تعلم C#
من الصفر للاحتراف

// أول برنامج C# — Hello World (أسلوب Top-Level في C# 9+)
Console.WriteLine("مرحباً بالعالم من Yahya.DEV! 🚀");
Console.WriteLine($"تاريخ اليوم: {DateTime.Now:dd/MM/yyyy}");

// أو بالأسلوب الكلاسيكي:
namespace MyFirstApp;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("مرحباً بالعالم!");
    }
}

# تثبيت .NET 9 SDK أولاً من: https://dotnet.microsoft.com/download

# إنشاء مشروع Console
dotnet new console -n MyProject

# الدخول للمجلد
cd MyProject

# تشغيل البرنامج
dotnet run

// Value Type — كل متغير له نسخته الخاصة على Stack
int a = 10;
int b = a;     // نسخة جديدة كاملة
b = 99;
Console.WriteLine(a); // 10 — لم يتأثر a أبداً

// Reference Type — المتغيران يشيران لنفس الكائن في Heap
var arr1 = new int[] { 1, 2, 3 };
var arr2 = arr1;   // arr2 يشير لنفس المصفوفة، لا نسخة جديدة
arr2[0] = 99;
Console.WriteLine(arr1[0]); // 99 — تأثّر arr1 أيضاً!

// ==============================
// 1. أنواع الأعداد الصحيحة
// ==============================
int     age    = 25;          // -2.1B إلى 2.1B   (32-bit)
long    pop    = 8_000_000_000L; // أعداد كبيرة جداً  (64-bit)
short   x      = 1000;        // -32K إلى 32K      (16-bit)
byte    b      = 255;         // 0 إلى 255          (8-bit)

// ==============================
// 2. أنواع الأعداد العشرية
// ==============================
double  pi     = 3.14159265; // دقة عالية          (64-bit)
float   temp   = 36.6f;      // دقة متوسطة         (32-bit)
decimal price  = 99.99m;     // للمال والدقة القصوى (128-bit)

// ==============================
// 3. النصوص والحروف
// ==============================
string  name   = "Yahya";
char    grade  = 'A';        // حرف واحد فقط — single quotes

// ==============================
// 4. المنطق Boolean
// ==============================
bool    isActive = true;
bool    isEmpty  = false;

// ==============================
// 5. var — استنتاج النوع تلقائياً
// ==============================
var city    = "Riyadh";   // string  (يحدده المترجم)
var count   = 42;         // int
var ratio   = 3.14;       // double

// ==============================
// 6. الثوابت const
// ==============================
const double PI = 3.14159265358979;
const string APP_NAME = "Yahya.DEV";

// ==============================
// 7. String Interpolation (C# 6+)
// ==============================
string msg = $"مرحباً {name}، عمرك {age} سنة";
Console.WriteLine(msg);

int score = 85;

// ==============================
// if / else if / else
// ==============================
if (score >= 90)
    Console.WriteLine("ممتاز 🌟");
else if (score >= 75)
    Console.WriteLine("جيد جداً 👍");
else if (score >= 60)
    Console.WriteLine("جيد");
else
    Console.WriteLine("راجع المادة");

// ==============================
// Ternary Operator ?: (مختصر)
// ==============================
string result = score >= 60 ? "ناجح ✅" : "راسب ❌";
Console.WriteLine(result);

// ==============================
// Switch Expression (C# 8+ الحديث)
// ==============================
string grade = score switch
{
    >= 90 => "A",
    >= 80 => "B",
    >= 70 => "C",
    >= 60 => "D",
    _      => "F"   // _ = default
};
Console.WriteLine($"التقدير: {grade}");

// ==============================
// Null Coalescing ?? و ?.
// ==============================
string? userName = null;
string  display  = userName ?? "زائر";       // إذا null → "زائر"
int?    len      = userName?.Length;         // إذا null → null (لا crash)

// ==============================
// 1. for — عدد معروف مسبقاً
// ==============================
for (int i = 1; i <= 5; i++)
    Console.WriteLine($"رقم {i}");

// ==============================
// 2. while — شرط غير معروف
// ==============================
int count = 0;
while (count < 3)
{
    Console.WriteLine($"count = {count}");
    count++;
}

// ==============================
// 3. do-while — ينفّذ مرة على الأقل
// ==============================
int x = 10;
do
{
    Console.WriteLine($"x = {x}");
    x--;
} while (x > 8);

// ==============================
// 4. foreach — للمجموعات
// ==============================
string[] langs = { "C#", "Python", "JavaScript" };
foreach (string lang in langs)
    Console.WriteLine($"لغة: {lang}");

// break و continue
for (int i = 0; i < 10; i++)
{
    if (i == 3) continue;  // تخطّ 3
    if (i == 6) break;     // أوقف عند 6
    Console.Write($"{i} ");
}

// ==============================
// 1D Arrays
// ==============================
int[] numbers  = { 10, 20, 30, 40 };
int[] zeros    = new int[5];    // [0,0,0,0,0]
int[] nums12   = [1, 2, 3];    // C# 12 Collection Expression

// الوصول والتعديل
Console.WriteLine(numbers[0]);   // 10
numbers[1] = 99;
Console.WriteLine(numbers.Length); // 4

// ==============================
// 2D Arrays
// ==============================
int[,] matrix = {
    { 1, 2, 3 },
    { 4, 5, 6 }
};
Console.WriteLine(matrix[1, 2]);  // 6

// ==============================
// Array Methods
// ==============================
int[] scores = { 85, 92, 71, 98, 65 };
Array.Sort(scores);
Array.Reverse(scores);
Console.WriteLine(string.Join(", ", scores));

// Index من النهاية (C# 8+)
Console.WriteLine(scores[^1]);   // آخر عنصر

// Range Slicing
int[] slice = scores[1..3];       // عناصر من 1 إلى 2

// ==============================
// دالة أساسية
// ==============================
static void Greet(string name)
{
    Console.WriteLine($"أهلاً {name}!");
}

// ==============================
// دالة تُرجع قيمة
// ==============================
static int Add(int a, int b) => a + b;  // Expression Body (مختصر)

// ==============================
// قيم افتراضية (Optional Parameters)
// ==============================
static string CreateUser(string name, int age = 18, string role = "user")
    => $"[{role}] {name} ({age})";

// ==============================
// ref & out
// ==============================
static void Swap(ref int a, ref int b)
{
    (a, b) = (b, a);  // Tuple Deconstruction
}

static bool TryParse(string input, out int result)
{
    return int.TryParse(input, out result);
}

// ==============================
// params — عدد متغير من الوسيط
// ==============================
static int Sum(params int[] nums) => nums.Sum();

// الاستخدام
Greet("Yahya");
Console.WriteLine(Add(5, 3));          // 8
Console.WriteLine(CreateUser("Ali"));   // [user] Ali (18)
Console.WriteLine(Sum(1, 2, 3, 4, 5)); // 15

// تعريف الكلاس
public class Developer
{
    // Properties (الخصائص)
    public string Name    { get; set; }
    public string Brand   { get; set; } = "Yahya.DEV";
    public int    YearsXP { get; private set; }

    // Field
    private string[] _skills;

    // Constructor الأساسي
    public Developer(string name, int years, string[] skills)
    {
        Name    = name;
        YearsXP = years;
        _skills  = skills;
    }

    // Primary Constructor (C# 12)
    // public Developer(string name) => Name = name;

    // Method
    public void Introduce()
    {
        Console.WriteLine($"🚀 {Name} | {Brand}");
        Console.WriteLine($"   خبرة: {YearsXP} سنوات");
        Console.WriteLine($"   مهارات: {string.Join(", ", _skills)}");
    }

    // Override ToString
    public override string ToString()
        => $"Developer: {Name} @ {Brand}";

    // Static Method
    public static Developer CreateJunior(string name)
        => new(name, 1, ["HTML", "CSS"]);
}

// الاستخدام
var dev = new Developer("Yahya", 3, ["C#", "Laravel", "JS"]);
dev.Introduce();
Console.WriteLine(dev);  // ToString

// Object Initializer Syntax
var dev2 = new Developer("Ali", 2, ["Python"])
{
    Brand = "AliDev"
};

// ==============================
// الكلاس الأساسي (Base Class)
// ==============================
public abstract class Animal
{
    public string Name   { get; init; }
    public int    Age    { get; init; }

    protected Animal(string name, int age)
        => (Name, Age) = (name, age);

    // abstract: يجب على الـ SubClass تنفيذها
    public abstract void Speak();

    // virtual: يمكن للـ SubClass تجاوزها
    public virtual string Describe()
        => $"{Name} ({Age} سنوات)";
}

// ==============================
// Sub Classes
// ==============================
public class Dog : Animal
{
    public string Breed { get; init; }

    public Dog(string name, int age, string breed)
        : base(name, age) => Breed = breed;

    public override void Speak()
        => Console.WriteLine($"{Name}: Woof! 🐕");

    public override string Describe()
        => $"{base.Describe()} — {Breed}";
}

public class Cat : Animal
{
    public Cat(string name, int age) : base(name, age) { }
    public override void Speak()
        => Console.WriteLine($"{Name}: Meow! 🐈");
}

// ==============================
// Polymorphism
// ==============================
Animal[] animals =
[
    new Dog("Rex", 3, "Husky"),
    new Cat("Luna", 2),
    new Dog("Buddy", 5, "Lab")
];

foreach (var a in animals)
{
    a.Speak();
    Console.WriteLine($"  ↳ {a.Describe()}");
}

// Interface = عقد: "من ينفّذني يجب أن يوفّر هذه الدوال"
public interface IPaymentGateway
{
    bool  ProcessPayment(decimal amount);
    string Name { get; }

    // Default Implementation (C# 8+)
    void LogTransaction(decimal amount)
        => Console.WriteLine($"[{Name}] معالجة: {amount:C}");
}

public interface IRefundable
{
    bool Refund(decimal amount);
}

// Class تنفّذ واجهتين
public class StripeGateway : IPaymentGateway, IRefundable
{
    public string Name => "Stripe";

    public bool ProcessPayment(decimal amount)
    {
        Console.WriteLine($"Stripe: دفع {amount:C} ✅");
        return true;
    }

    public bool Refund(decimal amount)
    {
        Console.WriteLine($"Stripe: استرداد {amount:C} 🔄");
        return true;
    }
}

// Dependency Injection مثال
void Checkout(IPaymentGateway gateway, decimal total)
{
    gateway.LogTransaction(total);
    gateway.ProcessPayment(total);
}

var stripe = new StripeGateway();
Checkout(stripe, 99.99m);

// Generic Method
static T GetMax<T>(T a, T b) where T : IComparable<T>
    => a.CompareTo(b) > 0 ? a : b;

Console.WriteLine(GetMax(10, 25));          // 25
Console.WriteLine(GetMax("Apple", "Mango")); // Mango

// Generic Class — Stack بسيط
public class SimpleStack<T>
{
    private List<T> _items = [];

    public void Push(T item) => _items.Add(item);

    public T Pop()
    {
        if (_items.Count == 0)
            throw new InvalidOperationException("Stack فارغ!");
        var item = _items[^1];
        _items.RemoveAt(_items.Count - 1);
        return item;
    }

    public int Count => _items.Count;
}

var stack = new SimpleStack<int>();
stack.Push(1); stack.Push(2); stack.Push(3);
Console.WriteLine(stack.Pop());  // 3

// ==============================
// List<T> — المصفوفة الديناميكية
// ==============================
var names = new List<string> { "Yahya", "Ali", "Sara" };
names.Add("Omar");
names.Remove("Ali");
names.Sort();
Console.WriteLine(string.Join(", ", names));

// ==============================
// Dictionary<K, V> — جدول البحث
// ==============================
var scores = new Dictionary<string, int>
{
    ["C#"]         = 95,
    ["JavaScript"] = 88,
    ["Python"]     = 82
};

scores["Go"] = 75;  // إضافة جديد

foreach (var (lang, score) in scores)
    Console.WriteLine($"{lang}: {score}");

// ==============================
// HashSet<T> — بدون تكرار
// ==============================
var tags = new HashSet<string> { "dev", "ui", "dev" };
tags.Add("ux");
Console.WriteLine(tags.Count);  // 3 (dev لا يتكرر)

// ==============================
// Queue<T> — FIFO (أول داخل أول خارج)
// ==============================
var queue = new Queue<string>();
queue.Enqueue("Request 1");
queue.Enqueue("Request 2");
Console.WriteLine(queue.Dequeue());  // "Request 1"

record Product(string Name, decimal Price, string Category);

var products = new List<Product>
{
    new("Laptop",   3500m, "Tech"),
    new("Mouse",    150m,  "Tech"),
    new("Desk",     800m,  "Furniture"),
    new("Chair",    1200m, "Furniture"),
    new("Keyboard", 250m,  "Tech")
};

// ==============================
// Method Syntax (الأكثر شيوعاً)
// ==============================

// Where — التصفية
var expensive = products
    .Where(p => p.Price > 500m)
    .OrderBy(p => p.Price);

// Select — التحويل
var names = products.Select(p => p.Name.ToUpper());

// GroupBy — التجميع
var byCategory = products
    .GroupBy(p => p.Category)
    .Select(g => new
    {
        Category = g.Key,
        Count    = g.Count(),
        AvgPrice = g.Average(p => p.Price)
    });

foreach (var cat in byCategory)
    Console.WriteLine($"{cat.Category}: {cat.Count} منتج، متوسط السعر {cat.AvgPrice:C}");

// Aggregate Functions
decimal total   = products.Sum(p => p.Price);
decimal maxPrice = products.Max(p => p.Price);
var     cheapest = products.MinBy(p => p.Price)!;

// ==============================
// Query Syntax (شبيه SQL)
// ==============================
var techItems =
    from p in products
    where p.Category == "Tech"
    orderby p.Price descending
    select $"{p.Name} — {p.Price:C}";

foreach (var item in techItems)
    Console.WriteLine(item);

// ==============================
// 1. Delegate — نوع يمثل دالة
// ==============================
delegate int MathOp(int a, int b);

MathOp add      = (a, b) => a + b;
MathOp multiply = (a, b) => a * b;

Console.WriteLine(add(5, 3));       // 8
Console.WriteLine(multiply(5, 3)); // 15

// ==============================
// 2. Func<T, TResult> (مدمج)
// ==============================
Func<int, int, int>  power  = (base_, exp) => (int)Math.Pow(base_, exp);
Func<string, string> upper  = s => s.ToUpper();
Action<string>        log    = msg => Console.WriteLine($"[LOG] {msg}");
Predicate<int>        isEven = n => n % 2 == 0;

Console.WriteLine(power(2, 10));  // 1024
log("تم تسجيل الدخول");
Console.WriteLine(isEven(7));     // False

// ==============================
// 3. Events — نظام الأحداث
// ==============================
public class Button
{
    public event Action<string>? Clicked;

    public void Click(string label)
    {
        Console.WriteLine($"تم النقر على: {label}");
        Clicked?.Invoke(label);
    }
}

var btn = new Button();
btn.Clicked += label => Console.WriteLine($"  → Handler 1: {label}");
btn.Clicked += label => Console.WriteLine($"  → Handler 2: تسجيل");
btn.Click("حفظ");

using System.Net.Http;
using System.Text.Json;

// ==============================
// 1. دالة async أساسية
// ==============================
static async Task<string> FetchDataAsync(string url)
{
    using var client = new HttpClient();
    Console.WriteLine($"جاري الجلب: {url}");
    string data = await client.GetStringAsync(url);
    return data[..Math.Min(100, data.Length)]; // أول 100 حرف
}

// ==============================
// 2. تشغيل عمليات بالتوازي
// ==============================
static async Task RunParallelAsync()
{
    var task1 = SimulateWorkAsync("DB Query",   1000);
    var task2 = SimulateWorkAsync("API Call",   1500);
    var task3 = SimulateWorkAsync("File Read",  800);

    // ينتهي الثلاثة معاً (لا تنتظر واحداً تلو الآخر)
    await Task.WhenAll(task1, task2, task3);
    Console.WriteLine("✅ كل العمليات اكتملت!");
}

static async Task<string> SimulateWorkAsync(string name, int ms)
{
    Console.WriteLine($"بدأ: {name}");
    await Task.Delay(ms);
    Console.WriteLine($"انتهى: {name}");
    return name;
}

// ==============================
// 3. try/catch مع async
// ==============================
static async Task<bool> SafeFetchAsync(string url)
{
    try
    {
        var result = await FetchDataAsync(url);
        Console.WriteLine($"نجح: {result.Length} حرف");
        return true;
    }
    catch (HttpRequestException ex)
    {
        Console.WriteLine($"خطأ شبكة: {ex.Message}");
        return false;
    }
}

// تشغيل
await RunParallelAsync();

// ==============================
// 1. try / catch / finally
// ==============================
try
{
    int[] arr = [1, 2, 3];
    Console.WriteLine(arr[10]); // IndexOutOfRangeException
}
catch (IndexOutOfRangeException ex)
{
    Console.WriteLine($"خطأ الفهرس: {ex.Message}");
}
catch (Exception ex) when (ex.Message.Contains("network"))
{
    Console.WriteLine("خطأ شبكة محدد");
}
catch (Exception ex)
{
    Console.WriteLine($"خطأ عام: {ex.GetType().Name}");
}
finally
{
    Console.WriteLine("✅ ينفّذ دائماً — للتنظيف");
}

// ==============================
// 2. Custom Exception
// ==============================
public class ValidationException : Exception
{
    public string Field { get; }

    public ValidationException(string field, string message)
        : base(message)
    {
        Field = field;
    }
}

static void ValidateAge(int age)
{
    if (age < 0 || age > 150)
        throw new ValidationException("age", $"العمر {age} غير صحيح");
}

try { ValidateAge(-5); }
catch (ValidationException ex)
{
    Console.WriteLine($"خطأ التحقق في [{ex.Field}]: {ex.Message}");
}

// ==============================
// Type Pattern
// ==============================
static string Describe(object obj) => obj switch
{
    int    n  when n > 0 => $"عدد موجب: {n}",
    int    n              => $"عدد: {n}",
    string { Length: 0 } => "نص فارغ",
    string s              => $"نص: {s}",
    null                   => "null",
    _                      => $"نوع: {obj.GetType().Name}"
};

Console.WriteLine(Describe(42));     // عدد موجب: 42
Console.WriteLine(Describe("Dev"));  // نص: Dev

// ==============================
// Property Pattern
// ==============================
record Order(decimal Amount, string Status, bool IsPremium);

static decimal CalcDiscount(Order o) => o switch
{
    { IsPremium: true, Amount: > 1000m } => o.Amount * 0.20m,
    { IsPremium: true }                   => o.Amount * 0.10m,
    { Status: "VIP", Amount: > 500m }   => o.Amount * 0.15m,
    _                                       => 0m
};

var order = new Order(1500m, "Regular", true);
Console.WriteLine($"الخصم: {CalcDiscount(order):C}"); // 300.00

// ==============================
// List Pattern (C# 11)
// ==============================
static string CheckList(int[] arr) => arr switch
{
    []              => "فارغ",
    [var single]   => $"عنصر واحد: {single}",
    [var first, ..] => $"يبدأ بـ: {first}"
};

Console.WriteLine(CheckList([]));           // فارغ
Console.WriteLine(CheckList([7]));          // عنصر واحد: 7
Console.WriteLine(CheckList([1, 2, 3]));   // يبدأ بـ: 1

// ==============================
// Record (Positional) — أبسط طريقة
// ==============================
record Point(double X, double Y);

var p1 = new Point(3.0, 4.0);
var p2 = new Point(3.0, 4.0);
var p3 = p1 with { X = 10.0 };     // نسخة معدّلة

Console.WriteLine(p1 == p2);        // True  (مقارنة بالقيمة)
Console.WriteLine(p1);              // Point { X = 3, Y = 4 }
Console.WriteLine(p3);              // Point { X = 10, Y = 4 }

// ==============================
// Record Class (مفصّل)
// ==============================
public record User
{
    public required string Id    { get; init; }
    public required string Name  { get; init; }
    public          string Email { get; init; } = string.Empty;

    // يمكن إضافة methods
    public string GetDisplayName() => $"@{Name.ToLower()}";
}

var user = new User { Id = "1", Name = "Yahya", Email = "y@dev.com" };
Console.WriteLine(user.GetDisplayName());  // @yahya

// user.Name = "X"; ← خطأ! init-only

// ==============================
// Record Struct (C# 10) — Value Type
// ==============================
readonly record struct Color(byte R, byte G, byte B)
{
    public string Hex => $"#{R:X2}{G:X2}{B:X2}";
}

var purple = new Color(124, 58, 237);
Console.WriteLine(purple.Hex);  // #7C3AED

// في .csproj: <Nullable>enable</Nullable>

string  name     = "Yahya";   // لا يقبل null
string? nickname = null;     // يقبل null (? = nullable)

// Null Conditional ?.
int? len = nickname?.Length;  // null بدل crash

// Null Coalescing ??
string display = nickname ?? "مجهول";

// Null Coalescing Assignment ??=
nickname ??= "Dev";  // يُعيّن فقط إذا كان null

// Null Forgiving ! (استخدم بحذر)
string guaranteed = nickname!;  // أنت مسؤول

// ==============================
// Pattern Matching مع Null
// ==============================
static void Process(string? value)
{
    if (value is null)
    {
        Console.WriteLine("القيمة null");
        return;
    }

    // هنا المترجم يعرف أن value ليست null
    Console.WriteLine(value.ToUpper());
}

// ==============================
// Required Properties (C# 11)
// ==============================
public class Config
{
    public required string ConnectionString { get; init; }
    public required string AppName          { get; init; }
    public          int    Timeout          { get; init; } = 30;
}

// خطأ وقت الترجمة إذا لم تُعيّن required:
var cfg = new Config
{
    ConnectionString = "Server=.;...",
    AppName          = "Yahya.DEV"
};

// ==============================
// 1. params Collections (C# 13)
// ==============================
// قبل C#13: فقط params int[] arr
// الآن يدعم List, Span, IEnumerable وغيرها
static int Sum(params IEnumerable<int> numbers)
    => numbers.Sum();

Console.WriteLine(Sum(1, 2, 3, 4, 5));      // 15
Console.WriteLine(Sum([10, 20, 30]));       // 60

// ==============================
// 2. New Lock Type (C# 13)
// ==============================
// أفضل من lock(object) القديم
var lockObj = new System.Threading.Lock();

lock (lockObj)
{
    Console.WriteLine("عملية thread-safe ✅");
}

// ==============================
// 3. Escape Sequence \e (C# 13)
// ==============================
// \e = ESC character (ASCII 27) للـ terminal colors
Console.WriteLine("\e[32mنص أخضر في الـ terminal\e[0m");

// ==============================
// 4. Primary Constructors (C# 12 - شائع جداً)
// ==============================
public class ApiService(HttpClient httpClient, string baseUrl)
{
    public async Task<string> GetAsync(string endpoint)
        => await httpClient.GetStringAsync($"{baseUrl}/{endpoint}");
}

// ==============================
// 5. Collection Expressions (C# 12)
// ==============================
int[]            arr   = [1, 2, 3];
List<string>     list  = ["a", "b"];
Span<int>         span  = [10, 20];

// Spread operator ..
int[] combined = [..arr, 4, 5, 6]; // [1,2,3,4,5,6]

// ==============================
// 6. Inline Arrays (C# 12) — للأداء
// ==============================
[System.Runtime.CompilerServices.InlineArray(10)]
public struct Buffer10
{
    private int _element;  // 10 int على الـ stack
}

namespace TaskManagerConsole.Models;

public enum TaskPriority { Low, Medium, High }

// Record — نوع غير قابل للتعديل (Immutable)، مثالي لتمثيل بيانات ثابتة
public record TaskItem(
    int Id,
    string Title,
    string Description,
    TaskPriority Priority,
    bool IsDone = false
);

namespace TaskManagerConsole.Repositories;

using TaskManagerConsole.Models;

public interface ITaskRepository
{
    List<TaskItem> GetAll();
    TaskItem? GetById(int id);
    void Add(TaskItem task);
    void MarkDone(int id);
    void Delete(int id);
}

namespace TaskManagerConsole.Repositories;

using System.Text.Json;
using TaskManagerConsole.Models;

public class JsonTaskRepository : ITaskRepository
{
    private readonly string _path;
    private List<TaskItem> _tasks;

    public JsonTaskRepository(string path)
    {
        _path = path;
        _tasks = File.Exists(path)
            ? JsonSerializer.Deserialize<List<TaskItem>>(File.ReadAllText(path)) ?? new()
            : new List<TaskItem>();
    }

    public List<TaskItem> GetAll() => _tasks;

    public TaskItem? GetById(int id) =>
        _tasks.FirstOrDefault(t => t.Id == id);

    public void Add(TaskItem task) { _tasks.Add(task); Save(); }

    public void MarkDone(int id)
    {
        var index = _tasks.FindIndex(t => t.Id == id);
        if (index >= 0)
            _tasks[index] = _tasks[index] with { IsDone = true }; // نسخة معدَّلة، الأصل ثابت
        Save();
    }

    public void Delete(int id) { _tasks.RemoveAll(t => t.Id == id); Save(); }

    private void Save() =>
        File.WriteAllText(_path,
            JsonSerializer.Serialize(_tasks, new JsonSerializerOptions { WriteIndented = true }));
}

namespace TaskManagerConsole.Services;

using TaskManagerConsole.Models;
using TaskManagerConsole.Repositories;

public class TaskService
{
    private readonly ITaskRepository _repo;

    public TaskService(ITaskRepository repo) => _repo = repo;

    public TaskItem CreateTask(string title, string description, TaskPriority priority)
    {
        if (string.IsNullOrWhiteSpace(title) || title.Length < 3)
            throw new ArgumentException("العنوان يجب أن يكون 3 أحرف على الأقل");

        var tasks = _repo.GetAll();
        var nextId = tasks.Count > 0 ? tasks.Max(t => t.Id) + 1 : 1;

        var task = new TaskItem(nextId, title, description, priority);
        _repo.Add(task);
        return task;
    }

    // LINQ — ترتيب حسب الأولوية تنازلياً
    public List<TaskItem> GetSortedByPriority() =>
        _repo.GetAll()
             .OrderByDescending(t => t.Priority)
             .ThenBy(t => t.IsDone)
             .ToList();
}

using TaskManagerConsole.Models;
using TaskManagerConsole.Repositories;
using TaskManagerConsole.Services;

ITaskRepository repo = new JsonTaskRepository("tasks.json");
var service = new TaskService(repo);

while (true)
{
    Console.WriteLine("\n1) إضافة  2) عرض الكل  3) إكمال  4) حذف  0) خروج");
    var choice = Console.ReadLine();

    try
    {
        switch (choice)
        {
            case "1":
                Console.Write("العنوان: ");
                var title = Console.ReadLine() ?? "";
                service.CreateTask(title, "", TaskPriority.Medium);
                Console.WriteLine("تمت الإضافة ✓");
                break;

            case "2":
                foreach (var t in service.GetSortedByPriority())
                    Console.WriteLine($"[{t.Id}] {t.Title} — {t.Priority} {(t.IsDone ? "✓" : "…")}");
                break;

            case "0": return;
        }
    }
    catch (ArgumentException ex)
    {
        Console.WriteLine($"خطأ: {ex.Message}");
    }
}