#nullable enable
using Swan.Formatters;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Swan.Net {
  /// <summary>
  /// Represents a HttpClient with extended methods to use with JSON payloads 
  /// and bearer tokens authentication.
  /// </summary>
  public static class JsonClient {
    private const String JsonMimeType = "application/json";
    private const String FormType = "application/x-www-form-urlencoded";

    private static readonly HttpClient HttpClient = new HttpClient();

    /// <summary>
    /// Post a object as JSON with optional authorization token.
    /// </summary>
    /// <typeparam name="T">The type of response object.</typeparam>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested type.
    /// </returns>
    public static async Task<T> Post<T>(Uri requestUri, Object payload, String? authorization = null, CancellationToken cancellationToken = default) where T : notnull {
      String jsonString = await PostString(requestUri, payload, authorization, cancellationToken).ConfigureAwait(false);

      return !String.IsNullOrEmpty(jsonString) ? Json.Deserialize<T>(jsonString) : default;
    }

    /// <summary>
    /// Posts the specified URL.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// A task with a result as a collection of key/value pairs.
    /// </returns>
    public static async Task<IDictionary<String, Object>?> Post(Uri requestUri, Object payload, String? authorization = null, CancellationToken cancellationToken = default) {
      String jsonString = await PostString(requestUri, payload, authorization, cancellationToken).ConfigureAwait(false);

      return String.IsNullOrWhiteSpace(jsonString) ? default : Json.Deserialize(jsonString) as IDictionary<String, Object>;
    }

    /// <summary>
    /// Posts the specified URL.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    /// <exception cref="ArgumentNullException">url.</exception>
    /// <exception cref="JsonRequestException">Error POST JSON.</exception>
    public static Task<String> PostString(Uri requestUri, Object payload, String? authorization = null, CancellationToken cancellationToken = default) => SendAsync(HttpMethod.Post, requestUri, payload, authorization, cancellationToken);

    /// <summary>
    /// Puts the specified URL.
    /// </summary>
    /// <typeparam name="T">The type of response object.</typeparam>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested type.
    /// </returns>
    public static async Task<T> Put<T>(Uri requestUri, Object payload, String? authorization = null, CancellationToken ct = default) where T : notnull {
      String jsonString = await PutString(requestUri, payload, authorization, ct).ConfigureAwait(false);

      return !String.IsNullOrEmpty(jsonString) ? Json.Deserialize<T>(jsonString) : default;
    }

    /// <summary>
    /// Puts the specified URL.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested collection of key/value pairs.
    /// </returns>
    public static async Task<IDictionary<String, Object>?> Put(Uri requestUri, Object payload, String? authorization = null, CancellationToken cancellationToken = default) {
      Object response = await Put<Object>(requestUri, payload, authorization, cancellationToken).ConfigureAwait(false);

      return response as IDictionary<String, Object>;
    }

    /// <summary>
    /// Puts as string.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    /// <exception cref="ArgumentNullException">url.</exception>
    /// <exception cref="JsonRequestException">Error PUT JSON.</exception>
    public static Task<String> PutString(Uri requestUri, Object payload, String? authorization = null, CancellationToken ct = default) => SendAsync(HttpMethod.Put, requestUri, payload, authorization, ct);

    /// <summary>
    /// Gets as string.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    /// <exception cref="ArgumentNullException">url.</exception>
    /// <exception cref="JsonRequestException">Error GET JSON.</exception>
    public static Task<String> GetString(Uri requestUri, String? authorization = null, CancellationToken ct = default) => GetString(requestUri, null, authorization, ct);

    /// <summary>
    /// Gets the string.
    /// </summary>
    /// <param name="uri">The URI.</param>
    /// <param name="headers">The headers.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The ct.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    public static async Task<String> GetString(Uri uri, IDictionary<String, IEnumerable<String>>? headers, String? authorization = null, CancellationToken ct = default) {
      HttpContent response = await GetHttpContent(uri, ct, authorization, headers).ConfigureAwait(false);

      return await response.ReadAsStringAsync().ConfigureAwait(false);
    }

    /// <summary>
    /// Gets the specified URL and return the JSON data as object
    /// with optional authorization token.
    /// </summary>
    /// <typeparam name="T">The response type.</typeparam>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested type.
    /// </returns>
    public static async Task<T> Get<T>(Uri requestUri, String? authorization = null, CancellationToken ct = default) where T : notnull {
      String jsonString = await GetString(requestUri, authorization, ct).ConfigureAwait(false);

      return !String.IsNullOrEmpty(jsonString) ? Json.Deserialize<T>(jsonString) : default;
    }

    /// <summary>
    /// Gets the specified URL and return the JSON data as object
    /// with optional authorization token.
    /// </summary>
    /// <typeparam name="T">The response type.</typeparam>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="headers">The headers.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested type.
    /// </returns>
    public static async Task<T> Get<T>(Uri requestUri, IDictionary<String, IEnumerable<String>>? headers, String? authorization = null, CancellationToken ct = default) where T : notnull {
      String jsonString = await GetString(requestUri, headers, authorization, ct).ConfigureAwait(false);

      return !String.IsNullOrEmpty(jsonString) ? Json.Deserialize<T>(jsonString) : default;
    }

    /// <summary>
    /// Gets the binary.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested byte array.
    /// </returns>
    /// <exception cref="ArgumentNullException">url.</exception>
    /// <exception cref="JsonRequestException">Error GET Binary.</exception>
    public static async Task<Byte[]> GetBinary(Uri requestUri, String? authorization = null, CancellationToken ct = default) {
      HttpContent response = await GetHttpContent(requestUri, ct, authorization).ConfigureAwait(false);

      return await response.ReadAsByteArrayAsync().ConfigureAwait(false);
    }

    /// <summary>
    /// Authenticate against a web server using Bearer Token.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="username">The username.</param>
    /// <param name="password">The password.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a Dictionary with authentication data.
    /// </returns>
    /// <exception cref="ArgumentNullException">url
    /// or
    /// username.</exception>
    /// <exception cref="SecurityException">Error Authenticating.</exception>
    public static async Task<IDictionary<String, Object>?> Authenticate(Uri requestUri, String username, String password, CancellationToken ct = default) {
      if(String.IsNullOrWhiteSpace(username)) {
        throw new ArgumentNullException(nameof(username));
      }

      // ignore empty password for now
      String content = $"grant_type=password&username={username}&password={password}";
      using StringContent requestContent = new StringContent(content, Encoding.UTF8, FormType);
      HttpResponseMessage response = await HttpClient.PostAsync(requestUri, requestContent, ct).ConfigureAwait(false);

      if(!response.IsSuccessStatusCode) {
        throw new SecurityException($"Error Authenticating. Status code: {response.StatusCode}.");
      }

      String jsonPayload = await response.Content.ReadAsStringAsync().ConfigureAwait(false);

      return Json.Deserialize(jsonPayload) as IDictionary<String, Object>;
    }

    /// <summary>
    /// Posts the file.
    /// </summary>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="buffer">The buffer.</param>
    /// <param name="fileName">Name of the file.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    public static Task<String> PostFileString(Uri requestUri, Byte[] buffer, String fileName, String? authorization = null, CancellationToken ct = default) => PostString(requestUri, new { Filename = fileName, Data = buffer }, authorization, ct);

    /// <summary>
    /// Posts the file.
    /// </summary>
    /// <typeparam name="T">The response type.</typeparam>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="buffer">The buffer.</param>
    /// <param name="fileName">Name of the file.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    public static Task<T> PostFile<T>(Uri requestUri, Byte[] buffer, String fileName, String? authorization = null, CancellationToken ct = default) where T : notnull => Post<T>(requestUri, new { Filename = fileName, Data = buffer }, authorization, ct);

    /// <summary>
    /// Sends the asynchronous request.
    /// </summary>
    /// <param name="method">The method.</param>
    /// <param name="requestUri">The request URI.</param>
    /// <param name="payload">The payload.</param>
    /// <param name="authorization">The authorization.</param>
    /// <param name="ct">The cancellation token.</param>
    /// <returns>
    /// A task with a result of the requested string.
    /// </returns>
    /// <exception cref="ArgumentNullException">requestUri.</exception>
    /// <exception cref="JsonRequestException">Error {method} JSON.</exception>
    public static async Task<String> SendAsync(HttpMethod method, Uri requestUri, Object payload, String? authorization = null, CancellationToken ct = default) {
      using HttpResponseMessage response = await GetResponse(requestUri, authorization, null, payload, method, ct).ConfigureAwait(false);
      if(!response.IsSuccessStatusCode) {
        throw new JsonRequestException(
            $"Error {method} JSON",
            (Int32)response.StatusCode,
            await response.Content.ReadAsStringAsync().ConfigureAwait(false));
      }

      return await response.Content.ReadAsStringAsync().ConfigureAwait(false);
    }

    private static async Task<HttpContent> GetHttpContent(Uri uri, CancellationToken ct, String? authorization = null, IDictionary<String, IEnumerable<String>>? headers = null) {
      HttpResponseMessage response = await GetResponse(uri, authorization, headers, ct: ct).ConfigureAwait(false);

      return response.IsSuccessStatusCode ? response.Content : throw new JsonRequestException("Error GET", (Int32)response.StatusCode);
    }

    private static async Task<HttpResponseMessage> GetResponse(Uri uri, String? authorization, IDictionary<String, IEnumerable<String>>? headers, Object? payload = null, HttpMethod? method = default, CancellationToken ct = default) {
      if(uri == null) {
        throw new ArgumentNullException(nameof(uri));
      }

      using HttpRequestMessage requestMessage = new HttpRequestMessage(method ?? HttpMethod.Get, uri);

      if(!String.IsNullOrWhiteSpace(authorization)) {
        requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", authorization);
      }

      if(headers != null) {
        foreach(KeyValuePair<String, IEnumerable<String>> header in headers) {
          requestMessage.Headers.Add(header.Key, header.Value);
        }
      }

      if(payload != null && requestMessage.Method != HttpMethod.Get) {
        requestMessage.Content = new StringContent(Json.Serialize(payload), Encoding.UTF8, JsonMimeType);
      }

      return await HttpClient.SendAsync(requestMessage, ct).ConfigureAwait(false);
    }
  }
}