using MongoDB.Driver;
using MongoDbGenericRepository.DataAccess.Base;
using MongoDbGenericRepository.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;

namespace MongoDbGenericRepository.DataAccess.Index
{
    /// <inheritdoc cref="MongoDbGenericRepository.DataAccess.Index.IMongoDbIndexHandler" />
    public class MongoDbIndexHandler : DataAccessBase, IMongoDbIndexHandler
    {
        /// <summary>
        /// The MongoDbIndexHandler constructor.
        /// </summary>
        /// <param name="mongoDbContext">The mongo db context</param>
        public MongoDbIndexHandler(IMongoDbContext mongoDbContext) : base(mongoDbContext)
        {
        }

        /// <summary>
        /// Returns the names of the indexes present on a collection.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="partitionKey">An optional partition key</param>
        /// <returns>A list containing the names of the indexes on on the concerned collection.</returns>
        public virtual async Task<List<string>> GetIndexesNamesAsync<TDocument, TKey>(string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var indexCursor = await HandlePartitioned<TDocument, TKey>(partitionKey).Indexes.ListAsync();
            var indexes = await indexCursor.ToListAsync();
            return indexes.Select(e => e["name"].ToString()).ToList();
        }

        /// <summary>
        /// Create a text index on the given field.
        /// IndexCreationOptions can be supplied to further specify 
        /// how the creation should be done.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="field">The field we want to index.</param>
        /// <param name="indexCreationOptions">Options for creating an index.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <returns>The result of the create index operation.</returns>
        public virtual async Task<string> CreateTextIndexAsync<TDocument, TKey>(Expression<Func<TDocument, object>> field, IndexCreationOptions indexCreationOptions = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            return await HandlePartitioned<TDocument, TKey>(partitionKey).Indexes
                                                                   .CreateOneAsync(
                                                                     new CreateIndexModel<TDocument>(
                                                                     Builders<TDocument>.IndexKeys.Text(field),
                                                                     indexCreationOptions == null ? null : MapIndexOptions(indexCreationOptions)
                                                                   ));
        }

        /// <summary>
        /// Creates an index on the given field in ascending order.
        /// IndexCreationOptions can be supplied to further specify 
        /// how the creation should be done.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="field">The field we want to index.</param>
        /// <param name="indexCreationOptions">Options for creating an index.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <returns>The result of the create index operation.</returns>
        public virtual async Task<string> CreateAscendingIndexAsync<TDocument, TKey>(Expression<Func<TDocument, object>> field, IndexCreationOptions indexCreationOptions = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            var createOptions = indexCreationOptions == null ? null : MapIndexOptions(indexCreationOptions);
            var indexKey = Builders<TDocument>.IndexKeys;
            return await collection.Indexes
                                   .CreateOneAsync(
                new CreateIndexModel<TDocument>(indexKey.Ascending(field), createOptions));
        }

        /// <summary>
        /// Creates an index on the given field in descending order.
        /// IndexCreationOptions can be supplied to further specify 
        /// how the creation should be done.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="field">The field we want to index.</param>
        /// <param name="indexCreationOptions">Options for creating an index.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <returns>The result of the create index operation.</returns>
        public virtual async Task<string> CreateDescendingIndexAsync<TDocument, TKey>(Expression<Func<TDocument, object>> field, IndexCreationOptions indexCreationOptions = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            var createOptions = indexCreationOptions == null ? null : MapIndexOptions(indexCreationOptions);
            var indexKey = Builders<TDocument>.IndexKeys;
            return await collection.Indexes
                                   .CreateOneAsync(
                new CreateIndexModel<TDocument>(indexKey.Descending(field), createOptions));
        }

        /// <summary>
        /// Creates a hashed index on the given field.
        /// IndexCreationOptions can be supplied to further specify 
        /// how the creation should be done.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="field">The field we want to index.</param>
        /// <param name="indexCreationOptions">Options for creating an index.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <returns>The result of the create index operation.</returns>
        public virtual async Task<string> CreateHashedIndexAsync<TDocument, TKey>(Expression<Func<TDocument, object>> field, IndexCreationOptions indexCreationOptions = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            var createOptions = indexCreationOptions == null ? null : MapIndexOptions(indexCreationOptions);
            var indexKey = Builders<TDocument>.IndexKeys;
            return await collection.Indexes
                                   .CreateOneAsync(
                new CreateIndexModel<TDocument>(indexKey.Hashed(field), createOptions));
        }

        /// <summary>
        /// Creates a combined text index.
        /// IndexCreationOptions can be supplied to further specify 
        /// how the creation should be done.
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="fields">The fields we want to index.</param>
        /// <param name="indexCreationOptions">Options for creating an index.</param>
        /// <param name="partitionKey">An optional partition key.</param>
        /// <returns>The result of the create index operation.</returns>
        public virtual async Task<string> CreateCombinedTextIndexAsync<TDocument, TKey>(IEnumerable<Expression<Func<TDocument, object>>> fields, IndexCreationOptions indexCreationOptions = null, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            var collection = HandlePartitioned<TDocument, TKey>(partitionKey);
            var createOptions = indexCreationOptions == null ? null : MapIndexOptions(indexCreationOptions);
            var listOfDefs = new List<IndexKeysDefinition<TDocument>>();
            foreach (var field in fields)
            {
                listOfDefs.Add(Builders<TDocument>.IndexKeys.Text(field));
            }
            return await collection.Indexes
                                   .CreateOneAsync(new CreateIndexModel<TDocument>(Builders<TDocument>.IndexKeys.Combine(listOfDefs), createOptions));
        }

        /// <summary>
        /// Drops the index given a field name
        /// </summary>
        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
        /// <typeparam name="TKey">The type of the primary key for a Document.</typeparam>
        /// <param name="indexName">The name of the index</param>
        /// <param name="partitionKey">An optional partition key</param>
        public virtual async Task DropIndexAsync<TDocument, TKey>(string indexName, string partitionKey = null)
            where TDocument : IDocument<TKey>
            where TKey : IEquatable<TKey>
        {
            await HandlePartitioned<TDocument, TKey>(partitionKey).Indexes.DropOneAsync(indexName);
        }
    }
}