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empty.go
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/
empty.go
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// Mgmt
// Copyright (C) 2013-2018+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package empty
import (
"fmt"
"sync"
"github.com/purpleidea/mgmt/engine"
"github.com/purpleidea/mgmt/gapi"
"github.com/purpleidea/mgmt/pgraph"
"github.com/urfave/cli"
)
const (
// Name is the name of this frontend.
Name = "empty"
)
func init() {
gapi.Register(Name, func() gapi.GAPI { return &GAPI{} }) // register
}
// GAPI implements the main lang GAPI interface.
type GAPI struct {
data gapi.Data
initialized bool
closeChan chan struct{}
wg *sync.WaitGroup // sync group for tunnel go routines
}
// Cli takes a cli.Context, and returns our GAPI if activated. All arguments
// should take the prefix of the registered name. On activation, if there are
// any validation problems, you should return an error. If this was not
// activated, then you should return a nil GAPI and a nil error.
func (obj *GAPI) Cli(c *cli.Context, fs engine.Fs) (*gapi.Deploy, error) {
if s := c.String(Name); c.IsSet(Name) {
if s == "" {
return nil, fmt.Errorf("input code is empty")
}
return &gapi.Deploy{
Name: Name,
//Noop: false,
GAPI: &GAPI{},
}, nil
}
return nil, nil // we weren't activated!
}
// CliFlags returns a list of flags used by this deploy subcommand.
func (obj *GAPI) CliFlags() []cli.Flag {
return []cli.Flag{
cli.StringFlag{
Name: Name,
Value: "",
Usage: "empty graph to deploy",
},
}
}
// Init initializes the lang GAPI struct.
func (obj *GAPI) Init(data gapi.Data) error {
if obj.initialized {
return fmt.Errorf("already initialized")
}
obj.data = data // store for later
obj.closeChan = make(chan struct{})
obj.wg = &sync.WaitGroup{}
obj.initialized = true
return nil
}
// Graph returns a current Graph.
func (obj *GAPI) Graph() (*pgraph.Graph, error) {
if !obj.initialized {
return nil, fmt.Errorf("%s: GAPI is not initialized", Name)
}
obj.data.Logf("generating empty graph...")
g, err := pgraph.NewGraph("empty")
if err != nil {
return nil, err
}
return g, nil
}
// Next returns nil errors every time there could be a new graph.
func (obj *GAPI) Next() chan gapi.Next {
ch := make(chan gapi.Next)
obj.wg.Add(1)
go func() {
defer obj.wg.Done()
defer close(ch) // this will run before the obj.wg.Done()
if !obj.initialized {
next := gapi.Next{
Err: fmt.Errorf("%s: GAPI is not initialized", Name),
Exit: true, // exit, b/c programming error?
}
select {
case ch <- next:
case <-obj.closeChan:
}
return
}
// send only one event
next := gapi.Next{
Exit: false,
Err: nil,
}
select {
case ch <- next: // trigger a run (send a msg)
// pass
// unblock if we exit while waiting to send!
case <-obj.closeChan:
return
}
}()
return ch
}
// Close shuts down the lang GAPI.
func (obj *GAPI) Close() error {
if !obj.initialized {
return fmt.Errorf("%s: GAPI is not initialized", Name)
}
close(obj.closeChan)
obj.wg.Wait()
obj.initialized = false // closed = true
return nil
}