package version

import (
	"context"

	protocolpkg "github.com/noahlann/nnet/pkg/protocol"
)

// HeaderIdentifier 基于帧头的版本识别器
type HeaderIdentifier struct {
	field   string
	offset  int
	mapping map[interface{}]string
}

// NewHeaderIdentifier 创建基于帧头的版本识别器
func NewHeaderIdentifier(field string, offset int, mapping map[interface{}]string) protocolpkg.VersionIdentifier {
	return &HeaderIdentifier{
		field:   field,
		offset:  offset,
		mapping: mapping,
	}
}

// Identify 识别协议版本
func (i *HeaderIdentifier) Identify(data []byte, ctx context.Context) (string, error) {
	if len(data) < i.offset+1 {
		return "", protocolpkg.NewError("data too short")
	}

	// 从指定偏移量读取版本信息
	versionByte := data[i.offset]

	// 查找映射
	if version, ok := i.mapping[versionByte]; ok {
		return version, nil
	}

	return "", protocolpkg.NewError("version not found")
}

// MessageHeaderIdentifier 基于消息头的版本识别器
type MessageHeaderIdentifier struct {
	path    string
	mapping map[interface{}]string
}

// NewMessageHeaderIdentifier 创建基于消息头的版本识别器
func NewMessageHeaderIdentifier(path string, mapping map[interface{}]string) protocolpkg.VersionIdentifier {
	return &MessageHeaderIdentifier{
		path:    path,
		mapping: mapping,
	}
}

// Identify 识别协议版本
func (i *MessageHeaderIdentifier) Identify(data []byte, ctx context.Context) (string, error) {
	// 这里需要解析消息头，实际实现可能需要根据具体的消息格式来解析
	// 简化实现：假设消息头包含版本信息
	if len(data) < 1 {
		return "", protocolpkg.NewError("data too short")
	}

	versionByte := data[0]
	if version, ok := i.mapping[versionByte]; ok {
		return version, nil
	}

	return "", protocolpkg.NewError("version not found")
}

// CustomIdentifier 自定义版本识别器
type CustomIdentifier struct {
	fn func(data []byte, ctx context.Context) (string, error)
}

// NewCustomIdentifier 创建自定义版本识别器
func NewCustomIdentifier(fn func(data []byte, ctx context.Context) (string, error)) protocolpkg.VersionIdentifier {
	return &CustomIdentifier{
		fn: fn,
	}
}

// Identify 识别协议版本
func (i *CustomIdentifier) Identify(data []byte, ctx context.Context) (string, error) {
	if i.fn == nil {
		return "", protocolpkg.NewError("identifier function is nil")
	}
	return i.fn(data, ctx)
}