json2go/transpiler.go (view raw)
Oleksandr Smirnov
Oleksandr Smirnov
olexsmir@gmail.com refactor: use an actual parser instead of reflection..., 11 days ago
olexsmir@gmail.com refactor: use an actual parser instead of reflection..., 11 days ago
| 1 | package json2go |
| 2 | |
| 3 | import ( |
| 4 | "strings" |
| 5 | "unicode" |
| 6 | ) |
| 7 | |
| 8 | // Transpiler transpiles AST [Value] to Go type definitions. |
| 9 | type Transpiler struct{} |
| 10 | |
| 11 | func NewTranspiler() *Transpiler { return &Transpiler{} } |
| 12 | |
| 13 | // Transpile converts a [Value] AST to Go type definitions. |
| 14 | // Nested types are emitted after the parent struct. |
| 15 | func (t *Transpiler) Transpile(structName string, v Value, includeTags bool) (string, error) { |
| 16 | var buf strings.Builder |
| 17 | var nested strings.Builder |
| 18 | |
| 19 | switch v.Kind { |
| 20 | case ArrayValue: |
| 21 | if len(v.Array) == 0 { |
| 22 | buf.WriteString("type ") |
| 23 | buf.WriteString(structName) |
| 24 | buf.WriteString(" []any") |
| 25 | } else { |
| 26 | itemType := t.writeWithNested(&buf, &nested, structName+"Item", v.Array[0], includeTags) |
| 27 | buf.WriteString("type ") |
| 28 | buf.WriteString(structName) |
| 29 | buf.WriteString(" []") |
| 30 | buf.WriteString(itemType) |
| 31 | } |
| 32 | |
| 33 | case ObjectValue: |
| 34 | t.writeStructDef(&buf, &nested, structName, v.Object, includeTags) |
| 35 | |
| 36 | default: |
| 37 | scalarType := t.inferType(structName, v) |
| 38 | buf.WriteString("type ") |
| 39 | buf.WriteString(structName) |
| 40 | buf.WriteByte(' ') |
| 41 | buf.WriteString(scalarType) |
| 42 | } |
| 43 | |
| 44 | if nested.Len() > 0 && buf.Len() > 0 { |
| 45 | buf.WriteString("\n\n") |
| 46 | buf.WriteString(nested.String()) |
| 47 | } |
| 48 | return buf.String(), nil |
| 49 | } |
| 50 | |
| 51 | func (t *Transpiler) writeWithNested(buf, nested *strings.Builder, name string, v Value, includeTags bool) string { |
| 52 | switch v.Kind { |
| 53 | case ObjectValue: |
| 54 | t.writeStructDef(nested, nested, name, v.Object, includeTags) |
| 55 | return name |
| 56 | |
| 57 | case ArrayValue: |
| 58 | if len(v.Array) == 0 { |
| 59 | return "[]any" |
| 60 | } |
| 61 | itemType := t.writeWithNested(buf, nested, name+"Item", v.Array[0], includeTags) |
| 62 | return "[]" + itemType |
| 63 | } |
| 64 | return t.inferType(name, v) |
| 65 | } |
| 66 | |
| 67 | func (t *Transpiler) writeStructDef(buf, nested *strings.Builder, name string, fields []Field, includeTags bool) { |
| 68 | if buf.Len() > 0 { |
| 69 | buf.WriteString("\n\n") |
| 70 | } |
| 71 | |
| 72 | buf.WriteString("type ") |
| 73 | buf.WriteString(name) |
| 74 | buf.WriteString(" struct {\n") |
| 75 | for _, f := range fields { |
| 76 | fieldName := t.sanitizeFieldName(f.K) |
| 77 | fieldType := t.writeWithNested(buf, nested, name+fieldName, f.V, includeTags) |
| 78 | if includeTags { |
| 79 | buf.WriteByte('\t') |
| 80 | buf.WriteString(fieldName) |
| 81 | buf.WriteByte(' ') |
| 82 | buf.WriteString(fieldType) |
| 83 | buf.WriteString(" `json:\"") |
| 84 | buf.WriteString(f.K) |
| 85 | buf.WriteString("\"`\n") |
| 86 | } else { |
| 87 | buf.WriteByte('\t') |
| 88 | buf.WriteString(fieldName) |
| 89 | buf.WriteByte(' ') |
| 90 | buf.WriteString(fieldType) |
| 91 | buf.WriteByte('\n') |
| 92 | } |
| 93 | } |
| 94 | buf.WriteString("}") |
| 95 | } |
| 96 | |
| 97 | func (t *Transpiler) inferType(name string, v Value) string { |
| 98 | switch v.Kind { |
| 99 | case ObjectValue: |
| 100 | return name |
| 101 | case ArrayValue: |
| 102 | if len(v.Array) == 0 { |
| 103 | return "[]any" |
| 104 | } |
| 105 | itemType := t.inferType(name+"Item", v.Array[0]) |
| 106 | return "[]" + itemType |
| 107 | case StringValue: |
| 108 | return "string" |
| 109 | case NumberValue: |
| 110 | return "int" |
| 111 | case DecimalValue: |
| 112 | return "float64" |
| 113 | case BoolValue: |
| 114 | return "bool" |
| 115 | case NullValue: |
| 116 | return "any" |
| 117 | default: |
| 118 | return "any" |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | func (t *Transpiler) sanitizeFieldName(jsonKey string) string { |
| 123 | if jsonKey == "" { |
| 124 | return "Field" |
| 125 | } |
| 126 | |
| 127 | var result strings.Builder |
| 128 | result.Grow(len(jsonKey)) |
| 129 | |
| 130 | capitalize := true |
| 131 | for _, r := range jsonKey { |
| 132 | if r == '_' { |
| 133 | capitalize = true |
| 134 | continue |
| 135 | } |
| 136 | if capitalize { |
| 137 | result.WriteRune(unicode.ToUpper(r)) |
| 138 | capitalize = false |
| 139 | } else { |
| 140 | result.WriteRune(r) |
| 141 | } |
| 142 | } |
| 143 | |
| 144 | name := result.String() |
| 145 | if name != "" && isValidIdentifier(name) { |
| 146 | return name |
| 147 | } |
| 148 | |
| 149 | return t.sanitizeInvalidIdentifier(jsonKey) |
| 150 | } |
| 151 | |
| 152 | func (t *Transpiler) sanitizeInvalidIdentifier(jsonKey string) string { |
| 153 | var result strings.Builder |
| 154 | for i, r := range jsonKey { |
| 155 | if unicode.IsLetter(r) || r == '_' || (i > 0 && unicode.IsDigit(r)) { |
| 156 | result.WriteRune(r) |
| 157 | } else if i > 0 && r == '-' { |
| 158 | result.WriteRune('_') |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | name := result.String() |
| 163 | if name == "" || (!unicode.IsLetter(rune(name[0])) && name[0] != '_') { |
| 164 | var b strings.Builder |
| 165 | b.Grow(len(name) + 1) |
| 166 | b.WriteByte('F') |
| 167 | b.WriteString(name) |
| 168 | return b.String() |
| 169 | } |
| 170 | |
| 171 | return name |
| 172 | } |