using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
using zero.Core.Caches.Internal;
using zero.Core.Database;
using zero.Core.Entities;
using zero.Core.Extensions;
using zero.Core.Handlers;
using zero.Core.Options;

namespace zero.Core
{
  public class ApplicationResolver : IApplicationResolver
  {
    ApplicationCache _applicationCache;
    BackofficeUserCache _backofficeUserCache;

    protected IZeroOptions Options { get; private set; }

    protected ILogger<ApplicationResolver> Logger { get; private set; }

    protected IHandlerHolder Handler { get; private set; }



    public ApplicationResolver(IZeroStore store, IZeroOptions options, ILogger<ApplicationResolver> logger, IHandlerHolder handler = null)
    {
      _applicationCache = new ApplicationCache(store);
      _backofficeUserCache = new BackofficeUserCache(store);
      Options = options;
      Logger = logger;
      Handler = handler;
    }


    /// <inheritdoc />
    public async Task<Application> Resolve(HttpContext context, ClaimsPrincipal user)
    {
      if (context?.Request == null)
      {
        Logger.LogWarning("Could not resolve application as HTTP request is null");
        return null;
      }

      Application app;

      if (context.IsBackofficeRequest(Options.BackofficePath))
      {
        app = await ResolveFromUser(user);
      }
      else
      {
        app = await ResolveFromRequest(context);
      }

      if (app == null)
      {
        //Logger.LogWarning("Could not resolve application for host {host}", context.Request.Host);
        app = _applicationCache.All.FirstOrDefault();
      }

      return app;
    }


    /// <inheritdoc />
    public async Task<Application> ResolveFromUser(ClaimsPrincipal user)
    {
      BackofficeUserCache.Result userEntity = GetBackofficeUser(user);
      return userEntity != null ? await ResolveFromUser(new BackofficeUser()
      {
        Id = userEntity.Id,
        AppId = userEntity.AppId,
        CurrentAppId = userEntity.CurrentAppId,
        Claims = userEntity.Claims,
        IsSuper = userEntity.IsSuper
      }) : null;
    }


    /// <inheritdoc />
    public Task<Application> ResolveFromUser(BackofficeUser user)
    {
      if (user == null)
      {
        return null;
      }

      string appId;
      string[] allowedAppIds = user.GetAllowedAppIds();

      if (!user.CurrentAppId.IsNullOrEmpty())
      {
        if (user.IsSuper || allowedAppIds.Contains(user.CurrentAppId, StringComparer.InvariantCultureIgnoreCase))
        {
          appId = user.CurrentAppId;
        }
        else
        {
          appId = user.AppId;
        }
      }
      else
      {
        appId = user.AppId;
      }

      if (appId.IsNullOrEmpty())
      {
        throw new Exception($"User entity ${user.Id} needs a valid AppId");
      }

      return Task.FromResult(_applicationCache.ById(appId));
    }


    /// <inheritdoc />
    public async Task<Application> ResolveFromRequest(HttpContext context)
    {
      return Handler.Get<IApplicationResolverHandler>()?.Resolve(context.Request, _applicationCache.All) ?? await ResolveFromUri(context.Request.GetEncodedUrl());
    }


    /// <inheritdoc />
    public Task<Application> ResolveFromUri(string uriString)
    {
      return Task.FromResult(ResolveFromUriInternal(new Uri(uriString, UriKind.Absolute), _applicationCache.All));
    }


    /// <inheritdoc />
    public Task<Application> ResolveFromUri(Uri uri)
    {
      return Task.FromResult(ResolveFromUriInternal(uri, _applicationCache.All));
    }


    /// <summary>
    /// Get matching application from an URI
    /// </summary>
    Application ResolveFromUriInternal(Uri uri, IEnumerable<Application> apps)
    {
      foreach (Application app in apps)
      {
        if (app.Domains?.Length < 1)
        {
          Logger.LogWarning("No domains specified for app {app}", app.Id);
          continue;
        }

        foreach (Uri domain in app.Domains)
        {
          int compareResult = Uri.Compare(uri, domain, UriComponents.HostAndPort, UriFormat.SafeUnescaped, StringComparison.OrdinalIgnoreCase);
          if (compareResult == 0)
          {
            return app;
          }
        }
      }

      return null;
    }


    /// <summary>
    /// Get backoffice user from claims principal
    /// </summary>
    BackofficeUserCache.Result GetBackofficeUser(ClaimsPrincipal user)
    {
      string userId = user.FindFirstValue(Constants.Auth.Claims.UserId);
      return _backofficeUserCache.ById(userId);
    }
  }


  public interface IApplicationResolver
  {
    /// <summary>
    /// Resolves the current application from either the backoffice user (in case it is backoffice request)
    /// or the domain (in case it is frontend request).
    /// </summary>
    Task<Application> Resolve(HttpContext context, ClaimsPrincipal user);

    /// <summary>
    /// Resolves the current application from the request path
    /// </summary>
    Task<Application> ResolveFromRequest(HttpContext context);

    /// <summary>
    /// Get matching application from an URI string
    /// </summary>
    Task<Application> ResolveFromUri(string uriString);

    /// <summary>
    /// Get matching application from an URI
    /// </summary>
    Task<Application> ResolveFromUri(Uri uri);

    /// <summary>
    /// Resolves the current application from the logged-in backoffice user.
    /// This method won't return apps the user has no access to.
    /// </summary>
    Task<Application> ResolveFromUser(ClaimsPrincipal user);

    /// <summary>
    /// Resolves the current application from a user.
    /// This method won't return apps the user has no access to.
    /// </summary>
    Task<Application> ResolveFromUser(BackofficeUser user);
  }
}