using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace Core.Blueprint.Mongo
{
    /// <summary>
    /// Provides methods for interacting with a MongoDB collection for a specific document type.
    /// Inherits from <see cref="MongoProvider"/> and implements <see cref="ICollectionsRepository{TDocument}"/>.
    /// This class encapsulates common database operations such as querying, inserting, updating, and deleting documents.
    /// </summary>
    /// <typeparam name="TDocument">The type of document stored in the collection, which must implement <see cref="IDocument"/>.</typeparam>
    public class CollectionRepository<TDocument>(IMongoDatabase database) : ICollectionsRepository<TDocument> where TDocument : IDocument
    {
        private IMongoCollection<TDocument> _collection;

        /// <summary>
        /// Initializes the MongoDB collection based on the <see cref="CollectionAttributeName"/> attribute
        /// applied to the <typeparamref name="TDocument"/> type. Throws an exception if the attribute is not present.
        /// </summary>
        public void CollectionInitialization()
        {
            var collectionAttribute = typeof(TDocument).GetCustomAttribute<CollectionAttributeName>();
            if (collectionAttribute == null)
            {
                throw new InvalidOperationException($"The class {typeof(TDocument).Name} is missing the CollectionAttributeName attribute.");
            }

            string collectionName = collectionAttribute.Name;

            _collection = database.GetCollection<TDocument>(collectionName);
        }

        /// <summary>
        /// Returns all documents from the collection as an enumerable list.
        /// </summary>
        /// <returns>A task that represents the asynchronous operation. The task result contains an enumerable list of documents.</returns>
        public virtual async ValueTask<IEnumerable<TDocument>> AsQueryable()
        {
            return await _collection.AsQueryable().ToListAsync();
        }

        /// <summary>
        /// Filters documents in the collection based on the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the documents.</param>
        /// <returns>A task that represents the asynchronous operation. The task result contains a list of documents that match the filter.</returns>
        public virtual async Task<IEnumerable<TDocument>> FilterBy(
            Expression<Func<TDocument, bool>> filterExpression)
        {
            var objectResult = await _collection.FindAsync(filterExpression).ConfigureAwait(false);
            return objectResult.ToList();
        }

        /// <summary>
        /// Filters documents in the collection based on the provided filter and projection expressions.
        /// Projects the filtered documents into a new type.
        /// </summary>
        /// <typeparam name="TProjected">The type to project the documents into.</typeparam>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the documents.</param>
        /// <param name="projectionExpression">A lambda expression that defines how the documents should be projected.</param>
        /// <returns>An enumerable collection of projected documents.</returns>
        public virtual IEnumerable<TProjected> FilterBy<TProjected>(
            Expression<Func<TDocument, bool>> filterExpression,
            Expression<Func<TDocument, TProjected>> projectionExpression)
        {
            return _collection.Find(filterExpression).Project(projectionExpression).ToEnumerable();
        }

        /// <summary>
        /// Finds a single document that matches the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the document.</param>
        /// <returns>The document that matches the filter, or <c>null</c> if no document is found.</returns>
        public virtual TDocument FindOne(Expression<Func<TDocument, bool>> filterExpression)
        {
            return _collection.Find(filterExpression).FirstOrDefault();
        }

        /// <summary>
        /// Filters documents in the collection based on the provided MongoDB filter definition.
        /// </summary>
        /// <param name="filterDefinition">A filter definition for MongoDB query.</param>
        /// <returns>A task that represents the asynchronous operation. The task result contains a list of documents that match the filter.</returns>
        public virtual async Task<IEnumerable<TDocument>> FilterByMongoFilterAsync(FilterDefinition<TDocument> filterDefinition)
        {
            var objectResult = await _collection.Find(filterDefinition).ToListAsync().ConfigureAwait(false);
            return objectResult;
        }

        /// <summary>
        /// Asynchronously finds a single document that matches the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the document.</param>
        /// <returns>A task that represents the asynchronous operation. The task result contains the document that matches the filter, or <c>null</c> if no document is found.</returns>
        public virtual Task<TDocument> FindOneAsync(Expression<Func<TDocument, bool>> filterExpression)
        {
            return Task.Run(() => _collection.Find(filterExpression).FirstOrDefaultAsync());
        }

        /// <summary>
        /// Finds a document by its unique identifier (ID).
        /// </summary>
        /// <param name="id">The unique identifier of the document.</param>
        /// <returns>The document that matches the specified ID, or <c>null</c> if no document is found.</returns>
        public virtual TDocument FindById(string id)
        {
            var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, id);
            return _collection.Find(filter).SingleOrDefault();
        }

        /// <summary>
        /// Asynchronously finds a document by its unique identifier (ID).
        /// </summary>
        /// <param name="id">The unique identifier of the document.</param>
        /// <returns>A task that represents the asynchronous operation. The task result contains the document that matches the specified ID, or <c>null</c> if no document is found.</returns>
        public virtual Task<TDocument> FindByIdAsync(string id)
        {
            return Task.Run(() =>
            {
                var objectId = new ObjectId(id);
                var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, id);
                return _collection.Find(filter).SingleOrDefaultAsync();
            });
        }

        /// <summary>
        /// Inserts a single document into the collection.
        /// </summary>
        /// <param name="document">The document to insert.</param>
        public virtual void InsertOne(TDocument document)
        {
            _collection.InsertOne(document);
        }

        /// <summary>
        /// Asynchronously inserts a single document into the collection.
        /// </summary>
        /// <param name="document">The document to insert.</param>
        /// <returns>A task that represents the asynchronous operation.</returns>
        public virtual Task InsertOneAsync(TDocument document)
        {
            return Task.Run(() => _collection.InsertOneAsync(document));
        }

        /// <summary>
        /// Inserts multiple documents into the collection.
        /// </summary>
        /// <param name="documents">The collection of documents to insert.</param>
        public void InsertMany(ICollection<TDocument> documents)
        {
            _collection.InsertMany(documents);
        }

        /// <summary>
        /// Asynchronously inserts multiple documents into the collection.
        /// </summary>
        /// <param name="documents">The collection of documents to insert.</param>
        /// <returns>A task that represents the asynchronous operation.</returns>
        public virtual async Task InsertManyAsync(ICollection<TDocument> documents)
        {
            await _collection.InsertManyAsync(documents);
        }

        /// <summary>
        /// Replaces an existing document in the collection.
        /// </summary>
        /// <param name="document">The document with the updated data.</param>
        public void ReplaceOne(TDocument document)
        {
            var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, document._Id);
            _collection.FindOneAndReplace(filter, document);
        }

        /// <summary>
        /// Asynchronously replaces an existing document in the collection and returns the updated version.
        /// </summary>
        /// <param name="document">The document with the updated data. Its _Id is used to locate the existing document.</param>
        /// <returns>
        /// The updated document if the replacement was successful; otherwise, <c>null</c> if no matching document was found.
        /// </returns>
        public virtual async Task<TDocument?> ReplaceOneAsync(TDocument document)
        {
            var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, document._Id);

            var options = new FindOneAndReplaceOptions<TDocument>
            {
                ReturnDocument = ReturnDocument.After // return the updated document
            };

            var result = await _collection.FindOneAndReplaceAsync(filter, document, options);

            return result;
        }


        /// <summary>
        /// Deletes a single document from the collection based on the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the document to delete.</param>
        public void DeleteOne(Expression<Func<TDocument, bool>> filterExpression)
        {
            _collection.FindOneAndDelete(filterExpression);
        }

        /// <summary>
        /// Asynchronously deletes a single document from the collection based on the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the document to delete.</param>
        /// <returns>A task that represents the asynchronous operation.</returns>
        public async Task<TDocument> DeleteOneAsync(Expression<Func<TDocument, bool>> filterExpression)
        {
            return await _collection.FindOneAndDeleteAsync(filterExpression);
        }

        /// <summary>
        /// Deletes a single document from the collection based on its unique identifier (ID).
        /// </summary>
        /// <param name="id">The unique identifier of the document to delete.</param>
        public void DeleteById(string id)
        {
            var objectId = new ObjectId(id);
            var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, id);
            _collection.FindOneAndDelete(filter);
        }

        /// <summary>
        /// Asynchronously deletes a single document from the collection based on its unique identifier (ID).
        /// </summary>
        /// <param name="id">The unique identifier of the document to delete.</param>
        /// <returns>A task that represents the asynchronous operation.</returns>
        public Task DeleteByIdAsync(string id)
        {
            return Task.Run(() =>
            {
                var objectId = new ObjectId(id);
                var filter = Builders<TDocument>.Filter.Eq(doc => doc._Id, id);
                _collection.FindOneAndDeleteAsync(filter);
            });
        }

        /// <summary>
        /// Deletes multiple documents from the collection based on the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the documents to delete.</param>
        public void DeleteMany(Expression<Func<TDocument, bool>> filterExpression)
        {
            _collection.DeleteMany(filterExpression);
        }

        /// <summary>
        /// Asynchronously deletes multiple documents from the collection based on the provided filter expression.
        /// </summary>
        /// <param name="filterExpression">A lambda expression that defines the filter criteria for the documents to delete.</param>
        /// <returns>A task that represents the asynchronous operation.</returns>
        public Task DeleteManyAsync(Expression<Func<TDocument, bool>> filterExpression)
        {
            return Task.Run(() => _collection.DeleteManyAsync(filterExpression));
        }

        /// <summary>
        /// Executes an aggregation pipeline and returns the first document in the result asynchronously.
        /// </summary>
        /// <typeparam name="TOutput">The type of the output document you expect from the pipeline.</typeparam>
        /// <param name="pipeline">The aggregation pipeline definition to execute.</param>
        /// <returns>The first document from the aggregation result, or null if none found.</returns>
        public virtual Task<TOutput> FindOnePipelineAsync<TOutput>(PipelineDefinition<TDocument, TOutput> pipeline)
        {
            return Task.Run(() => _collection.Aggregate(pipeline).FirstOrDefaultAsync());
        }
    }
}