using System;
using UnityEngine;
using Adrenak.Unex;
using System.Threading.Tasks;

namespace Adrenak.UniMap {
    public class PanoDownloader {
        /// <summary>
        /// Invoked everytime a request is finished. Null if the request was not successful
        /// </summary>
        public event Action<Texture32> OnLoaded;
        public event Action<Exception> OnFailed;
        public event Action OnStarted;

        GooglePanoDownloader m_GoogleDownloader;
        UserPanoDownloader m_UserDownloader;

        public PanoDownloader() {
            m_UserDownloader = new UserPanoDownloader();
            m_GoogleDownloader = new GooglePanoDownloader();

            m_UserDownloader.OnStarted += () => OnStarted?.Invoke();
            m_UserDownloader.OnLoaded += tex => OnLoaded?.Invoke(tex);
            m_UserDownloader.OnFailed += exception => OnFailed?.Invoke(exception);

            m_GoogleDownloader.OnStarted += () => OnStarted?.Invoke();
            m_GoogleDownloader.OnLoaded += tex => OnLoaded?.Invoke(tex);
            m_GoogleDownloader.OnFailed += exception => OnFailed?.Invoke(exception);
        }

        /// <summary>
        /// Starts the downloads of a panorama and doesn't return any objects to listen to it
        /// </summary>
        /// <param name="panoID"></param>
        /// <param name="size"></param>
        /// <param name="format"></param>
        public void DownloadAndForget(string panoID, PanoSize size, TextureFormat format) {
            Download(panoID, size, format, null, null);
        }

        /// <summary>
        /// Downloads the panorama texture as a Promise
        /// </summary>
        /// <param name="panoID">The ID of the panorama to be downloaded</param>
        /// <param name="size">Size of the texture to be downloaded</param>
        public Task<Texture32> Download(string panoID, PanoSize size, TextureFormat format) {
            var source = new TaskCompletionSource<Texture32>();
            Download(panoID, size, format,
                texture => source.SetResult(texture),
                exception => source.SetException(exception)
            );
            return source.Task;
        }

        /// <summary>
        /// Downloads the panorama texture.
        /// </summary>
        /// <param name="panoID">The ID of the panorama to be downloaded</param>
        /// <param name="size">Size of the texture to be downloaded</param>
        /// <param name="onResult">Callback when the download is successful</param>
        /// <param name="onException">Callback when the download is unsuccessful</param>
        public void Download(string panoID, PanoSize size, TextureFormat format, Action<Texture32> onResult, Action<Exception> onException) {
            // We first try to download as a Google Pano
            m_GoogleDownloader.IsAvailable(panoID, isGooglePano => {
                if (isGooglePano)
                    GoogleDownload(panoID, size, format, onResult, onException);
                else {
                    m_UserDownloader.IsAvailable(panoID, isUserPano => {
                        if (isUserPano)
                            UserDownload(panoID, size, format, onResult, onException);
                        else {
                            onException?.Invoke(new Exception("Pano cannot be downloaded!"));
                            Stop();
                        }
                    });
                }
            });
        }

        /// <summary>
        /// Stops downloading the panorama
        /// </summary>
        public void Stop() {
            if (m_GoogleDownloader != null)
                m_GoogleDownloader.Stop();
            if (m_UserDownloader != null)
                m_UserDownloader.Stop();
        }

        void GoogleDownload(string panoID, PanoSize size, TextureFormat format, Action<Texture32> onResult, Action<Exception> onException) {
            if (m_UserDownloader != null) {
                m_UserDownloader.ClearTexture();
                m_UserDownloader.Stop();
            }
            m_GoogleDownloader.Download(panoID, size, format, onResult, onException);
        }

        void UserDownload(string panoID, PanoSize size, TextureFormat format, Action<Texture32> onResult, Action<Exception> onException) {
            if (m_GoogleDownloader != null) {
                m_GoogleDownloader.ClearTexture();
                m_GoogleDownloader.Stop();
            }
            m_UserDownloader.Download(panoID, size, format, onResult, onException);
        }
    }
}