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Side by Side Diff: names/tagkind.go

Issue 12473043: names: add ParseTag
Patch Set: names: add ParseTag Created 10 years, 7 months ago
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1 // Copyright 2013 Canonical Ltd. 1 // Copyright 2013 Canonical Ltd.
2 // Licensed under the AGPLv3, see LICENCE file for details. 2 // Licensed under the AGPLv3, see LICENCE file for details.
3 3
4 package names 4 package names
5 5
6 import ( 6 import (
7 "fmt" 7 "fmt"
8 "strings" 8 "strings"
9 ) 9 )
10 10
11 const ( 11 const (
12 UnitTagKind = "unit" 12 UnitTagKind = "unit"
13 MachineTagKind = "machine" 13 MachineTagKind = "machine"
14 ServiceTagKind = "service" 14 ServiceTagKind = "service"
15 EnvironTagKind = "environment" 15 EnvironTagKind = "environment"
16 UserTagKind = "user" 16 UserTagKind = "user"
17 ) 17 )
18 18
19 var validKinds = map[string]bool{ 19 var validKinds = map[string]bool{
20 UnitTagKind: true, 20 UnitTagKind: true,
21 MachineTagKind: true, 21 MachineTagKind: true,
22 ServiceTagKind: true, 22 ServiceTagKind: true,
23 EnvironTagKind: true, 23 EnvironTagKind: true,
24 UserTagKind: true, 24 UserTagKind: true,
25 } 25 }
26 26
27 var fromTagName = map[string]func(string) string{
28 UnitTagKind: unitFromTagName,
dimitern 2013/08/06 09:35:40 unitFromTag and machineFromTag please. There's no
rog 2013/08/06 09:50:08 a tag has two parts - these functions operate on t
dimitern 2013/08/06 10:00:28 fromTagSuffix, as agreed.
rog 2013/08/06 10:04:20 Done (slightly differently)
29 MachineTagKind: machineFromTagName,
30 }
31
32 var verifyId = map[string]func(string) bool{
33 UnitTagKind: IsUnit,
34 MachineTagKind: IsMachine,
35 ServiceTagKind: IsService,
36 UserTagKind: IsUser,
37 EnvironTagKind: IsEnvironment,
38 }
39
27 // TagKind returns one of the *TagKind constants for the given tag, or 40 // TagKind returns one of the *TagKind constants for the given tag, or
28 // an error if none matches. 41 // an error if none matches.
29 func TagKind(tag string) (string, error) { 42 func TagKind(tag string) (string, error) {
30 i := strings.Index(tag, "-") 43 i := strings.Index(tag, "-")
31 if i <= 0 || !validKinds[tag[:i]] { 44 if i <= 0 || !validKinds[tag[:i]] {
32 return "", fmt.Errorf("%q is not a valid tag", tag) 45 return "", fmt.Errorf("%q is not a valid tag", tag)
33 } 46 }
34 return tag[:i], nil 47 return tag[:i], nil
35 } 48 }
36 49
37 func splitTag(tag string) (kind, rest string, err error) { 50 func splitTag(tag string) (kind, rest string, err error) {
38 kind, err = TagKind(tag) 51 kind, err = TagKind(tag)
39 if err != nil { 52 if err != nil {
40 return "", "", err 53 return "", "", err
41 } 54 }
42 return kind, tag[len(kind)+1:], nil 55 return kind, tag[len(kind)+1:], nil
43 } 56 }
44 57
45 func makeTag(kind, rest string) string { 58 func makeTag(kind, rest string) string {
46 return kind + "-" + rest 59 return kind + "-" + rest
47 } 60 }
61
62 // ParseTag parses a tag into its kind and identifier
63 // components. It returns an error if the tag is malformed,
64 // or if expectKind is not empty and the kind is
65 // not as expected.
66 func ParseTag(tag, expectKind string) (kind, id string, err error) {
67 kind, id, err = splitTag(tag)
68 if err != nil {
69 if expectKind != "" {
70 return "", "", fmt.Errorf("%q is not a valid %s tag", ta g, expectKind)
71 }
72 return "", "", fmt.Errorf("%q is not a valid tag", tag)
73 }
74 if expectKind != "" && kind != expectKind {
75 return "", "", fmt.Errorf("%q is not a valid %s tag", tag, expec tKind)
76 }
77 if fromTag := fromTagName[kind]; fromTag != nil {
dimitern 2013/08/06 09:35:40 if fromTagFunc := fromTag[kind]; fromTagFunc != ni
78 id = fromTag(id)
79 }
80 if verify := verifyId[kind]; verify != nil && !verify(id) {
81 return "", "", fmt.Errorf("%q is not a valid %s tag", tag, kind)
82 }
83 return kind, id, nil
84 }
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