package adverr

import "fmt"

var (
	// ErrTmplUsedAsErr is returned from ErrTmpl.Error() because an error template should never be used as an actual error value
	ErrTmplUsedAsErr = NewErrTmpl("ErrTmplUsedAsErr", "Error template used as error value: %s")
)

// ErrTmpl is an error template to define equalities between different errors
type ErrTmpl struct {
	name   string
	format string
}

// NewErrTmpl returns a new error template with the given format string as a predefined error message
func NewErrTmpl(name, format string) *ErrTmpl {
	return &ErrTmpl{name, format}
}

// Error implementation just for satisfying the error interface
// Please dont use ErrTmpls as actual errors
func (t *ErrTmpl) Error() string {
	return ErrTmplUsedAsErr.New(errtype(t)).Error()
}

// New returns a new Error in which the given values are being formatted into the format string of its template
func (t *ErrTmpl) New(args ...interface{}) *Error {
	return &Error{
		msg:       fmt.Sprintf(t.format, args...),
		cause:     nil,
		tmpl:      t,
		callTrace: Trace(2),
	}
}