Transform JSON to Go structs

.gitignore

@@ -0,0 +1,2 @@
+structify
+test.json

go.mod

@@ -0,0 +1,3 @@
+module git.snorba.art/max/structify
+
+go 1.18

main.go

@@ -0,0 +1,189 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"go/format"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+type StructField interface {
+	GetName() string
+	GetType() string
+	GetJSONTag() string
+	String() string
+}
+
+type StructType struct {
+	JSONField string
+	Name      string
+	Children  []StructField
+}
+
+func (s *StructType) GetJSONTag() string {
+	return fmt.Sprintf("`json:\"%s\"`", s.JSONField)
+}
+
+func (s *StructType) String() string {
+	var children []string
+	for _, v := range s.Children {
+		children = append(children, v.String())
+	}
+
+	return fmt.Sprintf(
+		"%s struct {\n%s\n}",
+		s.Name,
+		strings.Join(children, "\n"),
+	)
+}
+
+func (s *StructType) GetType() string {
+	return "struct"
+}
+
+func (s *StructType) GetName() string {
+	return s.Name
+}
+
+type SimpleType struct {
+	JSONField string
+	Name      string
+	Type      string
+}
+
+func (s *SimpleType) GetJSONTag() string {
+	return fmt.Sprintf("`json:\"%s\"`", s.JSONField)
+}
+
+func (s *SimpleType) String() string {
+	return fmt.Sprintf("%s %s", s.Name, s.Type)
+}
+
+func (s *SimpleType) GetName() string {
+	return s.Name
+}
+
+func (s *SimpleType) GetType() string {
+	return s.Type
+}
+
+func (s *StructType) AddChild(name string, value json.RawMessage) {
+	var i interface{}
+	json.Unmarshal(value, &i)
+	switch v := i.(type) {
+	case float64:
+		s.addChild(ParseNumberField(name, value))
+	case string, bool:
+		s.addChild(ParseSimpleField(name, fmt.Sprintf("%T", v)))
+	case []interface{}:
+		// To Do: parse slices
+		s.addChild(ParseSliceField(name, value))
+	case map[string]interface{}:
+		s.addChild(ParseStruct(name, value))
+	default:
+		fmt.Printf("%s %s %T\n", name, "dunno", v)
+	}
+}
+
+func (s *StructType) addChild(field StructField) {
+	s.Children = append(s.Children, field)
+}
+
+func ParseSliceField(name string, value json.RawMessage) *SimpleType {
+	var s []interface{}
+	err := json.Unmarshal(value, &s)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if len(s) == 0 {
+		return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: "[]interface{}"}
+	}
+
+	sliceType := fmt.Sprintf("%T", s[0])
+	for _, v := range s {
+		if sliceType != fmt.Sprintf("%T", v) {
+			return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: "[]interface{}"}
+		}
+	}
+
+	return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: fmt.Sprintf("[]%s", sliceType)}
+}
+
+func ParseNumberField(name string, value json.RawMessage) *SimpleType {
+	for _, b := range value {
+		if b == '.' {
+			return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: "float64"}
+		}
+	}
+	return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: "int"}
+}
+
+func ParseSimpleField(name, gotype string) *SimpleType {
+	return &SimpleType{JSONField: name, Name: SanitizeName(name), Type: gotype}
+}
+
+func ParseStruct(name string, data []byte) *StructType {
+	jsonMap := make(map[string]json.RawMessage)
+	err := json.Unmarshal(data, &jsonMap)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	s := &StructType{JSONField: name, Name: SanitizeName(name)}
+
+	for key, value := range jsonMap {
+		s.AddChild(key, value)
+	}
+	return s
+}
+
+func SanitizeName(name string) string {
+	return strings.ReplaceAll(strings.Title(strings.ReplaceAll(name, "_", "-")), "-", "")
+}
+
+func FormatStructType(s *StructType, inlineTypes bool) string {
+	var lines []string
+	var types []string
+	lines = append(lines, fmt.Sprintf("type %s struct {", s.Name))
+	for _, c := range s.Children {
+		switch v := c.(type) {
+		case *SimpleType:
+			lines = append(lines, fmt.Sprintf("%s %s", c.String(), c.GetJSONTag()))
+		case *StructType:
+			if inlineTypes {
+				lines = append(lines, fmt.Sprintf("%s %s", c.String(), c.GetJSONTag()))
+				continue
+			}
+			lines = append(lines, fmt.Sprintf("%s %s %s", c.GetName(), c.GetName(), c.GetJSONTag()))
+			types = append(types, FormatStructType(v, inlineTypes))
+		}
+	}
+
+	lines = append(lines, "}")
+	lines = append(lines, types...)
+
+	formatted, err := format.Source([]byte(strings.Join(lines, "\n")))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return string(formatted)
+}
+
+func main() {
+	log.Default().SetOutput(os.Stderr)
+	reader := bufio.NewReader(os.Stdin)
+	buf, err := io.ReadAll(reader)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	s := ParseStruct("AutoGenerated", buf)
+
+	fmt.Println(FormatStructType(s, false))
+}