blasphem/pkg/config/config.go

package config

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

	server "dynatron.me/x/blasphem/pkg/server/config"

	"gopkg.in/yaml.v3"
)

type Config struct {
	DataDir *string        `yaml:"data_dir,omitempty"`
	Server  *server.Config `yaml:"server"`
}

const (
	IncludeTag              = "!include"
	IncludeDirNamedTag      = "!include_dir_named"
	IncludeDirListTag       = "!include_dir_list"
	IncludeDirMergeNamedTag = "!include_dir_merge_named"
	SecretTag               = "!secret"
)

func (c *Config) UnmarshalYAML(y *yaml.Node) error {
	if y.Kind != yaml.MappingNode {
		return yerr(y, errors.New("config root must be a map"))
	}

	cV := reflect.ValueOf(c).Elem()

	components := make(map[string]reflect.Value, cV.NumField())
	for i := 0; i < cV.NumField(); i++ {
		if tag, ok := cV.Type().Field(i).Tag.Lookup("yaml"); ok {
			tags := strings.Split(tag, ",")
			components[tags[0]] = cV.Field(i)
		}
	}

	for i := 0; i < len(y.Content); i += 2 {
		k, v := y.Content[i], y.Content[i+1]

		switch v.LongTag() {
		case IncludeTag:
			fallthrough
		case IncludeDirNamedTag:
			fallthrough
		case IncludeDirMergeNamedTag:
			fallthrough
		case SecretTag:
			panic(fmt.Errorf("tag %s not implemented", v.LongTag()))
		default:
			var key string
			err := k.Decode(&key)
			if err != nil {
				return yerr(y, err)
			}

			if comp, ok := components[key]; ok {
				val := reflect.New(comp.Type())
				err := v.Decode(val.Interface())
				if err != nil {
					return yerr(y, err)
				}

				comp.Set(val.Elem())
			}
		}
	}

	return nil
}

func yerr(y *yaml.Node, ye error) error {
	return fmt.Errorf("line %d: %w", y.Line, ye)
}