using NATS.Server.JetStream.Models;

// Alias for the full Go-parity StreamState in this namespace.
using StorageStreamState = NATS.Server.JetStream.Storage.StreamState;

namespace NATS.Server.JetStream.Storage;

// Go: server/store.go:91
/// <summary>
/// Abstraction over a single stream's message store.
/// The async methods (AppendAsync, LoadAsync, …) are used by the current
/// high-level JetStream layer. The sync methods (StoreMsg, LoadMsg, State, …)
/// mirror Go's StreamStore interface exactly and will be the primary surface
/// once the block-engine FileStore implementation lands.
/// </summary>
public interface IStreamStore
{
    // -------------------------------------------------------------------------
    // Async helpers — used by the current JetStream layer
    // -------------------------------------------------------------------------

    ValueTask<ulong> AppendAsync(string subject, ReadOnlyMemory<byte> payload, CancellationToken ct);
    ValueTask<StoredMessage?> LoadAsync(ulong sequence, CancellationToken ct);
    ValueTask<StoredMessage?> LoadLastBySubjectAsync(string subject, CancellationToken ct);
    ValueTask<IReadOnlyList<StoredMessage>> ListAsync(CancellationToken ct);
    ValueTask<bool> RemoveAsync(ulong sequence, CancellationToken ct);
    ValueTask PurgeAsync(CancellationToken ct);
    ValueTask<byte[]> CreateSnapshotAsync(CancellationToken ct);
    ValueTask RestoreSnapshotAsync(ReadOnlyMemory<byte> snapshot, CancellationToken ct);

    // Returns Models.StreamState for API-layer JSON serialisation compatibility.
    // Existing MemStore/FileStore implementations return this type.
    ValueTask<ApiStreamState> GetStateAsync(CancellationToken ct);

    // Cached state properties — avoid GetStateAsync on the publish hot path.
    // These are maintained incrementally by FileStore/MemStore and are O(1).
    ulong LastSeq => throw new NotSupportedException("LastSeq not implemented.");
    ulong MessageCount => throw new NotSupportedException("MessageCount not implemented.");
    ulong TotalBytes => throw new NotSupportedException("TotalBytes not implemented.");
    ulong FirstSeq => throw new NotSupportedException("FirstSeq not implemented.");

    // -------------------------------------------------------------------------
    // Go-parity sync interface — mirrors server/store.go StreamStore
    // Default implementations throw NotSupportedException so existing
    // MemStore / FileStore implementations continue to compile while the
    // block-engine port is in progress.
    // -------------------------------------------------------------------------

    // Go: StreamStore.StoreMsg — append a message; returns (seq, timestamp)
    (ulong Seq, long Ts) StoreMsg(string subject, byte[]? hdr, byte[] msg, long ttl)
        => throw new NotSupportedException("Block-engine StoreMsg not yet implemented.");

    // Go: StreamStore.StoreRawMsg — store a raw message at a specified sequence
    void StoreRawMsg(string subject, byte[]? hdr, byte[] msg, ulong seq, long ts, long ttl, bool discardNewCheck)
        => throw new NotSupportedException("Block-engine StoreRawMsg not yet implemented.");

    // Go: StreamStore.SkipMsg — reserve a sequence without storing a message
    ulong SkipMsg(ulong seq)
        => throw new NotSupportedException("Block-engine SkipMsg not yet implemented.");

    // Go: StreamStore.SkipMsgs — reserve a range of sequences
    void SkipMsgs(ulong seq, ulong num)
        => throw new NotSupportedException("Block-engine SkipMsgs not yet implemented.");

    // Go: StreamStore.FlushAllPending — flush any buffered writes to backing storage
    Task FlushAllPending()
        => throw new NotSupportedException("Block-engine FlushAllPending not yet implemented.");

    // Go: StreamStore.LoadMsg — load message by exact sequence; sm is an optional reusable buffer
    StoreMsg LoadMsg(ulong seq, StoreMsg? sm)
        => throw new NotSupportedException("Block-engine LoadMsg not yet implemented.");

    // Go: StreamStore.LoadNextMsg — load next message at or after start matching filter;
    //     returns the message and the number of sequences skipped
    (StoreMsg Msg, ulong Skip) LoadNextMsg(string filter, bool wc, ulong start, StoreMsg? sm)
        => throw new NotSupportedException("Block-engine LoadNextMsg not yet implemented.");

    // Go: StreamStore.LoadLastMsg — load the most recent message on a given subject
    StoreMsg LoadLastMsg(string subject, StoreMsg? sm)
        => throw new NotSupportedException("Block-engine LoadLastMsg not yet implemented.");

    // Go: StreamStore.LoadPrevMsg — load message before start sequence
    StoreMsg LoadPrevMsg(ulong start, StoreMsg? sm)
        => throw new NotSupportedException("Block-engine LoadPrevMsg not yet implemented.");

    // Go: StreamStore.RemoveMsg — soft-delete a message by sequence; returns true if found
    bool RemoveMsg(ulong seq)
        => throw new NotSupportedException("Block-engine RemoveMsg not yet implemented.");

    // Go: StreamStore.EraseMsg — overwrite a message with random bytes before removing it
    bool EraseMsg(ulong seq)
        => throw new NotSupportedException("Block-engine EraseMsg not yet implemented.");

    // Go: StreamStore.Purge — remove all messages; returns count purged
    ulong Purge()
        => throw new NotSupportedException("Block-engine Purge not yet implemented.");

    // Go: StreamStore.PurgeEx — purge messages on subject up to seq keeping keep newest
    ulong PurgeEx(string subject, ulong seq, ulong keep)
        => throw new NotSupportedException("Block-engine PurgeEx not yet implemented.");

    // Go: StreamStore.Compact — remove all messages with seq < given sequence
    ulong Compact(ulong seq)
        => throw new NotSupportedException("Block-engine Compact not yet implemented.");

    // Go: StreamStore.Truncate — remove all messages with seq > given sequence
    void Truncate(ulong seq)
        => throw new NotSupportedException("Block-engine Truncate not yet implemented.");

    // Go: StreamStore.GetSeqFromTime — return first sequence at or after wall-clock time t
    ulong GetSeqFromTime(DateTime t)
        => throw new NotSupportedException("Block-engine GetSeqFromTime not yet implemented.");

    // Go: StreamStore.FilteredState — compact state for messages matching subject at or after seq
    SimpleState FilteredState(ulong seq, string subject)
        => throw new NotSupportedException("Block-engine FilteredState not yet implemented.");

    // Go: StreamStore.SubjectsState — per-subject SimpleState for all subjects matching filter
    Dictionary<string, SimpleState> SubjectsState(string filterSubject)
        => throw new NotSupportedException("Block-engine SubjectsState not yet implemented.");

    // Go: StreamStore.SubjectsTotals — per-subject message count for subjects matching filter
    Dictionary<string, ulong> SubjectsTotals(string filterSubject)
        => throw new NotSupportedException("Block-engine SubjectsTotals not yet implemented.");

    // Go: StreamStore.AllLastSeqs — last sequence for every subject in the stream
    ulong[] AllLastSeqs()
        => throw new NotSupportedException("Block-engine AllLastSeqs not yet implemented.");

    // Go: StreamStore.MultiLastSeqs — last sequences for subjects matching filters, up to maxSeq
    ulong[] MultiLastSeqs(string[] filters, ulong maxSeq, int maxAllowed)
        => throw new NotSupportedException("Block-engine MultiLastSeqs not yet implemented.");

    // Go: StreamStore.SubjectForSeq — return the subject stored at the given sequence
    string SubjectForSeq(ulong seq)
        => throw new NotSupportedException("Block-engine SubjectForSeq not yet implemented.");

    // Go: StreamStore.NumPending — count messages pending from sseq on filter subject;
    //     lastPerSubject restricts to one-per-subject semantics
    (ulong Total, ulong ValidThrough) NumPending(ulong sseq, string filter, bool lastPerSubject)
        => throw new NotSupportedException("Block-engine NumPending not yet implemented.");

    // Go: StreamStore.State — return full stream state (Go-parity, with deleted sets)
    StorageStreamState State()
        => throw new NotSupportedException("Block-engine State not yet implemented.");

    // Go: StreamStore.FastState — populate a pre-allocated StreamState with the minimum
    //     fields needed for replication without allocating a new struct
    void FastState(ref StorageStreamState state)
        => throw new NotSupportedException("Block-engine FastState not yet implemented.");

    // Go: StreamStore.EncodedStreamState — binary-encode stream state for NRG replication
    byte[] EncodedStreamState(ulong failed)
        => throw new NotSupportedException("Block-engine EncodedStreamState not yet implemented.");

    // Go: StreamStore.Type — the storage type (File or Memory)
    StorageType Type()
        => throw new NotSupportedException("Block-engine Type not yet implemented.");

    // Go: StreamStore.UpdateConfig — apply a new StreamConfig without restarting the store
    void UpdateConfig(StreamConfig cfg)
        => throw new NotSupportedException("Block-engine UpdateConfig not yet implemented.");

    // Go: StreamStore.Delete — stop and delete all data; inline=true means synchronous deletion
    void Delete(bool inline)
        => throw new NotSupportedException("Block-engine Delete not yet implemented.");

    // Go: StreamStore.Stop — flush and stop without deleting data
    void Stop()
        => throw new NotSupportedException("Block-engine Stop not yet implemented.");

    // Go: StreamStore.ConsumerStore — create or open a consumer store for the named consumer
    IConsumerStore ConsumerStore(string name, DateTime created, ConsumerConfig cfg)
        => throw new NotSupportedException("Block-engine ConsumerStore not yet implemented.");

    // Go: StreamStore.ResetState — reset internal state caches (used after NRG catchup)
    void ResetState()
        => throw new NotSupportedException("Block-engine ResetState not yet implemented.");
}