using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using xCategoryService.Extensions;
using xCategoryService.Interfaces;
using xCategoryService.Interfaces.Dtos;
using xCategoryService.Models.Dtos;
using xCommons.Extensions;
using xDataService.Extensions;
using xDataService.Models;
using xExceptions.Constants;
using xModels.Dtos;

namespace xCategoryService.Providers
{
    public abstract class XBaseCategoryProvider<TKey> : IXBaseCategoryProvider<TKey>
    {
        //
        #region Props ...
        /// <summary>
        /// Provider Identifier ...
        /// </summary>
        public string Provider { get; }

        /// <summary>
        /// Tag Provider for Maipulating Tags ...
        /// </summary>
        public IXCategoryServiceProvider CategoryProvider { get; }
        #endregion

        //
        #region Constructor ...
        public XBaseCategoryProvider(
            string providedFor,
            IXCategoryServiceProvider categoryProvider
        )
        {
            //
            Provider = providedFor;
            CategoryProvider = categoryProvider;
        }
        #endregion

        //
        #region Referenced Actions ...
        /// <summary>
        /// Get Specified Indexed Reference for Specific Provided ID ...
        /// </summary>
        /// <param name="providedForId"></param>
        /// <param name="forIndex"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<XCategoryDto> GetReference(
            TKey providedForId,
            int forIndex = 0,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            if (providedForId.IsNull())
            {
                XException.InvalidArgs.Throw();
            }

            //
            // Normalize ...
            if (forIndex < 0)
            {
                forIndex = 0;
            }

            //
            // Retrieve Last Index ...
            var maxIndex = (await GetReferencingIndexes(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            ))
            .Max();
            if (forIndex > maxIndex)
            {
                XException.NotFound.Throw();
            }

            //
            var indexedIdentifier = GetIndexedProvidedID(
                forIndex: forIndex,
                providedForId: providedForId
            );
            var result = await CategoryProvider.FindOneAsync(
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken,
                predicate: x => x.References.Contains(indexedIdentifier)
            );
            if (result.IsNullOrDefault())
            {
                XException.NotFound.Throw();
            }

            //
            return result;
        }

        /// <summary>
        /// Retrieve all Exists References of Specific Provided ID ...
        /// </summary>
        /// <param name="providedForId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<IEnumerable<XCategoryDto>> GetAllReferences(
            TKey providedForId,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            if (providedForId.IsNull())
            {
                XException.InvalidArgs.Throw();
            }

            //
            var identifier = GetProvidedID(providedForId);
            var result = await CategoryProvider.FindManyAsync(
                orderBuilder: null,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken,
                predicate: x => x.References.Contains(identifier)
            );

            //
            return result;
        }

        /// <summary>
        /// Extract all Referencing Models for Specified Key ...
        /// </summary>
        /// <param name="providedForId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns> 
        public async Task<IEnumerable<XReference<TKey>>> GetAllReferencings(
            TKey providedForId,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            var isValid =
                !providedForId.IsNull();
            if (!isValid)
            {
                XException.InvalidArgs.Throw();
            }

            //
            var identifier = GetProvidedID(providedForId);

            //
            var result = (await CategoryProvider.FindManyAsync(
                orderBuilder: null,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken,
                predicate: x => x.References.Contains(identifier)
            ))
            .Select(x => x.References)
            .ToList()
            .SelectMany(x => x.ParseXReferenceList<TKey>())
            .Where(x => x.ProvidedFor == Provider && $"{x.ReferencedTo}" == $"{providedForId}")
            .OrderBy(x => x.Index)
            .AsEnumerable();

            //
            return result;
        }

        /// <summary>
        /// Count References ...
        /// </summary>
        /// <param name="providedForId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<int> CountReferences(
            TKey providedForId,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            var isValid = !providedForId.IsNull();
            if (!isValid)
            {
                XException.InvalidArgs.Throw();
            }

            //
            var identifier = GetProvidedID(providedForId);
            var result = (await CategoryProvider.FindManyAsync(
                orderBuilder: null,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken,
                predicate: x => x.References.Contains(identifier)
            ))
            .Count();

            //
            return result;
        }

        /// <summary>
        /// Retrieve References of Specific Provided ID as Query ...
        /// </summary>
        /// <param name="query"></param>
        /// <param name="providedForId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<XQueryResult<XCategoryDto>> QueryReferences(
            XQuery query,
            TKey providedForId,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            if (query.IsNull() || providedForId.IsNull())
            {
                XException.InvalidArgs.Throw();
            }

            //
            var identifier = GetProvidedID(providedForId);
            var result = await CategoryProvider.QueryAsync(
                query: query,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken,
                orderBuilder: x => x.OrderBy(y => y.Id),
                predicate: x => x.References.Contains(identifier)
            );

            //
            return result;
        }

        /// <summary>
        /// Add Reference a Model to Specific Provided ID ...
        /// </summary>
        /// <param name="model"></param>
        /// <param name="providedForId"></param>
        /// <param name="connectionId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<bool> AddReference(
            XCategoryDto model,
            TKey providedForId,
            string connectionId = null,
            CancellationToken cancellationToken = default
        )
        {
            //
            var result = false;

            //
            // Validate ...
            result = !model.IsNullOrDefault() &&
                model.Id.IsValidIntId() &&
                !providedForId.IsNull();
            if (!result)
            {
                XException.InvalidArgs.Throw();
            }

            //
            // Check Model Exists ...
            result = await CategoryProvider.IsExistsAsync(model.Id);
            if (!result)
            {
                XException.NotFound.Throw();
            }

            //
            // Update Model by Retrieving ...
            model = await CategoryProvider.GetAsync(
                id: model.Id,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken
            );

            //
            // Retrieve all References ...
            var references = await GetAllReferences(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );

            //
            // Check isReferenced or not ...
            result = references
                .Any(r =>
                    r.Id == model.Id &&
                    r.GetReferences()
                    .Any(rf =>
                        rf.ProvidedFor == Provider &&
                        rf.ReferencedTo == $"{providedForId}"));
            if (result)
            {
                return result;
            }

            //
            // Here means there is not any reference to ProvidedForId ...
            int forIndex = await CountReferences(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );
            var modelReferences = model.GetReferences();
            modelReferences.Add(new XReference<string>
            {
                Index = forIndex,
                ProvidedFor = Provider,
                ReferencedTo = $"{providedForId}"
            });
            modelReferences = modelReferences
                .OrderBy(r => r.Index)
                .ToList();
            model = model.UpdateReferences(modelReferences);

            //
            // Update Data Base ...
            model = await CategoryProvider.UpdateAsync(
                id: model.Id,
                item: model,
                saveChanges: true,
                connectionId: connectionId,
                cancellationToken: cancellationToken
            );
            result = !model.IsNullOrDefault();

            //
            return result;
        }

        /// <summary>
        /// Add Reference a Model to Specific XRefence<TKey/> ...
        /// </summary>
        /// <param name="model"></param>
        /// <param name="reference"></param>
        /// <param name="connectionId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<bool> AddReference(
            XCategoryDto model,
            XReference<TKey> reference,
            string connectionId = null,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            // Since other Validations Handled in Calling, we Ignore them here ...
            var result =
                !model.IsNull() &&
                !reference.IsNullOrDefault() &&
                reference.ProvidedFor == Provider &&
                !reference.ReferencedTo.IsNull();
            if (!result)
            {
                XException.InvalidArgs.Throw();
            }

            //
            result = await AddReference(
                model: model,
                connectionId: connectionId,
                cancellationToken: cancellationToken,
                providedForId: reference.ReferencedTo
            );

            //
            return result;
        }

        /// <summary>
        /// Remove Reference a Model for Specific Provided ID ...
        /// </summary>
        /// <param name="model"></param>
        /// <param name="providedForId"></param>
        /// <param name="connectionId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<bool> RemoveReference(
            XCategoryDto model,
            TKey providedForId,
            string connectionId = null,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            var result =
                !providedForId.IsNull() &&
                !model.IsNullOrDefault() &&
                model.Id.IsValidIntId();
            if (!result)
            {
                XException.InvalidArgs.Throw();
            }

            //
            // Retrieve Model ...
            model = await CategoryProvider.GetAsync(
                id: model.Id,
                includeBuilder: null,
                ignoreSoftDeleteds: true,
                cancellationToken: cancellationToken
            );
            result = !model.IsNullOrDefault();
            if (!result)
            {
                XException.NotFound.Throw();
            }

            //
            // Reading Referencing Indexes ...
            var indexes = await GetReferencingIndexes(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );

            //
            // Check Model Reference to ID ...
            var referencesCount = await CountReferences(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );
            result = referencesCount == 0;
            if (result)
            {
                //
                // There is not any Reference to Remove ...
                return result;
            }

            //
            // Check Model is Trully Referenced to ProvidedForId or not ...
            var reference = model
                .GetReferences()
                .FirstOrDefault(r =>
                    r.ProvidedFor == Provider &&
                    r.ReferencedTo == $"{providedForId}");
            result = !reference.IsNullOrDefault();
            if (!result)
            {
                XException.ActionFailed.Throw();
            }

            //
            // Remove Referenced Item from Model ...
            var modelReferences = model
                .GetReferences()
                .Where(r =>
                    !(r.ProvidedFor == Provider &&
                    r.ReferencedTo == $"{providedForId}"))
                .ToList();
            model = model.UpdateReferences(modelReferences);

            //
            // Update DataBase ...
            model = await CategoryProvider.UpdateAsync(
                item: model,
                id: model.Id,
                saveChanges: true,
                connectionId: connectionId,
                cancellationToken: cancellationToken
            );

            //
            result = !model.IsNullOrDefault();
            if (!result)
            {
                XException.ActionFailed.Throw();
            }

            //
            // Get Max Exists Indexes ...
            var maxIndex = indexes.Max();

            //
            // Here We Have to Re Arrange Indexed ...
            if (reference.Index < maxIndex)
            {
                //
                var startIndex = reference.Index + 1;
                for (int i = startIndex; i <= maxIndex; i++)
                {
                    //
                    var dto = await GetReference(
                        forIndex: i,
                        providedForId: providedForId,
                        cancellationToken: cancellationToken
                    );
                    if (!dto.IsNullOrDefault())
                    {
                        //
                        var dtoReferences = dto.GetReferences();
                        dtoReferences
                        .ToList()
                        .ForEach(iref =>
                        {
                            //
                            if (
                                iref.Index == i &&
                                iref.ProvidedFor == Provider &&
                                iref.ReferencedTo == reference.ReferencedTo
                            )
                            {
                                iref.Index = i - 1;
                            }
                        });
                        dto = dto.UpdateReferences(dtoReferences);

                        //
                        dto = await CategoryProvider.UpdateAsync(
                            item: dto,
                            id: dto.Id,
                            saveChanges: true,
                            connectionId: connectionId,
                            cancellationToken: cancellationToken
                        );
                    }
                }
            }

            //
            return result;
        }

        /// <summary>
        /// Remove Reference a Model for Specific XRefence<TKey/> ...
        /// </summary>
        /// <param name="model"></param>
        /// <param name="reference"></param>
        /// <param name="connectionId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<bool> RemoveReference(
            XCategoryDto model,
            XReference<TKey> reference,
            string connectionId = null,
            CancellationToken cancellationToken = default
        )
        {
            //
            if (model.IsNullOrDefault() ||
                reference.IsNullOrDefault() ||
                reference.ReferencedTo.IsNull() ||
                reference.ProvidedFor != Provider)
            {
                XException.InvalidArgs.Throw();
            }

            //
            var result = await RemoveReference(
                model: model,
                connectionId: connectionId,
                cancellationToken: cancellationToken,
                providedForId: reference.ReferencedTo
            );

            //
            return result;
        }

        /// <summary>
        /// Remove All References to Specified Key ...
        /// </summary>
        /// <param name="providedForId"></param>
        /// <param name="connectionId"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public async Task<bool> RemoveReferences(
            TKey providedForId,
            string connectionId = null,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            if (providedForId.IsNull())
            {
                XException.InvalidArgs.Throw();
            }

            //
            var result = false;
            var references = await GetAllReferences(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );
            if (!references.IsNull() && references.HasChild())
            {
                //
                foreach (var reference in references)
                {
                    //
                    // Remove Reference ...
                    var itemReferences = reference.GetReferences()
                        .Where(r =>
                            r.ProvidedFor != Provider ||
                            (r.ProvidedFor == Provider &&
                                r.ReferencedTo != $"{providedForId}"))
                        .ToList();
                    var updatedModel = reference.UpdateReferences(itemReferences);
                    updatedModel = await CategoryProvider.UpdateAsync(
                        saveChanges: true,
                        item: updatedModel,
                        id: updatedModel.Id,
                        connectionId: connectionId,
                        cancellationToken: cancellationToken
                    );
                    if (!updatedModel.IsNullOrDefault())
                    {
                        result = true;
                    }
                }
            }

            //
            return result;
        }
        #endregion

        //
        #region Private ...
        private string GetProvidedID(
            TKey providedForId,
            char splitter = '_'
        )
        {
            //
            // Validate ...
            if (providedForId.IsNull())
            {
                XException.InvalidArgs.Throw();
            }

            //
            var result = $"{Provider}{splitter}{providedForId}";
            return result;
        }

        private string GetIndexedProvidedID(
            TKey providedForId,
            int forIndex,
            char splitter = '_'
        )
        {
            //
            var result = $"{GetProvidedID(providedForId, splitter)}{splitter}{forIndex}";

            //
            return result;
        }

        private async Task<IEnumerable<int>> GetReferencingIndexes(
            TKey providedForId,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Validate ...
            var isValid =
                !providedForId.IsNull();
            if (!isValid)
            {
                XException.InvalidArgs.Throw();
            }

            //
            var result = new List<int>();
            var referencings = await GetAllReferencings(
                providedForId: providedForId,
                cancellationToken: cancellationToken
            );
            isValid =
                !referencings.IsNull() &&
                referencings.HasChild();
            if (!isValid)
            {
                return result;
            }

            //
            result =
                referencings
                    .OrderBy(r => r.Index)
                    .Select(r => r.Index)
                    .ToList();

            //
            return result;
        }
        #endregion
    }
}