using System.Net.Http.Json;
using System.Text.Json.Serialization;
using Meezi.Core.Interfaces;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace Meezi.Infrastructure.ExternalServices;

public class ZarinPalGateway : IZarinPalGateway
{
    public async Task<bool> IsEnabledAsync(CancellationToken cancellationToken = default)
    {
        var enabled = await _platform.GetAsync("payment.zarinpal.enabled", cancellationToken);
        return enabled is not "false";
    }

    private readonly HttpClient _httpClient;
    private readonly IConfiguration _configuration;
    private readonly IPlatformRuntimeConfig _platform;
    private readonly IHostEnvironment _environment;
    private readonly ILogger<ZarinPalGateway> _logger;

    public ZarinPalGateway(
        HttpClient httpClient,
        IConfiguration configuration,
        IPlatformRuntimeConfig platform,
        IHostEnvironment environment,
        ILogger<ZarinPalGateway> logger)
    {
        _httpClient = httpClient;
        _configuration = configuration;
        _platform = platform;
        _environment = environment;
        _logger = logger;
    }

    public async Task<ZarinPalRequestResult> RequestPaymentAsync(
        long amountRials,
        string description,
        string callbackUrl,
        CancellationToken cancellationToken = default)
    {
        var merchantId = await GetMerchantIdAsync(cancellationToken);
        if (string.IsNullOrWhiteSpace(merchantId))
        {
            // Mock checkout exists ONLY for local development. In production a
            // missing merchant id must fail loudly — a fake-success here would
            // activate paid plans without any real payment.
            if (!_environment.IsDevelopment())
            {
                _logger.LogError("ZarinPal merchant id missing — refusing payment init in {Env}", _environment.EnvironmentName);
                return new ZarinPalRequestResult(false, null, null, "Payment gateway is not configured.");
            }

            var mockAuthority = Guid.NewGuid().ToString("N")[..16];
            var mockUrl = $"{callbackUrl}?Authority={mockAuthority}&Status=OK";
            _logger.LogInformation("ZarinPal mock payment {Authority} amount {Amount} Rials", mockAuthority, amountRials);
            return new ZarinPalRequestResult(true, mockAuthority, mockUrl, null);
        }

        var sandbox = await IsSandboxAsync(cancellationToken);
        var baseUrl = sandbox
            ? "https://sandbox.zarinpal.com/pg/v4/payment"
            : "https://api.zarinpal.com/pg/v4/payment";

        var payload = new
        {
            merchant_id = merchantId,
            amount = amountRials,
            description,
            callback_url = callbackUrl
        };

        var response = await _httpClient.PostAsJsonAsync($"{baseUrl}/request.json", payload, cancellationToken);
        var body = await response.Content.ReadFromJsonAsync<ZarinPalDataResponse>(cancellationToken: cancellationToken);

        if (body?.Data?.Code is 100 && !string.IsNullOrEmpty(body.Data.Authority))
        {
            var startUrl = sandbox
                ? $"https://sandbox.zarinpal.com/pg/StartPay/{body.Data.Authority}"
                : $"https://www.zarinpal.com/pg/StartPay/{body.Data.Authority}";
            return new ZarinPalRequestResult(true, body.Data.Authority, startUrl, null);
        }

        return new ZarinPalRequestResult(false, null, null, body?.Errors?.FirstOrDefault()?.Message ?? "ZarinPal request failed.");
    }

    public async Task<ZarinPalVerifyResult> VerifyPaymentAsync(
        string authority,
        long amountRials,
        CancellationToken cancellationToken = default)
    {
        var merchantId = await GetMerchantIdAsync(cancellationToken);
        if (string.IsNullOrWhiteSpace(merchantId))
        {
            if (!_environment.IsDevelopment())
            {
                _logger.LogError("ZarinPal merchant id missing — refusing payment verify in {Env}", _environment.EnvironmentName);
                return new ZarinPalVerifyResult(false, null, "Payment gateway is not configured.");
            }
            _logger.LogInformation("ZarinPal mock verify authority {Authority}", authority);
            return new ZarinPalVerifyResult(true, "MOCK-" + authority[..8], null);
        }

        var sandbox = await IsSandboxAsync(cancellationToken);
        var baseUrl = sandbox
            ? "https://sandbox.zarinpal.com/pg/v4/payment"
            : "https://api.zarinpal.com/pg/v4/payment";

        var payload = new
        {
            merchant_id = merchantId,
            amount = amountRials,
            authority
        };

        var response = await _httpClient.PostAsJsonAsync($"{baseUrl}/verify.json", payload, cancellationToken);
        var body = await response.Content.ReadFromJsonAsync<ZarinPalDataResponse>(cancellationToken: cancellationToken);

        if (body?.Data?.Code is 100 or 101)
            return new ZarinPalVerifyResult(true, body.Data.RefId?.ToString(), null);

        return new ZarinPalVerifyResult(false, null, body?.Errors?.FirstOrDefault()?.Message ?? "ZarinPal verify failed.");
    }

    private sealed class ZarinPalDataResponse
    {
        [JsonPropertyName("data")]
        public ZarinPalData? Data { get; set; }

        [JsonPropertyName("errors")]
        public List<ZarinPalError>? Errors { get; set; }
    }

    private sealed class ZarinPalData
    {
        [JsonPropertyName("code")]
        public int Code { get; set; }

        [JsonPropertyName("authority")]
        public string? Authority { get; set; }

        [JsonPropertyName("ref_id")]
        public long? RefId { get; set; }
    }

    private sealed class ZarinPalError
    {
        [JsonPropertyName("message")]
        public string? Message { get; set; }
    }

    private async Task<string?> GetMerchantIdAsync(CancellationToken cancellationToken)
    {
        var fromDb = await _platform.GetAsync("payment.zarinpal.merchantId", cancellationToken);
        if (!string.IsNullOrWhiteSpace(fromDb))
            return fromDb;
        return _configuration["ZarinPal:MerchantId"];
    }

    private async Task<bool> IsSandboxAsync(CancellationToken cancellationToken)
    {
        var fromDb = await _platform.GetAsync("payment.zarinpal.sandbox", cancellationToken);
        if (!string.IsNullOrWhiteSpace(fromDb))
            return fromDb is not "false";
        return _configuration.GetValue("ZarinPal:Sandbox", true);
    }
}