// Copyright 2024 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package structwalk

import (
	"reflect"
)

func Walk(v any, f func(sf reflect.StructField, depth int) error) error {
	return walkStruct(v, 0, f)
}

func walkStruct(v any, depth int, f func(sf reflect.StructField, depth int) error) error {
	t := reflect.TypeOf(v)
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}

	return walkFields(t, depth, f)
}

func walkFields(t reflect.Type, depth int, f func(sf reflect.StructField, depth int) error) error {
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		err := processField(field, depth, f)
		if err != nil {
			return err
		}
	}

	return nil
}

func processField(field reflect.StructField, depth int, f func(sf reflect.StructField, depth int) error) error {
	if err := f(field, depth); err != nil {
		return err
	}

	if field.Type.Kind() == reflect.Ptr || field.Type.Kind() == reflect.Slice {
		if field.Type.Elem().Kind() == reflect.Struct {
			t := field.Type.Elem()
			if err := walkFields(t, depth+1, f); err != nil {
				return err
			}
		}
	} else if field.Type.Kind() == reflect.Struct {
		if err := walkFields(field.Type, depth+1, f); err != nil {
			return err
		}
	}

	return nil
}