From 4d0c4d95660a329f17f1fc55b50ea98f37d315e5 Mon Sep 17 00:00:00 2001
From: Vincent Royer <vinistois@gmail.com>
Date: Fri, 26 Jun 2026 10:58:52 -0700
Subject: [PATCH] bodyweights: collapse to one row per local day (#30)

Bodyweight is read off each workout post, so logging two workouts on the
same calendar day produced two `bodyweights list` rows for that date
(both markdown and JSON). Downstream per-day trend and plateau math then
double-counts that day.

Deduplicate in loadBodyweightEntries (shared by `list` and `stats`),
keeping the latest measurement per local day. This also makes the stats
monthly averages one-sample-per-day, which is the intended model: a day
has a single bodyweight.

Adds tests covering the same-day collision (keep latest) and the
no-duplicate passthrough.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 cmd/bodyweights.go      | 22 ++++++++++++++++++
 cmd/bodyweights_test.go | 51 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 cmd/bodyweights_test.go

diff --git a/cmd/bodyweights.go b/cmd/bodyweights.go
index 78b536f..b55fc08 100644
--- a/cmd/bodyweights.go
+++ b/cmd/bodyweights.go
@@ -178,6 +178,8 @@ func loadBodyweightEntries(sinceFlag, untilFlag string) ([]bodyweightEntry, erro
 		})
 	}
 
+	entries = dedupeByDay(entries)
+
 	sort.Slice(entries, func(i, j int) bool {
 		return entries[i].date.Before(entries[j].date)
 	})
@@ -185,6 +187,26 @@ func loadBodyweightEntries(sinceFlag, untilFlag string) ([]bodyweightEntry, erro
 	return entries, nil
 }
 
+// dedupeByDay collapses entries to one per local calendar day. Bodyweight is
+// read off each workout post, so logging two workouts on the same day yields
+// two entries for that date (#30). When a day has more than one measurement,
+// keep the latest one (by StartedAt timestamp). Order is not guaranteed; the
+// caller sorts afterward.
+func dedupeByDay(entries []bodyweightEntry) []bodyweightEntry {
+	latest := make(map[string]bodyweightEntry, len(entries))
+	for _, e := range entries {
+		key := e.date.Format("2006-01-02")
+		if cur, ok := latest[key]; !ok || e.date.After(cur.date) {
+			latest[key] = e
+		}
+	}
+	out := make([]bodyweightEntry, 0, len(latest))
+	for _, e := range latest {
+		out = append(out, e)
+	}
+	return out
+}
+
 func printBodyweightStats(entries []bodyweightEntry) {
 	first := entries[0]
 	last := entries[len(entries)-1]
diff --git a/cmd/bodyweights_test.go b/cmd/bodyweights_test.go
new file mode 100644
index 0000000..853624d
--- /dev/null
+++ b/cmd/bodyweights_test.go
@@ -0,0 +1,51 @@
+package cmd
+
+import (
+	"sort"
+	"testing"
+	"time"
+)
+
+// Two workouts on the same calendar day must collapse to a single
+// bodyweight row, keeping the latest measurement that day. (#30)
+func TestDedupeByDay_KeepsLatestPerDay(t *testing.T) {
+	mk := func(ts string, w float64) bodyweightEntry {
+		d, err := time.Parse(time.RFC3339, ts)
+		if err != nil {
+			t.Fatalf("bad test timestamp %q: %v", ts, err)
+		}
+		return bodyweightEntry{date: d, weight: w}
+	}
+
+	in := []bodyweightEntry{
+		mk("2026-05-02T07:00:00Z", 175.0), // morning workout
+		mk("2026-05-02T18:00:00Z", 177.0), // evening workout, same day
+		mk("2026-05-03T08:00:00Z", 176.0),
+	}
+
+	out := dedupeByDay(in)
+	sort.Slice(out, func(i, j int) bool { return out[i].date.Before(out[j].date) })
+
+	if len(out) != 2 {
+		t.Fatalf("expected 2 rows after dedupe (one per day), got %d: %+v", len(out), out)
+	}
+	if got := out[0].date.Format("2006-01-02"); got != "2026-05-02" {
+		t.Errorf("first row date = %s, want 2026-05-02", got)
+	}
+	if out[0].weight != 177.0 {
+		t.Errorf("same-day collision should keep the latest measurement (177.0), got %v", out[0].weight)
+	}
+	if out[1].weight != 176.0 {
+		t.Errorf("second day weight = %v, want 176.0", out[1].weight)
+	}
+}
+
+// A single entry per day passes through unchanged.
+func TestDedupeByDay_NoDuplicates(t *testing.T) {
+	d1, _ := time.Parse(time.RFC3339, "2026-01-01T10:00:00Z")
+	d2, _ := time.Parse(time.RFC3339, "2026-01-02T10:00:00Z")
+	in := []bodyweightEntry{{date: d1, weight: 180}, {date: d2, weight: 181}}
+	if got := len(dedupeByDay(in)); got != 2 {
+		t.Errorf("expected 2 rows, got %d", got)
+	}
+}