package promptkit

import "fmt"

// RetryExhaustedError reports a built-in generation sequence whose positive
// transient retry budget ended with an eligible provider status. Its cause
// remains available through Unwrap, including GenerationError accessors.
// Engine-produced values are immutable. Default and Go-syntax formatting
// redact provider details, and there is no stable JSON representation.
type RetryExhaustedError struct {
	attempts uint64
	cause    error
}

func newRetryExhaustedError(attempts uint64, cause error) *RetryExhaustedError {
	return &RetryExhaustedError{attempts: attempts, cause: cause}
}

// Attempts returns the number of model attempts actually dispatched.
func (e *RetryExhaustedError) Attempts() uint64 {
	if e == nil {
		return 0
	}
	return e.attempts
}

// Error returns a redacted diagnostic. It is safe on a nil receiver.
func (e *RetryExhaustedError) Error() string {
	if e == nil || e.attempts == 0 {
		return ErrRetriesExhausted.Error()
	}
	return fmt.Sprintf("%s after %d attempts", ErrRetriesExhausted, e.attempts)
}

// GoString returns the same redacted diagnostic as Error.
func (e *RetryExhaustedError) GoString() string { return e.Error() }

// Unwrap returns the final failure cause, if present.
func (e *RetryExhaustedError) Unwrap() error {
	if e == nil {
		return nil
	}
	return e.cause
}

// Is matches ErrRetriesExhausted, including on nil and zero values.
func (e *RetryExhaustedError) Is(target error) bool {
	return target == ErrRetriesExhausted
}