go-rel/gin-example

package scores

import (
    "context"
    "errors"

    "github.com/go-rel/rel"
)

type earn struct {
    repository rel.Repository
}

func (e earn) Earn(ctx context.Context, name string, count int) error {
    var (
        score Score
    )

    return e.repository.Transaction(ctx, func(ctx context.Context) error {
        // for simplicity, assumes only one user, so there's only one score and always retrieve the first one.
        // this will probably lock the entire table since there's no where clause provided, but it's fine since we assume only one user.
        if err := e.repository.Find(ctx, &score, rel.ForUpdate()); err != nil {
            if !errors.Is(err, rel.ErrNotFound) {
                // unexpected error.
                return err
            }

            score.TotalPoint = count
            e.repository.MustInsert(ctx, &score)
        } else {
            score.TotalPoint += count
            e.repository.Update(ctx, &score)
        }

        // insert point history.
        e.repository.MustInsert(ctx, &Point{Name: name, Count: count, ScoreID: score.ID})
        return nil
    })
}