Add workload report functionality

This special kind of dynamic block inserts all planned tasks between two dates
and sums up it's efforts.  This could help in deciding what additional tasks to
accept or what dates to promise for completion of new tasks.

init.el

@@ -741,6 +741,7 @@
              db/org-clock-in-home-task
              db/org-clock-in-work-task
              db/show-current-org-task
+             org-dblock-write:db/org-workload-report
              endless/org-ispell
              db/org-agenda-list-deadlines
              db/org-agenda-skip-tag

site-lisp/db-org.el

@@ -376,6 +376,82 @@ should not be clocked."
   (interactive)
   (message org-clock-current-task))
 
+
+;;; Task Management
+
+(defun db/org-planned-tasks-in-range (start-date end-date)
+  "Return list of tasks planned between START-DATE and END-DATE.
+
+This function will search through the files returned by
+`org-agenda-files' (the function) for all tasks that are
+scheduled, have an active timestamp, or are deadline in the given
+time range.
+
+The result has the form (TOTAL-TIME . TASKS), where TASKS is a
+list of cons cells (ID . EFFORT).  The total time is given as an
+Org mode time string of the form hh:mm, as are all EFFORT
+entries."
+  (let* (;; Allow Org syntax for dates; the result should be understandable by
+         ;; `parse-time-string' and thus `org-ql-query' should be fine with that.
+         (start-date (org-read-date nil nil start-date))
+         (end-date (org-read-date nil nil end-date))
+         (tasks (org-ql-query
+                  :from (org-agenda-files)
+                  :select '(cons
+                            (org-id-get-create)
+                            (org-entry-get (point) "Effort"))
+                  :where `(and (todo)
+                               ;; Is this redundant?  Could we just stick with `ts-active'?
+                               (or (scheduled :from ,start-date :to ,end-date)
+                                   (deadline :from ,start-date :to ,end-date)
+                                   (ts-active :from ,start-date :to ,end-date)))))
+         (total-time (->> tasks
+                          (-map (-compose #'org-duration-to-minutes #'cdr))
+                          -sum
+                          org-duration-from-minutes)))
+    (cons total-time tasks)))
+
+(defun org-dblock-write:db/org-workload-report (params)
+  "Write workload report based on tasks in `org-agenda-files'.
+
+PARAMS is a property list of the following parameters:
+
+`:start-date':
+
+  Start date for the workload report.
+
+`:end-date':
+
+  End date of the workload report.
+
+All tasks between `:start-date' and `:end-date' will be collected
+and their effort summed up.  The date format is everything
+understood by `org-read-date'."
+  (let* ((start-date (plist-get params :start-date))
+         (end-date (plist-get params :end-date))
+         (task-summary (db/org-planned-tasks-in-range start-date end-date)))
+
+    (insert "| Task | Effort |\n|---|\n")
+    (pcase-dolist (`(,task-id . ,effort-string) (cdr task-summary))
+      (insert (format "| %s | %s |\n"
+                      (org-link-make-string (format "id:%s" task-id)
+                                            (org-entry-get (org-id-find task-id 'marker)
+                                                           "ITEM"))
+                      effort-string)))
+    (insert (format "|---|\n| Total | %s |\n|---|" (car task-summary)))
+    (org-table-align)))
+
+(defun db/org-insert-workload-report ()
+  "Create dynamic block of planned tasks in given time range."
+  (interactive)
+  (org-create-dblock
+   (list :name "db/org-workload-report"
+         :start-date (read-string "Start date: ")
+         :end-date (read-string "End date: ")))
+  (org-update-dblock))
+
+(org-dynamic-block-define "db/org-workload-report" #'db/org-insert-workload-report)
+
 
 ;;; Fixes