hledger-flow: gemini: exchange: cost-basis work-around for bitcoin.tax

Issue #51 describes at least a few undocumented bitcoin.tax issues:

  - Bicoin.tax gives unexpected cost-basis results when `Fee` is given
    with `Total` (when `Total` is given in place of `Price`). The
    expectation is that bitcoin.tax will perform the cost-basis
    calculation on `Total` when `Fee` is also given.

    However, bitcoin.tax *will* give expected cost-basis results if
    `Price` is given in place of `Total` (with `Fee` also given) *or* if
    `Total` is given *after* local cost-basis adjustments are made (but
    *without* `Fee` given).

    The rationale for why docker-finance doesn't use `Price`:

      * docker-finance has all of the `Total`s; so `Price` isn't
        necessary.

      * Local price information isn't available for most trades (and
        shouldn't be necessary since all `Total`s are available).

  - Additionally, when `Fee` is non-fiat (crypto), it now must be marked
    as a SPEND in order to be disposed (and to produce an accurate
    closing report).

  - Finally, if `FeeCurrency` *does* not match either `Symbol` or
    `Currency` (e.g., BTC-ETH w/ BNB fee), it's unknown if cost-basis
    must be calculated locally as well (if `Total` is given). Local
    calculations cannot be done because `Fee` price information is
    (almost certainly) not available for this type of trade.

Until upstream can assert that attaching the `Fee` will subsequently
adjust the cost-basis of `Total` *and* dispose of the `Fee` in the
process (while also allowing `Total` to be used in place of `Price`),
the `Fee` (and `FeeCurrency`) column(s) must not be populated and values
instead moved to SPEND (as described above).

Upstream is aware of these issues (since May) and they're in the process
of resolution. In the meantime, docker-finance work-arounds should
suffice for all trades that have a fiat `Fee` and/or a
`Fee`/`FeeCurrency` that matches one side of the trading pair.

container/src/hledger-flow/accounts/gemini/gemini-exchange-shared.rules

@@ -15,7 +15,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-fields code_,date,type,order_type,currency_one,currency_two,amount_,cost,fees,destination,txid,direction,subaccount
+fields code_,date,type,order_type,currency_one,currency_two,amount_,cost,fees,cost_basis,destination,txid,direction,subaccount
 
 date-format %Y-%m-%d %H:%M:%S
 description %date +0000
@@ -92,12 +92,24 @@ if %type ^TRADE$
 if %order_type ^Buy$
   amount %amount_ %currency_one @@ %cost %currency_two
   comment type:%type, order_type:%order_type, order_id:%txid, tid:%code_, taxed_as:BUY
-  comment2 %date +0000,BUY,gemini,%currency_one,%amount_,%currency_two,%cost,%currency_two,%fees
+  comment2 %date +0000,BUY,gemini,%currency_one,%amount_,%currency_two,%cost_basis,%currency_two,%fees
+# TODO: HACK: re: #51, FeeCurrency and Fee are added even though cost_basis is calculated (for non-fiat fee disposal, see lib_taxes)
+
+# TODO: HACK: see #51 and respective lib_taxes work-around
+if %order_type ^Buy$
+& %currency_two ^USD$
+  comment2 %date +0000,BUY,gemini,%currency_one,%amount_,%currency_two,%cost_basis,,
 
 if %order_type ^Sell$
   amount -%amount_ %currency_one @@ %cost %currency_two
   comment type:%type, order_type:%order_type, order_id:%txid, tid:%code_, taxed_as:SELL
-  comment2 %date +0000,SELL,gemini,%currency_one,%amount_,%currency_two,%cost,%currency_two,%fees
+  comment2 %date +0000,SELL,gemini,%currency_one,%amount_,%currency_two,%cost_basis,%currency_two,%fees
+# TODO: HACK: re: #51, FeeCurrency and Fee are added even though cost_basis is calculated (for non-fiat fee disposal, see lib_taxes)
+
+# TODO: HACK: see #51 and respective lib_taxes work-around
+if %order_type ^Sell$
+& %currency_two ^USD$
+  comment2 %date +0000,SELL,gemini,%currency_one,%amount_,%currency_two,%cost_basis,,
 
 # GUSD/USD workaround (see preprocess)
 if %type ^TRADE$

container/src/hledger-flow/accounts/gemini/gemini-shared.bash

@@ -111,6 +111,7 @@ function parse_transfers()
              }
            printf info_feeAmount OFS
 
+           printf OFS             # Cost-basis (N/A)
            printf $8 OFS          # Destination (info_destination)
            printf $9 OFS          # TXID (info_txHash)
 
@@ -176,6 +177,7 @@ function parse_transfers()
 
            printf OFS             # Price (N/A)
            printf OFS             # Fees (N/A)
+           printf OFS             # Cost-basis (N/A)
            printf $6 OFS          # Destination (info_destination)
            printf $7 OFS          # TXID (info_txHash)
 
@@ -250,6 +252,23 @@ function parse_trades()
          }
        printf fee_amount OFS  # Fees
 
+       # TODO: HACK: see #51 and respective lib_taxes work-around
+       # Calculate cost-basis
+       switch ($5)
+          {
+            case "Buy":
+              cost_basis=sprintf("%.8f", cost + fee_amount)
+              break
+            case "Sell":
+              cost_basis=sprintf("%.8f", cost - fee_amount)
+              break
+            default:
+              printf "FATAL: unsupported order type: " $5
+              print $0
+              exit
+          }
+       printf cost_basis OFS
+
        printf OFS      # Destination (N/A)
        printf $10 OFS  # TXID (tid)
 
@@ -309,6 +328,7 @@ function parse_earn()
        printf priceAmount OFS
 
        printf OFS  # Fees
+       printf OFS  # Cost-basis
        printf OFS  # Destination
        printf OFS  # TXID