using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using System.Web;
using Pathoschild.Http.Client;

namespace StardewModdingAPI.Web.Framework.LogParser
{
    /// <summary>An API client for Pastebin.</summary>
    internal class PastebinClient : IDisposable
    {
        /*********
        ** Properties
        *********/
        /// <summary>The underlying HTTP client.</summary>
        private readonly IClient Client;

        /// <summary>The user key used to authenticate with the Pastebin API.</summary>
        private readonly string UserKey;

        /// <summary>The developer key used to authenticate with the Pastebin API.</summary>
        private readonly string DevKey;


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="baseUrl">The base URL for the Pastebin API.</param>
        /// <param name="userAgent">The user agent for the API client.</param>
        /// <param name="userKey">The user key used to authenticate with the Pastebin API.</param>
        /// <param name="devKey">The developer key used to authenticate with the Pastebin API.</param>
        public PastebinClient(string baseUrl, string userAgent, string userKey, string devKey)
        {
            this.Client = new FluentClient(baseUrl).SetUserAgent(userAgent);
            this.UserKey = userKey;
            this.DevKey = devKey;
        }

        /// <summary>Fetch a saved paste.</summary>
        /// <param name="id">The paste ID.</param>
        public async Task<GetPasteResponse> GetAsync(string id)
        {
            try
            {
                // get from API
                string content = await this.Client
                    .GetAsync($"raw/{id}")
                    .AsString();

                // handle Pastebin errors
                if (string.IsNullOrWhiteSpace(content))
                    return new GetPasteResponse { Error = "Received an empty response from Pastebin." };
                if (content.StartsWith("<!DOCTYPE"))
                    return new GetPasteResponse { Error = $"Received a captcha challenge from Pastebin. Please visit https://pastebin.com/{id} in a new window to solve it." };
                return new GetPasteResponse { Success = true, Content = content };
            }
            catch (ApiException ex) when (ex.Status == HttpStatusCode.NotFound)
            {
                return new GetPasteResponse { Error = "There's no log with that ID." };
            }
            catch (Exception ex)
            {
                return new GetPasteResponse { Error = ex.ToString() };
            }
        }

        /// <summary>Save a paste to Pastebin.</summary>
        /// <param name="content">The paste content.</param>
        public async Task<SavePasteResponse> PostAsync(string content)
        {
            try
            {
                // validate
                if (string.IsNullOrWhiteSpace(content))
                    return new SavePasteResponse { Error = "The log content can't be empty." };

                // post to API
                string response = await this.Client
                    .PostAsync("api/api_post.php")
                    .WithBodyContent(this.GetFormUrlEncodedContent(new Dictionary<string, string>
                    {
                        ["api_option"] = "paste",
                        ["api_user_key"] = this.UserKey,
                        ["api_dev_key"] = this.DevKey,
                        ["api_paste_private"] = "1", // unlisted
                        ["api_paste_name"] = $"SMAPI log {DateTime.UtcNow:s}",
                        ["api_paste_expire_date"] = "N", // never expire
                        ["api_paste_code"] = content
                    }))
                    .AsString();

                // handle Pastebin errors
                if (string.IsNullOrWhiteSpace(response))
                    return new SavePasteResponse { Error = "Received an empty response from Pastebin." };
                if (response.StartsWith("Bad API request"))
                    return new SavePasteResponse { Error = response };
                if (!response.Contains("/"))
                    return new SavePasteResponse { Error = $"Received an unknown response: {response}" };

                // return paste ID
                string pastebinID = response.Split("/").Last();
                return new SavePasteResponse { Success = true, ID = pastebinID };
            }
            catch (Exception ex)
            {
                return new SavePasteResponse { Success = false, Error = ex.ToString() };
            }
        }

        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
        public void Dispose()
        {
            this.Client.Dispose();
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Build an HTTP content body with form-url-encoded content.</summary>
        /// <param name="data">The content to encode.</param>
        /// <remarks>This bypasses an issue where <see cref="FormUrlEncodedContent"/> restricts the body length to the maximum size of a URL, which isn't applicable here.</remarks>
        private HttpContent GetFormUrlEncodedContent(IDictionary<string, string> data)
        {
            string body = string.Join("&", from arg in data select $"{HttpUtility.UrlEncode(arg.Key)}={HttpUtility.UrlEncode(arg.Value)}");
            return new StringContent(body, Encoding.UTF8, "application/x-www-form-urlencoded");
        }
    }
}