Fix slow-ass code

internal/models/voters.go

@@ -6,7 +6,7 @@ import (
 )
 
 type VoterModelInterface interface {
-	Insert(identity string, electionID int) (int, error)
+	InsertMultiple(identities []string, electionID int) ([]int, error)
 	CountByElection(electionID int) (int, error)
 	Exists(voterIdentity string, electionID int) (bool, error)
 }
@@ -15,27 +15,45 @@ type VoterModel struct {
 	DB *sql.DB
 }
 
-func (v *VoterModel) Insert(identity string, electionID int) (int, error) {
+func (v *VoterModel) InsertMultiple(identities []string, electionID int) ([]int, error) {
 	tx, err := v.DB.Begin()
 	if err != nil {
-		return 0, err
+		return nil, err
 	}
 	defer tx.Rollback()
 
-	result, err := tx.Exec(`
+	// Prepare the statement once to reuse
+	stmt, err := tx.Prepare(`
         INSERT INTO voters (identity, election_id)
-        VALUES (?, ?)`,
-		identity, electionID)
+        VALUES (?, ?)`)
 	if err != nil {
-		return 0, err
+		return nil, err
+	}
+	defer stmt.Close()
+
+	// Store all voter IDs
+	voterIDs := make([]int, 0, len(identities))
+
+	// Execute statement for each identity
+	for _, identity := range identities {
+		result, err := stmt.Exec(identity, electionID)
+		if err != nil {
+			return nil, err
+		}
+
+		voterID, err := result.LastInsertId()
+		if err != nil {
+			return nil, err
+		}
+
+		voterIDs = append(voterIDs, int(voterID))
 	}
 
 	if err = tx.Commit(); err != nil {
-		return 0, err
+		return nil, err
 	}
 
-	voterId, err := result.LastInsertId()
-	return int(voterId), nil
+	return voterIDs, nil
 }
 
 func (v *VoterModel) CountByElection(electionID int) (int, error) {