[balsheet-pnl] accumulate column data report-dates

Previous would call gnc:account-get-balances-at-dates and
gnc:account-accumulate-at-dates to retrieve balances and
last-split. This commit reduces the O(2*N) operation to O(N) which
becomes significant with accounts with large number of splits.

Maybe we can reduce other account splitlist scans in the future; these
will be easier and would only require augmenting the record.

gnucash/report/standard-reports/balsheet-pnl.scm

@@ -31,9 +31,18 @@
 (use-modules (gnucash gettext))
 (use-modules (srfi srfi-1))
 (use-modules (srfi srfi-2))
+(use-modules (srfi srfi-9))
 
 (gnc:module-load "gnucash/report/report-system" 0)
 
+;; the column-data record. the gnc:account-accumulate-at-dates will
+;; create a record for each report-date with split-data as follows:
+(define-record-type :col-datum
+  (make-datum last-split split-balance)
+  col-datum?
+  (last-split col-datum-get-last-split)
+  (split-balance col-datum-get-split-balance))
+
 (define FOOTER-TEXT
   (gnc:make-html-text
    (_ "WARNING: Foreign currency conversions, and unrealized gains
@@ -770,12 +779,31 @@ also show overall period profit & loss."))
            ((eq? report-type 'pnl) (list startdate enddate))
            (else (list enddate))))
 
-         (accounts-balances (map
+         ;; an alist of (cons account account-cols-data) whereby
-                             (lambda (acc)
+         ;; account-cols-data is a list of col-datum records
-                               (cons acc
+         (accounts-cols-data
-                                     (gnc:account-get-balances-at-dates
+          (map
-                                      acc report-dates)))
+           (lambda (acc)
-                             accounts))
+             (let* ((comm (xaccAccountGetCommodity acc))
+                    (amt->monetary (lambda (amt) (gnc:make-gnc-monetary comm amt))))
+               (cons acc
+                     (gnc:account-accumulate-at-dates
+                      acc report-dates
+                      #:nosplit->elt (make-datum #f (amt->monetary 0))
+                      #:split->elt
+                      (lambda (s)
+                        (make-datum s (amt->monetary (xaccSplitGetBalance s))))))))
+           accounts))
+
+         ;; an alist of (cons account account-balances) whereby
+         ;; account-balances is a list of monetary amounts
+         (accounts-balances
+          (map
+           (lambda (acc)
+             (cons acc (let ((cols-data (assoc-ref accounts-cols-data acc)))
+                         (map col-datum-get-split-balance cols-data))))
+           accounts))
+
          (exchange-fn (and common-currency
                            (gnc:case-exchange-time-fn
                             price-source common-currency
@@ -906,13 +934,14 @@ also show overall period profit & loss."))
                   (and account-balance-list
                        (list-ref account-balance-list col-idx)))))
 
-             ;; an alist of account->last-split at date boundary
+             ;; an alist of (cons account vector-of-splits) where each
+             ;; split is the last one at date boundary
              (accounts-splits-dates
               (map
                (lambda (acc)
-                 (cons acc (list->vector
+                 (cons acc (let ((cols-data (assoc-ref accounts-cols-data acc)))
-                            (gnc:account-accumulate-at-dates
+                             (list->vector
-                             acc report-dates #:split->elt identity))))
+                              (map col-datum-get-last-split cols-data)))))
                accounts))
 
              (get-cell-anchor-fn