all repos

json2go @ 7a527f3

convert json to go type annotations

json2go/json2go.go(view raw) 

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
 
package json2go

import (
	"encoding/json"
	"errors"
	"fmt"
	"sort"
	"strings"
)

var ErrInvalidJSON = errors.New("invalid json")

type Transformer struct {
	structName string
}

func NewTransformer() *Transformer {
	return &Transformer{}
}

// Transform ...
// todo: take io.Reader as input?
// todo: output as io.Writer?
// todo: validate provided structName
func (t *Transformer) Transform(structName, jsonStr string) (string, error) {
	t.structName = structName

	var input any
	if err := json.Unmarshal([]byte(jsonStr), &input); err != nil {
		return "", errors.Join(ErrInvalidJSON, err)
	}

	type_ := t.getTypeAnnotation(structName, input)
	return type_, nil
}

func (t *Transformer) getTypeAnnotation(typeName string, input any) string {
	switch v := input.(type) {
	case map[string]any:
		return fmt.Sprintf("type %s %s", typeName, t.buildStruct(v))

	case []any:
		if len(v) == 0 {
			return fmt.Sprintf("type %s []any", t.structName)
		}

		type_ := t.getGoType(typeName+"Item", v[0])
		return fmt.Sprintf("type %s []%s", typeName, type_)

	case string:
		return fmt.Sprintf("type %s string", typeName)

	case float64:
		if float64(int(v)) == v {
			return fmt.Sprintf("type %s int", typeName)
		}
		return fmt.Sprintf("type %s float64", typeName)

	case bool:
		return fmt.Sprintf("type %s bool", typeName)

	default:
		return fmt.Sprintf("type %s any", typeName)

	}
}

// todo: input shouldn't be map, to preserve it's order
func (t *Transformer) buildStruct(input map[string]any) string {
	var fields strings.Builder
	for _, f := range mapToStructInput(input) {
		fieldName := t.toGoFieldName(f.field)
		if fieldName == "" {
			fieldName = "Field"
		}

		fieldType := t.getGoType(fieldName, f.type_)

		// todo: toggle json tags generation
		jsonTag := fmt.Sprintf("`json:\"%s\"`", f.field)

		// todo: figure out the indentation, since it might have nested struct
		fields.WriteString(fmt.Sprintf(
			"%s %s %s\n",
			fieldName,
			fieldType,
			jsonTag,
		))
	}

	return fmt.Sprintf("struct {\n%s}", fields.String())
}

func (t *Transformer) getGoType(fieldName string, value any) string {
	switch v := value.(type) {
	case map[string]any:
		return t.buildStruct(v)

	case []any:
		if len(v) == 0 {
			return "[]any"
		}

		type_ := t.getGoType(fieldName, v[0])
		return "[]" + type_

	case float64:
		if float64(int(v)) == v {
			return "int"
		}
		return "float64"

	case string:
		return "string"

	case bool:
		return "bool"

	default:
		return "any"
	}
}

func (t *Transformer) toGoFieldName(jsonField string) string {
	parts := strings.Split(jsonField, "_")

	var result strings.Builder
	for _, part := range parts {
		if part != "" {
			if len(part) > 0 {
				result.WriteString(strings.ToUpper(part[:1]) + part[1:])
			}
		}
	}

	return result.String()
}

type structInput struct {
	field string
	type_ any
}

func mapToStructInput(input map[string]any) []structInput {
	res := make([]structInput, 0, len(input))
	for k, v := range input {
		res = append(res, structInput{k, v})
	}

	sort.Slice(res, func(i, j int) bool {
		return res[i].field < res[j].field
	})

	return res
}