// Reference: golang/nats-server/server/store_test.go
// Tests ported in this file:
//   TestStoreLoadNextMsgWildcardStartBeforeFirstMatch  → LoadNextMsg_WildcardStartBeforeFirstMatch
//   TestStoreSubjectStateConsistency                   → SubjectStateConsistency_UpdatesFirstAndLast
//   TestStoreCompactCleansUpDmap                       → Compact_CleansUpDmap (parameterised)
//   TestStoreTruncateCleansUpDmap                      → Truncate_CleansUpDmap (parameterised)
//   TestStorePurgeExZero                               → PurgeEx_ZeroSeq_EquivalentToPurge
//   TestStoreUpdateConfigTTLState                      → UpdateConfigTTLState_MessageSurvivesWhenTtlDisabled
//   TestStoreStreamInteriorDeleteAccounting            → InteriorDeleteAccounting_MemStore (subset without FileStore restart)
//   TestStoreGetSeqFromTimeWithInteriorDeletesGap      → GetSeqFromTime_WithInteriorDeletesGap
//   TestStoreGetSeqFromTimeWithTrailingDeletes         → GetSeqFromTime_WithTrailingDeletes
//   TestStoreMaxMsgsPerUpdateBug                       → MaxMsgsPerUpdateBug_ReducesOnConfigUpdate
//   TestFileStoreMultiLastSeqsAndLoadLastMsgWithLazySubjectState → MultiLastSeqs_AndLoadLastMsg_WithLazySubjectState

using NATS.Server.JetStream.Models;
using NATS.Server.JetStream.Storage;

namespace NATS.Server.JetStream.Tests.JetStream.Storage;

/// <summary>
/// IStreamStore interface contract tests. Validates behaviour shared by all store
/// implementations using MemStore (the simplest implementation).
/// Each test mirrors a specific Go test from golang/nats-server/server/store_test.go.
/// </summary>
public sealed class StoreInterfaceTests
{
    // Helper: cast MemStore to IStreamStore to access sync interface methods.
    private static IStreamStore Sync(MemStore ms) => ms;

    // -------------------------------------------------------------------------
    // LoadNextMsg — wildcard start before first match
    // -------------------------------------------------------------------------

    // Go: TestStoreLoadNextMsgWildcardStartBeforeFirstMatch server/store_test.go:118
    [Fact]
    public void LoadNextMsg_WildcardStartBeforeFirstMatch()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Fill non-matching subjects first so the first wildcard match starts
        // strictly after the requested start sequence.
        for (var i = 0; i < 100; i++)
            s.StoreMsg($"bar.{i}", null, [], 0);

        var (seq, _) = s.StoreMsg("foo.1", null, [], 0);
        seq.ShouldBe(101UL);

        // Loading with wildcard "foo.*" from seq 1 should find the message at seq 101.
        var sm = new StoreMsg();
        var (msg, skip) = s.LoadNextMsg("foo.*", true, 1, sm);
        msg.Subject.ShouldBe("foo.1");
        // skip = seq - start, so seq 101 - start 1 = 100
        skip.ShouldBe(100UL);
        msg.Sequence.ShouldBe(101UL);

        // Loading after seq 101 should throw — no more foo.* messages.
        Should.Throw<KeyNotFoundException>(() => s.LoadNextMsg("foo.*", true, 102, null));
    }

    // -------------------------------------------------------------------------
    // SubjectStateConsistency
    // -------------------------------------------------------------------------

    // Go: TestStoreSubjectStateConsistency server/store_test.go:179
    [Fact]
    public void SubjectStateConsistency_UpdatesFirstAndLast()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        SimpleState GetSubjectState()
        {
            var ss = s.SubjectsState("foo");
            ss.TryGetValue("foo", out var state);
            return state;
        }

        ulong LoadFirstSeq()
        {
            var sm = new StoreMsg();
            var (msg, _) = s.LoadNextMsg("foo", false, 0, sm);
            return msg.Sequence;
        }

        ulong LoadLastSeq()
        {
            var sm = new StoreMsg();
            var msg = s.LoadLastMsg("foo", sm);
            return msg.Sequence;
        }

        // Publish an initial batch of messages.
        for (var i = 0; i < 4; i++)
            s.StoreMsg("foo", null, [], 0);

        // Expect 4 msgs, with first=1, last=4.
        var ss = GetSubjectState();
        ss.Msgs.ShouldBe(4UL);
        ss.First.ShouldBe(1UL);
        LoadFirstSeq().ShouldBe(1UL);
        ss.Last.ShouldBe(4UL);
        LoadLastSeq().ShouldBe(4UL);

        // Remove first message — first should update to seq 2.
        s.RemoveMsg(1).ShouldBeTrue();

        ss = GetSubjectState();
        ss.Msgs.ShouldBe(3UL);
        ss.First.ShouldBe(2UL);
        LoadFirstSeq().ShouldBe(2UL);
        ss.Last.ShouldBe(4UL);
        LoadLastSeq().ShouldBe(4UL);

        // Remove last message — last should update to seq 3.
        s.RemoveMsg(4).ShouldBeTrue();

        ss = GetSubjectState();
        ss.Msgs.ShouldBe(2UL);
        ss.First.ShouldBe(2UL);
        LoadFirstSeq().ShouldBe(2UL);
        ss.Last.ShouldBe(3UL);
        LoadLastSeq().ShouldBe(3UL);

        // Remove first message again.
        s.RemoveMsg(2).ShouldBeTrue();

        // Only one message left — first and last should both equal 3.
        ss = GetSubjectState();
        ss.Msgs.ShouldBe(1UL);
        ss.First.ShouldBe(3UL);
        LoadFirstSeq().ShouldBe(3UL);
        ss.Last.ShouldBe(3UL);
        LoadLastSeq().ShouldBe(3UL);

        // Publish some more messages so we can test another scenario.
        for (var i = 0; i < 3; i++)
            s.StoreMsg("foo", null, [], 0);

        ss = GetSubjectState();
        ss.Msgs.ShouldBe(4UL);
        ss.First.ShouldBe(3UL);
        LoadFirstSeq().ShouldBe(3UL);
        ss.Last.ShouldBe(7UL);
        LoadLastSeq().ShouldBe(7UL);

        // Remove last sequence.
        s.RemoveMsg(7).ShouldBeTrue();

        // Remove first sequence.
        s.RemoveMsg(3).ShouldBeTrue();

        // Remove (now) first sequence 5.
        s.RemoveMsg(5).ShouldBeTrue();

        // ss.First and ss.Last should both be recalculated and equal each other.
        ss = GetSubjectState();
        ss.Msgs.ShouldBe(1UL);
        ss.First.ShouldBe(6UL);
        LoadFirstSeq().ShouldBe(6UL);
        ss.Last.ShouldBe(6UL);
        LoadLastSeq().ShouldBe(6UL);

        // Store a new message and immediately remove it (marks lastNeedsUpdate),
        // then store another — that new one becomes the real last.
        s.StoreMsg("foo", null, [], 0); // seq 8
        s.RemoveMsg(8).ShouldBeTrue();
        s.StoreMsg("foo", null, [], 0); // seq 9

        ss = GetSubjectState();
        ss.Msgs.ShouldBe(2UL);
        ss.First.ShouldBe(6UL);
        LoadFirstSeq().ShouldBe(6UL);
        ss.Last.ShouldBe(9UL);
        LoadLastSeq().ShouldBe(9UL);
    }

    // -------------------------------------------------------------------------
    // CompactCleansUpDmap — parameterised over compact sequences 2, 3, 4
    // -------------------------------------------------------------------------

    // Go: TestStoreCompactCleansUpDmap server/store_test.go:449
    [Theory]
    [InlineData(2UL)]
    [InlineData(3UL)]
    [InlineData(4UL)]
    public void Compact_CleansUpDmap(ulong compactSeq)
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Publish 3 messages — no interior deletes.
        for (var i = 0; i < 3; i++)
            s.StoreMsg("foo", null, [], 0);

        var state = s.State();
        state.NumDeleted.ShouldBe(0);
        state.Deleted.ShouldBeNull();

        // Removing the middle message creates an interior delete.
        s.RemoveMsg(2).ShouldBeTrue();
        state = s.State();
        state.NumDeleted.ShouldBe(1);
        state.Deleted.ShouldNotBeNull();
        state.Deleted!.Length.ShouldBe(1);

        // Compacting must always clean up the interior delete.
        s.Compact(compactSeq);
        state = s.State();
        state.NumDeleted.ShouldBe(0);
        state.Deleted.ShouldBeNull();

        // Validate first/last sequence.
        var expectedFirst = Math.Max(3UL, compactSeq);
        state.FirstSeq.ShouldBe(expectedFirst);
        state.LastSeq.ShouldBe(3UL);
    }

    // -------------------------------------------------------------------------
    // TruncateCleansUpDmap — parameterised over truncate sequences 0, 1
    // -------------------------------------------------------------------------

    // Go: TestStoreTruncateCleansUpDmap server/store_test.go:500
    [Theory]
    [InlineData(0UL)]
    [InlineData(1UL)]
    public void Truncate_CleansUpDmap(ulong truncateSeq)
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Publish 3 messages — no interior deletes.
        for (var i = 0; i < 3; i++)
            s.StoreMsg("foo", null, [], 0);

        var state = s.State();
        state.NumDeleted.ShouldBe(0);
        state.Deleted.ShouldBeNull();

        // Removing the middle message creates an interior delete.
        s.RemoveMsg(2).ShouldBeTrue();
        state = s.State();
        state.NumDeleted.ShouldBe(1);
        state.Deleted.ShouldNotBeNull();
        state.Deleted!.Length.ShouldBe(1);

        // Truncating must always clean up the interior delete.
        s.Truncate(truncateSeq);
        state = s.State();
        state.NumDeleted.ShouldBe(0);
        state.Deleted.ShouldBeNull();

        // Validate first/last sequence after truncate.
        var expectedFirst = Math.Min(1UL, truncateSeq);
        state.FirstSeq.ShouldBe(expectedFirst);
        state.LastSeq.ShouldBe(truncateSeq);
    }

    // -------------------------------------------------------------------------
    // PurgeEx with zero sequence — must equal Purge
    // -------------------------------------------------------------------------

    // Go: TestStorePurgeExZero server/store_test.go:552
    [Fact]
    public void PurgeEx_ZeroSeq_EquivalentToPurge()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Simple purge all — stream should be empty but first seq = last seq + 1.
        s.Purge();
        var ss = s.State();
        ss.FirstSeq.ShouldBe(1UL);
        ss.LastSeq.ShouldBe(0UL);

        // PurgeEx with seq=0 must produce the same result.
        s.PurgeEx("", 0, 0);
        ss = s.State();
        ss.FirstSeq.ShouldBe(1UL);
        ss.LastSeq.ShouldBe(0UL);
    }

    // -------------------------------------------------------------------------
    // UpdateConfig TTL state — message survives when TTL is disabled
    // -------------------------------------------------------------------------

    // Go: TestStoreUpdateConfigTTLState server/store_test.go:574
    [Fact]
    [SlopwatchSuppress("SW004", "TTL expiry test requires real wall-clock time to elapse; Thread.Sleep waits for message TTL to expire or survive")]
    public void UpdateConfigTTLState_MessageSurvivesWhenTtlDisabled()
    {
        var cfg = new StreamConfig
        {
            Name = "TEST",
            Subjects = ["foo"],
            Storage = StorageType.Memory,
            AllowMsgTtl = false,
        };
        var ms = new MemStore(cfg);
        var s = Sync(ms);

        // TTLs disabled — message with ttl=1s should survive even after 2s.
        var (seq, _) = s.StoreMsg("foo", null, [], 1);
        Thread.Sleep(2_000);
        // Should not throw — message should still be present.
        var loaded = s.LoadMsg(seq, null);
        loaded.Sequence.ShouldBe(seq);

        // Now enable TTLs.
        cfg.AllowMsgTtl = true;
        s.UpdateConfig(cfg);

        // TTLs enabled — message with ttl=1s should expire.
        var (seq2, _) = s.StoreMsg("foo", null, [], 1);
        Thread.Sleep(2_500);
        // Should throw — message should have expired.
        Should.Throw<KeyNotFoundException>(() => s.LoadMsg(seq2, null));

        // Now disable TTLs again.
        cfg.AllowMsgTtl = false;
        s.UpdateConfig(cfg);

        // TTLs disabled — message with ttl=1s should survive.
        var (seq3, _) = s.StoreMsg("foo", null, [], 1);
        Thread.Sleep(2_000);
        // Should not throw — TTL wheel is gone so message stays.
        var loaded3 = s.LoadMsg(seq3, null);
        loaded3.Sequence.ShouldBe(seq3);
    }

    // -------------------------------------------------------------------------
    // StreamInteriorDeleteAccounting — MemStore subset (no FileStore restart)
    // -------------------------------------------------------------------------

    // Go: TestStoreStreamInteriorDeleteAccounting server/store_test.go:621
    // Tests TruncateWithRemove and TruncateWithErase variants on MemStore.
    [Theory]
    [InlineData(false, "TruncateWithRemove")]
    [InlineData(false, "TruncateWithErase")]
    [InlineData(false, "SkipMsg")]
    [InlineData(false, "SkipMsgs")]
    [InlineData(true, "TruncateWithRemove")]
    [InlineData(true, "TruncateWithErase")]
    [InlineData(true, "SkipMsg")]
    [InlineData(true, "SkipMsgs")]
    public void InteriorDeleteAccounting_StateIsCorrect(bool empty, string actionTitle)
    {
        var ms = new MemStore();
        var s = Sync(ms);

        ulong lseq = 0;
        if (!empty)
        {
            var (storedSeq, _) = s.StoreMsg("foo", null, [], 0);
            storedSeq.ShouldBe(1UL);
            lseq = storedSeq;
        }
        lseq++;

        switch (actionTitle)
        {
            case "TruncateWithRemove":
            {
                var (storedSeq, _) = s.StoreMsg("foo", null, [], 0);
                storedSeq.ShouldBe(lseq);
                s.RemoveMsg(lseq).ShouldBeTrue();
                s.Truncate(lseq);
                break;
            }
            case "TruncateWithErase":
            {
                var (storedSeq, _) = s.StoreMsg("foo", null, [], 0);
                storedSeq.ShouldBe(lseq);
                s.EraseMsg(lseq).ShouldBeTrue();
                s.Truncate(lseq);
                break;
            }
            case "SkipMsg":
            {
                s.SkipMsg(0);
                break;
            }
            case "SkipMsgs":
            {
                s.SkipMsgs(lseq, 1);
                break;
            }
        }

        // Confirm state.
        var before = s.State();
        if (empty)
        {
            before.Msgs.ShouldBe(0UL);
            before.FirstSeq.ShouldBe(2UL);
            before.LastSeq.ShouldBe(1UL);
        }
        else
        {
            before.Msgs.ShouldBe(1UL);
            before.FirstSeq.ShouldBe(1UL);
            before.LastSeq.ShouldBe(2UL);
        }
    }

    // -------------------------------------------------------------------------
    // GetSeqFromTime with interior deletes gap
    // -------------------------------------------------------------------------

    // Go: TestStoreGetSeqFromTimeWithInteriorDeletesGap server/store_test.go:874
    [Fact]
    public void GetSeqFromTime_WithInteriorDeletesGap()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Use StoreRawMsg with explicit timestamps to avoid flakiness under CPU pressure.
        var baseTs = (DateTime.UtcNow.Ticks - DateTime.UnixEpoch.Ticks) * 100L;
        for (var i = 0; i < 10; i++)
            s.StoreRawMsg("foo", null, [], (ulong)(i + 1), baseTs + i * 1_000_000L, 0, false);

        var startTs = baseTs + 1_000_000L; // timestamp of seq 2 (i == 1)

        // Create a delete gap in the middle: seqs 4-7 deleted.
        // A naive binary search would hit deleted sequences and return wrong result.
        for (var seq = 4UL; seq <= 7UL; seq++)
            s.RemoveMsg(seq).ShouldBeTrue();

        // Convert Unix nanoseconds timestamp to DateTime.
        var t = new DateTime(startTs / 100L + DateTime.UnixEpoch.Ticks, DateTimeKind.Utc);
        var found = s.GetSeqFromTime(t);
        found.ShouldBe(2UL);
    }

    // -------------------------------------------------------------------------
    // GetSeqFromTime with trailing deletes
    // -------------------------------------------------------------------------

    // Go: TestStoreGetSeqFromTimeWithTrailingDeletes server/store_test.go:900
    [Fact]
    public void GetSeqFromTime_WithTrailingDeletes()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        // Use StoreRawMsg with explicit timestamps to avoid flakiness under CPU pressure.
        var baseTs = (DateTime.UtcNow.Ticks - DateTime.UnixEpoch.Ticks) * 100L;
        for (var i = 0; i < 3; i++)
            s.StoreRawMsg("foo", null, [], (ulong)(i + 1), baseTs + i * 1_000_000L, 0, false);

        var startTs = baseTs + 1_000_000L; // timestamp of seq 2 (i == 1)

        // Delete last message — trailing delete.
        s.RemoveMsg(3).ShouldBeTrue();

        var t = new DateTime(startTs / 100L + DateTime.UnixEpoch.Ticks, DateTimeKind.Utc);
        var found = s.GetSeqFromTime(t);
        found.ShouldBe(2UL);
    }

    // -------------------------------------------------------------------------
    // MaxMsgsPerUpdateBug — per-subject limit enforced on config update
    // -------------------------------------------------------------------------

    // Go: TestStoreMaxMsgsPerUpdateBug server/store_test.go:405
    [Fact]
    public void MaxMsgsPerUpdateBug_ReducesOnConfigUpdate()
    {
        var cfg = new StreamConfig
        {
            Name = "TEST",
            Subjects = ["foo"],
            MaxMsgsPer = 0,
            Storage = StorageType.Memory,
        };
        var ms = new MemStore(cfg);
        var s = Sync(ms);

        for (var i = 0; i < 5; i++)
            s.StoreMsg("foo", null, [], 0);

        var state = s.State();
        state.Msgs.ShouldBe(5UL);
        state.FirstSeq.ShouldBe(1UL);
        state.LastSeq.ShouldBe(5UL);

        // Update max messages per-subject from 0 (infinite) to 1.
        // Since the per-subject limit was not specified before, messages should be
        // removed upon config update, leaving only the most recent.
        cfg.MaxMsgsPer = 1;
        s.UpdateConfig(cfg);

        state = s.State();
        state.Msgs.ShouldBe(1UL);
        state.FirstSeq.ShouldBe(5UL);
        state.LastSeq.ShouldBe(5UL);
    }

    // -------------------------------------------------------------------------
    // MultiLastSeqs and LoadLastMsg with lazy subject state
    // -------------------------------------------------------------------------

    // Go: TestFileStoreMultiLastSeqsAndLoadLastMsgWithLazySubjectState server/store_test.go:921
    [Fact]
    public void MultiLastSeqs_AndLoadLastMsg_WithLazySubjectState()
    {
        var ms = new MemStore();
        var s = Sync(ms);

        for (var i = 0; i < 3; i++)
            s.StoreMsg("foo", null, [], 0);

        // MultiLastSeqs for "foo" should return [3].
        var seqs = s.MultiLastSeqs(["foo"], 0, -1);
        seqs.Length.ShouldBe(1);
        seqs[0].ShouldBe(3UL);

        // Remove last message — lazy last needs update.
        s.RemoveMsg(3).ShouldBeTrue();

        seqs = s.MultiLastSeqs(["foo"], 0, -1);
        seqs.Length.ShouldBe(1);
        seqs[0].ShouldBe(2UL);

        // Store another and load it as last.
        s.StoreMsg("foo", null, [], 0); // seq 4
        var lastMsg = s.LoadLastMsg("foo", null);
        lastMsg.Sequence.ShouldBe(4UL);

        // Remove seq 4 — lazy last update again.
        s.RemoveMsg(4).ShouldBeTrue();
        lastMsg = s.LoadLastMsg("foo", null);
        lastMsg.Sequence.ShouldBe(2UL);
    }
}