loop/looprpc/client.proto

syntax = "proto3";

import "google/api/annotations.proto";

package looprpc;

/**
SwapClient is a service that handles the client side process of onchain/offchain
swaps. The service is designed for a single client.
*/
service SwapClient {
    /** loop: `out`
    LoopOut initiates an loop out swap with the given parameters. The call
    returns after the swap has been set up with the swap server. From that
    point onwards, progress can be tracked via the SwapStatus stream that is
    returned from Monitor().
    */
    rpc LoopOut(LoopOutRequest) returns (SwapResponse) {
        option (google.api.http) = {
            post: "/v1/loop/out"
            body: "*"
        };
    }

    /**
    LoopIn initiates a loop in swap with the given parameters. The call
    returns after the swap has been set up with the swap server. From that
    point onwards, progress can be tracked via the SwapStatus stream
    that is returned from Monitor().
    */
    rpc LoopIn(LoopInRequest) returns (SwapResponse);

    /** loop: `monitor`
    Monitor will return a stream of swap updates for currently active swaps.
    TODO: add MonitorSync version for REST clients.
    */
    rpc Monitor(MonitorRequest) returns(stream SwapStatus);

    /** loop: `terms`
    LoopOutTerms returns the terms that the server enforces for a loop out swap.
    */
    rpc LoopOutTerms(TermsRequest) returns(TermsResponse) {
        option (google.api.http) = {
            get: "/v1/loop/out/terms"
        };
    }

    /** loop: `quote`
    LoopOutQuote returns a quote for a loop out swap with the provided
    parameters.
    */
    rpc LoopOutQuote(QuoteRequest) returns(QuoteResponse) {
        option (google.api.http) = {
            get: "/v1/loop/out/quote/{amt}"
        };
    }

    /**
    GetTerms returns the terms that the server enforces for swaps.
    */
    rpc GetLoopInTerms(TermsRequest) returns(TermsResponse);

    /**
    GetQuote returns a quote for a swap with the provided parameters.
    */
    rpc GetLoopInQuote(QuoteRequest) returns(QuoteResponse);
}

message LoopOutRequest {
    /**
    Requested swap amount in sat. This does not include the swap and miner fee.
    */
    int64 amt = 1;

    /**
    Base58 encoded destination address for the swap.
    */
    string dest = 2;

    /**
    Maximum off-chain fee in msat that may be paid for payment to the server.
    This limit is applied during path finding. Typically this value is taken
    from the response of the GetQuote call.
    */
    int64 max_swap_routing_fee = 3;

    /**
    Maximum off-chain fee in msat that may be paid for payment to the server.
    This limit is applied during path finding. Typically this value is taken
    from the response of the GetQuote call.
    */
    int64 max_prepay_routing_fee = 4;

    /**
    Maximum we are willing to pay the server for the swap. This value is not
    disclosed in the swap initiation call, but if the server asks for a
    higher fee, we abort the swap. Typically this value is taken from the
    response of the GetQuote call. It includes the prepay amount.
    */
    int64 max_swap_fee = 5;

    /**
    Maximum amount of the swap fee that may be charged as a prepayment.
    */
    int64 max_prepay_amt = 6;

    /**
    Maximum in on-chain fees that we are willing to spent. If we want to
    sweep the on-chain htlc and the fee estimate turns out higher than this
    value, we cancel the swap. If the fee estimate is lower, we publish the
    sweep tx.

    If the sweep tx is not confirmed, we are forced to ratchet up fees until it
    is swept. Possibly even exceeding max_miner_fee if we get close to the htlc
    timeout. Because the initial publication revealed the preimage, we have no
    other choice. The server may already have pulled the off-chain htlc. Only
    when the fee becomes higher than the swap amount, we can only wait for fees
    to come down and hope - if we are past the timeout - that the server is not
    publishing the revocation.

    max_miner_fee is typically taken from the response of the GetQuote call.
    */
    int64 max_miner_fee = 7;

    /**
    The channel to loop out, the channel to loop out is selected based on the
    lowest routing fee for the swap payment to the server.
    */
    uint64 loop_out_channel = 8;

    /**
    The number of blocks from the on-chain HTLC's confirmation height that it
    should be swept within.
    */
    int32 sweep_conf_target = 9;
}

message LoopInRequest {
    /**
    Requested swap amount in sat. This does not include the swap and miner 
    fee.
    */
    int64 amt = 1;

    /**
    Maximum we are willing to pay the server for the swap. This value is not
    disclosed in the swap initiation call, but if the server asks for a
    higher fee, we abort the swap. Typically this value is taken from the
    response of the GetQuote call.
    */
    int64 max_swap_fee = 2;

    /**
    Maximum in on-chain fees that we are willing to spent. If we want to
    publish the on-chain htlc and the fee estimate turns out higher than this
    value, we cancel the swap. 

    max_miner_fee is typically taken from the response of the GetQuote call.
    */
    int64 max_miner_fee = 3;
    
    /**
    The channel to loop in. If zero, the channel to loop in is selected based
    on the lowest routing fee for the swap payment from the server.

    Note: NOT YET IMPLEMENTED
    */
    uint64 loop_in_channel = 4;

    /**
    If external_htlc is true, we expect the htlc to be published by an external
    actor.
    */
    bool external_htlc = 5;
}

message SwapResponse {
    /**
    Swap identifier to track status in the update stream that is returned from
    the Start() call. Currently this is the hash that locks the htlcs.
    */
    string id = 1;

    /**
    The address of the on-chain htlc.
    */
    string htlc_address = 2;
}

message MonitorRequest{
}

message SwapStatus {
    /**
    Requested swap amount in sat. This does not include the swap and miner
    fee.
    */
    int64 amt = 1;

    /**
    Swap identifier to track status in the update stream that is returned from
    the Start() call. Currently this is the hash that locks the htlcs.
    */
    string id = 2;

    /**
    Swap type
    */
    SwapType type = 3;

    /**
    State the swap is currently in, see State enum.
    */
    SwapState state = 4;

    /**
    Initiation time of the swap.
    */
    int64 initiation_time = 5;

    /**
    Initiation time of the swap.
    */
    int64 last_update_time = 6;

    /**
    Htlc address.
    */
    string htlc_address = 7;

    /// Swap server cost
    int64 cost_server = 8;

    // On-chain transaction cost
    int64 cost_onchain = 9;

    // Off-chain routing fees
    int64 cost_offchain = 10;
}

enum SwapType {
    // LOOP_OUT indicates an loop out swap (off-chain to on-chain)
    LOOP_OUT = 0;

    // LOOP_IN indicates a loop in swap (on-chain to off-chain)
    LOOP_IN = 1;
}

enum SwapState {
    /**
    INITIATED is the initial state of a swap. At that point, the initiation
    call to the server has been made and the payment process has been started
    for the swap and prepayment invoices.
    */
    INITIATED = 0;

    /**
    PREIMAGE_REVEALED is reached when the sweep tx publication is first
    attempted. From that point on, we should consider the preimage to no
    longer be secret and we need to do all we can to get the sweep confirmed.
    This state will mostly coalesce with StateHtlcConfirmed, except in the
    case where we wait for fees to come down before we sweep.
    */
    PREIMAGE_REVEALED = 1;

    /**
    HTLC_PUBLISHED is reached when the htlc tx has been published in a loop in
    swap.
    */
    HTLC_PUBLISHED = 2;

    /**
    SUCCESS is the final swap state that is reached when the sweep tx has
    the required confirmation depth.
    */
    SUCCESS = 3;

    /**
    FAILED is the final swap state for a failed swap with or without loss of
    the swap amount.
    */
    FAILED = 4;

     /**
    INVOICE_SETTLED is reached when the swap invoice in a loop in swap has been
    paid, but we are still waiting for the htlc spend to confirm.
    */
    INVOICE_SETTLED = 5;
}

message TermsRequest {
}

message TermsResponse {
    /**
    The node pubkey where the swap payment needs to be paid
    to. This can be used to test connectivity before initiating the swap.
    */
    string swap_payment_dest = 1;

    /**
    The base fee for a swap (sat)
    */
    int64 swap_fee_base = 2;

    /**
    The fee rate for a swap (parts per million)
    */
    int64 swap_fee_rate = 3;

    /**
    Required prepay amount
    */
    int64 prepay_amt = 4;

    /**
    Minimum swap amount (sat)
    */
    int64 min_swap_amount = 5;

    /**
    Maximum swap amount (sat)
    */
    int64 max_swap_amount = 6;

    /**
    On-chain cltv expiry delta
    */
    int32 cltv_delta = 7;
}

message QuoteRequest {
    /**
    The amount to swap in satoshis.
    */
    int64 amt = 1;

    /**
    The confirmation target that should be used either for the sweep of the
    on-chain HTLC broadcast by the swap server in the case of a Loop Out, or for
    the confirmation of the on-chain HTLC broadcast by the swap client in the
    case of a Loop In.
    */
    int32 conf_target = 2;
}

message QuoteResponse {
    /**
    The fee that the swap server is charging for the swap.
    */
    int64 swap_fee = 1;

    /**
    The part of the swap fee that is requested as a prepayment.
    */
    int64 prepay_amt = 2;

    /**
    An estimate of the on-chain fee that needs to be paid to sweep the HTLC.
    */
    int64 miner_fee = 3;
}