using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Examine;
using Examine.Search;
using Lucene.Net.QueryParsers.Classic;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using Umbraco.Cms.Core.Cache;
using Umbraco.Cms.Core.IO;
using Umbraco.Cms.Core.Models.ContentEditing;
using Umbraco.Cms.Infrastructure.Examine;
using Umbraco.Cms.Web.Common.Attributes;
using Umbraco.Extensions;
using Constants = Umbraco.Cms.Core.Constants;
using SearchResult = Umbraco.Cms.Core.Models.ContentEditing.SearchResult;

namespace Umbraco.Cms.Web.BackOffice.Controllers
{
    [PluginController(Constants.Web.Mvc.BackOfficeApiArea)]
    public class ExamineManagementController : UmbracoAuthorizedJsonController
    {
        private readonly IExamineManager _examineManager;
        private readonly ILogger<ExamineManagementController> _logger;
        private readonly IIndexDiagnosticsFactory _indexDiagnosticsFactory;
        private readonly IAppPolicyCache _runtimeCache;
        private readonly IIndexRebuilder _indexRebuilder;

        public ExamineManagementController(
            IExamineManager examineManager,
            ILogger<ExamineManagementController> logger,
            IIndexDiagnosticsFactory indexDiagnosticsFactory,
            AppCaches appCaches,
            IIndexRebuilder indexRebuilder)
        {
            _examineManager = examineManager;
            _logger = logger;
            _indexDiagnosticsFactory = indexDiagnosticsFactory;
            _runtimeCache = appCaches.RuntimeCache;
            _indexRebuilder = indexRebuilder;
        }

        /// <summary>
        /// Get the details for indexers
        /// </summary>
        /// <returns></returns>
        public IEnumerable<ExamineIndexModel> GetIndexerDetails()
            => _examineManager.Indexes
                .Select(index => CreateModel(index))
                .OrderBy(examineIndexModel => examineIndexModel.Name.TrimEnd("Indexer"));

        /// <summary>
        /// Get the details for searchers
        /// </summary>
        /// <returns></returns>
        public IEnumerable<ExamineSearcherModel> GetSearcherDetails()
        {
            var model = new List<ExamineSearcherModel>(
                _examineManager.RegisteredSearchers.Select(searcher => new ExamineSearcherModel { Name = searcher.Name })
                    .OrderBy(x => x.Name.TrimEnd("Searcher"))); //order by name , but strip the "Searcher" from the end if it exists
            return model;
        }

        public ActionResult<SearchResults> GetSearchResults(string searcherName, string query, int pageIndex = 0, int pageSize = 20)
        {
            query = query.Trim();

            if (query.IsNullOrWhiteSpace())
            {
                return SearchResults.Empty();
            }

            var msg = ValidateSearcher(searcherName, out var searcher);
            if (!msg.IsSuccessStatusCode())
                return msg;

            ISearchResults results;

            // NativeQuery will work for a single word/phrase too (but depends on the implementation) the lucene one will work.
            try
            {
                results = searcher
                        .CreateQuery()
                        .NativeQuery(query)
                        .Execute(QueryOptions.SkipTake(pageSize * pageIndex, pageSize));
            }
            catch (ParseException)
            {
                // will occur if the query parser cannot parse this (i.e. starts with a *)
                return SearchResults.Empty();
            }

            var pagedResults = results.Skip(pageIndex * pageSize);

            return new SearchResults
            {
                TotalRecords = results.TotalItemCount,
                Results = pagedResults.Select(x => new SearchResult
                {
                    Id = x.Id,
                    Score = x.Score,
                    Values = x.AllValues.OrderBy(y => y.Key).ToDictionary(y => y.Key, y => y.Value)
                })
            };
        }

        /// <summary>
        /// Check if the index has been rebuilt
        /// </summary>
        /// <param name="indexName"></param>
        /// <returns></returns>
        /// <remarks>
        /// This is kind of rudimentary since there's no way we can know that the index has rebuilt, we
        /// have a listener for the index op complete so we'll just check if that key is no longer there in the runtime cache
        /// </remarks>
        public ActionResult<ExamineIndexModel> PostCheckRebuildIndex(string indexName)
        {
            var validate = ValidateIndex(indexName, out var index);

            if (!validate.IsSuccessStatusCode())
            {
                return validate;
            }

            validate = ValidatePopulator(index);
            if (!validate.IsSuccessStatusCode())
            {
                return validate;
            }

            var cacheKey = "temp_indexing_op_" + indexName;
            var found = _runtimeCache.Get(cacheKey);

            //if its still there then it's not done
            return found != null
                ? null
                : CreateModel(index);
        }

        /// <summary>
        /// Rebuilds the index
        /// </summary>
        /// <param name="indexName"></param>
        /// <returns></returns>
        public IActionResult PostRebuildIndex(string indexName)
        {
            var validate = ValidateIndex(indexName, out var index);
            if (!validate.IsSuccessStatusCode())
                return validate;

            validate = ValidatePopulator(index);
            if (!validate.IsSuccessStatusCode())
                return validate;

            _logger.LogInformation("Rebuilding index '{IndexName}'", indexName);

            //remove it in case there's a handler there already
            index.IndexOperationComplete -= Indexer_IndexOperationComplete;

            //now add a single handler
            index.IndexOperationComplete += Indexer_IndexOperationComplete;

            try
            {
                var cacheKey = "temp_indexing_op_" + index.Name;
                //put temp val in cache which is used as a rudimentary way to know when the indexing is done
                _runtimeCache.Insert(cacheKey, () => "tempValue", TimeSpan.FromMinutes(5));

                _indexRebuilder.RebuildIndex(indexName);

                return new OkResult();
            }
            catch (Exception ex)
            {
                //ensure it's not listening
                index.IndexOperationComplete -= Indexer_IndexOperationComplete;
                _logger.LogError(ex, "An error occurred rebuilding index");
                var response = new ConflictObjectResult("The index could not be rebuilt at this time, most likely there is another thread currently writing to the index. Error: {ex}");

                HttpContext.SetReasonPhrase("Could Not Rebuild");
                return response;
            }
        }

        private ExamineIndexModel CreateModel(IIndex index)
        {
            var indexName = index.Name;

            var indexDiag = _indexDiagnosticsFactory.Create(index);

            var isHealth = indexDiag.IsHealthy();

            var properties = new Dictionary<string, object>
            {
                ["DocumentCount"] = indexDiag.GetDocumentCount(),
                ["FieldCount"] = indexDiag.GetFieldNames().Count(),
            };

            foreach (KeyValuePair<string, object> p in indexDiag.Metadata)
            {
                properties[p.Key] = p.Value;
            }

            var indexerModel = new ExamineIndexModel
            {
                Name = indexName,
                HealthStatus = isHealth.Success ? (isHealth.Result ?? "Healthy") : (isHealth.Result ?? "Unhealthy"),
                ProviderProperties = properties,
                CanRebuild = _indexRebuilder.CanRebuild(index.Name)
            };

            return indexerModel;
        }

        private ActionResult ValidateSearcher(string searcherName, out ISearcher searcher)
        {
            //try to get the searcher from the indexes
            if (_examineManager.TryGetIndex(searcherName, out IIndex index))
            {
                searcher = index.Searcher;
                return new OkResult();
            }

            //if we didn't find anything try to find it by an explicitly declared searcher
            if (_examineManager.TryGetSearcher(searcherName, out searcher))
            {
                return new OkResult();
            }

            var response1 = new BadRequestObjectResult($"No searcher found with name = {searcherName}");
            HttpContext.SetReasonPhrase("Searcher Not Found");
            return response1;
        }

        private ActionResult ValidatePopulator(IIndex index)
        {
            if (_indexRebuilder.CanRebuild(index.Name))
            {
                return new OkResult();
            }

            var response = new BadRequestObjectResult($"The index {index.Name} cannot be rebuilt because it does not have an associated {typeof(IIndexPopulator)}");
            HttpContext.SetReasonPhrase("Index cannot be rebuilt");
            return response;
        }

        private ActionResult ValidateIndex(string indexName, out IIndex index)
        {
            index = null;

            if (_examineManager.TryGetIndex(indexName, out index))
            {
                //return Ok!
                return new OkResult();
            }

            var response = new BadRequestObjectResult($"No index found with name = {indexName}");
            HttpContext.SetReasonPhrase("Index Not Found");
            return response;
        }

        private void Indexer_IndexOperationComplete(object sender, EventArgs e)
        {
            var indexer = (IIndex)sender;

            _logger.LogDebug("Logging operation completed for index {IndexName}", indexer.Name);

            //ensure it's not listening anymore
            indexer.IndexOperationComplete -= Indexer_IndexOperationComplete;

            _logger.LogInformation($"Rebuilding index '{indexer.Name}' done.");

            var cacheKey = "temp_indexing_op_" + indexer.Name;
            _runtimeCache.Clear(cacheKey);
        }
    }
}