Infer a default estimate from same-project/label averages

2 files changed, 160 insertions, 0 deletions

diff --git a/internal/store/estimate_inference.go b/internal/store/estimate_inference.go
new file mode 100644
index 0000000..d0a0034
--- /dev/null
+++ b/internal/store/estimate_inference.go
@@ -0,0 +1,70 @@
+package store
+
+import "encoding/json"
+
+// AverageEstimateForProject returns the rounded average estimated_minutes
+// across all user-estimated (estimated_minutes > 0) tasks under projectID.
+// ok is false when no such task exists -- there's no signal to infer from.
+func (s *Store) AverageEstimateForProject(projectID string) (int, bool, error) {
+	var sum, count int
+	rows, err := s.db.Query(`SELECT estimated_minutes FROM native_tasks WHERE project_id = ? AND estimated_minutes > 0`, projectID)
+	if err != nil {
+		return 0, false, err
+	}
+	defer func() { _ = rows.Close() }()
+	for rows.Next() {
+		var minutes int
+		if err := rows.Scan(&minutes); err != nil {
+			return 0, false, err
+		}
+		sum += minutes
+		count++
+	}
+	if err := rows.Err(); err != nil {
+		return 0, false, err
+	}
+	if count == 0 {
+		return 0, false, nil
+	}
+	return sum / count, true, nil
+}
+
+// AverageEstimateForLabel returns the rounded average estimated_minutes
+// across all user-estimated tasks carrying the given label. Labels are
+// stored as a JSON array column, not a joinable table, so this scans every
+// estimated task and filters in Go rather than risking a SQL substring
+// false-positive (e.g. LIKE '%"run"%' matching a task labeled "running").
+func (s *Store) AverageEstimateForLabel(label string) (int, bool, error) {
+	rows, err := s.db.Query(`SELECT labels, estimated_minutes FROM native_tasks WHERE estimated_minutes > 0`)
+	if err != nil {
+		return 0, false, err
+	}
+	defer func() { _ = rows.Close() }()
+
+	var sum, count int
+	for rows.Next() {
+		var labelsJSON string
+		var minutes int
+		if err := rows.Scan(&labelsJSON, &minutes); err != nil {
+			return 0, false, err
+		}
+		var labels []string
+		if err := json.Unmarshal([]byte(labelsJSON), &labels); err != nil {
+			continue
+		}
+		for _, l := range labels {
+			if l == label {
+				sum += minutes
+				count++
+				break
+			}
+		}
+	}
+	if err := rows.Err(); err != nil {
+		return 0, false, err
+	}
+	if count == 0 {
+		return 0, false, nil
+	}
+	return sum / count, true, nil
+}
diff --git a/internal/store/estimate_inference_test.go b/internal/store/estimate_inference_test.go
new file mode 100644
index 0000000..9321f11
--- /dev/null
+++ b/internal/store/estimate_inference_test.go
@@ -0,0 +1,90 @@
+// internal/store/estimate_inference_test.go
+package store
+
+import (
+	"testing"
+	"time"
+
+	"task-dashboard/internal/models"
+)
+
+func TestAverageEstimateForProject_AveragesUserEnteredEstimates(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+	project, err := s.CreateProject("Sailing prep", "#3B82F6")
+	if err != nil {
+		t.Fatal(err)
+	}
+	due := time.Now()
+	for _, minutes := range []int{30, 60} {
+		task := models.Task{ID: newTaskID(), Content: "task", ProjectID: project.ID, EstimatedMinutes: minutes, DueDate: &due}
+		if err := s.CreateNativeTask(task); err != nil {
+			t.Fatal(err)
+		}
+	}
+	// An unestimated task under the same project must not skew the average.
+	if err := s.CreateNativeTask(models.Task{ID: "t-unestimated", Content: "no estimate", ProjectID: project.ID}); err != nil {
+		t.Fatal(err)
+	}
+
+	avg, ok, err := s.AverageEstimateForProject(project.ID)
+	if err != nil {
+		t.Fatalf("AverageEstimateForProject: %v", err)
+	}
+	if !ok {
+		t.Fatal("expected ok = true")
+	}
+	if avg != 45 {
+		t.Errorf("avg = %d, want 45", avg)
+	}
+}
+
+func TestAverageEstimateForProject_NoEstimatedTasks_ReturnsNotOK(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+	project, err := s.CreateProject("Empty", "#111111")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, ok, err := s.AverageEstimateForProject(project.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ok {
+		t.Error("expected ok = false when no tasks have an estimate")
+	}
+}
+
+func TestAverageEstimateForLabel_AveragesUserEnteredEstimates(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+	for _, minutes := range []int{20, 40} {
+		task := models.Task{ID: newTaskID(), Content: "task", Labels: []string{"errands"}, EstimatedMinutes: minutes}
+		if err := s.CreateNativeTask(task); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := s.CreateNativeTask(models.Task{ID: "t-other-label", Content: "other", Labels: []string{"unrelated"}, EstimatedMinutes: 100}); err != nil {
+		t.Fatal(err)
+	}
+
+	avg, ok, err := s.AverageEstimateForLabel("errands")
+	if err != nil {
+		t.Fatalf("AverageEstimateForLabel: %v", err)
+	}
+	if !ok {
+		t.Fatal("expected ok = true")
+	}
+	if avg != 30 {
+		t.Errorf("avg = %d, want 30", avg)
+	}
+}
+
+func TestAverageEstimateForLabel_NoMatches_ReturnsNotOK(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+	_, ok, err := s.AverageEstimateForLabel("nonexistent")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ok {
+		t.Error("expected ok = false")
+	}
+}