lnd.xprv/watchtower/wtclient/candidate_iterator.go

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package wtclient
import (
"container/list"
"sync"
"github.com/lightningnetwork/lnd/watchtower/wtdb"
)
// TowerCandidateIterator provides an abstraction for iterating through possible
// watchtower addresses when attempting to create a new session.
type TowerCandidateIterator interface {
// Reset clears any internal iterator state, making previously taken
// candidates available as long as they remain in the set.
Reset() error
// Next returns the next candidate tower. The iterator is not required
// to return results in any particular order. If no more candidates are
// available, ErrTowerCandidatesExhausted is returned.
Next() (*wtdb.Tower, error)
}
// towerListIterator is a linked-list backed TowerCandidateIterator.
type towerListIterator struct {
mu sync.Mutex
candidates *list.List
nextCandidate *list.Element
}
// Compile-time constraint to ensure *towerListIterator implements the
// TowerCandidateIterator interface.
var _ TowerCandidateIterator = (*towerListIterator)(nil)
// newTowerListIterator initializes a new towerListIterator from a variadic list
// of lnwire.NetAddresses.
func newTowerListIterator(candidates ...*wtdb.Tower) *towerListIterator {
iter := &towerListIterator{
candidates: list.New(),
}
for _, candidate := range candidates {
iter.candidates.PushBack(candidate)
}
iter.Reset()
return iter
}
// Reset clears the iterators state, and makes the address at the front of the
// list the next item to be returned..
func (t *towerListIterator) Reset() error {
t.mu.Lock()
defer t.mu.Unlock()
// Reset the next candidate to the front of the linked-list.
t.nextCandidate = t.candidates.Front()
return nil
}
// Next returns the next candidate tower. This iterator will always return
// candidates in the order given when the iterator was instantiated. If no more
// candidates are available, ErrTowerCandidatesExhausted is returned.
func (t *towerListIterator) Next() (*wtdb.Tower, error) {
t.mu.Lock()
defer t.mu.Unlock()
// If the next candidate is nil, we've exhausted the list.
if t.nextCandidate == nil {
return nil, ErrTowerCandidatesExhausted
}
// Propose the tower at the front of the list.
tower := t.nextCandidate.Value.(*wtdb.Tower)
// Set the next candidate to the subsequent element.
t.nextCandidate = t.nextCandidate.Next()
return tower, nil
}
// TODO(conner): implement graph-backed candidate iterator for public towers.