package logger

import (
	"fmt"
	"reflect"
	"strings"
)

type structFormatter struct {
	val any
}

func (f *structFormatter) String() string {
	realVal := reflect.ValueOf(f.val)
	for {
		kind := realVal.Type().Kind()

		if kind == reflect.Struct {
			sb := strings.Builder{}
			f.structString(realVal, &sb)
			return sb.String()
		}

		if kind == reflect.Pointer {
			realVal = realVal.Elem()
			continue
		}

		return fmt.Sprintf("%v", f.val)
	}
}

func (f *structFormatter) structString(val reflect.Value, strBuilder *strings.Builder) {
	typ := val.Type()

	for i := 0; i < val.NumField(); i++ {
		fieldInfo := typ.Field(i)
		fieldValue := val.Field(i)
		fieldType := fieldInfo.Type
		fieldKind := fieldType.Kind()

		if i > 0 {
			strBuilder.WriteString(", ")
		}

		switch fieldKind {
		case reflect.Slice:
			if fieldValue.IsNil() {
				strBuilder.WriteString(fieldInfo.Name)
				strBuilder.WriteString(": <nil>")

			} else {
				strBuilder.WriteString("len(")
				strBuilder.WriteString(fieldInfo.Name)
				strBuilder.WriteString("): ")
				strBuilder.WriteString(fmt.Sprintf("%d", fieldValue.Len()))
			}

		case reflect.Array:
			strBuilder.WriteString("len(")
			strBuilder.WriteString(fieldInfo.Name)
			strBuilder.WriteString("): ")
			strBuilder.WriteString(fmt.Sprintf("%d", fieldValue.Len()))

		case reflect.Struct:
			if fieldInfo.Anonymous {
				f.structString(fieldValue, strBuilder)
			} else {
				strBuilder.WriteString(fieldInfo.Name)
				strBuilder.WriteString(": <")
				strBuilder.WriteString(fieldType.Name())
				strBuilder.WriteString(">")
			}

		case reflect.Pointer:
			strBuilder.WriteString(fieldInfo.Name)
			if fieldValue.IsNil() {
				strBuilder.WriteString(": <nil>")
			} else {
				strBuilder.WriteString(": &<")
				strBuilder.WriteString(fieldType.Elem().Name())
				strBuilder.WriteString(">")
			}

		default:
			strBuilder.WriteString(fieldInfo.Name)
			strBuilder.WriteString(": ")
			strBuilder.WriteString(fmt.Sprintf("%v", fieldValue))
		}
	}

}

// FormatStruct 输出结构体的内容。
// 1. 数组类型只会输出长度
// 2. 内部的结构体的内容不会再输出，包括embeded字段
func FormatStruct(val any) any {
	return &structFormatter{
		val: val,
	}
}