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

using FakeItEasy;
using NodaTime;
using Squidex.Infrastructure.TestHelpers;
using Xunit;

namespace Squidex.Infrastructure.States
{
    public class SimpleStateTests
    {
        private readonly CancellationTokenSource cts = new CancellationTokenSource();
        private readonly CancellationToken ct;
        private readonly TestState<MyDomainState> testState = new TestState<MyDomainState>(DomainId.NewGuid());
        private readonly SimpleState<MyDomainState> sut;

        public SimpleStateTests()
        {
            ct = cts.Token;

            sut = new SimpleState<MyDomainState>(testState.PersistenceFactory, GetType(), testState.Id);
        }

        [Fact]
        public void Should_init_with_base_data()
        {
            Assert.Equal(-1, sut.Version);
            Assert.NotNull(sut.Value);
        }

        [Fact]
        public async Task Should_get_state_from_persistence_on_load()
        {
            testState.Version = 42;
            testState.Snapshot = new MyDomainState { Value = 50 };

            await sut.LoadAsync(ct);

            Assert.Equal(42, sut.Version);
            Assert.Equal(50, sut.Value.Value);

            A.CallTo(() => testState.Persistence.ReadAsync(-2, ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_delete_when_clearing()
        {
            await sut.ClearAsync(ct);

            A.CallTo(() => testState.Persistence.DeleteAsync(ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_invoke_persistence_when_writing_state()
        {
            await sut.WriteAsync(ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_load_once_on_update()
        {
            await sut.UpdateAsync(x => true, ct: ct);
            await sut.UpdateAsync(x => true, ct: ct);

            A.CallTo(() => testState.Persistence.ReadAsync(-2, ct))
                .MustHaveHappenedOnceExactly();
        }

        [Fact]
        public async Task Should_write_state_on_update_when_callback_returns_true()
        {
            await sut.UpdateAsync(x => true, ct: ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_not_write_state_on_update_when_callback_returns_false()
        {
            await sut.UpdateAsync(x => true, ct: ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_write_state_on_update_and_return_when_callback_returns_true()
        {
            var result = await sut.UpdateAsync(x => (true, 42), ct: ct);

            Assert.Equal(42, result);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappened();
        }

        [Fact]
        public async Task Should_not_write_state_on_update_and_return_when_callback_returns_false()
        {
            var result = await sut.UpdateAsync(x => (false, 42), ct: ct);

            Assert.Equal(42, result);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustNotHaveHappened();
        }

        [Fact]
        public async Task Should_retry_update_when_failed_with_inconsistency_issue()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InconsistentStateException(1, 2)).NumberOfTimes(5);

            await sut.UpdateAsync(x => true, ct: ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 6);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 6);
        }

        [Fact]
        public async Task Should_give_up_update_after_too_many_inconsistency_issues()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InconsistentStateException(1, 2)).NumberOfTimes(100);

            await Assert.ThrowsAsync<InconsistentStateException>(() => sut.UpdateAsync(x => true, ct: ct));

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 20);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 20);
        }

        [Fact]
        public async Task Should_not_retry_update_with_other_exception()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InvalidOperationException());

            await Assert.ThrowsAsync<InvalidOperationException>(() => sut.UpdateAsync(x => true, ct: ct));

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 1);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 1);
        }

        [Fact]
        public async Task Should_retry_update_and_return_when_failed_with_inconsistency_issue()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InconsistentStateException(1, 2)).NumberOfTimes(5);

            await sut.UpdateAsync(x => (true, 42), ct: ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 6);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 6);
        }

        [Fact]
        public async Task Should_give_up_update_and_return_after_too_many_inconsistency_issues()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InconsistentStateException(1, 2)).NumberOfTimes(100);

            await Assert.ThrowsAsync<InconsistentStateException>(() => sut.UpdateAsync(x => (true, 42), ct: ct));

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 20);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 20);
        }

        [Fact]
        public async Task Should_not_retry_update_and_return_with_other_exception()
        {
            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .Throws(new InvalidOperationException());

            await Assert.ThrowsAsync<InvalidOperationException>(() => sut.UpdateAsync(x => (true, 42), ct: ct));

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 1);

            A.CallTo(() => testState.Persistence.ReadAsync(A<long>._, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 1);
        }

        [Fact]
        public async Task Should_not_written_if_period_not_over()
        {
            var now = SystemClock.Instance.GetCurrentInstant();

            var clock = A.Fake<IClock>();

            A.CallTo(() => clock.GetCurrentInstant())
                .Returns(now).NumberOfTimes(5).Then
                .Returns(now.Plus(Duration.FromSeconds(2)));

            sut.Clock = clock;

            for (var i = 0; i < 10; i++)
            {
                await sut.WriteAsync(1000, ct);
            }

            await sut.UpdateAsync(x => true, ct: ct);

            A.CallTo(() => testState.Persistence.WriteSnapshotAsync(sut.Value, ct))
                .MustHaveHappenedANumberOfTimesMatching(x => x == 3);
        }
    }
}