syntax = "proto3";
package waymaker.kv;

option go_package = "/apis/waymaker_kv";

// ============================================================
// WaymakerKvService — distributed key-value store implemented
// as a thin façade over the streams subsystem. Each KV bucket
// is backed by a stream named `kv:<bucket>`; KV revisions are
// stream sequence numbers; KV deletes are tombstones (per the
// WIRE_SPEC.md tombstone header convention).
//
// The service lives in its own proto so the wire surface is
// composable: an operator could ship a KV-only build, or layer
// KV on top of someone else's streams implementation.
// ============================================================

service WaymakerKvService {
  // ----- Bucket lifecycle -------------------------------------
  rpc CreateBucket (KvCreateBucketRequest) returns (KvCreateBucketResponse);
  rpc DeleteBucket (KvDeleteBucketRequest) returns (KvDeleteBucketResponse);

  // ----- Mutations --------------------------------------------
  rpc Put (KvPutRequest) returns (KvPutResponse);
  // CAS create — succeeds only when the key has never been
  // written or its current value is a tombstone.
  rpc Create (KvCreateRequest) returns (KvPutResponse);
  // CAS update — succeeds only when `expected_revision`
  // matches the server-side revision.
  rpc Update (KvUpdateRequest) returns (KvPutResponse);
  rpc Delete (KvDeleteRequest) returns (KvDeleteResponse);

  // ----- Reads ------------------------------------------------
  rpc Get (KvGetRequest) returns (KvGetResponse);
  rpc Keys (KvKeysRequest) returns (KvKeysResponse);
  rpc History (KvHistoryRequest) returns (KvHistoryResponse);

  // ----- TTL refresh ------------------------------------------
  rpc Touch (KvTouchRequest) returns (KvPutResponse);

  // ----- Watch ------------------------------------------------
  // Server-streamed event flow for a single bucket. When `key`
  // is empty, every put/delete in the bucket fans out; when
  // `key` is set, only events at that key are emitted.
  rpc Watch (KvWatchRequest) returns (stream KvWatchEvent);
}

message KvCreateBucketRequest {
  string bucket = 1;
  uint64 max_bytes = 2;       // 0 = unbounded
  uint64 max_value_size = 3;  // 0 = no per-value cap
  // Bucket-level TTL (ms). 0 = no time-based eviction.
  // Independent of per-key TTL set via Put.
  uint64 max_age_ms = 4;
  bool ephemeral = 5;
  // Per-key revision cap. 0 (default) = unbounded — history depth
  // is then bounded only by the bucket's stream-level retention
  // (max_age_ms / max_bytes). When N > 0, after each successful
  // write to a key, older revisions of *that key* beyond the N
  // most recent are dropped via per-message pruning. Useful when
  // one bucket hosts many keys with very different write rates —
  // a fast-churning key won't crowd out older revisions of a
  // slow-changing key. NATS JetStream's "MaxRevisions" semantic.
  uint64 max_revisions = 6;
}

message KvCreateBucketResponse {
  bool success = 1;
  string result_code = 2;     // "ok" | "already_exists" | "invalid_config" | "internal"
  string message = 3;
}

message KvDeleteBucketRequest { string bucket = 1; }
message KvDeleteBucketResponse {
  bool success = 1;
  string result_code = 2;     // "ok" | "no_such_bucket" | "internal"
  string message = 3;
}

message KvPutRequest {
  string bucket = 1;
  string key = 2;
  bytes value = 3;
  uint64 ttl_ms = 4;          // per-key TTL; 0 = no TTL
}

message KvCreateRequest {
  string bucket = 1;
  string key = 2;
  bytes value = 3;
  uint64 ttl_ms = 4;
}

message KvUpdateRequest {
  string bucket = 1;
  string key = 2;
  bytes value = 3;
  // The revision the caller believes is current. Server returns
  // wrong_revision if mismatch.
  uint64 expected_revision = 4;
  uint64 ttl_ms = 5;
}

message KvPutResponse {
  bool success = 1;
  // "ok" | "no_such_bucket" | "wrong_revision" | "invalid_key" | "internal"
  string result_code = 2;
  string message = 3;
  uint64 revision = 4;
}

message KvGetRequest {
  string bucket = 1;
  string key = 2;
}

message KvGetResponse {
  bool success = 1;
  string result_code = 2;
  string message = 3;
  optional KvEntry entry = 4;
}

message KvEntry {
  bytes value = 1;
  uint64 revision = 2;
  int64 ts_ms = 3;
}

message KvDeleteRequest {
  string bucket = 1;
  string key = 2;
}

message KvDeleteResponse {
  bool success = 1;
  string result_code = 2;
  string message = 3;
  uint64 revision = 4;
}

message KvKeysRequest { string bucket = 1; }

message KvKeysResponse {
  bool success = 1;
  string result_code = 2;
  string message = 3;
  repeated KvKeyEntry entries = 4;
}

message KvKeyEntry {
  string key = 1;
  uint64 revision = 2;
  bool deleted = 3;
}

message KvHistoryRequest {
  string bucket = 1;
  string key = 2;
  uint64 from_revision = 3;   // 0 = from beginning
  uint64 limit = 4;           // 0 = server default
}

message KvHistoryResponse {
  bool success = 1;
  string result_code = 2;
  string message = 3;
  repeated KvHistoryEntry entries = 4;
}

message KvHistoryEntry {
  bytes value = 1;
  uint64 revision = 2;
  int64 ts_ms = 3;
  bool deleted = 4;
}

message KvTouchRequest {
  string bucket = 1;
  string key = 2;
  uint64 ttl_ms = 3;
}

message KvWatchRequest {
  string bucket = 1;
  string key = 2;             // empty = whole bucket
}

message KvWatchEvent {
  oneof event {
    KvPutEvent put = 1;
    KvDeleteEvent delete = 2;
  }
}

message KvPutEvent {
  string key = 1;
  bytes value = 2;
  uint64 revision = 3;
  int64 ts_ms = 4;
}

message KvDeleteEvent {
  string key = 1;
  uint64 revision = 2;
  int64 ts_ms = 3;
}