package cabana

import (
	"context"

	"gorm.io/gorm"
)

type txContextKey struct{}

// withTx returns ctx carrying the transaction a write is running in.
func withTx(ctx context.Context, tx *gorm.DB) context.Context {
	if tx == nil {
		return ctx
	}
	return context.WithValue(ctx, txContextKey{}, tx)
}

// TxFromContext returns the database transaction a write route is running in,
// for the context handed to a lifecycle hook (pact.FormBeforeCreate and the
// other Form and Relation hooks) or a scope (pact.FormExtendQuery) that runs
// inside it. A hook that has to read the database should use this handle
// instead of the application pool: it then sees the same snapshot as the write
// and does not take a second connection while the transaction holds row locks.
// The handle is valid only until the hook returns. The second result is false
// on routes that do not run in a transaction, such as the list.
func TxFromContext(ctx context.Context) (*gorm.DB, bool) {
	if ctx == nil {
		return nil, false
	}
	tx, ok := ctx.Value(txContextKey{}).(*gorm.DB)
	return tx, ok && tx != nil
}