state.go

/*
   Copyright 2014 CoreOS, Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package machine

const (
	shortIDLen = 8
)

// MachineState represents a point-in-time snapshot of the
// state of the local host.
type MachineState struct {
	ID       string
	PublicIP string
	Metadata map[string]string
	Version  string
}

func (ms MachineState) ShortID() string {
	if len(ms.ID) <= shortIDLen {
		return ms.ID
	}
	return ms.ID[0:shortIDLen]
}

func (ms MachineState) MatchID(ID string) bool {
	return ms.ID == ID || ms.ShortID() == ID
}

// stackState is used to merge two MachineStates. Values configured on the top
// MachineState always take precedence over those on the bottom.
func stackState(top, bottom MachineState) MachineState {
	state := MachineState(bottom)

	if top.PublicIP != "" {
		state.PublicIP = top.PublicIP
	}

	if top.ID != "" {
		state.ID = top.ID
	}

	//FIXME: This will *always* overwrite the bottom's metadata,
	// but the only use-case we have today does not ever have
	// metadata on the bottom.
	if len(top.Metadata) > 0 {
		state.Metadata = top.Metadata
	}

	if top.Version != "" {
		state.Version = top.Version
	}

	return state
}