package structx

import (
	"reflect"
	"sync"
)

// FieldMapper 字段映射器接口
type FieldMapper interface {
	GetFieldMap(t reflect.Type) map[string]FieldInfo
}

var (
	// 全局缓存 避免重复计算 TODO: 考虑使用LRU缓存
	typeInfoCache = make(map[reflect.Type]map[string]FieldInfo)
	cacheMutex    = &sync.RWMutex{}
)

// defaultFieldMapper 默认字段映射器
type defaultFieldMapper struct{}

func (dm *defaultFieldMapper) GetFieldMap(t reflect.Type) map[string]FieldInfo {

	cacheMutex.RLock()
	if cached, exists := typeInfoCache[t]; exists {
		cacheMutex.RUnlock()
		return cached
	}
	cacheMutex.RUnlock()

	fieldMap := make(map[string]FieldInfo)
	dm.buildFieldMapRecursive(t, []int{}, fieldMap, "")

	cacheMutex.Lock()
	typeInfoCache[t] = fieldMap
	cacheMutex.Unlock()

	return fieldMap
}

// 递归构建字段映射表
func (dm *defaultFieldMapper) buildFieldMapRecursive(t reflect.Type, index []int, fieldMap map[string]FieldInfo, prefix string) {
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		if !field.IsExported() {
			continue
		}

		currentIndex := append(index, i)
		jsonTag := getJSONTagName(field)

		fullKey := jsonTag
		if prefix != "" {
			fullKey = prefix + "." + jsonTag
		}

		fieldType := field.Type
		isPtr := fieldType.Kind() == reflect.Ptr
		actualType := fieldType
		if isPtr {
			// 解引用
			actualType = fieldType.Elem()
		}

		if actualType.Kind() == reflect.Slice || actualType.Kind() == reflect.Array {
			fieldMap[fullKey] = FieldInfo{
				Index:     currentIndex,
				Name:      field.Name,
				IsPtr:     isPtr,
				FieldType: fieldType,
				IsSlice:   actualType.Kind() == reflect.Slice,
				IsArray:   actualType.Kind() == reflect.Array,
			}
			continue
		}

		if actualType.Kind() == reflect.Struct && !isBasicStructType(actualType) {
			dm.buildFieldMapRecursive(actualType, currentIndex, fieldMap, fullKey)
		}

		fieldMap[fullKey] = FieldInfo{
			Index:     currentIndex,
			Name:      field.Name,
			IsPtr:     isPtr,
			FieldType: fieldType,
		}
	}
}