
    fn get_price_change_24h(&self) -> Option<f64> {
        // TODO: Calculate 24h price change percentage
        None
    }
}

impl PortfolioAnalytics {
    fn new() -> Self {
        // TODO: Create empty analytics
        PortfolioAnalytics {
            total_invested: 0.0,
            total_value: 0.0,
            unrealized_pnl: 0.0,
            realized_pnl: 0.0,
            best_performing_crypto: None,
            worst_performing_crypto: None,
            portfolio_diversity_score: 0.0,
        }
    }
    
    fn update_analytics(
        &mut self,
        portfolio: &Portfolio,
        price_history: &HashMap<String, PriceHistory>,
    ) {
        // TODO: Calculate comprehensive portfolio analytics
        // - Total invested vs current value
        // - Unrealized and realized P&L
        // - Best/worst performing assets
        // - Diversity score (how spread out investments are)
    }
    
    fn get_recommendation(&self) -> String {
        // TODO: Provide investment recommendation based on analytics
        String::new()
    }
}

// Enhanced CryptoWallet with analytics
impl CryptoWallet {
    fn calculate_analytics(&self, price_history: &HashMap<String, PriceHistory>) -> PortfolioAnalytics {
        // TODO: Generate comprehensive portfolio analytics
        PortfolioAnalytics::new()
    }
    
    fn export_portfolio_csv(&self) -> String {
        // TODO: Export portfolio data to CSV format
        String::new()
    }
    
    fn import_transactions_csv(&mut self, csv_data: &str) -> Result<usize, String> {
        // TODO: Import transactions from CSV data
        // Return number of imported transactions
        Ok(0)
    }
    
    fn set_price_alerts(&mut self, symbol: String, target_price: f64) {
        // TODO: Set price alerts for cryptocurrencies
    }
    
    fn rebalance_portfolio(&mut self, target_allocations: HashMap<String, f64>) -> Result<Vec<String>, String> {
        // TODO: Rebalance portfolio to match target allocations
        // Return list of transactions needed
        Ok(vec![])
    }
}

fn main() {
    println!("=== Advanced Crypto Wallet ===");
    
    // Create wallet with settings
    let mut wallet = CryptoWallet::new(
        String::from("Alice"),
        String::from("1234")
    );
    
    // Create price history
    let mut price_history = HashMap::new();
    let mut btc_history = PriceHistory::new(String::from("BTC"));
    btc_history.add_price_point(1640995200, 45000.0);
    btc_history.add_price_point(1640995800, 46000.0);
    price_history.insert(String::from("BTC"), btc_history);
    
    // Unlock and make some trades
    wallet.unlock("1234").unwrap();
    wallet.buy_crypto(String::from("BTC"), 0.1, 45000.0).unwrap();
    wallet.buy_crypto(String::from("ETH"), 2.0, 3000.0).unwrap();
    
    // Calculate analytics
    let analytics = wallet.calculate_analytics(&price_history);
    println!("Analytics: {:?}", analytics);
    
    // Export portfolio
    let csv_export = wallet.export_portfolio_csv();
    println!("Portfolio CSV:\n{}", csv_export);
    
    // Set price alerts
    wallet.set_price_alerts(String::from("BTC"), 50000.0);
    
    // Test rebalancing
    let mut target_allocation = HashMap::new();
    target_allocation.insert(String::from("BTC"), 0.6);
    target_allocation.insert(String::from("ETH"), 0.4);
    
    match wallet.rebalance_portfolio(target_allocation) {
        Ok(transactions) => println!("Rebalancing transactions: {:?}", transactions),
        Err(e) => println!("Rebalancing failed: {}", e),
    }
}

use std::time::{SystemTime, UNIX_EPOCH};

#[derive(Debug, Clone)]
enum PetSpecies {
    Cat,
    Dog,
    Dragon,
    Robot,
}

#[derive(Debug, Clone)]
enum PetMood {
    Happy,
    Content,
    Sad,
    Angry,
    Sleepy,
}

#[derive(Debug, Clone)]
enum PetStage {
    Egg,
    Baby,
    Child,
    Adult,
    Elder,
}

#[derive(Debug)]
struct PetStats {
    hunger: u8,        // 0-100, higher = more hungry
    happiness: u8,     // 0-100, higher = happier
    health: u8,        // 0-100, higher = healthier
    energy: u8,        // 0-100, higher = more energetic
    age_days: u32,     // Age in days
}

#[derive(Debug)]
struct Pet {
    name: String,
    species: PetSpecies,
    stats: PetStats,
    stage: PetStage,
    mood: PetMood,
    last_update: u64,  // Timestamp of last status update
    is_alive: bool,
}

impl PetStats {
    fn new() -> Self {
        // TODO: Create initial pet stats
        PetStats {
            hunger: 50,
            happiness: 80,
            health: 100,
            energy: 100,
            age_days: 0,
        }
    }
    
    fn update_over_time(&mut self, hours_passed: u32) {
        // TODO: Update stats based on time passed
        // Hunger increases over time
        // Happiness decreases if hungry
        // Health decreases if very hungry or unhappy
        // Energy decreases during day, recovers during sleep
    }
    
    fn is_critical(&self) -> bool {
        // TODO: Check if any stat is critically low
        false
    }
    
    fn overall_condition(&self) -> String {
        // TODO: Return overall condition based on all stats
        String::new()
    }
}

impl Pet {
    fn new(name: String, species: PetSpecies) -> Self {
        // TODO: Create new pet
        Pet {
            name,
            species,
            stats: PetStats::new(),
            stage: PetStage::Egg,
            mood: PetMood::Content,
            last_update: get_current_timestamp(),
            is_alive: true,
        }
    }
    
    fn update_status(&mut self) {
        // TODO: Update pet status based on time passed
        let current_time = get_current_timestamp();
        let hours_passed = (current_time - self.last_update) / 3600;
        
        // Update stats
        // Check for evolution
        // Update mood based on stats
        // Check if pet is still alive
        
        self.last_update = current_time;
    }
    
    fn feed(&mut self, food_quality: u8) -> String {
        // TODO: Feed the pet, reducing hunger
        // Better quality food = more hunger reduction + happiness boost
        String::new()
    }
    
    fn play(&mut self, play_duration: u8) -> String {
        // TODO: Play with pet, increasing happiness but decreasing energy
        String::new()
    }
    
    fn let_sleep(&mut self, sleep_hours: u8) -> String {
        // TODO: Let pet sleep, recovering energy
        String::new()
    }
    
    fn give_medicine(&mut self) -> String {
        // TODO: Give medicine if pet is sick, improving health
        String::new()
    }
    
    fn get_status(&self) -> String {
        // TODO: Return formatted status string
        format!(
            "🐾 {} the {:?}\n\
             Stage: {:?} | Mood: {:?}\n\
             Hunger: {}/100 | Happiness: {}/100\n\
             Health: {}/100 | Energy: {}/100\n\
             Age: {} days | {}",
            self.name,
            self.species,
            self.stage,
            self.mood,
            self.stats.hunger,
            self.stats.happiness,
            self.stats.health,
            self.stats.energy,
            self.stats.age_days,
            if self.is_alive { "Alive" } else { "😢 Deceased" }
        )
    }
    
    fn check_evolution(&mut self) -> Option<String> {
        // TODO: Check if pet should evolve to next stage
        // Return evolution message if evolution occurred
        None
    }
    
    fn calculate_mood(&mut self) {
        // TODO: Calculate current mood based on stats
        // Happy: high happiness, low hunger
        // Sad: low happiness or very hungry
        // Sleepy: low energy
        // Angry: high hunger + low happiness
    }
}

fn get_current_timestamp() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_secs()
}

fn main() {
    println!("=== Virtual Pet Tamagotchi ===");
    
    // Create a new pet
    let mut pet = Pet::new(
        String::from("Fluffy"),
        PetSpecies::Cat
    );
    
    println!("Welcome! You have a new pet:");
    println!("{}", pet.get_status());
    
    // Simulate some time passing and care actions
    println!("\n--- After some time ---");
    pet.update_status();
    
    // Feed the pet
    let feed_result = pet.feed(80);
    println!("{}", feed_result);
    
    // Play with the pet
    let play_result = pet.play(30);
    println!("{}", play_result);
    
    // Let pet sleep
    let sleep_result = pet.let_sleep(8);
    println!("{}", sleep_result);
    
    // Check evolution
    if let Some(evolution_msg) = pet.check_evolution() {
        println!("{}", evolution_msg);
    }
    
    println!("\n--- Current Status ---");
    println!("{}", pet.get_status());
}

// Additional helper functions you might need:

fn simulate_time_passage(hours: u32) {
    // Simulate time passing for testing
    println!("⏰ {} hours pass...", hours);
}

fn get_care_recommendation(pet: &Pet) -> String {
    // Analyze pet stats and recommend care actions
    String::from("Your pet needs attention!")
}

use std::collections::HashMap;

#[derive(Debug, Clone)]
struct PersonalityTraits {
    friendliness: u8,    // How social the pet is
    energy_level: u8,    // Natural energy level
    appetite: u8,        // How much/often pet gets hungry
    intelligence: u8,    // Learning rate and trick ability
    stubbornness: u8,    // Resistance to care/training
}

#[derive(Debug, Clone)]
enum ItemType {
    Food { nutrition: u8, taste: u8 },
    Toy { fun_factor: u8, durability: u8 },
    Medicine { effectiveness: u8 },
    Accessory { happiness_boost: u8 },
}

#[derive(Debug, Clone)]
struct Item {
    name: String,
    item_type: ItemType,
    quantity: u32,
}

#[derive(Debug)]
struct Inventory {
    items: HashMap<String, Item>,
    money: u32,
}

#[derive(Debug, Clone)]
struct Skill {
    name: String,
    level: u8,
    experience: u32,
}

// Enhanced Pet with personality and skills
impl Pet {
    fn new_with_personality(
        name: String,
        species: PetSpecies,
        personality: PersonalityTraits,
    ) -> Self {
        // TODO: Create pet with personality traits affecting initial stats
        Pet {
            name,
            species,
            stats: PetStats::new(),
            stage: PetStage::Egg,
            mood: PetMood::Content,
            last_update: get_current_timestamp(),
            is_alive: true,
        }
    }
    
    fn learn_trick(&mut self, trick_name: String) -> Result<String, String> {
        // TODO: Teach pet a new trick based on intelligence and repetition
        Ok(String::new())
    }
    
    fn use_item(&mut self, item: &Item) -> String {
        // TODO: Use item on pet with effects based on item type
        String::new()
    }
    
    fn get_care_preferences(&self) -> Vec<String> {
        // TODO: Return care preferences based on personality
        vec![]
    }
    
    fn calculate_happiness_multiplier(&self) -> f32 {
        // TODO: Calculate happiness gain/loss multiplier based on personality
        1.0
    }
}

impl PersonalityTraits {
    fn random() -> Self {
        // TODO: Generate random personality traits
        PersonalityTraits {
            friendliness: 50,
            energy_level: 50,
            appetite: 50,
            intelligence: 50,
            stubbornness: 50,
        }
    }
    
    fn get_description(&self) -> String {
        // TODO: Generate personality description
        String::new()
    }
}

impl Inventory {
    fn new() -> Self {
        // TODO: Create starting inventory
        Inventory {
            items: HashMap::new(),
            money: 100,
        }
    }
    
    fn add_item(&mut self, item: Item) {
        // TODO: Add item to inventory
    }
    
    fn use_item(&mut self, item_name: &str) -> Option<Item> {
        // TODO: Remove and return item if available
        None
    }
    
    fn buy_item(&mut self, item: Item, cost: u32) -> Result<(), String> {
        // TODO: Buy item if enough money
        Ok(())
    }
}

#[derive(Debug)]
struct PetCareCenter {
    pets: Vec<Pet>,
    inventory: Inventory,
    care_log: Vec<String>,
}

impl PetCareCenter {
    fn new() -> Self {
        PetCareCenter {
            pets: Vec::new(),
            inventory: Inventory::new(),
            care_log: Vec::new(),
        }
    }
    
    fn adopt_pet(&mut self, name: String, species: PetSpecies) -> usize {
        // TODO: Create and add new pet, return pet ID
        0
    }
    
    fn care_for_pet(&mut self, pet_id: usize, action: CareAction) -> Result<String, String> {
        // TODO: Perform care action on specified pet
        Ok(String::new())
    }
    
    fn check_all_pets(&mut self) {
        // TODO: Update status for all pets
    }
    
    fn get_daily_report(&self) -> String {
        // TODO: Generate daily care report
        String::new()
    }
}

#[derive(Debug)]
enum CareAction {
    Feed(String),      // Item name
    Play(String),      // Activity type
    Train(String),     // Skill to train
    UseItem(String),   // Item name
    Sleep,
}

fn main() {
    println!("=== Advanced Pet Care Center ===");
    
    let mut care_center = PetCareCenter::new();
    
    // Adopt pets with different personalities
    let fluffy_id = care_center.adopt_pet(
        String::from("Fluffy"),
        PetSpecies::Cat
    );
    
    let buddy_id = care_center.adopt_pet(
        String::from("Buddy"),
        PetSpecies::Dog
    );
    
    // Add some items to inventory
    care_center.inventory.add_item(Item {
        name: String::from("Premium Cat Food"),
        item_type: ItemType::Food { nutrition: 90, taste: 85 },
        quantity: 5,
    });
    
    // Care for pets
    care_center.care_for_pet(fluffy_id, CareAction::Feed(String::from("Premium Cat Food"))).unwrap();
    care_center.care_for_pet(buddy_id, CareAction::Play(String::from("Fetch"))).unwrap();
    
    // Check all pets
    care_center.check_all_pets();
    
    // Generate report
    println!("{}", care_center.get_daily_report());
}

use std::collections::HashMap;

#[derive(Debug, Clone)]
struct Book {
    isbn: String,
    title: String,
    author: String,
    genre: String,
    publication_year: u32,
    total_copies: u32,
    available_copies: u32,
}

#[derive(Debug, Clone)]
struct Patron {
    id: u32,
    name: String,
    email: String,
    phone: String,
    borrowed_books: Vec<String>, // ISBNs of borrowed books
    fines_owed: f64,
    is_active: bool,
}

#[derive(Debug, Clone)]
struct BorrowRecord {
    patron_id: u32,
    isbn: String,
    borrow_date: u64,
    due_date: u64,
    return_date: Option<u64>,
    fine_amount: f64,
}

#[derive(Debug)]
struct Library {
    name: String,
    books: HashMap<String, Book>,      // ISBN -> Book
    patrons: HashMap<u32, Patron>,     // ID -> Patron
    borrow_records: Vec<BorrowRecord>,
    next_patron_id: u32,
}

impl Book {
    fn new(
        isbn: String,
        title: String,
        author: String,
        genre: String,
        publication_year: u32,
        total_copies: u32,
    ) -> Self {
        // TODO: Create new book with all copies available
        Book {
            isbn,
            title,
            author,
            genre,
            publication_year,
            total_copies,
            available_copies: total_copies,
        }
    }
    
    fn is_available(&self) -> bool {
        // TODO: Check if book has available copies
        false
    }
    
    fn borrow_copy(&mut self) -> Result<(), String> {
        // TODO: Reduce available copies by 1 if possible
        Ok(())
    }
    
    fn return_copy(&mut self) -> Result<(), String> {
        // TODO: Increase available copies by 1 if not at max
        Ok(())
    }
    
    fn get_info(&self) -> String {
        // TODO: Return formatted book information
        format!(
            "📖 {} by {}\n\
             ISBN: {} | Genre: {} | Year: {}\n\
             Available: {}/{} copies",
            self.title,
            self.author,
            self.isbn,
            self.genre,
            self.publication_year,
            self.available_copies,
            self.total_copies
        )
    }
}

impl Patron {
    fn new(id: u32, name: String, email: String, phone: String) -> Self {
        // TODO: Create new patron
        Patron {
            id,
            name,
            email,
            phone,
            borrowed_books: Vec::new(),
            fines_owed: 0.0,
            is_active: true,
        }
    }
    
    fn can_borrow(&self) -> bool {
        // TODO: Check if patron can borrow (active, not too many books, low fines)
        false
    }
    
    fn add_borrowed_book(&mut self, isbn: String) {
        // TODO: Add book to borrowed list
    }
    
    fn remove_borrowed_book(&mut self, isbn: &str) -> bool {
        // TODO: Remove book from borrowed list, return true if found
        false
    }
    
    fn add_fine(&mut self, amount: f64) {
        // TODO: Add fine amount
    }
    
    fn pay_fine(&mut self, amount: f64) -> f64 {
        // TODO: Pay fine, return amount actually paid
        0.0
    }
    
    fn get_summary(&self) -> String {
        // TODO: Return patron summary
        String::new()
    }
}

impl BorrowRecord {
    fn new(patron_id: u32, isbn: String, borrow_date: u64, loan_period_days: u32) -> Self {
        // TODO: Create new borrow record with calculated due date
        BorrowRecord {
            patron_id,
            isbn,
            borrow_date,
            due_date: borrow_date + (loan_period_days as u64 * 24 * 3600),
            return_date: None,
            fine_amount: 0.0,
        }
    }
    
    fn mark_returned(&mut self, return_date: u64, daily_fine_rate: f64) {
        // TODO: Mark as returned and calculate fine if late
    }
    
    fn is_overdue(&self, current_date: u64) -> bool {
        // TODO: Check if book is overdue
        false
    }
    
    fn calculate_fine(&self, current_date: u64, daily_fine_rate: f64) -> f64 {
        // TODO: Calculate fine based on days overdue
        0.0
    }
}

impl Library {
    fn new(name: String) -> Self {
        // TODO: Create new library
        Library {
            name,
            books: HashMap::new(),
            patrons: HashMap::new(),
            borrow_records: Vec::new(),
            next_patron_id: 1,
        }
    }
    
    fn add_book(&mut self, book: Book) {
        // TODO: Add book to catalog
    }
    
    fn register_patron(&mut self, name: String, email: String, phone: String) -> u32 {
        // TODO: Register new patron and return their ID
        0
    }
    
    fn borrow_book(&mut self, patron_id: u32, isbn: &str) -> Result<String, String> {
        // TODO: Process book borrowing
        // Check patron can borrow, book is available
        // Create borrow record, update book and patron
        Ok(String::new())
    }
    
    fn return_book(&mut self, patron_id: u32, isbn: &str) -> Result<String, String> {
        // TODO: Process book return
        // Find borrow record, calculate fines, update records
        Ok(String::new())
    }
    
    fn search_books(&self, query: &str) -> Vec<&Book> {
        // TODO: Search books by title, author, or ISBN
        vec![]
    }
    
    fn get_overdue_books(&self, current_date: u64) -> Vec<&BorrowRecord> {
        // TODO: Return list of overdue borrow records
        vec![]
    }
    
    fn generate_report(&self) -> String {
        // TODO: Generate library statistics report
        String::new()
    }
}

fn get_current_timestamp() -> u64 {
    // Simplified timestamp for testing
    1640995200
}

fn main() {
    println!("=== Library Management System ===");
    
    // Create library
    let mut library = Library::new(String::from("City Central Library"));
    
    // Add some books
    library.add_book(Book::new(
        String::from("978-0-123456-78-9"),
        String::from("The Rust Programming Language"),
        String::from("Steve Klabnik"),
        String::from("Programming"),
        2018,
        3,
    ));
    
    library.add_book(Book::new(
        String::from("978-1-234567-89-0"),
        String::from("Blockchain Development"),
        String::from("Jane Smith"),
        String::from("Technology"),
        2021,
        2,
    ));
    
    // Register patrons
    let alice_id = library.register_patron(
        String::from("Alice Johnson"),
        String::from("alice@email.com"),
        String::from("555-0123"),
    );
    
    let bob_id = library.register_patron(
        String::from("Bob Wilson"),
        String::from("bob@email.com"),
        String::from("555-0456"),
    );
    
    // Borrow books
    match library.borrow_book(alice_id, "978-0-123456-78-9") {
        Ok(msg) => println!("✅ {}", msg),
        Err(e) => println!("❌ {}", e),
    }
    
    match library.borrow_book(bob_id, "978-1-234567-89-0") {
        Ok(msg) => println!("✅ {}", msg),
        Err(e) => println!("❌ {}", e),
    }
    
    // Search books
    let search_results = library.search_books("Rust");
    println!("\nSearch results for 'Rust':");
    for book in search_results {
        println!("{}", book.get_info());
    }
    
    // Generate report
    println!("\n=== Library Report ===");
    println!("{}", library.generate_report());
}

use std::collections::{HashMap, VecDeque};

#[derive(Debug, Clone)]
enum ResourceType {
    PhysicalBook,
    EBook,
    AudioBook,
    DVD,
    Magazine,
    Newspaper,
}

#[derive(Debug, Clone)]
struct DigitalResource {
    resource_type: ResourceType,
    file_format: String,
    file_size_mb: u32,
    download_limit: Option<u32>,
    streaming_available: bool,
}

#[derive(Debug, Clone)]
struct Reservation {
    patron_id: u32,
    isbn: String,
    reservation_date: u64,
    expiry_date: u64,
    position_in_queue: usize,
}

#[derive(Debug)]
struct ReservationQueue {
    isbn: String,
    queue: VecDeque<Reservation>,
}

// Enhanced Library with reservations and digital resources
impl Library {
    fn reserve_book(&mut self, patron_id: u32, isbn: &str) -> Result<String, String> {
        // TODO: Add patron to reservation queue for book
        Ok(String::new())
    }
    
    fn cancel_reservation(&mut self, patron_id: u32, isbn: &str) -> Result<String, String> {
        // TODO: Remove patron from reservation queue
        Ok(String::new())
    }
    
    fn process_reservation_queue(&mut self, isbn: &str) {
        // TODO: Notify next patron in queue when book becomes available
    }
    
    fn add_digital_resource(&mut self, book: Book, digital_info: DigitalResource) {
        // TODO: Add digital resource to catalog
    }
    
    fn download_ebook(&mut self, patron_id: u32, isbn: &str) -> Result<String, String> {
        // TODO: Process ebook download
        Ok(String::new())
    }
    
    fn get_patron_recommendations(&self, patron_id: u32) -> Vec<&Book> {
        // TODO: Generate book recommendations based on borrowing history
        vec![]
    }
    
    fn generate_analytics(&self) -> LibraryAnalytics {
        // TODO: Generate comprehensive analytics
        LibraryAnalytics::new()
    }
}

#[derive(Debug)]
struct LibraryAnalytics {
    total_books: usize,
    total_patrons: usize,
    books_borrowed_today: usize,
    most_popular_books: Vec<String>,
    busiest_patrons: Vec<u32>,
    overdue_rate: f64,
    average_loan_duration: f64,
}

impl LibraryAnalytics {
    fn new() -> Self {
        LibraryAnalytics {
            total_books: 0,
            total_patrons: 0,
            books_borrowed_today: 0,
            most_popular_books: vec![],
            busiest_patrons: vec![],
            overdue_rate: 0.0,
            average_loan_duration: 0.0,
        }
    }
    
    fn display_report(&self) -> String {
        // TODO: Format analytics report
        String::new()
    }
}

fn main() {
    println!("=== Advanced Library System ===");
    
    // Create library with advanced features
    let mut library = Library::new(String::from("University Library"));
    
    // Add physical and digital books
    let rust_book = Book::new(
        String::from("978-0-123456-78-9"),
        String::from("The Rust Programming Language"),
        String::from("Steve Klabnik"),
        String::from("Programming"),
        2018,
        2, // Only 2 physical copies
    );
    
    let digital_rust = DigitalResource {
        resource_type: ResourceType::EBook,
        file_format: String::from("PDF"),
        file_size_mb: 15,
        download_limit: Some(3),
        streaming_available: true,
    };
    
    library.add_book(rust_book);
    library.add_digital_resource(
        library.books["978-0-123456-78-9"].clone(),
        digital_rust,
    );
    
    // Register patrons
    let alice_id = library.register_patron(
        String::from("Alice"),
        String::from("alice@university.edu"),
        String::from("555-0123"),
    );
    
    // Test reservation system
    match library.reserve_book(alice_id, "978-0-123456-78-9") {
        Ok(msg) => println!("Reservation: {}", msg),
        Err(e) => println!("Reservation failed: {}", e),
    }
    
    // Test digital resources
    match library.download_ebook(alice_id, "978-0-123456-78-9") {
        Ok(msg) => println!("Download: {}", msg),
        Err(e) => println!("Download failed: {}", e),
    }
    
    // Generate analytics
    let analytics = library.generate_analytics();
    println!("\n{}", analytics.display_report());
}