ObsidianDragon/src/chat/chat_protocol.h

#pragma once

#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>
#include <vector>

#ifndef DRAGONX_ENABLE_CHAT
#define DRAGONX_ENABLE_CHAT 0
#endif

namespace dragonx::chat {

enum class HushChatHeaderType {
    Message,
    ContactRequest,
    Control        // a self-addressed control signal (delete / restore / mark sensitive); carries an `op`
};

struct HushChatHeader {
    int header_number = 0;
    int version = 0;
    std::string reply_zaddr;
    std::string conversation_id;
    HushChatHeaderType type = HushChatHeaderType::Message;
    std::string op;   // Control only ("del" / "res" / "sensitive" / "unsensitive" / future ops); empty otherwise
    std::string secretstream_header_hex;
    std::string public_key_hex;
    // Message only: how many payload outputs this message's ciphertext is split across (header "n").
    // 1 = the classic single-payload message (field omitted on the wire). >1 means the payloads are
    // index-prefixed ciphertext chunks reassembled in order. For tier 2 all N chunks ride ONE tx; for
    // tier 3 (message_id set) "n" is the TOTAL chunk count spread across several sibling transactions.
    int parts = 1;
    // Message only, larger-messages tier 3: when a message needs more chunks than one tx can carry, it
    // is split across several transactions that all share this random id (header "mid"); each tx's
    // payloads carry their GLOBAL chunk index (0..parts-1). Empty = a single-tx message (tier 1/2).
    std::string message_id;
    // Optional sender-stamped compose time (header "ts", Unix seconds). 0 = absent (older sender) → the
    // receiver falls back to the tx/receive time. Lets both sides show the SAME (send) time.
    std::int64_t sent_at = 0;
};

struct HushChatHeaderParseResult {
    bool ok = false;
    HushChatHeader header;
    std::string error;
};

struct HushChatMemoOutput {
    std::size_t position = 0;
    std::string memo;
};

struct HushChatMemoPair {
    HushChatHeader header;
    std::size_t header_position = 0;
    std::size_t payload_position = 0;
    std::string payload_memo;
    // Larger-messages tier 3: a single transaction that carries only PART of a bigger message (the rest
    // ride sibling txs sharing message_id). payload_memo is then empty; partial_chunks holds this tx's
    // (global index, ciphertext-hex chunk) pairs and total_parts is the whole message's chunk count.
    std::string message_id;
    int total_parts = 0;
    std::vector<std::pair<int, std::string>> partial_chunks;
};

enum class HushChatMemoGroupingIssue {
    InvalidHeader,
    MissingPayload,
    DuplicateHeader,
    OversizedMemo
};

struct HushChatMemoGroupingIssueInfo {
    HushChatMemoGroupingIssue issue = HushChatMemoGroupingIssue::InvalidHeader;
    std::size_t position = 0;
    std::string detail;
};

struct HushChatMemoGroupingResult {
    std::vector<HushChatMemoPair> pairs;
    std::vector<HushChatMemoGroupingIssueInfo> issues;
    std::size_t ignored_memo_count = 0;
};

struct HushChatTransactionInput {
    std::string txid;
    std::vector<HushChatMemoOutput> outputs;
};

struct HushChatTransactionMetadata {
    std::string txid;
    HushChatHeaderType type = HushChatHeaderType::Message;
    std::string op;                      // Control only: the control op ("del"/"res"/...); empty otherwise
    std::string conversation_id;
    std::string reply_zaddr;
    std::size_t header_position = 0;
    std::size_t payload_position = 0;
    std::size_t payload_size = 0;
    // Decrypt inputs carried through from the paired header + payload memos so the chat
    // service can actually decrypt (a Message) or read the request (a ContactRequest).
    std::string sender_public_key_hex;   // header "p": peer crypto_kx public key (hex)
    std::string secretstream_header_hex; // header "e": secretstream header (hex; empty for ContactRequest)
    std::string payload_memo;            // ciphertext hex (Message) or plaintext request text (ContactRequest)
    std::int64_t sent_at = 0;            // header "ts": sender compose time (Unix s); 0 = absent → use tx time
    // Larger-messages tier 3 (a multi-transaction Message): message_id ties this tx's slice to its
    // siblings, total_parts is the whole message's chunk count, and partial_chunks are this tx's
    // (global index, ciphertext-hex) chunks. Empty message_id = an ordinary single-tx message (payload
    // in payload_memo). The chat service accumulates partials by message_id and reassembles when whole.
    std::string message_id;
    int total_parts = 0;
    std::vector<std::pair<int, std::string>> partial_chunks;
};

struct HushChatTransactionExtractionResult {
    bool feature_enabled = false;
    std::vector<HushChatTransactionMetadata> metadata;
    std::vector<HushChatMemoGroupingIssueInfo> issues;
    std::size_t ignored_memo_count = 0;
};

constexpr int kHushChatSupportedVersion = 0;
constexpr std::size_t kHushChatMemoByteLimit = 512;
// Larger-messages tier 2: the most payload outputs a single transaction may carry (one tx). Keeps the
// chat tx well under the shielded max_tx_size after Sietch decoy padding + proving cost. A message
// needing more chunks than this spills into sibling transactions (tier 3), up to kHushChatMaxMessageChunks.
constexpr int kHushChatMaxMessageParts = 16;
// Larger-messages tier 3: the most chunks a single message may span IN TOTAL, across all its sibling
// transactions (ceil(chunks / kHushChatMaxMessageParts) txs, each a separate 0-value chat send + fee).
// Bounds the on-chain cost / broadcast time of one message; beyond this compose returns TooLong. The
// 2-hex global part index (below) tops out at 256, so this must stay ≤ 256.
constexpr int kHushChatMaxMessageChunks = 64;
// Each multi-part payload chunk is prefixed with a 2-hex-char (1-byte) part index so the receiver can
// reorder chunks after the daemon shuffles a tx's outputs. 2 hex covers indices 0..255 (>> the cap).
constexpr std::size_t kHushChatPartIndexHexLen = 2;
constexpr std::size_t kHushChatPublicKeyHexLength = 64;
constexpr std::size_t kHushChatSecretstreamHeaderHexLength = 48;

constexpr bool hushChatFeatureEnabledAtBuild()
{
    return DRAGONX_ENABLE_CHAT != 0;
}

HushChatHeaderParseResult parseHushChatHeaderMemo(const std::string& memo);
HushChatMemoGroupingResult groupHushChatMemoOutputs(const std::vector<HushChatMemoOutput>& outputs);
HushChatTransactionExtractionResult extractHushChatTransactionMetadata(
    const HushChatTransactionInput& transaction,
    bool featureEnabled = hushChatFeatureEnabledAtBuild());
const char* hushChatHeaderTypeName(HushChatHeaderType type);
const char* hushChatMemoGroupingIssueName(HushChatMemoGroupingIssue issue);

} // namespace dragonx::chat