using System.Net;
using System.Net.Http.Headers;
using System.Text;

namespace Uwaa.Pleroma;

delegate void AddPair(string key, string value);

/// <summary>
/// A pleroma client.
/// </summary>
public class Pleroma
{
    static readonly JsonSerializerOptions SerializerOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        NumberHandling = JsonNumberHandling.AllowReadingFromString,
    };

    static string CreateQuery(Action<AddPair> generator)
    {
        StringBuilder sb = new StringBuilder();
        void addPair(string key, string value)
        {
            if (sb.Length == 0)
                sb.Append('?');
            else
                sb.Append('&');
            sb.Append(WebUtility.UrlEncode(key));
            sb.Append('=');
            sb.Append(WebUtility.UrlEncode(value));
        }
        generator(addPair);
        return sb.ToString();
    }


    public HttpClient HttpClient;

    public Pleroma(string host, string? authorization, string? userAgent = "Uwaa.Pleroma/0.0")
    {
        UriBuilder builder = new UriBuilder();
        builder.Scheme = "https";
        builder.Host = host;

        HttpClient = new HttpClient();
        HttpClient.DefaultRequestHeaders.Add("User-agent", userAgent);
        HttpClient.BaseAddress = builder.Uri;
        HttpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        if (authorization != null)
            HttpClient.DefaultRequestHeaders.Authorization = AuthenticationHeaderValue.Parse(authorization);
    }

    async Task<T?> Retry<T>(HttpRequestMessage req)
    {
        while (true)
        {
            HttpResponseMessage res = await HttpClient.SendAsync(req);

            if (res.StatusCode == HttpStatusCode.NotFound)
                return default;

            if (res.Content == null)
                throw new HttpRequestException("Server responded with no content");

            string text = await res.Content.ReadAsStringAsync();

            if (res.StatusCode is >= (HttpStatusCode)400 and < (HttpStatusCode)600)
            {
                try
                {
                    PleromaException? err = JsonSerializer.Deserialize<PleromaException>(text, SerializerOptions);
                    if (err != null && err.Text != null)
                    {
                        if (err.Text == "Throttled")
                        {
                            await Task.Delay(5000);
                            continue; //Retry
                        }
                        else
                        {
                            throw err;
                        }
                    }
                }
                catch (JsonException)
                {
                    //Not an error
                }
            }

            if (res.StatusCode is >= (HttpStatusCode)200 and < (HttpStatusCode)300)
                return JsonSerializer.Deserialize<T>(text, SerializerOptions) ?? throw new HttpRequestException("Couldn't deserialize response");
            else
                throw new HttpRequestException("Unknown error occurred");
        }
    }

    /// <summary>
    /// Posts a status.
    /// </summary>
    /// <param name="status">The status data to send, including the content, visibility, etc.</param>
    /// <exception cref="HttpRequestException">Thrown if something goes wrong while uploading the status.</exception>
    /// <returns>The status if posting was successful.</returns>
    public Task<Status> PostStatus(string content,
                                   bool sensitive = false,
                                   int? expiresIn = null,
                                   string? replyTo = null,
                                   string? quoting = null,
                                   string? language = null,
                                   StatusVisibility visibility = StatusVisibility.Public)
    {
        MemoryStream mem = new MemoryStream();
        
        {
            Utf8JsonWriter writer = new Utf8JsonWriter(mem, new JsonWriterOptions() { SkipValidation = true });
            writer.WriteStartObject();

            writer.WritePropertyName("status");
            writer.WriteStringValue(content);

            writer.WritePropertyName("content-type");
            writer.WriteStringValue("text/plain");

            if (sensitive)
            {
                writer.WritePropertyName("sensitive");
                writer.WriteBooleanValue(true);
            }

            if (expiresIn.HasValue)
            {
                writer.WritePropertyName("expires_in");
                writer.WriteNumberValue(expiresIn.Value);
            }

            if (replyTo != null)
            {
                writer.WritePropertyName("in_reply_to_id");
                writer.WriteStringValue(replyTo);
            }

            if (quoting != null)
            {
                writer.WritePropertyName("quote_id");
                writer.WriteStringValue(quoting);
            }

            if (language != null)
            {
                writer.WritePropertyName("language");
                writer.WriteStringValue(language);
            }

            if (visibility != StatusVisibility.Public)
            {
                writer.WritePropertyName("visibility");
                writer.WriteStringValue(visibility.ToString().ToLowerInvariant());
            }

            writer.WriteEndObject();
            writer.Flush();
        }

        mem.Position = 0;
        HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Post, "/api/v1/statuses");
        req.Content = new StreamContent(mem);
        req.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        return Retry<Status>(req)!;
    }

    /// <summary>
    /// Fetches the latest statuses from the public timeline.
    /// </summary>
    public Task<Status[]> GetTimeline()
    {
        //TODO: Parameters and selecting different timelines (home, public, bubble)

        return Retry<Status[]>(new HttpRequestMessage(HttpMethod.Get, "/api/v1/timelines/public"))!;
    }

    
    /// <summary>
    /// Fetches the latest statuses from a user's timeline.
    /// </summary>
    public Task<Status[]> GetTimeline(Account account)
        => GetTimeline(account.ID);

    /// <summary>
    /// Fetches the latest statuses from a user's timeline.
    /// </summary>
    public Task<Status[]> GetTimeline(string account_id)
    {
        return Retry<Status[]>(new HttpRequestMessage(HttpMethod.Get, $"/api/v1/accounts/{account_id}/statuses"))!;
    }

    /// <summary>
    /// Fetches the account of the pleroma client.
    /// </summary>
    public Task<Account> GetAccount()
    {
        return Retry<Account>(new HttpRequestMessage(HttpMethod.Get, "/api/v1/accounts/verify_credentials"))!;
    }

    /// <summary>
    /// Fetches an account.
    /// </summary>
    public Task<Account?> GetAccount(string id)
    {
        return Retry<Account?>(new HttpRequestMessage(HttpMethod.Get, $"/api/v1/accounts/{id}"));
    }

    /// <summary>
    /// Fetches the context of a status.
    /// </summary>
    public Task<Context?> GetContext(Status status)
        => GetContext(status.ID);

    /// <summary>
    /// Fetches the context of a status.
    /// </summary>
    public Task<Context?> GetContext(string status_id)
    {
        return Retry<Context?>(new HttpRequestMessage(HttpMethod.Get, $"/api/v1/statuses/{status_id}/context"));
    }

    /// <summary>
    /// Fetches a status.
    /// </summary>
    public Task<Status?> GetStatus(string status_id)
    {
        return Retry<Status?>(new HttpRequestMessage(HttpMethod.Get, $"/api/v1/statuses/{status_id}"));
    }

    /// <summary>
    /// Deletes a status.
    /// </summary>
    public Task Delete(Status status)
        => Delete(status.ID);

    /// <summary>
    /// Deletes a status by ID.
    /// </summary>
    public Task Delete(string status_id)
    {
        //TODO: Test
        return Retry<object?>(new HttpRequestMessage(HttpMethod.Delete, $"/api/v1/statuses/{status_id}"));
    }

    /// <summary>
    /// Searches for an accounts, hashtags, and/or statuses.
    /// </summary>
    /// <param name="query">What to search for</param>
    /// <param name="account_id">If provided, statuses returned will be authored only by this account</param>
    /// <param name="type">Search type</param>
    /// <param name="resolve">Attempt WebFinger lookup</param>
    /// <param name="following">Only include accounts that the user is following</param>
    /// <param name="max_id">Return items older than this ID</param>
    /// <param name="min_id">Return the oldest items newer than this ID</param>
    /// <param name="since_id">Return the newest items newer than this ID</param>
    /// <param name="offset">Return items past this number of items</param>
    /// <param name="limit">Maximum number of items to return. Will be ignored if it's more than 40</param>
    /// <returns></returns>
    public Task<SearchResults> Search(string query,
                                      string? account_id = null,
                                      SearchType type = SearchType.All,
                                      bool resolve = false,
                                      bool following = false,
                                      string? max_id = null,
                                      string? min_id = null,
                                      string? since_id = null,
                                      int offset = 0,
                                      int limit = 20)
    {
        HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Get, "/api/v2/search" + CreateQuery(addPair =>
        {
            addPair("q", query);
            if (account_id != null) addPair("account_id", account_id);
            if (type != SearchType.All) addPair("type", type.ToString().ToLowerInvariant());
            if (resolve) addPair("resolve", "true");
            if (following) addPair("following", "true");
            if (max_id != null) addPair("max_id", max_id);
            if (min_id != null) addPair("min_id", min_id);
            if (since_id != null) addPair("since_id", since_id);
            if (offset > 0) addPair("offset", offset.ToString());
            if (limit != 20) addPair("limit", limit.ToString());
        }));
        return Retry<SearchResults>(req)!;
    }
}