1// SPDX-License-Identifier: MIT
2
3package template
4
5import "fmt"
6
7// TokenError is an error about a token, positioned at it. It is what the
8// Assert functions return.
9type TokenError struct {
10 Token Token
11 Message string
12}
13
14func (e *TokenError) Error() string { return e.Message }
15
16func assertErr(t Token, desc string, want string) error {
17 return &TokenError{Token: t, Message: fmt.Sprintf("Unexpected type '%s' encountered while reading '%s'. The type '%s' was expected.", t.Kind(), desc, want)}
18}
19
20// AssertString returns t as a string token or a [*TokenError] worded like the
21// reference's "Unexpected type 'X' encountered while reading 'desc'".
22func AssertString(t Token, desc string) (*String, error) {
23 if s, ok := t.(*String); ok {
24 return s, nil
25 }
26 return nil, assertErr(t, desc, KindString.String())
27}
28
29// AssertBoolean returns t as a boolean token or a [*TokenError].
30func AssertBoolean(t Token, desc string) (*Boolean, error) {
31 if s, ok := t.(*Boolean); ok {
32 return s, nil
33 }
34 return nil, assertErr(t, desc, KindBoolean.String())
35}
36
37// AssertNumber returns t as a number token or a [*TokenError].
38func AssertNumber(t Token, desc string) (*Number, error) {
39 if s, ok := t.(*Number); ok {
40 return s, nil
41 }
42 return nil, assertErr(t, desc, KindNumber.String())
43}
44
45// AssertSequence returns t as a sequence token or a [*TokenError].
46func AssertSequence(t Token, desc string) (*Sequence, error) {
47 if s, ok := t.(*Sequence); ok {
48 return s, nil
49 }
50 return nil, assertErr(t, desc, KindSequence.String())
51}
52
53// AssertMapping returns t as a mapping token or a [*TokenError].
54func AssertMapping(t Token, desc string) (*Mapping, error) {
55 if s, ok := t.(*Mapping); ok {
56 return s, nil
57 }
58 return nil, assertErr(t, desc, KindMapping.String())
59}
60
61// AssertScalar returns t when it is neither a sequence nor a mapping, or a
62// [*TokenError].
63func AssertScalar(t Token, desc string) (Token, error) {
64 if IsScalar(t) {
65 return t, nil
66 }
67 return nil, assertErr(t, desc, "ScalarToken")
68}