// ── نمونه اتصال C#‎ (.NET 6+) — درگاه پرداخت اعتباری راتک‌لند ────────────────
using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;

public class RatekCreditGatewayClient
{
    private static readonly HttpClient Http = new() { Timeout = TimeSpan.FromSeconds(30) };
    private const string BaseUrl = "https://your-rateklend-host.example.com";

    private readonly string _clientId, _clientSecret, _username, _password;

    public RatekCreditGatewayClient(string clientId, string clientSecret, string username, string password)
        => (_clientId, _clientSecret, _username, _password) = (clientId, clientSecret, username, password);

    // ۱) دریافت Access Token
    public async Task<string> GetAccessTokenAsync()
    {
        var basic = Convert.ToBase64String(Encoding.UTF8.GetBytes($"{_clientId}:{_clientSecret}"));
        var req = new HttpRequestMessage(HttpMethod.Post, $"{BaseUrl}/api/v1/auth/token");
        req.Headers.Authorization = new AuthenticationHeaderValue("Basic", basic);
        req.Content = new FormUrlEncodedContent(new Dictionary<string, string>
        {
            ["grant_type"] = "password",
            ["scope"] = "credit-gateway",
            ["username"] = _username,
            ["password"] = _password,
        });
        var res = await Http.SendAsync(req);
        var json = JsonDocument.Parse(await res.Content.ReadAsStringAsync());
        res.EnsureSuccessStatusCode();
        return json.RootElement.GetProperty("data").GetProperty("access_token").GetString()!;
    }

    // ۲) بررسی امکان پرداخت
    public async Task<JsonElement> CheckEligibilityAsync(string jwt, long amountIrr)
    {
        var req = new HttpRequestMessage(HttpMethod.Get,
            $"{BaseUrl}/api/v1/credit-offers/eligibility?amount={amountIrr}");
        req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", jwt);
        var res = await Http.SendAsync(req);
        var json = JsonDocument.Parse(await res.Content.ReadAsStringAsync());
        return json.RootElement.GetProperty("data").Clone();
    }

    // ۳) ایجاد جلسهٔ پرداخت
    public async Task<JsonElement> InitiatePaymentAsync(
        string jwt, long amountIrr, string mobile, string callbackUrl, string merchantOrderId)
    {
        var payload = new
        {
            amount = amountIrr,
            discountAmount = 0,
            otherSourceAmount = 0,
            mobile,
            callbackUrl,
            merchantOrderId,
            orderLines = new[]
            {
                new
                {
                    lineId = 1,
                    shippingIncluded = true,
                    taxIncluded = true,
                    shippingFee = 0,
                    tax = 0,
                    lineTotal = amountIrr,
                    items = new[]
                    {
                        new { id = 101, name = "سفارش", category = "general",
                              count = 1, amount = amountIrr, feeCategory = 100 },
                    },
                },
            },
        };
        return await PostJsonAsync(jwt, "initiate", payload);
    }

    // ۴) confirm / finalize / reverse / void
    public Task<JsonElement> ConfirmAsync(string jwt, string reference) =>
        PostJsonAsync(jwt, "confirm", new { paymentReference = reference });

    public Task<JsonElement> FinalizeAsync(string jwt, string reference) =>
        PostJsonAsync(jwt, "finalize", new { paymentReference = reference });

    public Task<JsonElement> VoidAsync(string jwt, string reference) =>
        PostJsonAsync(jwt, "void", new { paymentReference = reference });

    // ۵) استعلام وضعیت
    public async Task<JsonElement> GetStatusAsync(string jwt, string reference)
    {
        var req = new HttpRequestMessage(HttpMethod.Get,
            $"{BaseUrl}/api/v1/credit-payments/status?paymentReference={Uri.EscapeDataString(reference)}");
        req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", jwt);
        var res = await Http.SendAsync(req);
        var json = JsonDocument.Parse(await res.Content.ReadAsStringAsync());
        return json.RootElement.GetProperty("data").Clone();
    }

    private async Task<JsonElement> PostJsonAsync(string jwt, string action, object payload)
    {
        var req = new HttpRequestMessage(HttpMethod.Post, $"{BaseUrl}/api/v1/credit-payments/{action}");
        req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", jwt);
        req.Content = new StringContent(JsonSerializer.Serialize(payload), Encoding.UTF8, "application/json");
        var res = await Http.SendAsync(req);
        return JsonDocument.Parse(await res.Content.ReadAsStringAsync()).RootElement.Clone();
    }
}