using SQLInsight.Core.Data;
using SQLInsight.Core.Findings;
using SQLInsight.Rules.Concurrency;
using SQLInsight.Rules.Engine;
using SQLInsight.Rules.Performance;
using static SQLInsight.Rules.Tests.TestInstances;

namespace SQLInsight.Rules.Tests;

public class PerformanceRuleTests
{
    private static readonly TimeSpan FiveMinutes = TimeSpan.FromMinutes(5);

    private static RuleResult Run(IRule rule, RuleContext context) => Assert.Single(new RuleEngine([rule]).Evaluate(context));

    private static IRule Wait(string id) => WaitRules.Create().Single(r => r.Id == id);

    [Fact]
    public void First_wait_sample_is_not_measurable()
    {
        var snapshot = new WaitStatsSnapshot { CapturedAt = Now, SqlServerStartTime = Now.UtcDateTime, Waits = [] };
        var context = With(new CumulativeSample<WaitStatsSnapshot, WaitStatsDelta>(snapshot, null));

        var result = Run(Wait("SQLI-WAIT-003"), context);

        Assert.Equal(RuleOutcome.NotMeasurable, result.Outcome);
        Assert.Contains("to målinger", result.Reason, StringComparison.Ordinal);
    }

    [Fact]
    public void Threadpool_waits_are_critical()
    {
        var context = With(Waits(FiveMinutes, new WaitStat("THREADPOOL", 50, 25_000, 0)));

        Assert.Equal(Severity.Critical, Assert.Single(Run(Wait("SQLI-WAIT-001"), context).Findings).Severity);
    }

    [Fact]
    public void Lock_waits_need_both_share_and_volume()
    {
        // 300 s interval: 0.5 waiters = 150,000 ms.
        var busy = With(Waits(FiveMinutes, new WaitStat("LCK_M_X", 100, 600_000, 100), new WaitStat("PAGEIOLATCH_SH", 1000, 100_000, 100)));
        var idle = With(Waits(FiveMinutes, new WaitStat("LCK_M_X", 1, 5_000, 0))); // 100 % share, but trivial

        Assert.Equal(RuleOutcome.Findings, Run(Wait("SQLI-WAIT-003"), busy).Outcome);
        Assert.Equal(RuleOutcome.Passed, Run(Wait("SQLI-WAIT-003"), idle).Outcome);
    }

    [Fact]
    public void Heavy_lock_waits_are_high()
    {
        var context = With(Waits(FiveMinutes, new WaitStat("LCK_M_U", 500, 2_000_000, 0)));

        Assert.Equal(Severity.High, Assert.Single(Run(Wait("SQLI-WAIT-003"), context).Findings).Severity);
    }

    [Theory]
    [InlineData(10_000, 30_000, RuleOutcome.Passed)]    // 3 ms
    [InlineData(10_000, 80_000, RuleOutcome.Findings)]  // 8 ms
    [InlineData(500, 50_000, RuleOutcome.Passed)]       // too few commits to judge
    public void WriteLog_average_latency(long tasks, long ms, RuleOutcome expected)
    {
        var context = With(Waits(FiveMinutes, new WaitStat("WRITELOG", tasks, ms, 0)));

        Assert.Equal(expected, Run(Wait("SQLI-WAIT-005"), context).Outcome);
    }

    [Fact]
    public void High_signal_wait_ratio_means_cpu_pressure()
    {
        var context = With(Waits(FiveMinutes, new WaitStat("SOS_SCHEDULER_YIELD", 100_000, 400_000, 400_000), new WaitStat("PAGEIOLATCH_SH", 1000, 400_000, 10_000)));

        Assert.Equal(Severity.High, Assert.Single(Run(Wait("SQLI-WAIT-002"), context).Findings).Severity);
    }

    [Theory]
    [InlineData("ROWS", 5000, 50_000, 0, 0, RuleOutcome.Passed)]     // 10 ms
    [InlineData("ROWS", 5000, 150_000, 0, 0, RuleOutcome.Findings)]  // 30 ms
    [InlineData("ROWS", 500, 150_000, 0, 0, RuleOutcome.Passed)]     // too few reads
    public void Data_file_read_latency(string type, long reads, long stall, long writes, long writeStall, RuleOutcome expected)
    {
        Assert.Equal(expected, Run(new DataFileReadLatencyRule(), With(Io(File(type, reads, stall, writes, writeStall)))).Outcome);
    }

    [Theory]
    [InlineData(10_000, 20_000, RuleOutcome.Passed)]     // 2 ms
    [InlineData(10_000, 200_000, RuleOutcome.Findings)]  // 20 ms
    public void Log_write_latency(long writes, long stall, RuleOutcome expected)
    {
        var result = Run(new LogFileWriteLatencyRule(), With(Io(File("LOG", writes: writes, writeStallMs: stall))));

        Assert.Equal(expected, result.Outcome);
        if (expected == RuleOutcome.Findings)
        {
            Assert.Equal(Severity.High, Assert.Single(result.Findings).Severity);
        }
    }

    private static CpuUtilization Cpu(int sql, int idle, int minutes = 15, string platform = "Windows") => new()
    {
        CapturedAt = Now,
        HostPlatform = platform,
        Samples = Enumerable.Range(0, minutes).Select(i => new CpuSample(Now.AddMinutes(i - minutes), sql, idle)).ToList(),
    };

    [Fact]
    public void Cpu_distinguishes_sql_server_from_other_processes()
    {
        Assert.Equal(["cpu: sqlserver"], Run(new CpuRule(), With(Cpu(sql: 92, idle: 5))).Findings.Select(f => f.Subject));
        Assert.Equal(["cpu: other"], Run(new CpuRule(), With(Cpu(sql: 20, idle: 40))).Findings.Select(f => f.Subject));
        Assert.Equal(RuleOutcome.Passed, Run(new CpuRule(), With(Cpu(sql: 30, idle: 65))).Outcome);
    }

    [Fact]
    public void Other_processes_are_not_judged_on_linux()
    {
        // SystemIdle reads near 0 in Linux containers, which would look like 98 % CPU used by others.
        Assert.Equal(RuleOutcome.Passed, Run(new CpuRule(), With(Cpu(sql: 2, idle: 0, platform: "Linux"))).Outcome);
    }

    [Fact]
    public void Cpu_needs_enough_history()
    {
        Assert.Equal(RuleOutcome.NotMeasurable, Run(new CpuRule(), With(Cpu(sql: 99, idle: 0, minutes: 3))).Outcome);
    }

    [Fact]
    public void Memory_grants_pending()
    {
        var counters = new PerformanceCounterSnapshot { CapturedAt = Now, SqlServerStartTime = Now.UtcDateTime, MemoryGrantsPending = 3, MemoryGrantsOutstanding = 20 };

        var finding = Assert.Single(Run(new MemoryGrantsPendingRule(), With(new CumulativeSample<PerformanceCounterSnapshot, PerformanceCounterRates>(counters, null))).Findings);

        Assert.Equal(Severity.High, finding.Severity);
    }

    private static SessionInfo Session(int id, int? blockedBy = null, string status = "suspended", long waitMs = 0, int openTran = 0) => new()
    {
        SessionId = id,
        BlockingSessionId = blockedBy,
        Status = status,
        WaitType = blockedBy is null ? null : "LCK_M_S",
        WaitTimeMs = waitMs,
        WaitResource = "KEY: 5:72057594043236352 (8194443284a0)",
        OpenTransactionCount = openTran,
        SqlText = $"statement {id}",
    };

    [Fact]
    public void Sleeping_head_blocker_with_open_transaction_gets_specific_advice()
    {
        var snapshot = new BlockingSnapshot
        {
            CapturedAt = Now,
            Sessions =
            [
                Session(51, status: "sleeping", openTran: 1),
                Session(60, blockedBy: 51, waitMs: 45_000),
                Session(61, blockedBy: 60, waitMs: 40_000), // chained behind 60
            ],
        };

        var finding = Assert.Single(Run(new BlockingRule(), With(snapshot)).Findings);

        Assert.Equal("session: 51", finding.Subject);
        Assert.Contains("åben transaktion", finding.Title, StringComparison.Ordinal);
        Assert.Contains(finding.Evidence, e => e.Name == "Blokerede sessioner" && e.Value == "2");
        Assert.Contains("XACT_ABORT", finding.Recommendation, StringComparison.Ordinal);
    }

    [Fact]
    public void Short_blocking_is_normal()
    {
        var snapshot = new BlockingSnapshot { CapturedAt = Now, Sessions = [Session(51, status: "running"), Session(60, blockedBy: 51, waitMs: 2_000)] };

        Assert.Equal(RuleOutcome.Passed, Run(new BlockingRule(), With(snapshot)).Outcome);
    }

    [Fact]
    public void Deadlocks_report_the_processes()
    {
        var deadlock = new DeadlockEvent
        {
            Time = Now,
            GraphXml = "<deadlock/>",
            Processes =
            [
                new DeadlockProcess { Id = "p1", IsVictim = true, SessionId = 60, LockMode = "U", WaitResource = "KEY: 5:1", InputBuffer = "UPDATE a" },
                new DeadlockProcess { Id = "p2", SessionId = 61, LockMode = "X", WaitResource = "KEY: 5:2", InputBuffer = "UPDATE b" },
            ],
        };
        var snapshot = new DeadlockSnapshot { CapturedAt = Now, NewDeadlocks = [deadlock] };

        var finding = Assert.Single(Run(new DeadlockRule(), With(snapshot)).Findings);

        Assert.Equal(Severity.Medium, finding.Severity);
        Assert.Contains(finding.Evidence, e => e.Name.Contains("offer session 60", StringComparison.Ordinal));
    }

    [Fact]
    public void No_new_deadlocks_passes()
    {
        Assert.Equal(RuleOutcome.Passed, Run(new DeadlockRule(), With(new DeadlockSnapshot { CapturedAt = Now, NewDeadlocks = [] })).Outcome);
    }
}