wm/src/bsp/cfg/cfg.go

package cfg

import (
	"fmt"
	"reflect"
	"strconv"
	"strings"

	"tuxpa.in/t/wm/src/copies"
)

// Read will return the first non nil value or the default value
func Read[T any](xs ...*T) T {
	for _, v := range xs {
		if v != nil {
			return *v
		}
	}
	// zero value if all else fails
	return *new(T)
}

func ReadFunc[T any, V any](fn func(*T) *V, xs ...*T) V {
	for _, v := range xs {
		if v == nil {
			continue
		}
		vv := fn(v)
		if vv != nil {
			return *vv
		}
	}
	return *new(V)
}

type Modifier[T any] struct {
	Ref T

	setters map[string]func(v string) error
	getters map[string]func() (string, error)
}

func NewModifier[T any](start T) *Modifier[T] {
	m := &Modifier[T]{
		Ref:     start,
		setters: map[string]func(v string) error{},
		getters: map[string]func() (string, error){},
	}
	m.setup()
	return m
}

func (m *Modifier[T]) Set(k, v string) error {
	fn, ok := m.setters[k]
	if !ok {
		// TODO: some error here
		return nil
	}
	return fn(v)
}
func (m *Modifier[T]) GetString(k string) (string, error) {
	fn, ok := m.getters[k]
	if !ok {
		// TODO: some error here
		return "", fmt.Errorf("config key '%s' not found", k)
	}
	return fn()
}

func (m *Modifier[T]) FillDefaults() {
	rt := reflect.TypeOf(m.Ref).Elem()
	for i := 0; i < rt.NumField(); i++ {
		ft := rt.Field(i)
		k := ft.Tag.Get("cfg")
		dv := ft.Tag.Get("default")
		if dv == "" {
			continue
		}
		m.Set(k, dv)
	}
	return
}

func (m *Modifier[T]) setup() {
	// grab the value
	rv := reflect.ValueOf(m.Ref).Elem()
	rt := reflect.TypeOf(m.Ref).Elem()
	for i := 0; i < rv.NumField(); i++ {
		fv := rv.Field(i)
		ft := rt.Field(i)
		k := ft.Tag.Get("cfg")
		kind := ft.Type.Elem().Kind()
		switch kind {
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			m.setters[k] = func(v string) error {
				val, err := strconv.ParseUint(v, 10, 64)
				if err != nil {
					return copies.NewInvalidValueErr(k, v)
				}
				if fv.IsNil() {
					fv.Set(reflect.New(ft.Type.Elem()))
				}
				fv.Elem().SetUint(uint64(val))
				return nil
			}
			m.getters[k] = func() (string, error) {
				if fv.IsNil() {
					return "", nil
				}
				return fmt.Sprintf("%v", fv.Elem()), nil
			}
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			m.setters[k] = func(v string) error {
				val, err := strconv.Atoi(v)
				if err != nil {
					return copies.NewInvalidValueErr(k, v)
				}
				if fv.IsNil() {
					fv.Set(reflect.New(ft.Type.Elem()))
				}
				fv.Elem().SetInt(int64(val))
				return nil
			}
			m.getters[k] = func() (string, error) {
				if fv.IsNil() {
					return "", nil
				}
				return fmt.Sprintf("%v", fv.Elem()), nil
			}
		case reflect.Bool:
			m.setters[k] = func(v string) error {
				var b bool
				switch strings.ToLower(v) {
				case "true", "on":
					b = true
				case "false", "off":
					b = false
				default:
					return copies.NewInvalidValueErr(k, v)
				}
				if fv.IsNil() {
					fv.Set(reflect.New(ft.Type.Elem()))
				}
				fv.Elem().SetBool(b)
				return nil
			}
			m.getters[k] = func() (string, error) {
				if fv.IsNil() {
					return "", nil
				}
				return fmt.Sprintf("%v", fv.Elem()), nil
			}
		case reflect.String:
			m.setters[k] = func(v string) error {
				if fv.IsNil() {
					fv.Set(reflect.New(ft.Type.Elem()))
				}
				fv.Elem().SetString(strings.TrimSpace(v))
				return nil
			}
			m.getters[k] = func() (string, error) {
				if fv.IsNil() {
					return "", nil
				}
				return fmt.Sprintf("%v", fv.Elem()), nil
			}
		}
	}
}

func getStructTag(f reflect.StructField, tagName string) string {
	return string(f.Tag.Get(tagName))
}