syntax = "proto3";

package lattice;

// 1. The Wrapper (What flies over the wire)
message SignedEntry {
  // The serialized bytes of the 'Entry' message.
  // We keep this as raw bytes so the signature verification is stable.
  bytes entry_bytes = 1;
  
  // Ed25519 Signature of 'entry_bytes'
  bytes signature = 2;
  
  // Public Key of the author (32 bytes)
  bytes author_id = 3;
}

// 2. The Log Entry (The Atomic Unit)
message Entry {
  // Versioning allows us to change the format radically later if needed
  uint32 version = 1;

  // Store this entry belongs to (16-byte UUID)
  bytes store_id = 6;

  // Ordering Metadata
  bytes prev_hash = 2;   // Link to previous sigchain entry (32 bytes)
  uint64 seq = 3;        // Monotonic sequence number
  HLC timestamp = 4;     // Hybrid Logical Clock

  // DAG ancestry: hashes of entries this supersedes (separate from sigchain)
  repeated bytes parent_hashes = 7;

  // The Batch of Operations
  repeated Operation ops = 5;
}

// HeadInfo: a tip/head in the DAG for a key
message HeadInfo {
  bytes value = 1;       // The value at this head
  uint64 hlc = 2;        // Combined HLC for ordering (wall_time_ms << 16 | counter)
  bytes author = 3;      // Author's public key (32 bytes)
  bytes hash = 4;        // Hash of the SignedEntry that created this head
  bool tombstone = 5;    // True if this head represents a delete
}

// HeadList: wrapper for storing multiple heads per key in state.db
message HeadList {
  repeated HeadInfo heads = 1;
}

// AuthorState: tracks last applied entry per author for replay optimization
message AuthorState {
  uint64 seq = 1;        // Last applied seq for this author's sigchain
  bytes hash = 2;        // Hash of last applied entry
  uint64 log_offset = 3; // Byte offset in log file for fast resume
}

// Hybrid Logical Clock
message HLC {
  uint64 wall_time = 1;  // Unix timestamp (ms)
  uint32 counter = 2;    // Logical counter for same-ms ordering
}

// 3. The Operation (The Change)
message Operation {
  // "oneof" is how Protobuf handles Rust Enums
  oneof op_type {
    PutOp put = 1;
    DeleteOp delete = 2;
    // Future: MergeOp merge = 3;
  }
}

message PutOp {
  bytes key = 1;
  bytes value = 2;
}

message DeleteOp {
  bytes key = 1;
}

// 4. The Sync Handshake (Vector Clocks)
message SyncState {
  repeated Frontier frontiers = 1;
  HLC sender_hlc = 2;  // Sender's current clock (for peer time awareness)
}

message Frontier {
  bytes author_id = 1;  // Ed25519 public key (32 bytes)
  uint64 max_seq = 2;   // Highest sequence number seen from this author
  repeated bytes head_hashes = 3;  // All head hashes for this author
}

// 5. Log File Record (wrapper for storage)
message LogRecord {
  bytes hash = 1;         // BLAKE3 hash of entry_bytes (32 bytes)
  bytes entry_bytes = 2;  // Serialized SignedEntry
}

// 6. Join Protocol Messages (new node joining existing mesh)
message JoinRequest {
  bytes node_pubkey = 1;  // Joining node's public key (32 bytes)
}

message JoinResponse {
  bytes store_uuid = 1;   // Root store UUID (16 bytes) for new node to create
  bytes inviter_pubkey = 2;  // Inviter's public key for verification
}

// 7. Sync Protocol Messages (bidirectional sync after join)
message SyncRequest {
  SyncState state = 1;    // Sender's sync state (for incremental sync)
  bool full_sync = 2;     // If true, request all entries (for join)
}

message SyncResponse {
  SyncState state = 1;    // Responder's sync state
}

message SyncEntry {
  bytes signed_entry = 1; // Serialized SignedEntry
  bytes hash = 2;         // Hash for verification
}

message SyncDone {
  uint64 entries_sent = 1;
}

// 8. Peer Message Wrapper (for proper message type discrimination)
message PeerMessage {
  oneof message {
    JoinRequest join_request = 1;
    JoinResponse join_response = 2;
    SyncRequest sync_request = 3;
    SyncResponse sync_response = 4;
    SyncEntry sync_entry = 5;
    SyncDone sync_done = 6;
  }
}