using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

public class AtonHealthAuth
{
    private readonly HttpClient _httpClient;
    private readonly string _clientId;
    private readonly string _clientSecret;
    private readonly string _scope;
    private string _accessToken;
    private DateTime _expiresAt;

    public AtonHealthAuth()
    {
        _httpClient = new HttpClient();
        _clientId = Environment.GetEnvironmentVariable("ATON_CLIENT_ID");
        _clientSecret = Environment.GetEnvironmentVariable("ATON_CLIENT_SECRET");
        _scope = Environment.GetEnvironmentVariable("ATON_API_SCOPE");
    }

    public async Task<string> GetAccessTokenAsync()
    {
        if (!string.IsNullOrEmpty(_accessToken) && _expiresAt > DateTime.UtcNow)
        {
            return _accessToken;
        }

        var url = $"https://login.microsoftonline.com/5178eeaf-1f56-44cb-940e-012fe79c2845/oauth2/v2.0/token";

        var parameters = new List<KeyValuePair<string, string>>
        {
            new KeyValuePair<string, string>("grant_type", "client_credentials"),
            new KeyValuePair<string, string>("client_id", _clientId),
            new KeyValuePair<string, string>("client_secret", _clientSecret),
            new KeyValuePair<string, string>("scope", _scope)
        };

        var content = new FormUrlEncodedContent(parameters);

        var response = await _httpClient.PostAsync(url, content);
        response.EnsureSuccessStatusCode();

        var jsonResponse = await response.Content.ReadAsStringAsync();
        var tokenResponse = JsonConvert.DeserializeObject<TokenResponse>(jsonResponse);

        _accessToken = tokenResponse.AccessToken;
        _expiresAt = DateTime.UtcNow.AddSeconds(tokenResponse.ExpiresIn - 60); // 1 minute buffer before actual expiration

        return _accessToken;
    }

    public async Task<HttpResponseMessage> MakeAuthenticatedRequestAsync(HttpMethod method, string url, HttpContent content = null)
    {
        var token = await GetAccessTokenAsync();

        var request = new HttpRequestMessage(method, url);
        request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);

        if (content != null)
        {
            request.Content = content;
        }

        return await _httpClient.SendAsync(request);
    }

    private class TokenResponse
    {
        [JsonProperty("access_token")]
        public string AccessToken { get; set; }

        [JsonProperty("expires_in")]
        public int ExpiresIn { get; set; }

        [JsonProperty("token_type")]
        public string TokenType { get; set; }
    }
}