view.go

package azamat

import (
	"fmt"

	sq "github.com/Masterminds/squirrel"
)

// View can be used when an entity doesn't map precisely to a specific table. This is
// not to be confused with "SQL views," but it is similar in concept. A View is
// associated with a custom query. This can be useful when you have an entity where
// some of the fields come from joining multiple tables.
type View[T any] struct {
	// When we GetByID, we may need to know what table ID comes from. This is
	// optional and only needed if there is an ambiguity in the custom query where
	// multiple referenced tables have an "id" column
	IDFrom fmt.Stringer

	// Query is the custom query that will be used to fetch the entity
	Query func() sq.SelectBuilder
}

func (v View[T]) GetAll(runner Runner) ([]T, error) {
	sql, args, err := v.Query().ToSql()
	if err != nil {
		return nil, err
	}

	var rows []T
	err = runner.Select(&rows, sql, args...)
	return rows, err
}

func (v View[T]) GetByID(runner Runner, id int) (T, error) {
	var row T

	idColumn := "id"
	idFrom := v.IDFrom.String()
	if idFrom != "" {
		idColumn = fmt.Sprintf("%s.id", idFrom)
	}

	sql, args, err := v.Query().Where(sq.Eq{idColumn: id}).ToSql()
	if err != nil {
		return row, err
	}

	var rows []T
	if err := runner.Select(&rows, sql, args...); err != nil {
		return row, err
	}

	if len(rows) == 0 {
		return row, fmt.Errorf("none found")
	}

	if len(rows) != 1 {
		return row, fmt.Errorf("expected to only get row")
	}

	return rows[0], nil
}

func (v View[T]) GetByIDs(runner Runner, ids ...int) ([]T, error) {
	idColumn := "id"
	idFrom := v.IDFrom.String()
	if idFrom != "" {
		idColumn = fmt.Sprintf("%s.id", idFrom)
	}

	sql, args, err := v.Query().Where(sq.Eq{idColumn: ids}).ToSql()
	if err != nil {
		return nil, err
	}

	var rows []T
	err = runner.Select(&rows, sql, args...)
	return rows, err
}