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package chord
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import (
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	"runtime"
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	"sync/atomic"
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	"go.miragespace.co/specter/spec/chord"
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	"github.com/zhangyunhao116/skipmap"
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)
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type nodeState struct {
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	state   atomic.Uint64
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	history *skipmap.Uint64Map[chord.State]
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}
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func newNodeState(initial chord.State) *nodeState {
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	s := &nodeState{
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		state:   atomic.Uint64{},
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		history: skipmap.NewUint64[chord.State](),
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	}
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	var index uint64 = 0
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	var state uint64 = (uint64)(initial)
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	s.state.Store((index << 4) | state)
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	s.history.Store(0, initial)
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	return s
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}
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func (s *nodeState) Transition(exp chord.State, nxt chord.State) (chord.State, bool) {
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	curr := s.state.Load()
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	currIndex := curr >> 4
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	prev := (currIndex << 4) | (uint64)(exp)
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	nextIndex := currIndex + 1
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	next := (nextIndex << 4) | (uint64)(nxt)
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	if s.state.CompareAndSwap(prev, next) {
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		s.history.Store(nextIndex, nxt)
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		return nxt, true
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	}
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	return chord.State(curr & 0b1111), false
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}
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func (s *nodeState) Set(val chord.State) {
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	for {
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		if _, ok := s.Transition(s.Get(), val); ok {
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			break
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		}
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		runtime.Gosched()
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	}
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}
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func (s *nodeState) Get() chord.State {
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	return chord.State(s.state.Load() & 0b1111)
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}
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func (s *nodeState) History() []chord.State {
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	h := make([]chord.State, 0)
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	s.history.Range(func(_ uint64, state chord.State) bool {
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		h = append(h, state)
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		return true
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	})
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	return h
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}