common/protocol/marshal.go

package protocol

import (
	"errors"
	"fmt"
	"reflect"
	"strings"

	rpcv1 "code.icb4dc0.de/buildr/api/generated/rpc/v1"
)

var ErrExpectedStruct = errors.New("expected struct")

func Marshal(in any) (*rpcv1.ModuleSpec, error) {
	cfg := marshalConfig{
		TagName: "hcl",
	}

	val := reflect.ValueOf(in)
	if val.Kind() == reflect.Ptr {
		val = val.Elem()
	}

	if val.Kind() != reflect.Struct {
		return nil, fmt.Errorf("%w: got %T", ErrExpectedStruct, in)
	}

	return cfg.marshal(val)
}

type marshalConfig struct {
	TagName string
}

func (cfg marshalConfig) marshal(in reflect.Value) (*rpcv1.ModuleSpec, error) {
	numField := in.NumField()

	out := &rpcv1.ModuleSpec{
		Values: make(map[string]*rpcv1.ModuleSpec_Value, numField),
	}

	// TODO consider tag for field name

	inputType := in.Type()

	for i := 0; i < numField; i++ {
		structField := inputType.Field(i)
		if !structField.IsExported() {
			continue
		}

		fieldName := cfg.fieldName(structField)

		out.Values[fieldName] = cfg.mapReflectValueToSpecValue(in.Field(i))
	}

	return out, nil
}

func (cfg marshalConfig) mapReflectValueToSpecValue(in reflect.Value) *rpcv1.ModuleSpec_Value {
	switch in.Kind() {
	case reflect.Map:
		return cfg.mapValue(in)
	case reflect.Bool:
		return boolValue(in.Bool())
	case reflect.String:
		return stringValue(in.String())
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return intValue(in.Int())
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return intValue(in.Uint())
	case reflect.Float32, reflect.Float64:
		return floatValue(in.Float())
	case reflect.Struct:
		return cfg.structValue(in)
	case reflect.Slice, reflect.Array:
		switch in.Type().Elem().Kind() {
		case reflect.Bool:
			return boolSliceValue(in)
		case reflect.String:
			return stringSliceValue(in)
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			return intSliceValue(in, reflect.Value.Int)
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			return intSliceValue(in, func(v reflect.Value) int64 {
				return int64(v.Uint())
			})
		case reflect.Float32, reflect.Float64:
			return floatSliceValue(in)
		default:
			return nil
		}
	default:
		return nil
	}
}

func (cfg marshalConfig) fieldName(field reflect.StructField) string {
	tagVal, ok := field.Tag.Lookup(cfg.TagName)
	if !ok {
		return field.Name
	}

	split := strings.Split(tagVal, ",")

	switch {
	case len(split) == 0:
		fallthrough
	case split[0] == "":
		return strings.ToLower(field.Name)
	default:
		return strings.ToLower(split[0])
	}
}

func (cfg marshalConfig) mapValue(in reflect.Value) *rpcv1.ModuleSpec_Value {
	result := &rpcv1.ModuleSpec_Value{
		Type:         rpcv1.ModuleSpec_ValueTypeMap,
		ComplexValue: make(map[string]*rpcv1.ModuleSpec_Value, in.Len()),
	}

	iter := in.MapRange()
	for iter.Next() {
		result.ComplexValue[iter.Key().String()] = cfg.mapReflectValueToSpecValue(iter.Value())
	}

	return result
}

func (cfg marshalConfig) structValue(in reflect.Value) *rpcv1.ModuleSpec_Value {
	inputType := in.Type()
	numFields := inputType.NumField()
	result := &rpcv1.ModuleSpec_Value{
		Type:         rpcv1.ModuleSpec_ValueTypeObject,
		ComplexValue: make(map[string]*rpcv1.ModuleSpec_Value, numFields),
	}

	for i := 0; i < numFields; i++ {
		structField := inputType.Field(i)
		if !structField.IsExported() {
			continue
		}

		result.ComplexValue[structField.Name] = cfg.mapReflectValueToSpecValue(in.Field(i))
	}

	return result
}

func boolValue(in bool) *rpcv1.ModuleSpec_Value {
	return &rpcv1.ModuleSpec_Value{
		Type: rpcv1.ModuleSpec_ValueTypeSingle,
		SingleValue: &rpcv1.ModuleSpec_Value_BoolValue{
			BoolValue: in,
		},
	}
}

func boolSliceValue(val reflect.Value) *rpcv1.ModuleSpec_Value {
	result := &rpcv1.ModuleSpec_Value{
		Type:       rpcv1.ModuleSpec_ValueTypeBoolSlice,
		BoolValues: make([]bool, 0, val.Len()),
	}

	for i := 0; i < val.Len(); i++ {
		result.BoolValues = append(result.BoolValues, val.Index(i).Bool())
	}

	return result
}

func intValue[T Integer](in T) *rpcv1.ModuleSpec_Value {
	return &rpcv1.ModuleSpec_Value{
		Type: rpcv1.ModuleSpec_ValueTypeSingle,
		SingleValue: &rpcv1.ModuleSpec_Value_IntValue{
			IntValue: int64(in),
		},
	}
}

func intSliceValue(val reflect.Value, selector func(v reflect.Value) int64) *rpcv1.ModuleSpec_Value {
	result := &rpcv1.ModuleSpec_Value{
		Type:      rpcv1.ModuleSpec_ValueTypeIntSlice,
		IntValues: make([]int64, 0, val.Len()),
	}

	for i := 0; i < val.Len(); i++ {
		result.IntValues = append(result.IntValues, selector(val.Index(i)))
	}

	return result
}

func floatValue[T Float](in T) *rpcv1.ModuleSpec_Value {
	return &rpcv1.ModuleSpec_Value{
		Type: rpcv1.ModuleSpec_ValueTypeSingle,
		SingleValue: &rpcv1.ModuleSpec_Value_DoubleValue{
			DoubleValue: float64(in),
		},
	}
}

func floatSliceValue(val reflect.Value) *rpcv1.ModuleSpec_Value {
	result := &rpcv1.ModuleSpec_Value{
		Type:         rpcv1.ModuleSpec_ValueTypeDoubleSlice,
		DoubleValues: make([]float64, 0, val.Len()),
	}

	for i := 0; i < val.Len(); i++ {
		result.DoubleValues = append(result.DoubleValues, val.Index(i).Float())
	}

	return result
}

func stringValue(in string) *rpcv1.ModuleSpec_Value {
	return &rpcv1.ModuleSpec_Value{
		Type: rpcv1.ModuleSpec_ValueTypeSingle,
		SingleValue: &rpcv1.ModuleSpec_Value_StringValue{
			StringValue: in,
		},
	}
}

func stringSliceValue(val reflect.Value) *rpcv1.ModuleSpec_Value {
	result := &rpcv1.ModuleSpec_Value{
		Type:         rpcv1.ModuleSpec_ValueTypeStringSlice,
		StringValues: make([]string, 0, val.Len()),
	}

	for i := 0; i < val.Len(); i++ {
		result.StringValues = append(result.StringValues, val.Index(i).String())
	}

	return result
}