Show one row per recurring chore in the flat task list

The recurrence scheduler materializes a series' next instance once the
current one comes due, regardless of whether it was completed -- that's
deliberate, so ignoring an occurrence doesn't stall the series. The side
effect is that the flat task list shows an unfinished chore and its
already-generated successor at the same time: "Bills" appears twice right
now (Sep 1 overdue + Oct 1), as does "Bones's meds".

CollapseRecurringSeries keeps only the earliest-due open instance per
series, which is the one actually owed. Applied to the atoms list only --
the timeline and widget are date-anchored, where each instance correctly
belongs to its own day, so they keep all of them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018AwnALZL6bD4VBtATDVv3B

1 files changed, 40 insertions, 0 deletions

diff --git a/internal/models/recurrence.go b/internal/models/recurrence.go
index f42183c..f407688 100644
--- a/internal/models/recurrence.go
+++ b/internal/models/recurrence.go
@@ -55,3 +55,43 @@ func nextWeeklyOccurrence(due time.Time, interval int, weekdays []int) time.Time
 	daysToNextWeekStart := 7 - dueWeekday
 	return due.AddDate(0, 0, daysToNextWeekStart+sorted[0]+7*(interval-1))
 }
+
+// CollapseRecurringSeries reduces each recurrence series to its single
+// earliest-due instance, preserving input order otherwise.
+//
+// The scheduler deliberately materializes a series' next instance once the
+// current one comes due, whether or not it was completed, so that ignoring one
+// occurrence doesn't stall the series (see
+// GetSeriesNeedingNextIteration). The side effect is that an unfinished
+// recurring chore and its already-generated successor both sit in the flat task
+// list at once -- "Bills" appearing twice, once overdue from Sep 1 and once for
+// Oct 1. Only the earliest open one is a thing you actually owe right now.
+//
+// This is for flat "what's open" views only. Date-anchored views (timeline,
+// widget) should keep every instance, since there each one legitimately belongs
+// to its own day.
+func CollapseRecurringSeries(tasks []Task) []Task {
+	earliest := make(map[string]*Task)
+	for i := range tasks {
+		t := &tasks[i]
+		if t.RecurrenceSeriesID == "" || t.DueDate == nil {
+			continue
+		}
+		cur, ok := earliest[t.RecurrenceSeriesID]
+		if !ok || t.DueDate.Before(*cur.DueDate) {
+			earliest[t.RecurrenceSeriesID] = t
+		}
+	}
+
+	out := make([]Task, 0, len(tasks))
+	for i := range tasks {
+		t := tasks[i]
+		// An undated recurring row has no position in the series ordering, so it
+		// is never collapsed away -- only dated instances compete.
+		if keep, ok := earliest[t.RecurrenceSeriesID]; ok && t.DueDate != nil && keep.ID != t.ID {
+			continue
+		}
+		out = append(out, t)
+	}
+	return out
+}