github.com/facebookincubator/go-belt@v0.0.0-20230703220935-39cd348f1a38/pkg/valuesparser/values_parser.go

// Copyright 2022 Meta Platforms, Inc. and affiliates.
//
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package valuesparser

import (
	"fmt"
	"io"
	"reflect"
	"strings"

	"github.com/facebookincubator/go-belt/pkg/field"
)

// AnySlice a handler for arbitrary values, which extracts structured fields/values
// by method ForEachField() and provides everything else as a string by method WriteUnparsed.
//
// It also implements fields.AbstractFields, so it could be directly used as a collection
// of structured fields right after just a type-casting ([]any -> AnySlice). It is
// supposed to be a zero allocation implementation in future.
//
// For example it is used to parse all the arguments of logger.Logger.Log.
type AnySlice []any

// ForEachField implements field.AbstractFields.
func (p *AnySlice) ForEachField(callback func(f *field.Field) bool) bool {
	for idx := 0; idx < len(*p); {
		value := (*p)[idx]

		if value == nil {
			idx++
			continue
		}

		switch v := value.(type) {
		case field.ForEachFieldser:
			if !v.ForEachField(callback) {
				return false
			}
			idx++
			continue
		case error:
			callback(&field.Field{
				Key:        "error",
				Value:      v,
				Properties: nil,
			})
		}

		v := reflect.Indirect(reflect.ValueOf(value))
		switch v.Kind() {
		case reflect.Map:
			r := ParseMapValue(v, callback)
			(*p)[idx] = nil
			if !r {
				return false
			}
		case reflect.Struct:
			r := ParseStructValue(nil, v, callback)
			(*p)[idx] = nil
			if !r {
				return false
			}
		default:
			idx++
			continue
		}
	}
	return true
}

// ParseMapValue calls the callback for each pair in the map until first false is returned
//
// It returns false if callback returned false.
func ParseMapValue(m reflect.Value, callback func(f *field.Field) bool) bool {
	var f field.Field
	for _, keyV := range m.MapKeys() {
		valueV := m.MapIndex(keyV)
		switch key := keyV.Interface().(type) {
		case field.Key:
			f.Key = key
		default:
			f.Key = fmt.Sprint(key)
		}
		f.Value = valueV.Interface()
		if !callback(&f) {
			return false
		}
	}
	return true
}

// ParseStructValue parses a structure to a collection of fields.
//
// `fieldPath` is the prefix of the field-name.
// `_struct` is the structure to be parsed (provided as a reflect.Value).
// `callback` is the function called for each found field, until first false is returned.
//
// It returns false if callback returned false.
func ParseStructValue(fieldPath []string, _struct reflect.Value, callback func(f *field.Field) bool) bool {
	s := reflect.Indirect(_struct)

	var f field.Field
	// TODO: optimize this
	t := s.Type()

	fieldPath = append(fieldPath, "")

	fieldCount := s.NumField()
	for fieldNum := 0; fieldNum < fieldCount; fieldNum++ {
		structFieldType := t.Field(fieldNum)
		if structFieldType.PkgPath != "" {
			// unexported
			continue
		}
		logTag := structFieldType.Tag.Get("log")
		if logTag == "-" {
			continue
		}
		structField := s.Field(fieldNum)
		if structField.IsZero() {
			continue
		}
		value := reflect.Indirect(structField)

		pathComponent := structFieldType.Name
		if logTag != "" {
			pathComponent = logTag
		}
		fieldPath[len(fieldPath)-1] = pathComponent

		if value.Kind() == reflect.Struct {
			if !ParseStructValue(fieldPath, value, callback) {
				return false
			}
			continue
		}

		f.Key = strings.Join(fieldPath, ".")
		f.Value = value.Interface()
		if !callback(&f) {
			return false
		}
	}

	return true
}

// Len implements field.AbstractFields.
func (p *AnySlice) Len() int {
	return len(*p)
}

// WriteUnparsed writes unstructured data (everything that was never considered as a structured field by
// ForEachField method) to the given io.Writer.
func (p *AnySlice) WriteUnparsed(w io.Writer) {
	for _, value := range *p {
		if value == nil {
			continue
		}

		fmt.Fprint(w, value)
	}
}