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eskip.go
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eskip.go
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// Copyright 2015 Zalando SE
//
// 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 main
import (
"errors"
"fmt"
"io"
"os"
)
type (
command string
commandFunc func(cmdArgs) error
)
const (
check command = "check"
print command = "print"
upsert command = "upsert"
reset command = "reset"
delete command = "delete"
patch command = "patch"
ver command = "version"
)
var (
version string
commit string
)
// map command string to command function
var commands = map[command]commandFunc{
check: checkCmd,
print: printCmd,
upsert: upsertCmd,
reset: resetCmd,
delete: deleteCmd,
patch: patchCmd,
ver: versionCmd}
var (
missingCommand = errors.New("missing command")
invalidCommand = errors.New("invalid command")
)
var stdout io.Writer = os.Stdout
type cmdArgs struct {
in, out *medium
allMedia []*medium
}
func printStderr(args ...interface{}) {
fmt.Fprintln(os.Stderr, args...)
}
// exit with 0 if no error.
// print error, print hint if set and exit with
// non-0.
func exitErrHint(err error, hint bool) {
if err == nil {
os.Exit(0)
}
printStderr(err)
if hint {
printStderr()
printStderr(helpHint)
}
os.Exit(-1)
}
func exitHint(err error) { exitErrHint(err, true) }
func exit(err error) { exitErrHint(err, false) }
// second argument must be the ('sub') command.
func getCommand(args []string) (command, error) {
if len(args) < 2 {
return "", missingCommand
}
cmd := command(args[1])
if cmd[0] == '-' {
return "", missingCommand
}
if _, ok := commands[cmd]; ok {
return cmd, nil
} else {
return "", invalidCommand
}
}
func versionCmd(cmdArgs) error {
fmt.Printf(
"eskip version %s (commit: %s)\n",
version, commit,
)
return nil
}
func main() {
// print detailed usage if requested and exit:
if isHelp() {
usage()
exit(nil)
}
cmd, err := getCommand(os.Args)
if err != nil {
exitHint(err)
}
if cmd == ver {
commands[cmd](cmdArgs{})
exit(nil)
}
// process arguments, not checking if they make any sense:
media, err := processArgs()
if err != nil {
exitHint(err)
}
// check if the arguments make sense, and select input/output
// based on the rules of the current command.
cmdArgs, err := validateSelectMedia(cmd, media)
if err != nil {
exitHint(err)
}
cmdArgs, err = addDefaultMedia(cmd, cmdArgs)
if err != nil {
exitHint(err)
}
// execute command:
exit(commands[cmd](cmdArgs))
}