using AsbCloudDb.Model;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Memory;
using Moq;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

namespace AsbCloudWebApi.Tests
{
    internal static class TestHelpter
    {
        public static IMemoryCache MemoryCache = new MemoryCache(new MemoryCacheOptions());

        public static AsbCloudDbContext MakeRealTestContext()
        {
            var options = new DbContextOptionsBuilder<AsbCloudDbContext>()
                .UseNpgsql("Host=localhost;Database=tests;Username=postgres;Password=q;Persist Security Info=True;Include Error Detail=True")
                .Options;
            var context = new AsbCloudDbContext(options);
            context.Database.EnsureCreated();
            return context;
        }

        public static Mock<IAsbCloudDbContext> AddDbSetMock<T>(this Mock<IAsbCloudDbContext> contextMock, IEnumerable<T> dbSetData)
            where T : class
        {
            var dbSetMock = MakeDbSetMock(dbSetData);
            contextMock.Setup(o => o.Set<T>())
                .Returns(() => dbSetMock.Object);

            var dbSetProperty = typeof(IAsbCloudDbContext)
                .GetProperties()
                .FirstOrDefault(p => p.PropertyType.IsPublic && p.PropertyType == typeof(DbSet<T>));

            if (dbSetProperty is not null)
            {
                // https://learn.microsoft.com/ru-ru/dotnet/api/system.linq.expressions.expression?view=net-7.0
                var objParameterExpr = Expression.Parameter(typeof(IAsbCloudDbContext), "instance");
                var propertyExpr = Expression.Property(objParameterExpr, dbSetProperty);
                var expression = Expression.Lambda<Func<IAsbCloudDbContext, DbSet<T>>>(propertyExpr, objParameterExpr);
                contextMock.SetupGet(expression).Returns(dbSetMock.Object);
            }

            return contextMock;
        }

        public static Mock<DbSet<T>> MakeDbSetMock<T>()
            where T : class
        => MakeDbSetMock(new List<T>());
        
        class DummyAsyncQueriable<T> : IQueryable<T>, IAsyncEnumerable<T>            
        {
            private readonly IQueryable<T> queriable;

            public Type ElementType => queriable.ElementType;

            public Expression Expression => queriable.Expression;

            public IQueryProvider Provider => queriable.Provider;

            class QueriableAsyncEminaretor<T2> : IAsyncEnumerator<T2>
            {
                private readonly IEnumerator<T2> syncEnumerator;

                public QueriableAsyncEminaretor(IEnumerator<T2> syncEnumerator)
                {
                    this.syncEnumerator = syncEnumerator;
                }

                public T2 Current => syncEnumerator.Current;

                public ValueTask DisposeAsync()
                {
                    syncEnumerator.Dispose();
                    return ValueTask.CompletedTask;
                }
                
                public ValueTask<bool> MoveNextAsync() 
                {
                    var result = syncEnumerator.MoveNext();
                    return ValueTask.FromResult(result);
                }
            }

            public DummyAsyncQueriable(IEnumerable<T> dbSetData)
            {
                queriable = dbSetData.ToList().AsQueryable();
            }

            public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
            {
                var enumerator = this.AsEnumerable().GetEnumerator();
                return new QueriableAsyncEminaretor<T>(enumerator);
            }

            public IEnumerator<T> GetEnumerator()
            => queriable.GetEnumerator();

            IEnumerator IEnumerable.GetEnumerator()
            => queriable.GetEnumerator();
        }

        public static Mock<DbSet<T>> MakeDbSetMock<T>(IEnumerable<T> dbSetData)
            where T : class
        {
            var dbSetDataQueriable = new DummyAsyncQueriable<T>(dbSetData);

            Mock<DbSet<T>> dbSetMock = new();
            dbSetMock.As<IQueryable<T>>().Setup(o => o.Provider).Returns(() => dbSetDataQueriable.Provider);
            dbSetMock.As<IQueryable<T>>().Setup(o => o.Expression).Returns(() => dbSetDataQueriable.Expression);
            dbSetMock.As<IQueryable<T>>().Setup(o => o.ElementType).Returns(() => dbSetDataQueriable.ElementType);
            dbSetMock.As<IQueryable<T>>().Setup(o => o.GetEnumerator()).Returns(() => dbSetDataQueriable.GetEnumerator());

            dbSetMock.As<IAsyncEnumerable<T>>()
                .Setup(o => o.GetAsyncEnumerator(It.IsAny<CancellationToken>()))
                .Returns(() => dbSetDataQueriable.GetAsyncEnumerator());

            return dbSetMock;
        }
    }
}