using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json.Nodes;
using System.Text.RegularExpressions;

using var client = new DidbanClient(Environment.GetEnvironmentVariable("DIDBAN_API_URL") ?? "http://127.0.0.1:4321",
                                    Environment.GetEnvironmentVariable("DIDBAN_API_KEY") ?? "");
var invoice = await client.CreateInvoice("CS-ORDER-1001", "550680");
// Save id beside the permanent order identifier; redirect the customer to payment_url.
Console.WriteLine("Payment URL: " + invoice["payment_url"]);
var state = await client.GetInvoice(invoice["id"]!.GetValue<string>());
Console.WriteLine($"Status: {state["status"]} | Requires review: {state["requires_review"]}");
// Only live invoices with a verified bank approval can report paid=true. Never fulfill an order from test_payment.

sealed class DidbanClient : IDisposable
{
    private readonly HttpClient http;
    public DidbanClient(string baseUrl, string apiKey)
    {
        var uri = new Uri(baseUrl, UriKind.Absolute);
        if (uri.UserInfo.Length > 0 || uri.Query.Length > 0 || uri.Fragment.Length > 0 || uri.AbsolutePath != "/"
            || !(uri.Scheme == "https" || uri.Scheme == "http" && (uri.Host == "localhost" || uri.Host == "127.0.0.1")))
            throw new ArgumentException("Use an HTTPS origin or localhost.");
        if (!Regex.IsMatch(apiKey, @"\Adb_(test|live)_[A-Za-z0-9_-]{43}\z")) throw new ArgumentException("Invalid API key.");
        http = new HttpClient(new HttpClientHandler { AllowAutoRedirect = false }) { BaseAddress = uri, Timeout = TimeSpan.FromSeconds(20) };
        http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
        http.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    }
    public Task<JsonObject> CreateInvoice(string requestId, string amountRial, string presentation = "hosted", int? ttlMinutes = null) => Send(HttpMethod.Post, "/api/v1/invoices",
        new { request_id = requestId, amount_rial = amountRial, ttl_minutes = ttlMinutes, presentation });
    public Task<JsonObject> GetInvoice(string id)
    {
        if (!Regex.IsMatch(id, @"\A[0-9a-f-]{36}\z")) throw new ArgumentException("Invalid invoice ID.");
        return Send(HttpMethod.Get, "/api/v1/invoices/" + id, null);
    }
    public Task<JsonObject> GetPaymentData(string id)
    {
        if (!Regex.IsMatch(id, @"\A[0-9a-f-]{36}\z")) throw new ArgumentException("Invalid invoice ID.");
        return Send(HttpMethod.Get, "/api/v1/invoices/" + id + "/payment-data", null);
    }
    public Task<JsonObject> GetWallet() => Send(HttpMethod.Get, "/api/v1/wallet", null);
    private async Task<JsonObject> Send(HttpMethod method, string path, object? body)
    {
        using var request = new HttpRequestMessage(method, path);
        if (body is not null) request.Content = JsonContent.Create(body);
        using var response = await http.SendAsync(request);
        if (!response.IsSuccessStatusCode) throw new HttpRequestException($"Didban HTTP {(int)response.StatusCode}");
        return await response.Content.ReadFromJsonAsync<JsonObject>() ?? throw new HttpRequestException("Invalid response.");
    }
    public void Dispose() => http.Dispose();
}