using Dalamud.Bindings.ImGui;
using Dalamud.Plugin.SelfTest;
using HellionChat.Ui.Components.Settings;
using HellionChat.Util;

namespace HellionChat.SelfTests;

// The gate has fourteen unit tests. None of them prove that the workers are
// wired to it, and that is where the mistake actually happened: the metadata
// refresh reached the store without taking the gate at all, and its flag was
// missing from the tab's shared busy state, so a wipe could start while it held
// the read lock.
//
// A unit test cannot see that. It needs the real singleton, the real flags and
// the real settings tab, so it lives here.
internal sealed class DbGateWiringStep : ISelfTestStep
{
    private readonly Plugin _plugin;

    public DbGateWiringStep(Plugin plugin) => _plugin = plugin;

    public string Name => "Hellion Chat - DB gate wiring";

    public SelfTestStepResult RunStep()
    {
        var failures = new List<string>();

        // Nothing may be running when the probe starts, or the assertions below
        // measure somebody else's operation.
        if (_plugin.DbOperations.IsBusy)
            failures.Add($"gate already held by {_plugin.DbOperations.Current} before the probe");

        CheckEveryOperationRoundTrips(failures);
        CheckRefusalLeavesTheOwnerAlone(failures);
        CheckRevisionTracksMutations(failures);
        CheckTabSeesTheGate(failures);

        foreach (var f in failures)
            ImGui.Text(f);

        SelfTestReport.Append(Name, failures.Count == 0 ? "PASS" : "FAIL", failures);
        return failures.Count == 0 ? SelfTestStepResult.Pass : SelfTestStepResult.Fail;
    }

    private void CheckEveryOperationRoundTrips(List<string> failures)
    {
        foreach (var op in EnumValues<DbOperation>.All)
        {
            if (op == DbOperation.None)
                continue;

            if (!_plugin.DbOperations.TryBegin(op))
            {
                failures.Add($"{op}: TryBegin refused on a free gate");
                continue;
            }

            if (_plugin.DbOperations.Current != op)
                failures.Add($"{op}: gate reports {_plugin.DbOperations.Current} after TryBegin");

            if (_plugin.DbOperations.TryBegin(op))
                failures.Add($"{op}: a second TryBegin succeeded while it was held");

            _plugin.DbOperations.End(op);

            if (_plugin.DbOperations.IsBusy)
                failures.Add($"{op}: still busy after End");
        }
    }

    private void CheckRefusalLeavesTheOwnerAlone(List<string> failures)
    {
        if (!_plugin.DbOperations.TryBegin(DbOperation.Export))
        {
            failures.Add("could not take the gate for the refusal check");
            return;
        }

        // A worker whose TryBegin was refused still runs its finally. Releasing
        // there must not hand away somebody else's lock.
        _plugin.DbOperations.End(DbOperation.Clear);

        if (_plugin.DbOperations.Current != DbOperation.Export)
            failures.Add("a foreign End released the gate");

        _plugin.DbOperations.End(DbOperation.Export);
    }

    private void CheckRevisionTracksMutations(List<string> failures)
    {
        var before = _plugin.DbOperations.Revision;

        _plugin.DbOperations.TryBegin(DbOperation.Export);
        _plugin.DbOperations.End(DbOperation.Export);
        if (_plugin.DbOperations.Revision != before)
            failures.Add("export moved the revision; it cannot change a row");

        _plugin.DbOperations.TryBegin(DbOperation.Cleanup);
        _plugin.DbOperations.End(DbOperation.Cleanup);
        if (_plugin.DbOperations.Revision == before)
            failures.Add(
                "cleanup did not move the revision; a stale preview would pass as current"
            );
    }

    // The settings tab decides whether the destructive buttons are live. If it
    // cannot see a held gate, two of them are clickable at once.
    private void CheckTabSeesTheGate(List<string> failures)
    {
        if (!_plugin.DbOperations.TryBegin(DbOperation.Clear))
        {
            failures.Add("could not take the gate for the tab check");
            return;
        }

        try
        {
            if (!_plugin.DataPrivacyTab.AnythingRunningForSelfTest)
                failures.Add("the data and privacy tab does not see a held gate");
        }
        finally
        {
            _plugin.DbOperations.End(DbOperation.Clear);
        }

        if (_plugin.DataPrivacyTab.AnythingRunningForSelfTest)
            failures.Add("the tab still reports busy after the gate was released");
    }

    public void CleanUp() { }
}