package main

import (
	"encoding/binary"
	"fmt"
	"log"
	"time"
	"unsafe"

	"github.com/vmihailenco/msgpack/v5"
	"golang.org/x/sys/windows"
)

// TickData 行情数据结构
type TickData map[string]interface{}

// TickReader 共享内存读取器
type TickReader struct {
	shmName       string
	bufferSize    int
	mappedFile    windows.Handle
	view          uintptr
	lastTimestamp uint32 // 上次读取的时间戳
}

// NewTickReader 创建新的读取器
func NewTickReader(shmName string, bufferSize int) (*TickReader, error) {
	if shmName == "" {
		shmName = "tick_ipc"
	}
	if bufferSize == 0 {
		bufferSize = 10 * 1024 * 1024 // 10MB
	}

	reader := &TickReader{
		shmName:       shmName,
		bufferSize:    bufferSize,
		lastTimestamp: 0,
	}

	// 打开共享内存
	err := reader.openSharedMemory()
	if err != nil {
		return nil, fmt.Errorf("打开共享内存失败: %w", err)
	}

	log.Printf("✓ 成功连接到共享内存: %s (大小: %d bytes)", shmName, bufferSize)
	return reader, nil
}

// openSharedMemory 打开 Windows 共享内存
func (r *TickReader) openSharedMemory() error {
	// 打开已存在的共享内存（Python 创建的）
	namePtr, err := windows.UTF16PtrFromString(r.shmName)
	if err != nil {
		return fmt.Errorf("转换字符串失败: %w", err)
	}

	// 使用 syscall 直接调用 Windows API
	kernel32 := windows.NewLazySystemDLL("kernel32.dll")
	openFileMappingProc := kernel32.NewProc("OpenFileMappingW")
	mapViewOfFileProc := kernel32.NewProc("MapViewOfFile")

	// 调用 OpenFileMappingW
	handle, _, callErr := openFileMappingProc.Call(
		uintptr(windows.FILE_MAP_READ),
		0, // bInheritHandle
		uintptr(unsafe.Pointer(namePtr)),
	)
	if callErr != nil && callErr.Error() != "The operation completed successfully." {
		return fmt.Errorf("打开文件映射失败: %w", callErr)
	}
	if handle == 0 {
		return fmt.Errorf("打开文件映射失败: 返回空句柄")
	}
	mappingHandle := windows.Handle(handle)

	// 映射视图
	view, _, callErr := mapViewOfFileProc.Call(
		uintptr(mappingHandle),
		uintptr(windows.FILE_MAP_READ),
		0,
		0,
		uintptr(r.bufferSize),
	)
	if callErr != nil && callErr.Error() != "The operation completed successfully." {
		windows.CloseHandle(mappingHandle)
		return fmt.Errorf("映射视图失败: %w", callErr)
	}
	if view == 0 {
		windows.CloseHandle(mappingHandle)
		return fmt.Errorf("映射视图失败: 返回空地址")
	}

	r.mappedFile = mappingHandle
	r.view = view

	return nil
}

// ReadLatestTick 读取最新的行情数据
func (r *TickReader) ReadLatestTick() (TickData, error) {
	if r.view == 0 {
		return nil, fmt.Errorf("共享内存未初始化")
	}

	// 读取头部信息（16字节）
	// 格式: [version(4)] [write_pos(4)] [last_data_len(4)] [timestamp(4)]
	header := unsafeByteSlice(r.view, 0, 16)

	// 解析时间戳
	currentTimestamp := binary.LittleEndian.Uint32(header[12:16])

	// 检查数据是否更新
	if currentTimestamp == r.lastTimestamp {
		return nil, fmt.Errorf("数据未更新")
	}

	// 解析最后数据长度
	lastDataLen := binary.LittleEndian.Uint32(header[8:12])
	if lastDataLen == 0 {
		return nil, fmt.Errorf("无可用数据")
	}

	// 解析写入位置
	writePos := binary.LittleEndian.Uint32(header[4:8])

	// 计算数据起始位置
	var dataStart uint32
	if writePos >= lastDataLen+4 {
		dataStart = 16 + writePos - lastDataLen - 4
	} else {
		dataStart = 16
	}

	// 读取数据长度
	dataLenBytes := unsafeByteSlice(r.view, int(dataStart), 4)
	dataLen := binary.LittleEndian.Uint32(dataLenBytes)

	// 读取 msgpack 数据
	packedData := unsafeByteSlice(r.view, int(dataStart)+4, int(dataLen))

	// 反序列化 msgpack
	var tickData TickData
	err := msgpack.Unmarshal(packedData, &tickData)
	if err != nil {
		return nil, fmt.Errorf("反序列化失败: %w", err)
	}

	// 更新最后时间戳
	r.lastTimestamp = currentTimestamp

	return tickData, nil
}

// unsafeByteSlice 将内存地址转换为字节切片
func unsafeByteSlice(base uintptr, offset int, length int) []byte {
	return (*[1 << 30]byte)(unsafe.Pointer(base + uintptr(offset)))[:length:length]
}

// Close 关闭读取器
func (r *TickReader) Close() {
	if r.view != 0 {
		windows.UnmapViewOfFile(r.view)
		r.view = 0
	}
	if r.mappedFile != 0 {
		windows.CloseHandle(r.mappedFile)
		r.mappedFile = 0
	}
	log.Println("✓ 共享内存连接已关闭")
}

// StartContinuousRead 持续读取行情数据
func (r *TickReader) StartContinuousRead(interval time.Duration, handler func(TickData)) {
	log.Printf("开始持续读取，间隔: %v", interval)

	ticker := time.NewTicker(interval)
	defer ticker.Stop()

	for range ticker.C {
		tick, err := r.ReadLatestTick()
		if err != nil {
			continue
		}

		if handler != nil {
			handler(tick)
		}
	}
}

func main() {
	// 创建读取器
	reader, err := NewTickReader("tick_ipc", 0)
	if err != nil {
		log.Fatalf("初始化失败: %v", err)
	}
	defer reader.Close()

	// 示例2：持续读取（取消注释以启用）
	fmt.Println("\n=== 持续读取示例（按 Ctrl+C 停止）===")
	reader.StartContinuousRead(time.Second, func(tick TickData) {
		fmt.Printf("\n[%s] 接收到新行情:%d个标的\n", time.Now().Format("15:04:05"), len(tick))
	})
}