using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.ScadaBridge.AuditLog.Central;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Audit;

namespace ZB.MOM.WW.ScadaBridge.AuditLog.Tests.Central;

/// <summary>
/// Policy tests for <see cref="AuditLogHashChainService"/> (ScadaBridge#41) over a scripted
/// <see cref="IAuditLogHashChain"/>: default-off, draining a backlog within the per-tick
/// cap, yielding to the peer node's lock, and containing failures. The SQL chaining itself
/// is covered by <c>AuditLogHashChainTests</c> in ConfigurationDatabase.Tests.
/// </summary>
public class AuditLogHashChainServiceTests
{
    private sealed class ScriptedChain(params AuditChainBatchResult[] script) : IAuditLogHashChain
    {
        private int _next;
        public int Calls => _next;
        public Exception? Throw { get; init; }

        public Task<AuditChainBatchResult> ChainPendingAsync(int batchSize, CancellationToken ct = default)
        {
            if (Throw is not null) throw Throw;
            var i = _next++;
            return Task.FromResult(i < script.Length ? script[i] : new AuditChainBatchResult(0, false));
        }

        public Task<AuditChainVerificationResult> VerifyMonthAsync(DateTime monthStartUtc, CancellationToken ct = default)
            => throw new NotSupportedException();
    }

    private static AuditLogHashChainService Create(IAuditLogHashChain chain, AuditLogHashChainOptions options)
    {
        var services = new ServiceCollection();
        services.AddScoped(_ => chain);
        return new AuditLogHashChainService(
            services.BuildServiceProvider().GetRequiredService<IServiceScopeFactory>(),
            Options.Create(options),
            NullLogger<AuditLogHashChainService>.Instance);
    }

    /// <summary>The job is off by default and starting it then does nothing.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Disabled_ByDefault_StartsNoLoop()
    {
        var chain = new ScriptedChain(new AuditChainBatchResult(5, false));
        Assert.False(new AuditLogHashChainOptions().Enabled);
        using var service = Create(chain, new AuditLogHashChainOptions());

        await service.StartAsync(CancellationToken.None);
        await Task.Delay(50);
        await service.StopAsync(CancellationToken.None);

        Assert.Equal(0, chain.Calls);
    }

    /// <summary>A tick drains batches until one comes back empty.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Tick_DrainsUntilEmpty()
    {
        var chain = new ScriptedChain(
            new AuditChainBatchResult(10, false), new AuditChainBatchResult(10, false), new AuditChainBatchResult(3, false));
        using var service = Create(chain, new AuditLogHashChainOptions { Enabled = true, BatchSize = 10 });

        Assert.Equal(23, await service.TickAsync(CancellationToken.None));
        Assert.Equal(4, chain.Calls); // the 4th returns 0 and ends the tick
    }

    /// <summary>The peer node holding the lock ends the tick at once.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Tick_StopsWhenPeerHoldsTheLock()
    {
        var chain = new ScriptedChain(new AuditChainBatchResult(0, LockBusy: true), new AuditChainBatchResult(10, false));
        using var service = Create(chain, new AuditLogHashChainOptions { Enabled = true });

        Assert.Equal(0, await service.TickAsync(CancellationToken.None));
        Assert.Equal(1, chain.Calls);
    }

    /// <summary>A backlog yields after MaxBatchesPerTick batches.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Tick_RespectsMaxBatchesPerTick()
    {
        var chain = new ScriptedChain(Enumerable.Repeat(new AuditChainBatchResult(10, false), 50).ToArray());
        using var service = Create(chain, new AuditLogHashChainOptions { Enabled = true, MaxBatchesPerTick = 3 });

        Assert.Equal(30, await service.TickAsync(CancellationToken.None));
        Assert.Equal(3, chain.Calls);
    }

    /// <summary>A failing tick is contained (logged), never thrown out of the loop.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Tick_ContainsFailures()
    {
        var chain = new ScriptedChain { Throw = new InvalidOperationException("sql down") };
        using var service = Create(chain, new AuditLogHashChainOptions { Enabled = true });

        Assert.Equal(0, await service.TickAsync(CancellationToken.None));
    }

    /// <summary>Invalid tuning fails startup validation.</summary>
    /// <param name="interval">IntervalSeconds.</param>
    /// <param name="batch">BatchSize.</param>
    /// <param name="maxBatches">MaxBatchesPerTick.</param>
    [Theory]
    [InlineData(0, 1000, 100)]
    [InlineData(60, 0, 100)]
    [InlineData(60, 10_001, 100)]
    [InlineData(60, 1000, 0)]
    public void Validator_RejectsInvalidTuning(int interval, int batch, int maxBatches)
    {
        var result = new AuditLogHashChainOptionsValidator().Validate(null,
            new AuditLogHashChainOptions { IntervalSeconds = interval, BatchSize = batch, MaxBatchesPerTick = maxBatches });
        Assert.False(result.Succeeded);
        Assert.True(new AuditLogHashChainOptionsValidator().Validate(null, new AuditLogHashChainOptions()).Succeeded);
    }
}