qv/internal/models/voters.go

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 {
	DB *sql.DB
}

func (v *VoterModel) Insert(identity string, electionID int) (int, error) {
	tx, err := v.DB.Begin()
	if err != nil {
		return 0, err
	}
	defer tx.Rollback()

	result, err := tx.Exec(`
        INSERT INTO voters (identity, election_id)
        VALUES (?, ?)`,
		identity, electionID)
	if err != nil {
		return 0, err
	}

	if err = tx.Commit(); err != nil {
		return 0, err
	}

	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
}