using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Azaion.Common.DTO;

using Newtonsoft.Json;
using Serilog;

namespace Azaion.Common.Services;

public interface IAzaionApi
{
    ApiCredentials Credentials { get; }
    Task<User> GetCurrentUserAsync();
    Task UpdateOffsetsAsync(UserQueueOffsets offsets);
}

public class AzaionApi(ILogger logger, HttpClient client, ICache cache, ApiCredentials credentials) : IAzaionApi
{
    private readonly SemaphoreSlim _authLock = new(1, 1);
    private string? _jwtToken;
    const string APP_JSON = "application/json";
    
    public ApiCredentials Credentials => credentials;

    public async Task<User> GetCurrentUserAsync()
    {
        var user = await cache.GetFromCacheAsync(Constants.CURRENT_USER_CACHE_KEY,
            async () => await GetAsync<User>("users/current"));
        return user ?? throw new Exception("Can't get current user");
    }

    public async Task UpdateOffsetsAsync(UserQueueOffsets offsets)
    {
        var user = await GetCurrentUserAsync();
        await PutAsync("/users/queue-offsets/set", new { Email = user.Email, Offsets = offsets });
    }

    private async Task<T?> GetAsync<T>(string url)
    {
        var response = await SendWithAuthAsync(() => client.GetAsync(url));
        return JsonConvert.DeserializeObject<T>(await response.Content.ReadAsStringAsync());
    }

    private async Task PutAsync<T>(string url, T obj)
    {
        var content = new StringContent(JsonConvert.SerializeObject(obj), Encoding.UTF8, APP_JSON);
        await SendWithAuthAsync(() => client.PutAsync(url, content));
    }

    private async Task<HttpResponseMessage> SendWithAuthAsync(Func<Task<HttpResponseMessage>> sendAction)
    {
        if (string.IsNullOrEmpty(_jwtToken))
            await AuthorizeAsync();

        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _jwtToken);
        var response = await sendAction();

        if (response.StatusCode == HttpStatusCode.Unauthorized)
        {
            await AuthorizeAsync();
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _jwtToken);
            response = await sendAction();
        }

        if (!response.IsSuccessStatusCode)
        {
            var content = await response.Content.ReadAsStringAsync();
            if (response.StatusCode == HttpStatusCode.Conflict)
            {
                var error = JsonConvert.DeserializeObject<BusinessExceptionDto>(content);
                throw new Exception($"Failed: {response.StatusCode}! Error Code: {error?.ErrorCode}. Message: {error?.Message}");
            }
            throw new Exception($"Failed: {response.StatusCode}! Result: {content}");
        }

        return response;
    }

    private async Task AuthorizeAsync()
    {
        await _authLock.WaitAsync();
        try
        {
            if (string.IsNullOrEmpty(credentials.Email) || credentials.Password.Length == 0)
                throw new Exception("Email or password is empty!");

            var content = new StringContent(
                JsonConvert.SerializeObject(new { email = credentials.Email, password = credentials.Password }), 
                Encoding.UTF8, APP_JSON);
            
            client.DefaultRequestHeaders.Authorization = null;
            var response = await client.PostAsync("login", content);

            if (!response.IsSuccessStatusCode)
                throw new Exception($"Authorization failed: {response.StatusCode}");

            var result = JsonConvert.DeserializeObject<LoginResponse>(await response.Content.ReadAsStringAsync())
                ?? throw new Exception("JWT Token not found in response");

            _jwtToken = result.Token ?? throw new Exception("JWT Token not found in response");
        }
        catch (Exception e)
        {
            logger.Error(e, e.Message);
            throw;
        }
        finally
        {
            _authLock.Release();
        }
    }
}