bind/field.go

package bind

import (
	"fmt"
	"github.com/iancoleman/strcase"
	"reflect"
	"strings"
	"unicode"
)

func pathString(f Field) string {
	return strings.Join(f.path, ":")
}

func nameFromPath(p []string) string {
	var pp []string
	for _, pi := range p {
		pp = append(pp, strcase.ToKebab(pi))
	}

	return strings.Join(pp, "-")
}

func exported(name string) bool {
	return unicode.IsUpper([]rune(name)[0])
}

func filterFields(predicate func(Field) bool, f []Field) ([]Field, []Field) {
	var yes, no []Field
	for _, fi := range f {
		if predicate(fi) {
			yes = append(yes, fi)
			continue
		}

		no = append(no, fi)
	}

	return yes, no
}

func fieldHasCircRef(f Field) bool {
	return hasCircularReference(reflect.ValueOf(f.Value()))
}

func hasPath(f Field) bool {
	return len(f.path) > 0
}

func fields(t reflect.Type) []Field {
	t = unpackType(t, pointer)
	list := t.Kind() == reflect.Slice
	t = unpackType(t, pointer|slice)
	if t.Kind() != reflect.Struct {
		return nil
	}

	var f []Field
	for i := 0; i < t.NumField(); i++ {
		tfi := t.Field(i)
		if !exported(tfi.Name) && !tfi.Anonymous {
			continue
		}

		if acceptsScalar(tfi.Type) {
			var fi Field
			ft := unpackType(tfi.Type, pointer|slice)
			fi.isBool = ft.Kind() == reflect.Bool
			fi.list = acceptsList(tfi.Type)
			fi.name = strcase.ToKebab(tfi.Name)
			fi.path = []string{tfi.Name}
			f = append(f, fi)
			continue
		}

		ffi := fields(tfi.Type)
		if !tfi.Anonymous {
			for i := range ffi {
				ffi[i].name = fmt.Sprintf(
					"%s-%s",
					strcase.ToKebab(tfi.Name),
					ffi[i].name,
				)

				ffi[i].path = append(
					[]string{tfi.Name},
					ffi[i].path...,
				)
			}
		}

		f = append(f, ffi...)
	}

	if list {
		for i := range f {
			f[i].list = true
		}
	}

	return f
}

func fieldFromValue(v reflect.Value) Field {
	var fi Field
	fi.value = v.Interface()
	fi.isBool = v.Kind() == reflect.Bool
	return fi
}

func prependFieldName(name string, f []Field) {
	for i := range f {
		if f[i].name == "" {
			f[i].name = strcase.ToKebab(name)
			f[i].path = []string{name}
			continue
		}

		f[i].name = fmt.Sprintf("%s-%s", strcase.ToKebab(name), f[i].name)
		f[i].path = append([]string{name}, f[i].path...)
	}
}

func freeFields(f []Field) {
	for i := range f {
		f[i].free = true
	}
}

func scalarMapFields(v reflect.Value) []Field {
	var f []Field
	for _, key := range v.MapKeys() {
		name := key.Interface().(string)
		value := v.MapIndex(key)
		fk := fieldValues(value)
		prependFieldName(name, fk)
		freeFields(fk)
		f = append(f, fk...)
	}

	return f
}

func fieldValues(v reflect.Value) []Field {
	var f []Field
	v = unpackValue(v, pointer|anytype|iface)
	t := v.Type()
	if isScalar(t) {
		return []Field{fieldFromValue(v)}
	}

	if v.Kind() == reflect.Slice {
		for i := 0; i < v.Len(); i++ {
			f = append(f, fieldValues(v.Index(i))...)
		}

		return f
	}

	if isScalarMap(t) {
		return scalarMapFields(v)
	}

	if t.Kind() != reflect.Struct {
		return nil
	}

	for i := 0; i < t.NumField(); i++ {
		tfi := t.Field(i)
		if !exported(tfi.Name) && !tfi.Anonymous {
			continue
		}

		vfi := v.Field(i)
		vfi = unpackValue(vfi, pointer|iface|anytype)
		switch {
		case vfi.Kind() == reflect.Struct && tfi.Anonymous:
			ff := fieldValues(vfi)
			f = append(f, ff...)
		default:
			ff := fieldValues(vfi)
			prependFieldName(tfi.Name, ff)
			f = append(f, ff...)
		}
	}

	return f
}

func takeFieldValues(f []Field) []any {
	var v []any
	for _, fi := range f {
		v = append(v, fi.Value())
	}

	return v
}

func bindScalarField(receiver reflect.Value, values []Field) bool {
	v := takeFieldValues(values)
	if !receiver.CanSet() {
		return bindScalar(receiver, v)
	}

	rv, ok := allocate(receiver.Type(), len(v))
	if !ok {
		return false
	}

	if ok = bindScalar(rv, v); ok {
		receiver.Set(rv)
	}

	return ok
}

func bindListField(receiver reflect.Value, values []Field) bool {
	if receiver.Len() < len(values) && !receiver.CanSet() {
		return false
	}

	if receiver.Len() < len(values) {
		newList, ok := allocate(receiver.Type(), len(values))
		if !ok {
			return false
		}

		reflect.Copy(newList, receiver)
		receiver.Set(newList)
	}

	for i := range values {
		if !bindField(receiver.Index(i), values[i:i+1]) {
			return false
		}
	}

	return true
}

func bindMapField(receiver reflect.Value, values []Field) bool {
	for _, v := range values {
		if len(v.path) > 1 {
			return false
		}
	}

	if receiver.IsZero() && !receiver.CanSet() {
		return false
	}

	var key string
	fp, nfp := filterFields(hasPath, values)
	if len(fp) > 0 {
		key = fp[0].path[0]
	} else {
		key = nfp[0].name
	}

	v := takeFieldValues(values)
	t := receiver.Type()
	kt := t.Key()
	vt := t.Elem()
	kv, ok := bindScalarCreate(kt, []any{key})
	if !ok {
		return false
	}

	vv, ok := bindScalarCreate(vt, v)
	if !ok {
		return false
	}

	if receiver.IsZero() {
		rv, ok := allocate(receiver.Type(), 1)
		if !ok {
			return false
		}

		receiver.Set(rv)
	}

	receiver.SetMapIndex(kv, vv)
	return true
}

func trimNameAndPath(name string, values []Field) []Field {
	name = strcase.ToKebab(name)
	v := make([]Field, len(values))
	copy(v, values)
	for i := range v {
		if len(v[i].path) > 0 {
			v[i].path = v[i].path[1:]
		}

		if v[i].name == name {
			v[i].name = ""
		}

		if strings.HasPrefix(v[i].name, fmt.Sprintf("%s-", name)) {
			v[i].name = v[i].name[len(name)+1:]
		}
	}

	return v
}

func bindStructField(receiver reflect.Value, values []Field) bool {
	var name, pathName string
	fp, nfp := filterFields(hasPath, values)
	if len(fp) > 0 {
		pathName = fp[0].path[0]
	}

	if len(nfp) > 0 {
		name = nfp[0].name
	}

	t := receiver.Type()
	for i := 0; i < t.NumField(); i++ {
		sf := t.Field(i)
		if sf.Anonymous {
			continue
		}

		if sf.Name == pathName {
			values = trimNameAndPath(pathName, values)
			return bindField(receiver.Field(i), values)
		}

		sfn := strcase.ToKebab(sf.Name)
		if name == sfn ||
			strings.HasPrefix(name, fmt.Sprintf("%s-", sfn)) {
			values = trimNameAndPath(sfn, values)
			return bindField(receiver.Field(i), values)
		}
	}

	for i := 0; i < t.NumField(); i++ {
		sf := t.Field(i)
		if !sf.Anonymous {
			continue
		}

		if bindField(receiver.Field(i), values) {
			return true
		}
	}

	return false
}

func bindField(receiver reflect.Value, values []Field) bool {
	if values[0].name == "" && len(values[0].path) == 0 {
		return bindScalarField(receiver, values)
	}

	listReceiver := unpackValue(receiver, pointer|iface|anytype)
	if listReceiver.Kind() == reflect.Slice {
		return bindListField(listReceiver, values)
	}

	fieldReceiver := unpackValue(receiver, pointer|slice|iface)
	if isScalarMap(fieldReceiver.Type()) {
		return bindMapField(fieldReceiver, values)
	}

	if fieldReceiver.Kind() == reflect.Struct {
		return bindStructField(fieldReceiver, values)
	}

	if !receiver.CanSet() {
		return false
	}

	t := receiver.Type()
	ut := unpackType(t, pointer)
	if ut.Kind() == reflect.Slice ||
		isScalarMap(ut) ||
		ut.Kind() == reflect.Struct {
		l := 1
		if ut.Kind() == reflect.Slice {
			l = len(values)
		}

		rv, ok := allocate(t, l)
		if !ok {
			return false
		}

		if !bindField(rv, values) {
			return false
		}

		receiver.Set(rv)
		return true
	}

	return false
}

func fieldsReflect[T any]() []Field {
	t := reflect.TypeFor[T]()
	if hasCircularType(t) {
		return nil
	}

	return fields(t)
}

func fieldValuesReflect(structure any) []Field {
	v := reflect.ValueOf(structure)
	if hasCircularReference(v) {
		return nil
	}

	return fieldValues(v)
}

func groupFields(f []Field) [][]Field {
	withPath, withoutPath := filterFields(hasPath, f)
	paths := make(map[string][]Field)
	for _, ff := range withPath {
		ps := pathString(ff)
		paths[ps] = append(paths[ps], ff)
	}

	names := make(map[string][]Field)
	for _, ff := range withoutPath {
		names[ff.name] = append(names[ff.name], ff)
	}

	var groups [][]Field
	for _, group := range paths {
		nfp := nameFromPath(group[0].path)
		group = append(group, names[nfp]...)
		delete(names, nfp)
		groups = append(groups, group)
	}

	for _, group := range names {
		groups = append(groups, group)
	}

	return groups
}

func bindFieldsReflect(structure any, values []Field) []Field {
	receiver := reflect.ValueOf(structure)
	if hasCircularReference(receiver) {
		return values
	}

	if !acceptsFields(receiver.Type()) {
		return values
	}

	unmatched, try := filterFields(fieldHasCircRef, values)
	groups := groupFields(try)
	for _, g := range groups {
		if !bindField(receiver, g) {
			unmatched = append(unmatched, g...)
		}
	}

	return unmatched
}