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package wait
import (
"errors"
"slices"
)
var (
// ErrVisitStop is used as a return value from [VisitFunc] to stop the walk.
// It is not returned as an error by any function.
ErrVisitStop = errors.New("stop the walk")
// Deprecated: use [ErrVisitStop] instead.
VisitStop = ErrVisitStop
// ErrVisitRemove is used as a return value from [VisitFunc] to have the current node removed.
// It is not returned as an error by any function.
ErrVisitRemove = errors.New("remove this strategy")
// Deprecated: use [ErrVisitRemove] instead.
VisitRemove = ErrVisitRemove
)
// VisitFunc is a function that visits a strategy node.
// If it returns [ErrVisitStop], the walk stops.
// If it returns [ErrVisitRemove], the current node is removed.
type VisitFunc func(root Strategy) error
// Walk walks the strategies tree and calls the visit function for each node.
func Walk(root *Strategy, visit VisitFunc) error {
if root == nil {
return errors.New("root strategy is nil")
}
if err := walk(root, visit); err != nil {
if errors.Is(err, ErrVisitRemove) || errors.Is(err, ErrVisitStop) {
return nil
}
return err
}
return nil
}
// walk walks the strategies tree and calls the visit function for each node.
// It returns an error if the visit function returns an error.
func walk(root *Strategy, visit VisitFunc) error {
if *root == nil {
// No strategy.
return nil
}
// Allow the visit function to customize the behaviour of the walk before visiting the children.
if err := visit(*root); err != nil {
if errors.Is(err, ErrVisitRemove) {
*root = nil
}
return err
}
if s, ok := (*root).(*MultiStrategy); ok {
var i int
for range s.Strategies {
if err := walk(&s.Strategies[i], visit); err != nil {
if errors.Is(err, ErrVisitRemove) {
s.Strategies = slices.Delete(s.Strategies, i, i+1)
if errors.Is(err, VisitStop) {
return VisitStop
}
continue
}
return err
}
i++
}
}
return nil
}
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