fake-coinjoin.sh

#!/usr/bin/env bash

# shellcheck disable=SC1091
# shellcheck source=./inc.common.sh
. "$(dirname "$(readlink -m "$0")")/inc.common.sh"

if [ "$3" == "" ]; then
    echo "Usage: $(basename "$0") [options] amount address1 address2..."
    echo "Where:"
    echo "  amount              - amount to send in BTC"
    echo "  address...          - destination addresses (2 or more)"
    exit
fi

# Some configs, names match of those of JoinMarket and values are JM defaults

# Transaction fee to use
# Values below 1000 are treated as estimated blocks to confirm,
# 1000 and above as sat/kB.
tx_fees=3
# [fraction, 0-1] / variance around the average fee. Ex: 1000 fee, 0.2 var = fee is btw 800-1200
txfee_factor=0.3
# Abort if TX fee per KB is above this number (satoshis)
absurd_fee_per_kb=150000
# Coin selection ("merge") algorithm.
# Not the same as JM algos currently.
# "default" is a dumb coin selection, using random order.
# "greediest" is for rapid dust sweeping, ordering UTXO's from the smallest upwards.
merge_algorithm=default

# Dust threshold in satoshis, don't create smaller outputs
DUST_THRESHOLD=27300

# End of configs

check_multiwallet

amount=$(echo "$1" | btc_amount_format)
shift

if (( tx_fees >= 1000 )); then
    fee="$(echo "$tx_fees * 0.00000001" | bc | btc_amount_format)"
else
    fee="$($(dirname "$(readlink -m "$0")")/estimatesmartfee.sh $bitcoin_cli_options $tx_fees)"
    if [ "$fee" == "" ]; then
        echoerr "estimatesmartfee failed"
        exit 1
    fi
fi
fee="$(randamount \
    "$(bc_float_calc "$fee * (1 - $txfee_factor)")" \
    "$(bc_float_calc "$fee * (1 + $txfee_factor)")")"
mempoolminfee="$(call_bitcoin_cli getmempoolinfo | jq_btc_float ".mempoolminfee")"
if is_btc_lt "$fee" "$mempoolminfee"; then
    echo "Feerate $fee is below minimum mempool fee, raising to $mempoolminfee"
    fee="$mempoolminfee"
fi
if is_btc_gte "$fee" "$(bc_float_calc "$absurd_fee_per_kb * 0.00000001")"; then
    echoerr -n "Estimated fee per KB ($fee) is greater than absurd value: "
    echoerr "$(bc_float_calc "$absurd_fee_per_kb * 0.00000001"), quitting."
    exit 1
fi
echo "Using fee $fee per KB"

recipients=()
p2pkh_recipient_count=0
p2sh_recipient_count=0
bech32_recipient_count=0

while (( ${#} > 0 )); do
    address=$1
    if ! is_valid_bitcoin_address "$address"; then
        echoerr "Invalid address $address"
        exit 1
    fi
    recipients+=("$address")
    if is_p2pkh_bitcoin_address "$address"; then
        ((p2pkh_recipient_count++))
    elif is_p2sh_bitcoin_address "$address"; then
        ((p2sh_recipient_count++))
    else
        ((bech32_recipient_count++))
    fi
    shift
done

if (( p2pkh_recipient_count > 1 )); then
    if (( p2sh_recipient_count > 1 )) || (( bech32_recipient_count > 1 )); then
        echoerr "Only one recipient can be a different kind! (P2PKH, P2SH or bech32)"
        exit 2
    fi
elif (( p2sh_recipient_count > 1 )) && (( bech32_recipient_count > 1 )); then
    echoerr "Only one recipient can be a different kind! (P2PKH, P2SH or bech32)"
    exit 2
fi

if (( ${#recipients[@]} > $(( TX_OUTPUTS_MAX / 2 )) )); then
    echoerr "More than $(( TX_OUTPUTS_MAX / 2 )) recipients aren't supported!"
    exit 3
fi

if (( p2pkh_recipient_count > 1 )); then
    input_type="p2pkh"
    if (( bech32_recipient_count > 0 )); then
        echoerr "Bech32 recipient cannot be combined with multiple P2PKH recipients!"
        exit 2
    fi
elif (( p2sh_recipient_count > 1 )); then
    input_type="p2sh_segwit"
else
    input_type="bech32"
fi

echo "Recipients: ${recipients[*]}"
echo "input_type: $input_type"

function select_default()
{
    jq -c "." | shuf | jq "."
}

function select_greediest()
{
    jq -s "sort_by(.amount) | .[]"
}

utxo="$(call_bitcoin_cli listunspent 1 999999 "[]" false | jq ".[] | select(.spendable)")"
if [ "$merge_algorithm" == "greediest" ]; then
    utxo="$(echo "$utxo" | select_greediest)"
else
    utxo="$(echo "$utxo" | select_default)"
fi

readarray -t utxo_txids < <( echo "$utxo" | jq -r ".txid" )
readarray -t utxo_vouts < <( echo "$utxo" | jq -r ".vout" )
readarray -t utxo_addresses < <( echo "$utxo" | jq -r ".address" )
readarray -t utxo_amounts < <( echo "$utxo" | jq_btc_float ".amount" )

# Filter out unwanted input address types
# Also ignore UTXO's with address reuse, JoinMarket normally don't have them
utxo_reused_addresses="$(printf '%s ' "${utxo_addresses[@]}" | \
    awk '!($0 in seen){seen[$0];next} 1')"
utxo_txids_filtered=()
utxo_vouts_filtered=()
utxo_addresses_filtered=()
utxo_amounts_filtered=()
for i in $(seq 0 $(( ${#utxo_addresses[@]} - 1 ))); do
    if \
        eval "is_${input_type}_bitcoin_address ${utxo_addresses[$i]}" && \
        grep -qsv "${utxo_addresses[$i]}" <<< "$utxo_reused_addresses"
    then
        utxo_txids_filtered+=("${utxo_txids[$i]}")
        utxo_vouts_filtered+=("${utxo_vouts[$i]}")
        utxo_addresses_filtered+=("${utxo_addresses[$i]}")
        utxo_amounts_filtered+=("${utxo_amounts[$i]}")
    fi
done
unset utxo_txids
unset utxo_vouts
unset utxo_addresses
unset utxo_amounts

#printf '%s\n' "${utxo_addresses_filtered[@]}"
#printf '%s\n' "${utxo_amounts_filtered[@]}"
#echo "${#utxo_addresses_filtered[@]}"

# Calculate fees, TX input/output bytes, etc here

# Select "maker" inputs
maker_utxo_idxs=()
utxo_idx=0
maker_change_outputs=()
maker_change_amounts=()
total_maker_fees=0
# minimum taker amount must be above amount + dust
minimum_taker_amount="$(bc_float_calc "$amount + ($DUST_THRESHOLD * 0.00000001) + 0.00000001")"
for i in $(seq 0 $(( ${#recipients[@]} - 2 ))); do
    current_set_inputs_sum=0
    maker_used_txids=()
    while
        (( utxo_idx < ${#utxo_addresses_filtered[@]} )) && \
        is_btc_gte "$minimum_taker_amount" "$current_set_inputs_sum";
    do
        # Stonewall rule: Utxos resulting from the same transaction are never used together in a same set.
        if ! grep -qs "${utxo_txids_filtered[$utxo_idx]}" <<< "${maker_used_txids[@]}"; then
            current_set_inputs_sum=$(bc_float_calc "$current_set_inputs_sum + ${utxo_amounts_filtered[$utxo_idx]}")
            maker_utxo_idxs+=("$utxo_idx")
            maker_used_txids+=("${utxo_txids_filtered[$utxo_idx]}")
#        else
#            echo "Skipping utxo_idx $utxo_idx for a maker, as txid ${utxo_txids_filtered[$utxo_idx]} already used"
        fi
        ((utxo_idx++))
    done
    if ! is_btc_gte "$minimum_taker_amount" "$current_set_inputs_sum"; then
        # Add some simple random "maker fee" (10 .. 1200)
        # Interval is choosen by looking at real-world JM orderbook and https://github.com/JoinMarket-Org/joinmarket-clientserver/pull/166
        makerfee="$(bc_float_calc "$(( RANDOM % 1190 + 10 )) * 0.00000001")"
        echo "Using \"maker fee\" $makerfee"
        maker_change_outputs+=("$(eval "getnewaddress_$input_type")")
        maker_change_amounts+=("$(bc_float_calc "$current_set_inputs_sum - $amount + $makerfee")")
        total_maker_fees="$(bc_float_calc "$total_maker_fees + $makerfee")"
    fi
done

echo "Selected maker inputs:"
for i in $(seq 0 $(( ${#maker_utxo_idxs[@]} - 1 ))); do
    echo "${maker_utxo_idxs[$i]}: ${utxo_amounts_filtered[${maker_utxo_idxs[$i]}]} ${utxo_addresses_filtered[${maker_utxo_idxs[$i]}]}"
done

echo "Calculated maker outputs:"
for i in $(seq 0 $(( ${#maker_change_amounts[@]} - 1 ))); do
    echo "$i: ${maker_change_amounts[$i]} ${maker_change_outputs[$i]}"
done

if is_btc_gte "$minimum_taker_amount" "$current_set_inputs_sum"; then
    echoerr "Not enough good inputs, aborting."
    exit 1
fi

# Calculate fees
# https://bitcoincore.org/en/segwit_wallet_dev/#transaction-fee-estimation

# Recipients
tx_vsize=$(( p2pkh_recipient_count * TX_P2PKH_OUT_SIZE ))
tx_vsize=$(( tx_vsize + p2sh_recipient_count * TX_P2SH_OUT_SIZE ))
tx_vsize=$(( tx_vsize + bech32_recipient_count * TX_P2WPKH_OUT_SIZE ))
# Fixed size + "maker" inputs + "maker" change outputs
if [ "$input_type" == "p2pkh" ]; then
    tx_vsize=$(( tx_vsize + TX_FIXED_SIZE ))
    tx_vsize=$(( tx_vsize + ${#maker_utxo_idxs[@]} * TX_P2PKH_IN_SIZE ))
    tx_vsize=$(( tx_vsize + ${#maker_change_outputs[@]} * TX_P2PKH_OUT_SIZE ))
elif [ "$input_type" == "p2sh_segwit" ]; then
    tx_vsize=$(( tx_vsize + TX_SEGWIT_FIXED_SIZE ))
    # P2SH segwit maker inputs
    tx_vsize=$(( tx_vsize + ${#maker_utxo_idxs[@]} * TX_P2SH_SEGWIT_IN_SIZE ))
    # P2SH maker change outputs (recipient outputs already calculated above)
    tx_vsize=$(( tx_vsize + ${#maker_change_outputs[@]} * TX_P2SH_OUT_SIZE ))
elif [ "$input_type" == "bech32" ]; then
    tx_vsize=$(( tx_vsize + TX_SEGWIT_FIXED_SIZE ))
    # Bech32 segwit maker inputs
    tx_vsize=$(( tx_vsize + ${#maker_utxo_idxs[@]} * TX_P2WPKH_IN_SIZE ))
    # Bech32 maker change outputs (recipient outputs already calculated above)
    tx_vsize=$(( tx_vsize + ${#maker_change_outputs[@]} * TX_P2WPKH_OUT_SIZE ))
else
    echoerr "DESIGN ERROR: Invalid input_type $input_type in recipient selection!"
    exit 3
fi

# Calculate taker fee
taker_amount=$(bc_float_calc "$amount + $tx_vsize * $fee * 0.001 + $total_maker_fees")
echo "taker_amount = $taker_amount"

# Select "taker" inputs

taker_utxo_idxs=()
current_set_inputs_sum=0
taker_used_txids=()
while
    (( utxo_idx < ${#utxo_addresses_filtered[@]} )) && \
    is_btc_gte "$taker_amount" "$current_set_inputs_sum";
do
    # Stonewall rule: Utxos resulting from the same transaction are never used together in a same set.
    if ! grep -qs "${utxo_txids_filtered[$utxo_idx]}" <<< "${taker_used_txids[@]}"; then
        current_set_inputs_sum=$(bc_float_calc "$current_set_inputs_sum + ${utxo_amounts_filtered[$utxo_idx]}")
        taker_utxo_idxs+=("$utxo_idx")
        taker_used_txids+=("${utxo_txids_filtered[$utxo_idx]}")
#    else
#        echo "Skipping utxo_idx $utxo_idx for a taker, as txid ${utxo_txids_filtered[$utxo_idx]} already used"
    fi
    ((utxo_idx++))
    if [ "$input_type" == "p2pkh" ]; then
        tx_vsize=$(( tx_vsize + TX_P2PKH_IN_SIZE ))
        taker_amount=$(bc_float_calc "$taker_amount + $TX_P2PKH_IN_SIZE * $fee * 0.001")
    elif [ "$input_type" == "p2sh_segwit" ]; then
        tx_vsize=$(( tx_vsize + TX_P2SH_SEGWIT_IN_SIZE ))
        taker_amount=$(bc_float_calc "$taker_amount + $TX_P2SH_SEGWIT_IN_SIZE * $fee * 0.001")
    elif [ "$input_type" == "bech32" ]; then
        tx_vsize=$(( tx_vsize + TX_P2SH_SEGWIT_IN_SIZE ))
        taker_amount=$(bc_float_calc "$taker_amount + $TX_P2WPKH_IN_SIZE * $fee * 0.001")
    else
        echoerr "DESIGN ERROR: Invalid input_type $input_type in taker input selection!"
        exit 3
    fi
done

echo "Calculated taker inputs:"
for i in $(seq 0 $(( ${#taker_utxo_idxs[@]} - 1 ))); do
    echo "${taker_utxo_idxs[$i]}: ${utxo_amounts_filtered[${taker_utxo_idxs[$i]}]} ${utxo_addresses_filtered[${taker_utxo_idxs[$i]}]}"
done

if is_btc_gte "$taker_amount" "$current_set_inputs_sum"; then
    echoerr "Not enough good inputs, aborting."
    exit 1
fi

taker_change_amount="$(bc_float_calc "$current_set_inputs_sum - $taker_amount")"
if [ "$input_type" == "p2pkh" ]; then
    taker_change_amount="$(bc_float_calc "$taker_change_amount - ($TX_P2PKH_OUT_SIZE * 0.00000001)")"
elif [ "$input_type" == "p2sh_segwit" ]; then
    taker_change_amount="$(bc_float_calc "$taker_change_amount - ($TX_P2SH_OUT_SIZE * 0.00000001)")"
elif [ "$input_type" == "bech32" ]; then
    taker_change_amount="$(bc_float_calc "$taker_change_amount - ($TX_P2WPKH_OUT_SIZE * 0.00000001)")"
else
    echoerr "DESIGN ERROR: Invalid input_type $input_type in taker change amount calculation!"
    exit 3
fi
if is_btc_gte "$taker_change_amount" "$(bc_float_calc "$DUST_THRESHOLD * 0.00000001")"; then
    taker_change_output="$(eval "getnewaddress_$input_type")"
    if [ "$input_type" == "p2pkh" ]; then
        tx_vsize=$(( tx_vsize + TX_P2PKH_OUT_SIZE ))
    elif [ "$input_type" == "p2sh_segwit" ]; then
        tx_vsize=$(( tx_vsize + TX_P2SH_OUT_SIZE ))
    elif [ "$input_type" == "bech32" ]; then
        tx_vsize=$(( tx_vsize + TX_P2WPKH_OUT_SIZE ))
    else
        echoerr "DESIGN ERROR: Invalid input_type $input_type in taker change output fee calculation!"
        exit 3
    fi
else
    echo "Not creating dust amount taker change output, adding to the fees."
fi

if [ "$taker_change_output" != "" ]; then
    echo "Calculated taker outputs:"
    echo "0: $taker_change_amount $taker_change_output"
fi

echo "tx_vsize = $tx_vsize"
echo "Calculated TX fee: $(bc_float_calc "$tx_vsize * $fee * 0.001")"

# Join all inputs and outputs together so we can randomize order

input_utxo_txids=()
input_utxo_vouts=()
output_addresses=()
output_amounts=()

for i in $(seq 0 $(( ${#maker_utxo_idxs[@]} - 1 ))); do
    input_utxo_txids+=("${utxo_txids_filtered[${maker_utxo_idxs[$i]}]}")
    input_utxo_vouts+=("${utxo_vouts_filtered[${maker_utxo_idxs[$i]}]}")
done
for i in $(seq 0 $(( ${#taker_utxo_idxs[@]} - 1 ))); do
    input_utxo_txids+=("${utxo_txids_filtered[${taker_utxo_idxs[$i]}]}")
    input_utxo_vouts+=("${utxo_vouts_filtered[${taker_utxo_idxs[$i]}]}")
done

for i in $(seq 0 $(( ${#recipients[@]} - 1 ))); do
    output_addresses+=("${recipients[$i]}")
    output_amounts+=("$amount")
done
for i in $(seq 0 $(( ${#maker_change_amounts[@]} - 1 ))); do
    output_addresses+=("${maker_change_outputs[$i]}")
    output_amounts+=("${maker_change_amounts[$i]}")
done
if [ "$taker_change_output" != "" ]; then
    output_addresses+=("$taker_change_output")
    output_amounts+=("$taker_change_amount")
fi

# Randomize order
input_it=$(seq 0 $(( ${#input_utxo_txids[@]} - 1 )) | shuf)
output_it=$(seq 0 $(( ${#output_addresses[@]} - 1 )) | shuf)

# DO TX

rawtx_inputs="["
needs_comma=0
for i in $input_it; do
    if [ "$needs_comma" == "1" ]; then
        rawtx_inputs="$rawtx_inputs,"
    fi
    rawtx_inputs="$rawtx_inputs{\"txid\":\"${input_utxo_txids[$i]}\",\"vout\":${input_utxo_vouts[$i]}}"
    needs_comma=1
done
rawtx_inputs="$rawtx_inputs]"
echo "rawtx_inputs: $rawtx_inputs"

rawtx_outputs="{"
needs_comma=0
for i in $output_it; do
    if [ "$needs_comma" == "1" ]; then
        rawtx_outputs="$rawtx_outputs,"
    fi
    rawtx_outputs="$rawtx_outputs\"${output_addresses[$i]}\":\"${output_amounts[$i]}\""
    needs_comma=1
done
rawtx_outputs="$rawtx_outputs}"
echo "rawtx_outputs: $rawtx_outputs"

rawtx=$(call_bitcoin_cli createrawtransaction "$rawtx_inputs" "$rawtx_outputs")
echo "Raw transaction: $rawtx"
call_bitcoin_cli decoderawtransaction "$rawtx"

read -p "Sign and broadcast this transaction? " -n 1 -r
echo

if [[ $REPLY =~ ^[Yy]$ ]]; then
    signedtx=$(signrawtransactionwithwallet "$rawtx")
    txid=$(call_bitcoin_cli sendrawtransaction "$signedtx")
    echo "Sent transaction $txid"
fi