Dirty implementation of createVotes

internal/models/voters.go

@@ -2,10 +2,13 @@ package models
 
 import (
 	"database/sql"
+	"errors"
 )
 
 type VoterModelInterface interface {
 	Insert(identity string, electionID int) (int, error)
+	CountByElection(electionID int) (int, error)
+	Exists(voterIdentity string, electionID int) (bool, error)
 }
 
 type VoterModel struct {
@@ -34,3 +37,53 @@ func (v *VoterModel) Insert(identity string, electionID int) (int, error) {
 	voterId, err := result.LastInsertId()
 	return int(voterId), nil
 }
+
+func (v *VoterModel) CountByElection(electionID int) (int, error) {
+	// use a transaction to prevent race conditions
+	tx, err := v.DB.Begin()
+	if err != nil {
+		return 0, err
+	}
+	defer tx.Rollback()
+
+	query := `
+		SELECT COUNT(identity)
+		FROM voters
+		WHERE election_id = ?
+		GROUP BY election_id;
+	`
+
+	row := tx.QueryRow(query, electionID)
+
+	var voterCount int
+
+	err = row.Scan(&voterCount)
+	if err != nil {
+		return 0, err
+	}
+
+	tx.Commit()
+
+	return voterCount, nil
+}
+
+func (v *VoterModel) Exists(voterIdentity string, electionID int) (bool, error) {
+	query := `
+		SELECT EXISTS (
+			SELECT 1
+			FROM voters
+			WHERE identity = ? AND election_id = ?
+		)
+	`
+
+	var exists bool
+
+	err := v.DB.QueryRow(query, voterIdentity, electionID).Scan(&exists)
+	if err != nil {
+		if errors.Is(sql.ErrNoRows, err) {
+			return false, nil
+		}
+		return false, err
+	}
+	return exists, nil
+}