// Ported from golang/nats-server/server/jetstream_test.go
// Go reference: server/stream.go:1500-1600 (stream.update immutable field validation)
// Covers: TestJetStreamStreamUpdate, TestJetStreamStreamUpdateMaxConsumers

using NATS.Server.JetStream;
using NATS.Server.JetStream.Api;
using NATS.Server.JetStream.Models;
using Shouldly;

namespace NATS.Server.JetStream.Tests.JetStream.Streams;

public class ConfigUpdateValidationTests
{
    // Go ref: server/stream.go:1500-1600 (stream.update)
    // A valid update that only changes mutable fields (MaxMsgs) should produce no errors.
    [Fact]
    public void ValidateConfigUpdate_allows_valid_changes()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Retention = RetentionPolicy.Limits,
            Subjects = ["orders.*"],
            MaxMsgs = 100,
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Retention = RetentionPolicy.Limits,
            Subjects = ["orders.*"],
            MaxMsgs = 500,
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldBeEmpty();
    }

    // Go ref: server/stream.go:1511-1513 (storage type immutability check)
    // Changing storage type from Memory to File must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_storage_type_change()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.File,
            Subjects = ["orders.*"],
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("storage type"));
    }

    // Go ref: server/stream.go:1530-1535 (mirror immutability)
    // Changing the mirror origin must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_mirror_change()
    {
        var existing = new StreamConfig
        {
            Name = "MIRROR_STREAM",
            Storage = StorageType.Memory,
            Mirror = "ORIGIN_A",
        };
        var proposed = new StreamConfig
        {
            Name = "MIRROR_STREAM",
            Storage = StorageType.Memory,
            Mirror = "ORIGIN_B",
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("mirror configuration"));
    }

    // Go ref: server/stream.go:1520-1525 (retention policy immutability)
    // Changing the retention policy must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_retention_change()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Retention = RetentionPolicy.Limits,
            Subjects = ["orders.*"],
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Retention = RetentionPolicy.WorkQueue,
            Subjects = ["orders.*"],
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("retention policy"));
    }

    // Go ref: server/stream.go:1500-1502 (sealed stream guard)
    // Any modification attempt on a sealed stream must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_sealed_stream_changes()
    {
        var existing = new StreamConfig
        {
            Name = "SEALED",
            Storage = StorageType.Memory,
            Sealed = true,
            Subjects = ["sealed.*"],
        };
        var proposed = new StreamConfig
        {
            Name = "SEALED",
            Storage = StorageType.Memory,
            Sealed = true,
            Subjects = ["sealed.new.*"],
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("sealed stream"));
    }

    // Go ref: server/stream.go:1537-1542 (sources immutability)
    // Changing the sources list after creation must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_source_change()
    {
        var existing = new StreamConfig
        {
            Name = "AGG",
            Storage = StorageType.Memory,
            Sources =
            [
                new StreamSourceConfig { Name = "SRC_A" },
                new StreamSourceConfig { Name = "SRC_B" },
            ],
        };
        var proposed = new StreamConfig
        {
            Name = "AGG",
            Storage = StorageType.Memory,
            Sources =
            [
                new StreamSourceConfig { Name = "SRC_A" },
                new StreamSourceConfig { Name = "SRC_C" },
            ],
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("sources cannot be changed"));
    }

    // Go ref: server/jetstream.go — subject overlap detection between streams.
    // Proposing subjects that collide with another stream's subjects must be rejected.
    [Fact]
    public void ValidateConfigUpdate_detects_subject_overlap()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.>"],
        };
        var otherStreams = new[]
        {
            new StreamConfig
            {
                Name = "ARCHIVE",
                Storage = StorageType.Memory,
                Subjects = ["orders.archived"],
            },
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed, otherStreams);

        errors.ShouldContain(e => e.Contains("ARCHIVE"));
    }

    // Go ref: server/jetstream.go — no error for non-overlapping subject sets.
    // Proposing subjects that do not overlap with other streams must succeed.
    [Fact]
    public void ValidateConfigUpdate_allows_non_overlapping_subjects()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.>"],
        };
        var otherStreams = new[]
        {
            new StreamConfig
            {
                Name = "EVENTS",
                Storage = StorageType.Memory,
                Subjects = ["events.*"],
            },
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed, otherStreams);

        errors.ShouldBeEmpty();
    }

    // Go ref: server/stream.go — MaxConsumers may not be decreased.
    // Decreasing MaxConsumers from a positive value must be rejected.
    [Fact]
    public void ValidateConfigUpdate_rejects_max_consumers_decrease()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            MaxConsumers = 10,
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            MaxConsumers = 5,
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldContain(e => e.Contains("max consumers can only be increased"));
    }

    // Go ref: server/stream.go — MaxConsumers may be raised without restriction.
    [Fact]
    public void ValidateConfigUpdate_allows_max_consumers_increase()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            MaxConsumers = 5,
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            MaxConsumers = 20,
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldBeEmpty();
    }

    // Go ref: server/stream.go — Go server supports even replica counts (e.g., R2).
    // Even replicas should be accepted by config update validation.
    [Fact]
    public void ValidateConfigUpdate_accepts_even_replicas()
    {
        var existing = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            Replicas = 1,
        };
        var proposed = new StreamConfig
        {
            Name = "ORDERS",
            Storage = StorageType.Memory,
            Subjects = ["orders.*"],
            Replicas = 2,
        };

        var errors = StreamManager.ValidateConfigUpdate(existing, proposed);

        errors.ShouldBeEmpty();
    }

    // Go ref: server/stream.go:1500-1600 (stream.update) — integration via StreamManager.
    // CreateOrUpdate must reject an update that changes storage type.
    [Fact]
    public void CreateOrUpdate_rejects_invalid_config_update()
    {
        var manager = new StreamManager();

        var createResult = manager.CreateOrUpdate(new StreamConfig
        {
            Name = "EVENTS",
            Storage = StorageType.Memory,
            Subjects = ["events.*"],
        });
        createResult.Error.ShouldBeNull();

        var updateResult = manager.CreateOrUpdate(new StreamConfig
        {
            Name = "EVENTS",
            Storage = StorageType.File,
            Subjects = ["events.*"],
        });

        updateResult.Error.ShouldNotBeNull();
        updateResult.Error!.Description.ShouldContain("storage type");
    }
}