// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System.Globalization;
using System.Linq.Expressions;
using System.Runtime.CompilerServices;
using MongoDB.Bson;
using MongoDB.Driver;
using Squidex.Infrastructure.States;

namespace Squidex.Infrastructure.MongoDb
{
    public static class MongoExtensions
    {
        private static readonly ReplaceOptions UpsertReplace = new ReplaceOptions { IsUpsert = true };

        public static async Task<bool> CollectionExistsAsync(this IMongoDatabase database, string collectionName,
            CancellationToken ct = default)
        {
            var options = new ListCollectionNamesOptions
            {
                Filter = new BsonDocument("name", collectionName)
            };

            var collections = await database.ListCollectionNamesAsync(options, ct);

            return await collections.AnyAsync(ct);
        }

        public static Task<bool> AnyAsync<T>(this IMongoCollection<T> collection,
            CancellationToken ct = default)
        {
            var find = collection.Find(new BsonDocument()).Limit(1);

            return find.AnyAsync(ct);
        }

        public static async Task<bool> InsertOneIfNotExistsAsync<T>(this IMongoCollection<T> collection, T document,
            CancellationToken ct = default)
        {
            try
            {
                await collection.InsertOneAsync(document, null, ct);
            }
            catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
            {
                return false;
            }

            return true;
        }

        public static async IAsyncEnumerable<T> ToAsyncEnumerable<T>(this IFindFluent<T, T> find,
            [EnumeratorCancellation] CancellationToken ct = default)
        {
            var cursor = await find.ToCursorAsync(ct);

            while (await cursor.MoveNextAsync(ct))
            {
                foreach (var item in cursor.Current)
                {
                    ct.ThrowIfCancellationRequested();

                    yield return item;
                }
            }
        }

        public static IFindFluent<T, BsonDocument> Only<T>(this IFindFluent<T, T> find,
            Expression<Func<T, object>> include)
        {
            return find.Project<BsonDocument>(Builders<T>.Projection.Include(include));
        }

        public static IFindFluent<T, BsonDocument> Only<T>(this IFindFluent<T, T> find,
            Expression<Func<T, object>> include1,
            Expression<Func<T, object>> include2)
        {
            return find.Project<BsonDocument>(Builders<T>.Projection.Include(include1).Include(include2));
        }

        public static IFindFluent<T, BsonDocument> Only<T>(this IFindFluent<T, T> find,
            Expression<Func<T, object>> include1,
            Expression<Func<T, object>> include2,
            Expression<Func<T, object>> include3)
        {
            return find.Project<BsonDocument>(Builders<T>.Projection.Include(include1).Include(include2).Include(include3));
        }

        public static IFindFluent<T, T> Not<T>(this IFindFluent<T, T> find,
            Expression<Func<T, object>> exclude)
        {
            return find.Project<T>(Builders<T>.Projection.Exclude(exclude));
        }

        public static IFindFluent<T, T> Not<T>(this IFindFluent<T, T> find,
            Expression<Func<T, object>> exclude1,
            Expression<Func<T, object>> exclude2)
        {
            return find.Project<T>(Builders<T>.Projection.Exclude(exclude1).Exclude(exclude2));
        }

        public static long ToLong(this BsonValue value)
        {
            switch (value.BsonType)
            {
                case BsonType.Int32:
                    return value.AsInt32;
                case BsonType.Int64:
                    return value.AsInt64;
                case BsonType.Double:
                    return (long)value.AsDouble;
                default:
                    throw new InvalidCastException($"Cannot cast from {value.BsonType} to long.");
            }
        }

        public static async Task<bool> UpsertVersionedAsync<T, TKey>(this IMongoCollection<T> collection, TKey key, long oldVersion, long newVersion, T document,
            CancellationToken ct = default)
            where T : IVersionedEntity<TKey> where TKey : notnull
        {
            try
            {
                document.DocumentId = key;
                document.Version = newVersion;

                Expression<Func<T, bool>> filter =
                    oldVersion > EtagVersion.Any ?
                    x => x.DocumentId.Equals(key) && x.Version == oldVersion :
                    x => x.DocumentId.Equals(key);

                var result = await collection.ReplaceOneAsync(filter, document, UpsertReplace, ct);

                return result.IsAcknowledged && result.ModifiedCount == 1;
            }
            catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
            {
                var existingVersion =
                    await collection.Find(x => x.DocumentId.Equals(key)).Only(x => x.DocumentId, x => x.Version)
                        .FirstOrDefaultAsync(ct);

                if (existingVersion != null)
                {
                    var field = Field.Of<T>(x => nameof(x.Version));

                    throw new InconsistentStateException(existingVersion[field].AsInt64, oldVersion);
                }
                else
                {
                    throw new InconsistentStateException(EtagVersion.Any, oldVersion);
                }
            }
        }

        public static async Task<int> GetMajorVersionAsync(this IMongoDatabase database,
            CancellationToken ct = default)
        {
            var command =
                new BsonDocumentCommand<BsonDocument>(new BsonDocument
                {
                    { "buildInfo", 1 }
                });

            var document = await database.RunCommandAsync(command, cancellationToken: ct);

            var versionString = document["version"].AsString;
            var versionMajor = versionString.Split('.')[0];

            int.TryParse(versionMajor, NumberStyles.Integer, CultureInfo.InvariantCulture, out int result);

            return result;
        }
    }
}