database/sqlite: introduce sqliteTime type

This implements sql.Scanner and sql/driver.Valuer, so that we can
load/store time values into SQLite with the format we want, and
properly handle NULL (which the go-sqlite3 package doesn't do
correctly).

database/sqlite.go

@@ -5,6 +5,7 @@ package database
 import (
 	"context"
 	"database/sql"
+	sqldriver "database/sql/driver"
 	"fmt"
 	"math"
 	"strings"
@@ -20,8 +21,36 @@ const sqliteQueryTimeout = 5 * time.Second
 
 const sqliteTimeLayout = "2006-01-02T15:04:05.000Z"
 
-func formatSqliteTime(t time.Time) string {
+type sqliteTime struct {
-	return t.UTC().Format(sqliteTimeLayout)
+	time.Time
+}
+
+var (
+	_ sql.Scanner      = (*sqliteTime)(nil)
+	_ sqldriver.Valuer = sqliteTime{}
+)
+
+func (t *sqliteTime) Scan(value interface{}) error {
+	if value == nil {
+		t.Time = time.Time{}
+		return nil
+	}
+	if s, ok := value.(string); ok {
+		tt, err := time.Parse(sqliteTimeLayout, s)
+		if err != nil {
+			return err
+		}
+		t.Time = tt
+		return nil
+	}
+	return fmt.Errorf("cannot scan time from type %T", value)
+}
+
+func (t sqliteTime) Value() (sqldriver.Value, error) {
+	if t.Time.IsZero() {
+		return nil, nil
+	}
+	return t.UTC().Format(sqliteTimeLayout), nil
 }
 
 const sqliteSchema = `
@@ -800,18 +829,14 @@ func (db *SqliteDB) GetReadReceipt(ctx context.Context, networkID int64, name st
 		sql.Named("network", networkID),
 		sql.Named("target", name),
 	)
-	var timestamp string
+	var timestamp sqliteTime
 	if err := row.Scan(&receipt.ID, &timestamp); err != nil {
 		if err == sql.ErrNoRows {
 			return nil, nil
 		}
 		return nil, err
 	}
-	if t, err := time.Parse(sqliteTimeLayout, timestamp); err != nil {
+	receipt.Timestamp = timestamp.Time
-		return nil, err
-	} else {
-		receipt.Timestamp = t
-	}
 	return receipt, nil
 }
 
@@ -821,7 +846,7 @@ func (db *SqliteDB) StoreReadReceipt(ctx context.Context, networkID int64, recei
 
 	args := []interface{}{
 		sql.Named("id", receipt.ID),
-		sql.Named("timestamp", formatSqliteTime(receipt.Timestamp)),
+		sql.Named("timestamp", sqliteTime{receipt.Timestamp}),
 		sql.Named("network", networkID),
 		sql.Named("target", receipt.Target),
 	}
@@ -884,7 +909,7 @@ func (db *SqliteDB) StoreWebPushConfig(ctx context.Context, config *WebPushConfi
 		VALUES (:now, :vapid_key_public, :vapid_key_private)`,
 		sql.Named("vapid_key_public", config.VAPIDKeys.Public),
 		sql.Named("vapid_key_private", config.VAPIDKeys.Private),
-		sql.Named("now", formatSqliteTime(time.Now())))
+		sql.Named("now", sqliteTime{time.Now()}))
 	if err != nil {
 		return err
 	}
@@ -933,7 +958,7 @@ func (db *SqliteDB) StoreWebPushSubscription(ctx context.Context, userID, networ
 			Int64: networkID,
 			Valid: networkID != 0,
 		}),
-		sql.Named("now", formatSqliteTime(time.Now())),
+		sql.Named("now", sqliteTime{time.Now()}),
 		sql.Named("endpoint", sub.Endpoint),
 		sql.Named("key_auth", sub.Keys.Auth),
 		sql.Named("key_p256dh", sub.Keys.P256DH),