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https://github.com/ChronosX88/go-gun.git
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80 lines
3.2 KiB
Go
80 lines
3.2 KiB
Go
package gun
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import (
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"bytes"
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"encoding/json"
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"time"
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)
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// State represents the conflict state of this value. It is usually the Unix
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// time in milliseconds.
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type State float64 // TODO: what if larger?
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// StateNow is the current machine state (i.e. current Unix time in ms).
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func StateNow() State {
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// TODO: Should I use timeNowUniqueUnix or otherwise set decimal spots to disambiguate?
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return State(timeNowUnixMs())
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}
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// StateFromTime converts a time to a State (i.e. converts to Unix ms).
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func StateFromTime(t time.Time) State { return State(timeToUnixMs(t)) }
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// ConflictResolution is how to handle two values for the same field.
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type ConflictResolution int
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const (
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// ConflictResolutionNeverSeenUpdate occurs when there is no existing value.
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// It means an update should always occur.
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ConflictResolutionNeverSeenUpdate ConflictResolution = iota
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// ConflictResolutionTooFutureDeferred occurs when the update is after our
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// current machine state. It means the update should be deferred.
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ConflictResolutionTooFutureDeferred
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// ConflictResolutionOlderHistorical occurs when the update happened before
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// the existing value's last update. It means it can be noted, but the
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// update should be discarded.
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ConflictResolutionOlderHistorical
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// ConflictResolutionNewerUpdate occurs when the update happened after last
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// update but is not beyond ur current machine state. It means the update
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// should overwrite.
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ConflictResolutionNewerUpdate
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// ConflictResolutionSameKeep occurs when the update happened at the same
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// time and it is lexically not the one chosen. It means the update should
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// be discarded.
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ConflictResolutionSameKeep
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// ConflictResolutionSameUpdate occurs when the update happened at the same
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// time and it is lexically the one chosen. It means the update should
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// overwrite.
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ConflictResolutionSameUpdate
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)
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// IsImmediateUpdate returns true for ConflictResolutionNeverSeenUpdate,
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// ConflictResolutionNewerUpdate, and ConflictResolutionSameUpdate
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func (c ConflictResolution) IsImmediateUpdate() bool {
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return c == ConflictResolutionNeverSeenUpdate || c == ConflictResolutionNewerUpdate || c == ConflictResolutionSameUpdate
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}
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// ConflictResolve checks the existing val/state, new val/state, and the current
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// machine state to choose what to do with the update. Note, the existing val
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// should always exist meaning it will never return
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// ConflictResolutionNeverSeenUpdate.
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func ConflictResolve(existingVal Value, existingState State, newVal Value, newState State, sysState State) ConflictResolution {
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// Existing gunjs impl serializes to JSON first to do lexical comparisons, so we will too
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if sysState < newState {
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return ConflictResolutionTooFutureDeferred
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} else if newState < existingState {
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return ConflictResolutionOlderHistorical
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} else if existingState < newState {
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return ConflictResolutionNewerUpdate
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} else if existingVal == newVal {
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return ConflictResolutionSameKeep
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} else if existingJSON, err := json.Marshal(existingVal); err != nil {
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panic(err)
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} else if newJSON, err := json.Marshal(newVal); err != nil {
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panic(err)
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} else if bytes.Compare(existingJSON, newJSON) < 0 {
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return ConflictResolutionSameUpdate
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} else {
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return ConflictResolutionSameKeep
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}
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}
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