package convert

import (
	"encoding/json"
	"reflect"
	"strings"
	"sync"
	"sync/atomic"

	"apigo.cc/go/cast"
	"gopkg.in/yaml.v3"
)

// To 将 source 中的数据深度映射到 destination 中。
// 核心哲学：意图优先。根据 destination 的类型推断用户的意图，并尽力转化数据。
func To(source, destination any) {
	if destination == nil {
		return
	}
	convertedResult := performConversion(source, destination)
	if convertedResult != nil {
		destinationValue := reflect.ValueOf(destination)
		
		// 循环解开指针直到目标值，在此过程中自动初始化 nil 指针
		for destinationValue.Kind() == reflect.Ptr {
			if destinationValue.IsNil() && destinationValue.CanSet() {
				destinationValue.Set(reflect.New(destinationValue.Type().Elem()))
			}
			destinationValue = destinationValue.Elem()
		}
		
		if destinationValue.CanSet() {
			destinationValue.Set(*convertedResult)
		}
	}
}

func performConversion(source, destination any) *reflect.Value {
	var sourceValue reflect.Value
	var destinationValue reflect.Value

	if val, ok := source.(reflect.Value); ok {
		sourceValue = val
	} else {
		sourceValue = reflect.ValueOf(source)
	}

	if val, ok := destination.(reflect.Value); ok {
		destinationValue = val
	} else {
		destinationValue = reflect.ValueOf(destination)
	}

	// 1. 初始化目标容器
	ensureInitialized(destinationValue)

	// 2. 获取底层业务数据
	realSource := cast.RealValue(sourceValue)
	realDestination := cast.RealValue(destinationValue)

	if !realDestination.IsValid() {
		return nil
	}

	// 3. 处理 Unmarshaler 接口
	if realDestination.CanAddr() {
		address := realDestination.Addr().Interface()
		if unmarshaler, isJSONUnmarshaler := address.(json.Unmarshaler); isJSONUnmarshaler {
			_ = unmarshaler.UnmarshalJSON(cast.MustJsonBytes(realSource.Interface()))
			return nil
		}
		if unmarshaler, isYAMLUnmarshaler := address.(yaml.Unmarshaler); isYAMLUnmarshaler {
			_ = unmarshaler.UnmarshalYAML(&yaml.Node{Value: cast.String(realSource.Interface())})
			return nil
		}
	}

	// 4. 核心转换逻辑
	sourceType := getActualType(realSource)
	destinationType := realDestination.Type()

	// 兼容 interface{} 目标
	if destinationType.Kind() == reflect.Interface {
		if realDestination.CanSet() {
			realDestination.Set(reflect.ValueOf(realSource.Interface()))
			return nil
		}
	}

	// 极致去摩擦：如果目标是单值，但输入是切片，自动取第一个元素进行后续处理
	effectiveSource := realSource
	if sourceType.Kind() == reflect.Slice && realSource.Len() > 0 && destinationType.Kind() != reflect.Slice && destinationType.Kind() != reflect.Array {
		effectiveSource = cast.RealValue(realSource.Index(0))
	}

	var allocatedValue *reflect.Value

	switch destinationType.Kind() {
	case reflect.Bool:
		applyValue(realDestination, reflect.ValueOf(cast.Bool(effectiveSource.Interface())), &allocatedValue)
	case reflect.String:
		applyValue(realDestination, reflect.ValueOf(cast.String(effectiveSource.Interface())), &allocatedValue)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		applyValue(realDestination, reflect.ValueOf(cast.Int64(effectiveSource.Interface())).Convert(destinationType), &allocatedValue)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		applyValue(realDestination, reflect.ValueOf(cast.Uint64(effectiveSource.Interface())).Convert(destinationType), &allocatedValue)
	case reflect.Float32, reflect.Float64:
		applyValue(realDestination, reflect.ValueOf(cast.Float64(effectiveSource.Interface())).Convert(destinationType), &allocatedValue)

	case reflect.Slice:
		if destinationType.Elem().Kind() == reflect.Uint8 {
			applyValue(realDestination, reflect.ValueOf(cast.MustJsonBytes(realSource.Interface())), &allocatedValue)
		} else {
			normalizedSource := realSource
			if sourceType.Kind() == reflect.String {
				sourceStr := realSource.String()
				if !strings.HasPrefix(sourceStr, "[") && strings.Contains(sourceStr, ",") {
					normalizedSource = reflect.ValueOf(cast.Split(sourceStr, ","))
				} else if !strings.HasPrefix(sourceStr, "[") {
					tempSlice := reflect.MakeSlice(reflect.SliceOf(sourceType), 1, 1)
					tempSlice.Index(0).Set(realSource)
					normalizedSource = tempSlice
				} else {
					var rawList []any
					cast.UnJson(sourceStr, &rawList)
					normalizedSource = reflect.ValueOf(rawList)
				}
			} else if sourceType.Kind() != reflect.Slice {
				tempSlice := reflect.MakeSlice(reflect.SliceOf(sourceType), 1, 1)
				tempSlice.Index(0).Set(realSource)
				normalizedSource = tempSlice
			}
			return convertSliceToSlice(normalizedSource, realDestination)
		}

	case reflect.Struct:
		switch effectiveSource.Kind() {
		case reflect.Map:
			convertMapToStruct(effectiveSource, realDestination)
		case reflect.Struct:
			convertStructToStruct(effectiveSource, realDestination)
		case reflect.String:
			var rawMap map[string]any
			cast.UnJson(effectiveSource.String(), &rawMap)
			convertMapToStruct(reflect.ValueOf(rawMap), realDestination)
		}

	case reflect.Map:
		if realDestination.IsNil() {
			realDestination = reflect.MakeMap(destinationType)
			allocatedValue = &realDestination
		}
		switch realSource.Kind() {
		case reflect.Map:
			convertMapToMap(realSource, realDestination)
		case reflect.Struct:
			convertStructToMap(realSource, realDestination)
		case reflect.String:
			var rawMap map[string]any
			cast.UnJson(realSource.String(), &rawMap)
			convertMapToMap(reflect.ValueOf(rawMap), realDestination)
		}

	case reflect.Func:
		if realSource.Kind() == reflect.Func {
			realDestination.Set(reflect.MakeFunc(destinationType, func(args []reflect.Value) []reflect.Value {
				inParameters := make([]reflect.Value, 0)
				for i := 0; i < destinationType.NumIn(); i++ {
					if i < realSource.Type().NumIn() {
						paramPtr := reflect.New(realSource.Type().In(i))
						performConversion(args[i].Interface(), paramPtr)
						inParameters = append(inParameters, paramPtr.Elem())
					}
				}
				results := realSource.Call(inParameters)
				outParameters := make([]reflect.Value, 0)
				for i := 0; i < destinationType.NumOut(); i++ {
					resultPtr := reflect.New(destinationType.Out(i))
					if i < len(results) {
						performConversion(results[i].Interface(), resultPtr)
					}
					outParameters = append(outParameters, resultPtr.Elem())
				}
				return outParameters
			}))
		}
	}

	return allocatedValue
}

func applyValue(destination, value reflect.Value, allocatedValue **reflect.Value) {
	if destination.CanSet() {
		destination.Set(value)
	} else {
		*allocatedValue = &value
	}
}

func ensureInitialized(value reflect.Value) {
	currentType := value.Type()
	for currentType.Kind() == reflect.Ptr {
		if value.IsNil() {
			value.Set(reflect.New(value.Type().Elem()))
		}
		value = value.Elem()
		currentType = currentType.Elem()
	}
	if currentType.Kind() == reflect.Slice && value.IsNil() {
		value.Set(reflect.MakeSlice(value.Type(), 0, 0))
	}
	if currentType.Kind() == reflect.Map && value.IsNil() {
		value.Set(reflect.MakeMap(value.Type()))
	}
}

func getActualType(value reflect.Value) reflect.Type {
	if !value.IsValid() {
		return reflect.TypeOf(nil)
	}
	actualType := value.Type()
	for actualType.Kind() == reflect.Ptr {
		actualType = actualType.Elem()
	}
	return actualType
}

var (
	structFieldCache   sync.Map
	structCacheCount   int32
	maxStructCacheSize = int32(10000)
)

func toLowerCamelCase(s string) string {
	if len(s) == 0 {
		return s
	}
	for i := 0; i < len(s); i++ {
		if s[i] >= 'a' && s[i] <= 'z' {
			if i == 0 {
				return s
			}
			return strings.ToLower(s[:i]) + s[i:]
		}
	}
	return strings.ToLower(s)
}

func normalizeKey(key string) string {
	var b strings.Builder
	b.Grow(len(key))
	for _, r := range key {
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
			b.WriteRune(r)
		} else if r >= 'A' && r <= 'Z' {
			b.WriteRune(r + 32)
		}
	}
	return b.String()
}

func buildFieldMap(t reflect.Type) map[string]int {
	m := make(map[string]int, t.NumField()*3)
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		if field.Anonymous {
			continue
		}
		idx := i + 1
		m[field.Name] = idx
		m[toLowerCamelCase(field.Name)] = idx
		m[normalizeKey(field.Name)] = idx
	}
	return m
}

func getFieldMap(t reflect.Type) map[string]int {
	if val, ok := structFieldCache.Load(t); ok {
		return val.(map[string]int)
	}

	m := buildFieldMap(t)

	if atomic.LoadInt32(&structCacheCount) < maxStructCacheSize {
		structFieldCache.Store(t, m)
		atomic.AddInt32(&structCacheCount, 1)
	}
	return m
}

func convertMapToStruct(sourceMap, destinationStruct reflect.Value) {
	fieldMap := getFieldMap(destinationStruct.Type())
	for _, key := range sourceMap.MapKeys() {
		sourceKeyName := cast.String(key.Interface())
		
		normalizedKey := sourceKeyName
		idx, ok := fieldMap[normalizedKey]
		if !ok {
			normalizedKey = toLowerCamelCase(sourceKeyName)
			idx, ok = fieldMap[normalizedKey]
			if !ok {
				normalizedKey = normalizeKey(sourceKeyName)
				idx, ok = fieldMap[normalizedKey]
				if !ok {
					continue
				}
			}
		}

		fieldIdx := idx - 1
		fieldValue := destinationStruct.Field(fieldIdx)
		sourceValue := sourceMap.MapIndex(key)

		// 检查是否存在 ParseHook
		structType := destinationStruct.Type()
		fieldInfo := structType.Field(fieldIdx)
		if destinationStruct.CanAddr() {
			if method, exists := destinationStruct.Addr().Type().MethodByName("Parse" + fieldInfo.Name); exists {
				argumentPointer := reflect.New(method.Type.In(1))
				performConversion(sourceValue.Interface(), argumentPointer)
				hookResults := method.Func.Call([]reflect.Value{destinationStruct.Addr(), argumentPointer.Elem()})
				fieldValue.Set(hookResults[0])
				continue
			}
		}

		convertedValue := performConversion(sourceValue.Interface(), fieldValue)
		if convertedValue != nil {
			fieldValue.Set(*convertedValue)
		}
	}
}

func convertStructToStruct(sourceStruct, destinationStruct reflect.Value) {
	destFieldMap := getFieldMap(destinationStruct.Type())
	
	sourceType := sourceStruct.Type()
	for i := 0; i < sourceType.NumField(); i++ {
		field := sourceType.Field(i)
		if field.Anonymous {
			convertStructToStruct(sourceStruct.Field(i), destinationStruct)
			continue
		}
		
		sourceName := field.Name
		
		normalizedKey := sourceName
		var fieldIdx int
		var ok bool
		
		if fieldIdx, ok = destFieldMap[normalizedKey]; !ok {
			normalizedKey = toLowerCamelCase(sourceName)
			if fieldIdx, ok = destFieldMap[normalizedKey]; !ok {
				normalizedKey = normalizeKey(sourceName)
				if fieldIdx, ok = destFieldMap[normalizedKey]; !ok {
					continue
				}
			}
		}

		destFieldValue := destinationStruct.Field(fieldIdx - 1)
		convertedValue := performConversion(sourceStruct.Field(i).Interface(), destFieldValue)
		if convertedValue != nil {
			destFieldValue.Set(*convertedValue)
		}
	}
}

func convertMapToMap(sourceMap, destinationMap reflect.Value) {
	destinationType := destinationMap.Type()
	for _, key := range sourceMap.MapKeys() {
		newKey := reflect.New(destinationType.Key()).Elem()
		convertKey := performConversion(key, newKey)
		if convertKey != nil {
			newKey = *convertKey
		}
		newValue := reflect.New(destinationType.Elem()).Elem()
		convertedValue := performConversion(sourceMap.MapIndex(key).Interface(), newValue)
		if convertedValue != nil {
			destinationMap.SetMapIndex(newKey, *convertedValue)
		} else {
			destinationMap.SetMapIndex(newKey, newValue)
		}
	}
}

func convertStructToMap(sourceStruct, destinationMap reflect.Value) {
	destinationType := destinationMap.Type()
	sourceType := sourceStruct.Type()
	fieldCount := sourceStruct.NumField()
	for i := 0; i < fieldCount; i++ {
		fieldInfo := sourceType.Field(i)
		if fieldInfo.Name[0] < 'A' || fieldInfo.Name[0] > 'Z' {
			continue
		}
		newKey := reflect.New(destinationType.Key()).Elem()
		convertKey := performConversion(cast.GetLowerName(fieldInfo.Name), newKey)
		if convertKey != nil {
			newKey = *convertKey
		}
		newValue := reflect.New(destinationType.Elem()).Elem()
		convertedValue := performConversion(sourceStruct.Field(i).Interface(), newValue)
		if convertedValue != nil {
			destinationMap.SetMapIndex(newKey, *convertedValue)
		} else {
			destinationMap.SetMapIndex(newKey, newValue)
		}
	}
}

func convertSliceToSlice(sourceSlice, destinationSlice reflect.Value) *reflect.Value {
	destinationType := destinationSlice.Type()
	sourceLen := sourceSlice.Len()
	for i := 0; i < sourceLen; i++ {
		newItem := reflect.New(destinationType.Elem()).Elem()
		convertedValue := performConversion(sourceSlice.Index(i).Interface(), newItem)
		if convertedValue != nil {
			destinationSlice = reflect.Append(destinationSlice, *convertedValue)
		} else {
			destinationSlice = reflect.Append(destinationSlice, newItem)
		}
	}
	return &destinationSlice
}

type StructInfo struct {
	Fields       []reflect.StructField
	Values       map[string]reflect.Value
	Methods      []reflect.Method
	MethodValues map[string]reflect.Value
}

func FlatStruct(data any) *StructInfo               { return FlattenStruct(data, true) }
func FlatStructWithUnexported(data any) *StructInfo { return FlattenStruct(data, false) }

func FlattenStruct(data any, exportOnly bool) *StructInfo {
	info := &StructInfo{
		Fields:       []reflect.StructField{},
		Values:       make(map[string]reflect.Value),
		Methods:      []reflect.Method{},
		MethodValues: make(map[string]reflect.Value),
	}
	
	reflectValue := reflect.ValueOf(data)
	for reflectValue.Kind() == reflect.Ptr {
		reflectValue = reflectValue.Elem()
	}

	// 收集方法 (仅当为指针类型时)
	if reflect.TypeOf(data).Kind() == reflect.Ptr {
		methodCount := reflectValue.NumMethod()
		for i := 0; i < methodCount; i++ {
			method := reflectValue.Type().Method(i)
			if !exportOnly || method.IsExported() {
				info.Methods = append(info.Methods, method)
				info.MethodValues[method.Name] = reflectValue.Method(i)
			}
		}
	}

	walkStruct(reflectValue, exportOnly, 0, func(field reflect.StructField, value reflect.Value) {
		info.Fields = append(info.Fields, field)
		info.Values[field.Name] = value
	})
	
	return info
}

type fieldVisitor func(field reflect.StructField, value reflect.Value)

func walkStruct(value reflect.Value, exportOnly bool, depth int, visitor fieldVisitor) {
	if depth > 10 {
		return
	}
	
	for value.Kind() == reflect.Ptr {
		value = value.Elem()
	}

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

	structType := value.Type()
	for i := 0; i < value.NumField(); i++ {
		field := structType.Field(i)
		if exportOnly && !field.IsExported() {
			continue
		}
		
		val := value.Field(i)
		if field.Anonymous {
			walkStruct(val, exportOnly, depth+1, visitor)
		} else {
			visitor(field, val)
		}
	}
}