🔨 Lesson 9.2: Building Your Project

import json
import os

FILENAME = "contacts.json"


class Contact:
    """Represents a single contact in the address book."""

    def __init__(self, name, email="", phone="", category="General"):
        self.name = name
        self.email = email
        self.phone = phone
        self.category = category

    def to_dict(self):
        return {
            "name": self.name,
            "email": self.email,
            "phone": self.phone,
            "category": self.category,
        }

    @classmethod
    def from_dict(cls, data):
        return cls(
            name=data["name"],
            email=data.get("email", ""),
            phone=data.get("phone", ""),
            category=data.get("category", "General"),
        )

    def __str__(self):
        return f"{self.name} | {self.email} | {self.phone} | {self.category}"


# ---- PHASE 1 TEST (delete after verifying) ----
if __name__ == "__main__":
    c1 = Contact("Alice", "alice@example.com", "555-0101", "Friend")
    c2 = Contact("Bob", "bob@work.com", "555-0202", "Work")
    print(c1)
    print(c2)

    # Test serialization round-trip
    d = c1.to_dict()
    print(f"Dict: {d}")
    c1_copy = Contact.from_dict(d)
    print(f"Restored: {c1_copy}")
    print("✅ Phase 1 passed!" if c1_copy.name == "Alice" else "❌ Bug!")

const fs = require("fs");
const readline = require("readline");

const FILENAME = "contacts.json";

class Contact {
    constructor(name, email = "", phone = "", category = "General") {
        this.name = name;
        this.email = email;
        this.phone = phone;
        this.category = category;
    }

    toJSON() {
        return {
            name: this.name,
            email: this.email,
            phone: this.phone,
            category: this.category,
        };
    }

    static fromJSON(data) {
        return new Contact(
            data.name,
            data.email || "",
            data.phone || "",
            data.category || "General"
        );
    }

    toString() {
        return `${this.name} | ${this.email} | ${this.phone} | ${this.category}`;
    }
}

// ---- PHASE 1 TEST (delete after verifying) ----
const c1 = new Contact("Alice", "alice@example.com", "555-0101", "Friend");
const c2 = new Contact("Bob", "bob@work.com", "555-0202", "Work");
console.log(c1.toString());
console.log(c2.toString());

const d = c1.toJSON();
console.log("Dict:", d);
const c1Copy = Contact.fromJSON(d);
console.log("Restored:", c1Copy.toString());
console.log(c1Copy.name === "Alice" ? "✅ Phase 1 passed!" : "❌ Bug!");

using System.Text.Json;
using System.Text.Json.Serialization;

const string Filename = "contacts.json";

// ---- Contact class ----
class Contact
{
    [JsonPropertyName("name")]
    public string Name { get; set; } = "";

    [JsonPropertyName("email")]
    public string Email { get; set; } = "";

    [JsonPropertyName("phone")]
    public string Phone { get; set; } = "";

    [JsonPropertyName("category")]
    public string Category { get; set; } = "General";

    public Contact() { }

    public Contact(string name, string email = "", string phone = "", string category = "General")
    {
        Name = name; Email = email; Phone = phone; Category = category;
    }

    public override string ToString()
        => $"{Name} | {Email} | {Phone} | {Category}";
}

// ---- PHASE 1 TEST (delete after verifying) ----
var c1 = new Contact("Alice", "alice@example.com", "555-0101", "Friend");
var c2 = new Contact("Bob", "bob@work.com", "555-0202", "Work");
Console.WriteLine(c1);
Console.WriteLine(c2);

string json = JsonSerializer.Serialize(c1);
Console.WriteLine($"JSON: {json}");
var c1Copy = JsonSerializer.Deserialize<Contact>(json)!;
Console.WriteLine($"Restored: {c1Copy}");
Console.WriteLine(c1Copy.Name == "Alice" ? "✅ Phase 1 passed!" : "❌ Bug!");

def save_contacts(contacts, filename=FILENAME):
    """Save a list of Contact objects to a JSON file."""
    data = [c.to_dict() for c in contacts]
    with open(filename, "w") as f:
        json.dump(data, f, indent=2)
    print(f"💾 Saved {len(contacts)} contacts to {filename}")


def load_contacts(filename=FILENAME):
    """Load contacts from a JSON file. Returns empty list if file missing."""
    if not os.path.exists(filename):
        return []
    try:
        with open(filename, "r") as f:
            data = json.load(f)
        contacts = [Contact.from_dict(d) for d in data]
        print(f"📂 Loaded {len(contacts)} contacts from {filename}")
        return contacts
    except (json.JSONDecodeError, KeyError) as e:
        print(f"⚠️ Error reading {filename}: {e}")
        print("Starting with empty contact list.")
        return []


# ---- PHASE 2 TEST ----
if __name__ == "__main__":
    test_contacts = [
        Contact("Alice", "alice@example.com", "555-0101", "Friend"),
        Contact("Bob", "bob@work.com", "555-0202", "Work"),
    ]
    save_contacts(test_contacts, "test_contacts.json")
    loaded = load_contacts("test_contacts.json")
    print(f"Loaded {len(loaded)} contacts")
    for c in loaded:
        print(f"  {c}")
    os.remove("test_contacts.json")  # Clean up test file
    print("✅ Phase 2 passed!" if len(loaded) == 2 else "❌ Bug!")

function saveContacts(contacts, filename = FILENAME) {
    const data = contacts.map(c => c.toJSON());
    fs.writeFileSync(filename, JSON.stringify(data, null, 2));
    console.log(`💾 Saved ${contacts.length} contacts to ${filename}`);
}

function loadContacts(filename = FILENAME) {
    if (!fs.existsSync(filename)) return [];
    try {
        const text = fs.readFileSync(filename, "utf-8");
        const data = JSON.parse(text);
        const contacts = data.map(d => Contact.fromJSON(d));
        console.log(`📂 Loaded ${contacts.length} contacts from ${filename}`);
        return contacts;
    } catch (err) {
        console.log(`⚠️ Error reading ${filename}: ${err.message}`);
        console.log("Starting with empty contact list.");
        return [];
    }
}

// ---- PHASE 2 TEST ----
const testContacts = [
    new Contact("Alice", "alice@example.com", "555-0101", "Friend"),
    new Contact("Bob", "bob@work.com", "555-0202", "Work"),
];
saveContacts(testContacts, "test_contacts.json");
const loaded = loadContacts("test_contacts.json");
console.log(`Loaded ${loaded.length} contacts`);
loaded.forEach(c => console.log(`  ${c}`));
fs.unlinkSync("test_contacts.json");
console.log(loaded.length === 2 ? "✅ Phase 2 passed!" : "❌ Bug!");

static void SaveContacts(List<Contact> contacts, string filename = Filename)
{
    var options = new JsonSerializerOptions { WriteIndented = true };
    string json = JsonSerializer.Serialize(contacts, options);
    File.WriteAllText(filename, json);
    Console.WriteLine($"💾 Saved {contacts.Count} contacts to {filename}");
}

static List<Contact> LoadContacts(string filename = Filename)
{
    if (!File.Exists(filename)) return new List<Contact>();
    try
    {
        string json = File.ReadAllText(filename);
        var contacts = JsonSerializer.Deserialize<List<Contact>>(json) ?? new List<Contact>();
        Console.WriteLine($"📂 Loaded {contacts.Count} contacts from {filename}");
        return contacts;
    }
    catch (Exception ex)
    {
        Console.WriteLine($"⚠️ Error reading {filename}: {ex.Message}");
        Console.WriteLine("Starting with empty contact list.");
        return new List<Contact>();
    }
}

// ---- PHASE 2 TEST ----
var testContacts = new List<Contact>
{
    new Contact("Alice", "alice@example.com", "555-0101", "Friend"),
    new Contact("Bob", "bob@work.com", "555-0202", "Work"),
};
SaveContacts(testContacts, "test_contacts.json");
var loadedList = LoadContacts("test_contacts.json");
Console.WriteLine($"Loaded {loadedList.Count} contacts");
foreach (var c in loadedList) Console.WriteLine($"  {c}");
File.Delete("test_contacts.json");
Console.WriteLine(loadedList.Count == 2 ? "✅ Phase 2 passed!" : "❌ Bug!");

def get_input(prompt, required=False):
    """Get user input with optional 'required' validation."""
    while True:
        value = input(prompt).strip()
        if required and not value:
            print("This field is required. Please try again.")
            continue
        return value


def add_contact(contacts):
    """Prompt user for contact info and add to the list."""
    print("\n--- Add New Contact ---")
    name = get_input("Name (required): ", required=True)
    email = get_input("Email: ")
    phone = get_input("Phone: ")
    category = get_input("Category [General]: ") or "General"

    contact = Contact(name, email, phone, category)
    contacts.append(contact)
    print(f"✅ Added: {contact}")


def display_contacts(contacts):
    """Display all contacts in a formatted table."""
    if not contacts:
        print("\n📭 No contacts yet.")
        return

    print(f"\n{'#':<4} {'Name':<20} {'Email':<25} {'Phone':<15} {'Category':<12}")
    print("-" * 76)
    for i, c in enumerate(contacts, 1):
        print(f"{i:<4} {c.name:<20} {c.email:<25} {c.phone:<15} {c.category:<12}")
    print(f"\nTotal: {len(contacts)} contacts")


def search_contacts(contacts):
    """Search contacts by name or category."""
    if not contacts:
        print("\n📭 No contacts to search.")
        return

    print("\nSearch by: (1) Name  (2) Category")
    choice = get_input("Choice: ")
    term = get_input("Search term: ").lower()

    if choice == "1":
        results = [c for c in contacts if term in c.name.lower()]
    elif choice == "2":
        results = [c for c in contacts if term in c.category.lower()]
    else:
        print("Invalid choice.")
        return

    if not results:
        print(f"No contacts found matching '{term}'.")
    else:
        print(f"\nFound {len(results)} result(s):")
        for c in results:
            print(f"  • {c}")


def edit_contact(contacts):
    """Find a contact by name and update their fields."""
    if not contacts:
        print("\n📭 No contacts to edit.")
        return

    name = get_input("Enter name of contact to edit: ").lower()
    found = [c for c in contacts if name in c.name.lower()]

    if not found:
        print(f"No contact found matching '{name}'.")
        return
    if len(found) > 1:
        print("Multiple matches:")
        for i, c in enumerate(found, 1):
            print(f"  {i}. {c}")
        idx = int(get_input("Which one? ")) - 1
        contact = found[idx]
    else:
        contact = found[0]

    print(f"Editing: {contact}")
    print("(Press Enter to keep current value)")
    contact.name = get_input(f"Name [{contact.name}]: ") or contact.name
    contact.email = get_input(f"Email [{contact.email}]: ") or contact.email
    contact.phone = get_input(f"Phone [{contact.phone}]: ") or contact.phone
    contact.category = get_input(f"Category [{contact.category}]: ") or contact.category
    print(f"✅ Updated: {contact}")


def delete_contact(contacts):
    """Find a contact by name and delete after confirmation."""
    if not contacts:
        print("\n📭 No contacts to delete.")
        return

    name = get_input("Enter name of contact to delete: ").lower()
    found = [c for c in contacts if name in c.name.lower()]

    if not found:
        print(f"No contact found matching '{name}'.")
        return

    contact = found[0]
    confirm = get_input(f"Delete '{contact.name}'? (y/n): ").lower()
    if confirm == "y":
        contacts.remove(contact)
        print(f"🗑️ Deleted: {contact.name}")
    else:
        print("Cancelled.")

// Readline helper for async prompts
const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
const prompt = (q) => new Promise((resolve) => rl.question(q, resolve));

async function getInput(question, required = false) {
    while (true) {
        const value = (await prompt(question)).trim();
        if (required && !value) {
            console.log("This field is required. Please try again.");
            continue;
        }
        return value;
    }
}

async function addContact(contacts) {
    console.log("\n--- Add New Contact ---");
    const name = await getInput("Name (required): ", true);
    const email = await getInput("Email: ");
    const phone = await getInput("Phone: ");
    const category = (await getInput("Category [General]: ")) || "General";

    const contact = new Contact(name, email, phone, category);
    contacts.push(contact);
    console.log(`✅ Added: ${contact}`);
}

function displayContacts(contacts) {
    if (contacts.length === 0) { console.log("\n📭 No contacts yet."); return; }

    console.log(`\n${"#".padEnd(4)} ${"Name".padEnd(20)} ${"Email".padEnd(25)} ${"Phone".padEnd(15)} Category`);
    console.log("-".repeat(76));
    contacts.forEach((c, i) => {
        console.log(`${String(i + 1).padEnd(4)} ${c.name.padEnd(20)} ${c.email.padEnd(25)} ${c.phone.padEnd(15)} ${c.category}`);
    });
    console.log(`\nTotal: ${contacts.length} contacts`);
}

async function searchContacts(contacts) {
    if (contacts.length === 0) { console.log("\n📭 No contacts to search."); return; }

    console.log("\nSearch by: (1) Name  (2) Category");
    const choice = await getInput("Choice: ");
    const term = (await getInput("Search term: ")).toLowerCase();

    let results;
    if (choice === "1") results = contacts.filter(c => c.name.toLowerCase().includes(term));
    else if (choice === "2") results = contacts.filter(c => c.category.toLowerCase().includes(term));
    else { console.log("Invalid choice."); return; }

    if (results.length === 0) console.log(`No contacts found matching '${term}'.`);
    else {
        console.log(`\nFound ${results.length} result(s):`);
        results.forEach(c => console.log(`  • ${c}`));
    }
}

async function editContact(contacts) {
    if (contacts.length === 0) { console.log("\n📭 No contacts to edit."); return; }

    const name = (await getInput("Enter name of contact to edit: ")).toLowerCase();
    const found = contacts.filter(c => c.name.toLowerCase().includes(name));
    if (found.length === 0) { console.log(`No contact found matching '${name}'.`); return; }

    const contact = found[0];
    console.log(`Editing: ${contact}`);
    console.log("(Press Enter to keep current value)");
    contact.name = (await getInput(`Name [${contact.name}]: `)) || contact.name;
    contact.email = (await getInput(`Email [${contact.email}]: `)) || contact.email;
    contact.phone = (await getInput(`Phone [${contact.phone}]: `)) || contact.phone;
    contact.category = (await getInput(`Category [${contact.category}]: `)) || contact.category;
    console.log(`✅ Updated: ${contact}`);
}

async function deleteContact(contacts) {
    if (contacts.length === 0) { console.log("\n📭 No contacts to delete."); return; }

    const name = (await getInput("Enter name of contact to delete: ")).toLowerCase();
    const idx = contacts.findIndex(c => c.name.toLowerCase().includes(name));
    if (idx === -1) { console.log(`No contact found matching '${name}'.`); return; }

    const confirm = (await getInput(`Delete '${contacts[idx].name}'? (y/n): `)).toLowerCase();
    if (confirm === "y") {
        console.log(`🗑️ Deleted: ${contacts[idx].name}`);
        contacts.splice(idx, 1);
    } else console.log("Cancelled.");
}

static string GetInput(string prompt, bool required = false)
{
    while (true)
    {
        Console.Write(prompt);
        string value = Console.ReadLine()?.Trim() ?? "";
        if (required && string.IsNullOrEmpty(value))
        { Console.WriteLine("This field is required. Please try again."); continue; }
        return value;
    }
}

static void AddContact(List<Contact> contacts)
{
    Console.WriteLine("\n--- Add New Contact ---");
    string name = GetInput("Name (required): ", true);
    string email = GetInput("Email: ");
    string phone = GetInput("Phone: ");
    string cat = GetInput("Category [General]: ");
    if (string.IsNullOrEmpty(cat)) cat = "General";

    var contact = new Contact(name, email, phone, cat);
    contacts.Add(contact);
    Console.WriteLine($"✅ Added: {contact}");
}

static void DisplayContacts(List<Contact> contacts)
{
    if (contacts.Count == 0) { Console.WriteLine("\n📭 No contacts yet."); return; }

    Console.WriteLine($"\n{"#",-4} {"Name",-20} {"Email",-25} {"Phone",-15} {"Category",-12}");
    Console.WriteLine(new string('-', 76));
    for (int i = 0; i < contacts.Count; i++)
    {
        var c = contacts[i];
        Console.WriteLine($"{i + 1,-4} {c.Name,-20} {c.Email,-25} {c.Phone,-15} {c.Category,-12}");
    }
    Console.WriteLine($"\nTotal: {contacts.Count} contacts");
}

static void SearchContacts(List<Contact> contacts)
{
    if (contacts.Count == 0) { Console.WriteLine("\n📭 No contacts to search."); return; }

    Console.WriteLine("\nSearch by: (1) Name  (2) Category");
    string choice = GetInput("Choice: ");
    string term = GetInput("Search term: ").ToLower();

    List<Contact> results = choice switch
    {
        "1" => contacts.Where(c => c.Name.ToLower().Contains(term)).ToList(),
        "2" => contacts.Where(c => c.Category.ToLower().Contains(term)).ToList(),
        _ => new List<Contact>()
    };

    if (results.Count == 0) Console.WriteLine($"No contacts found matching '{term}'.");
    else { Console.WriteLine($"\nFound {results.Count} result(s):"); results.ForEach(c => Console.WriteLine($"  • {c}")); }
}

static void EditContact(List<Contact> contacts)
{
    if (contacts.Count == 0) { Console.WriteLine("\n📭 No contacts to edit."); return; }
    string name = GetInput("Enter name of contact to edit: ").ToLower();
    var contact = contacts.FirstOrDefault(c => c.Name.ToLower().Contains(name));
    if (contact == null) { Console.WriteLine($"No contact found matching '{name}'."); return; }

    Console.WriteLine($"Editing: {contact}");
    Console.WriteLine("(Press Enter to keep current value)");
    string val;
    val = GetInput($"Name [{contact.Name}]: "); if (!string.IsNullOrEmpty(val)) contact.Name = val;
    val = GetInput($"Email [{contact.Email}]: "); if (!string.IsNullOrEmpty(val)) contact.Email = val;
    val = GetInput($"Phone [{contact.Phone}]: "); if (!string.IsNullOrEmpty(val)) contact.Phone = val;
    val = GetInput($"Category [{contact.Category}]: "); if (!string.IsNullOrEmpty(val)) contact.Category = val;
    Console.WriteLine($"✅ Updated: {contact}");
}

static void DeleteContact(List<Contact> contacts)
{
    if (contacts.Count == 0) { Console.WriteLine("\n📭 No contacts to delete."); return; }
    string name = GetInput("Enter name of contact to delete: ").ToLower();
    var contact = contacts.FirstOrDefault(c => c.Name.ToLower().Contains(name));
    if (contact == null) { Console.WriteLine($"No contact found matching '{name}'."); return; }

    string confirm = GetInput($"Delete '{contact.Name}'? (y/n): ").ToLower();
    if (confirm == "y") { contacts.Remove(contact); Console.WriteLine($"🗑️ Deleted: {contact.Name}"); }
    else Console.WriteLine("Cancelled.");
}

def show_menu():
    """Display the main menu."""
    print("\n╔══════════════════════════════╗")
    print("║     📒 Contact Manager       ║")
    print("╠══════════════════════════════╣")
    print("║  1. Add Contact              ║")
    print("║  2. View All Contacts        ║")
    print("║  3. Search Contacts          ║")
    print("║  4. Edit Contact             ║")
    print("║  5. Delete Contact           ║")
    print("║  6. Save & Quit              ║")
    print("╚══════════════════════════════╝")


def main():
    """Main program loop."""
    print("Welcome to Contact Manager!")
    contacts = load_contacts()

    while True:
        show_menu()
        choice = input("Enter choice (1-6): ").strip()

        if choice == "1":
            add_contact(contacts)
        elif choice == "2":
            display_contacts(contacts)
        elif choice == "3":
            search_contacts(contacts)
        elif choice == "4":
            edit_contact(contacts)
        elif choice == "5":
            delete_contact(contacts)
        elif choice == "6":
            save_contacts(contacts)
            print("Goodbye! 👋")
            break
        else:
            print("❌ Invalid choice. Please enter 1-6.")


if __name__ == "__main__":
    main()

function showMenu() {
    console.log("\n╔══════════════════════════════╗");
    console.log("║     📒 Contact Manager       ║");
    console.log("╠══════════════════════════════╣");
    console.log("║  1. Add Contact              ║");
    console.log("║  2. View All Contacts        ║");
    console.log("║  3. Search Contacts          ║");
    console.log("║  4. Edit Contact             ║");
    console.log("║  5. Delete Contact           ║");
    console.log("║  6. Save & Quit              ║");
    console.log("╚══════════════════════════════╝");
}

async function main() {
    console.log("Welcome to Contact Manager!");
    const contacts = loadContacts();

    while (true) {
        showMenu();
        const choice = (await prompt("Enter choice (1-6): ")).trim();

        if (choice === "1") await addContact(contacts);
        else if (choice === "2") displayContacts(contacts);
        else if (choice === "3") await searchContacts(contacts);
        else if (choice === "4") await editContact(contacts);
        else if (choice === "5") await deleteContact(contacts);
        else if (choice === "6") {
            saveContacts(contacts);
            console.log("Goodbye! 👋");
            rl.close();
            break;
        }
        else console.log("❌ Invalid choice. Please enter 1-6.");
    }
}

main();

static void ShowMenu()
{
    Console.WriteLine("\n╔══════════════════════════════╗");
    Console.WriteLine("║     📒 Contact Manager       ║");
    Console.WriteLine("╠══════════════════════════════╣");
    Console.WriteLine("║  1. Add Contact              ║");
    Console.WriteLine("║  2. View All Contacts        ║");
    Console.WriteLine("║  3. Search Contacts          ║");
    Console.WriteLine("║  4. Edit Contact             ║");
    Console.WriteLine("║  5. Delete Contact           ║");
    Console.WriteLine("║  6. Save & Quit              ║");
    Console.WriteLine("╚══════════════════════════════╝");
}

// ---- Main program ----
Console.WriteLine("Welcome to Contact Manager!");
var contacts = LoadContacts();

while (true)
{
    ShowMenu();
    string choice = GetInput("Enter choice (1-6): ");

    switch (choice)
    {
        case "1": AddContact(contacts); break;
        case "2": DisplayContacts(contacts); break;
        case "3": SearchContacts(contacts); break;
        case "4": EditContact(contacts); break;
        case "5": DeleteContact(contacts); break;
        case "6":
            SaveContacts(contacts);
            Console.WriteLine("Goodbye! 👋");
            return;
        default:
            Console.WriteLine("❌ Invalid choice. Please enter 1-6.");
            break;
    }
}

# Wrap main() to handle Ctrl+C gracefully:
if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        print("\n\n⚠️ Interrupted. Saving contacts before exit...")
        # Note: contacts isn't accessible here in this simple version.
        # In a production app, you'd store contacts at module level
        # or use a class-based approach.
        print("Goodbye! 👋")

# Add to edit_contact() — handle invalid index:
    if len(found) > 1:
        print("Multiple matches:")
        for i, c in enumerate(found, 1):
            print(f"  {i}. {c}")
        try:
            idx = int(get_input("Which one? ")) - 1
            if idx < 0 or idx >= len(found):
                print("Invalid selection.")
                return
            contact = found[idx]
        except ValueError:
            print("Please enter a number.")
            return

# Add a pause function for better UX:
def pause():
    input("\nPress Enter to continue...")

// Handle process signals for graceful exit:
process.on("SIGINT", () => {
    console.log("\n\n⚠️ Interrupted. Goodbye! 👋");
    rl.close();
    process.exit(0);
});

// Add a pause function for better UX:
async function pause() {
    await prompt("\nPress Enter to continue...");
}

// After display or search operations, add:
// await pause();

// Handle Ctrl+C gracefully:
Console.CancelKeyPress += (sender, e) =>
{
    e.Cancel = true;  // Prevent immediate termination
    Console.WriteLine("\n\n⚠️ Interrupted. Saving contacts before exit...");
    SaveContacts(contacts);
    Console.WriteLine("Goodbye! 👋");
    Environment.Exit(0);
};

// Add a pause method:
static void Pause()
{
    Console.Write("\nPress Enter to continue...");
    Console.ReadLine();
}