// Copyright (c) 2019-2021 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://www.opensource.org/licenses/mit-license.php .

syntax = "proto3";
package cash.z.wallet.sdk.rpc;
option go_package = "lightwalletd/walletrpc";
option swift_prefix = "";

// Remember that proto3 fields are all optional. A field that is not present will be set to its zero value.
// bytes fields of hashes are in canonical little-endian format.

// ChainMetadata represents information about the state of the chain as of a given block.
message ChainMetadata {
    uint32 saplingCommitmentTreeSize = 1; // the size of the Sapling note commitment tree as of the end of this block
    uint32 orchardCommitmentTreeSize = 2; // the size of the Orchard note commitment tree as of the end of this block
}

// CompactBlock is a packaging of ONLY the data from a block that's needed to:
//   1. Detect a payment to your shielded Sapling address
//   2. Detect a spend of your shielded Sapling notes
//   3. Update your witnesses to generate new Sapling spend proofs.
message CompactBlock {
    uint32 protoVersion = 1;         // the version of this wire format, for storage
    uint64 height = 2;               // the height of this block
    bytes hash = 3;                  // the ID (hash) of this block, same as in block explorers
    bytes prevHash = 4;              // the ID (hash) of this block's predecessor
    uint32 time = 5;                 // Unix epoch time when the block was mined
    bytes header = 6;                // (hash, prevHash, and time) OR (full header)
    repeated CompactTx vtx = 7;      // zero or more compact transactions from this block
    ChainMetadata chainMetadata = 8; // information about the state of the chain as of this block
}

// CompactTx contains the minimum information for a wallet to know if this transaction
// is relevant to it (either pays to it or spends from it) via shielded elements
// only. This message will not encode a transparent-to-transparent transaction.
message CompactTx {
    // Index and hash will allow the receiver to call out to chain
    // explorers or other data structures to retrieve more information
    // about this transaction.
    uint64 index = 1;   // the index within the full block
    bytes hash = 2;     // the ID (hash) of this transaction, same as in block explorers

    // The transaction fee: present if server can provide. In the case of a
    // stateless server and a transaction with transparent inputs, this will be
    // unset because the calculation requires reference to prior transactions.
    // If there are no transparent inputs, the fee will be calculable as:
    //    valueBalanceSapling + valueBalanceOrchard + sum(vPubNew) - sum(vPubOld) - sum(tOut)
    uint32 fee = 3;

    repeated CompactSaplingSpend spends = 4;
    repeated CompactSaplingOutput outputs = 5;
    repeated CompactOrchardAction actions = 6;
}

// CompactSaplingSpend is a Sapling Spend Description as described in 7.3 of the Zcash
// protocol specification.
message CompactSaplingSpend {
    bytes nf = 1;   // nullifier (see the Zcash protocol specification)
}

// output encodes the `cmu` field, `ephemeralKey` field, and a 52-byte prefix of the
// `encCiphertext` field of a Sapling Output Description. These fields are described in
// section 7.4 of the Zcash protocol spec:
// https://zips.z.cash/protocol/protocol.pdf#outputencodingandconsensus
// Total size is 116 bytes.
message CompactSaplingOutput {
    bytes cmu = 1;          // note commitment u-coordinate
    bytes ephemeralKey = 2; // ephemeral public key
    bytes ciphertext = 3;   // first 52 bytes of ciphertext
}

// https://github.com/zcash/zips/blob/main/zip-0225.rst#orchard-action-description-orchardaction
// (but not all fields are needed)
message CompactOrchardAction {
    bytes nullifier = 1;        // [32] The nullifier of the input note
    bytes cmx = 2;              // [32] The x-coordinate of the note commitment for the output note
    bytes ephemeralKey = 3;     // [32] An encoding of an ephemeral Pallas public key
    bytes ciphertext = 4;       // [52] The first 52 bytes of the encCiphertext field
}