#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <zlib.h> // 引入 zlib 库
#include <fec.h>  // 引入 libfec 库
#include "hx_serial.h"
#include "hx_ringbuffer.h"
#include <pthread.h> // 引入 pthread 库

// 宏定义
#ifdef USE_FEC
#define FEC_SIZE 32 // 前向纠错冗余数据大小
#else
#define FEC_SIZE 0 // 前向纠错冗余数据大小
#endif
#define FRAME_HEADER 0xAA55                                                         // 帧头
#define FRAME_TAIL 0x0D7E                                                           // 帧尾
#define FRAME_SIZE (240)                                                            // 每帧大小
#define HEADER_SIZE (4)                                                             // 帧头 + 帧序号 + 数据长度
#define TAIL_SIZE (2)                                                               // 帧尾
#define CHECKSUM_SIZE (4)                                                           // CRC32 校验和大小（4 字节）
#define DATA_SIZE (FRAME_SIZE - HEADER_SIZE - CHECKSUM_SIZE - FEC_SIZE - TAIL_SIZE) // 数据段大小
#define RING_BUFFER_SIZE (1024 * 10)                                                // 环形缓冲区大小 - default 10KB
#define QUEUE_MAX_SIZE 1024                                                         // 队列最大容量

// 全局变量
static by_serial_t serial_port;
static by_ringbuf_t ring_buffer;
static unsigned char send_buffer[FRAME_SIZE];
static unsigned char recv_ack_data_buffer[DATA_SIZE];
static unsigned char frame_counter = 0;
static unsigned char data_len = 0;
static unsigned char ack_flag = 0;
unsigned char output_data[8192]; // FIXME 有可能越界
static int output_len = 0;
static unsigned char ack_data_dummy[4] = {0x00, 0x00, 0x00, 0x00};
static unsigned char ack_data[DATA_SIZE - 2] = {0};
static int ack_data_len = 0;

// 定义队列结构体
typedef struct
{
    unsigned char *data;
    int length;
} FrameData;

// 队列相关定义
static FrameData frame_queue[QUEUE_MAX_SIZE];                   // 存储接收到的数据帧
static int queue_head = 0;                                      // 队列头指针
static int queue_tail = 0;                                      // 队列尾指针
static pthread_mutex_t queue_mutex = PTHREAD_MUTEX_INITIALIZER; // 保护队列的互斥锁
static int stop_receiving = false;                              // 控制接收线程停止的标志

// 前向声明
void *receive_thread_func(void *arg);
int generate_response(unsigned char *data, int length, int ack);

// 计算 CRC32 校验和
unsigned long calculate_crc32(const unsigned char *data, size_t length)
{
    return crc32(0, data, length);
}

// 解析一帧数据
int parse_frame(by_ringbuf_t *ringbuf, unsigned char *output_data, int *output_len)
{
    unsigned char frame[FRAME_SIZE];
    unsigned char buffer[FRAME_SIZE * 3];
    int available_data = by_ringbuf_available_data(ringbuf);
    while (by_ringbuf_available_data(ringbuf) < FRAME_SIZE)
    {
        int ret = by_serial_read(&serial_port, buffer, FRAME_SIZE);
        if (ret > 0)
        {
            by_ringbuf_append(&ring_buffer, buffer, ret);
        }
    }

    // TODO 有无必要
    // 检查是否有足够的数据解析一帧
    if (available_data < FRAME_SIZE)
    {
        return -1; // 数据不足，无法解析
    }
    // 查找帧头
    unsigned short header = FRAME_HEADER;
    unsigned short tail = FRAME_TAIL;
    int header_pos = by_ringbuf_find(ringbuf, (unsigned char *)&header, 2);
    if (header_pos < 0)
    {
        return -1; // 没有找到帧头
    }
    // 弹出帧头之前的数据
    by_ringbuf_pop(ringbuf, frame, header_pos);
    // 检查是否有足够的数据解析一帧
    if (by_ringbuf_available_data(ringbuf) < FRAME_SIZE)
    {
        return -1; // 数据不足，无法解析
    }
    // 读取帧数据
    by_ringbuf_pop(ringbuf, frame, HEADER_SIZE);
    int tail_pos = by_ringbuf_find(ringbuf, (unsigned char *)&tail, 2);
    if (tail_pos < FRAME_SIZE - HEADER_SIZE - TAIL_SIZE - 1)
    {
        printf(" fail, next frame header pos: %d\n", header_pos);
        return -2; // 下一帧帧头小于 FRAME_SIZE，丢弃该帧
    }
    else
    {
        by_ringbuf_pop(ringbuf, frame + HEADER_SIZE, tail_pos + TAIL_SIZE);
    }
    // 解析帧序号、有效数据长度、数据段和 CRC32
    unsigned char seq = frame[2];
    unsigned char valid_data_len = frame[2 + 1];
    unsigned char *data_segment = &frame[2 + 1 + 1];
    unsigned int received_crc = *(unsigned long *)&frame[HEADER_SIZE + DATA_SIZE];
    // 计算 CRC32 校验
    unsigned int calculated_crc = calculate_crc32(frame, HEADER_SIZE + DATA_SIZE + FEC_SIZE);
    if (received_crc != calculated_crc)
    {
        printf("CRC mismatch! Expected: %08X, Received: %08X\n", calculated_crc, received_crc);
        return -2; // CRC 校验失败，丢弃该帧，严重错误
    }

    if (0xFF == seq)
    {
        // printf("Received ACK frame!\r\n");
        *output_len = 0;
        if (0x1926 == *(unsigned short *)(data_segment))
        {
            memcpy(recv_ack_data_buffer, data_segment + 2, valid_data_len - 2);
            ack_data_len = valid_data_len - 2;
            printf("Received ACK frame!\r\n");
            return 2;
        }

        memset(recv_ack_data_buffer, 0, DATA_SIZE);
        return 3;
    }

    // 将有效数据拼接到输出缓冲区
    memcpy(&output_data[*output_len], data_segment, valid_data_len);
    *output_len += valid_data_len;
    printf("output len: %d\n", *output_len);
    printf("Received frame: seq=%d, len=%d\r\n", seq, valid_data_len);
    // 判断是否为最后一帧
    if (valid_data_len < DATA_SIZE)
    {
        printf("Received last frame!\n");
        return 1; // 最后一帧，解析完成
    }
    return 0; // 成功解析一帧，但可能还有更多帧
}

// 接收线程函数
void *receive_thread_func(void *arg)
{
    while (!stop_receiving)
    {
        while (1)
        {
            int parse_result = parse_frame(&ring_buffer, output_data, &output_len);
            if (parse_result == 1)
            {
                int ack_data_len_t = 0;

                if (ack_data_len > DATA_SIZE - 2)
                {
                    ack_data_len_t = DATA_SIZE - 2;
                }
                else
                {
                    ack_data_len_t = ack_data_len;
                }

                if (ack_data[0] == 0x00)
                {
                    generate_response(ack_data_dummy, sizeof(ack_data_dummy), 1);
                }
                else
                {
                    generate_response(ack_data, ack_data_len_t, 1);
                    // generate_response(ack_data_dummy, sizeof(ack_data_dummy), 1);
                }

                // 将解析后的数据放入队列
                pthread_mutex_lock(&queue_mutex);
                if ((queue_tail + 1) % QUEUE_MAX_SIZE != queue_head)
                { // 队列未满
                    frame_queue[queue_tail].data = malloc(output_len);
                    memcpy(frame_queue[queue_tail].data, output_data, output_len);
                    printf("output_len2: %d\n", output_len);
                    frame_queue[queue_tail].length = output_len;
                    queue_tail = (queue_tail + 1) % QUEUE_MAX_SIZE;
                }
                else
                {
                    printf("Queue is full, dropping frame!\n");
                }
                output_len = 0;
                pthread_mutex_unlock(&queue_mutex);
                break;
            }
            else if (parse_result == 0)
            {
                printf("Parsed data length: %d\n", output_len);
                break; // 数据不足或解析失败，退出循环
            }
            else if (parse_result == -2)
            {
                // TODO 此处不能回应 NAK，必须等数据发完
                output_len = 0;
                break; // 严重错误，丢弃包
            }
            else if (parse_result == 2)
            {
                ack_flag = 1;
                printf("Received ACK frame!\r\n");
                break;
            }
            else if (parse_result == 3)
            {
                ack_flag = 2;
                printf("Received NACK frame!\r\n");
                break;
            }
        }
        usleep(1000); // 避免占用过多 CPU
    }
    return NULL;
}

int generate_response(unsigned char *data, int length, int ack)
{
    // 响应帧结构（与普通帧相似，帧号为 0xFF，数据段前 2 个字节为 ACK 标志，负载数据必须小于普通帧满数据大小，以确保被识别成孤立帧）

    unsigned char send_buffer[FRAME_SIZE];
    memset(send_buffer, 0, FRAME_SIZE);

    // 构造帧头
    unsigned short header = FRAME_HEADER;
    memcpy(send_buffer, &header, 2);
    // 构造帧序号和数据长度
    // memcpy(send_buffer + 2, 0xFF, 1);
    *(send_buffer + 2) = 0xFF;

    length += 2; // 包含 ACK 标志长度
    if (length > DATA_SIZE)
    {
        return -1; // 数据超长
    }

    memcpy(send_buffer + 3, &length, 1);

    // magic number for ack
    unsigned short ack_flag = 0x1926;
    if (ack)
    {
        memcpy(send_buffer + HEADER_SIZE, &ack_flag, 2);
    }
    else
    {
        memset(send_buffer + HEADER_SIZE, 0, 2);
    }

    // 拷贝该帧对应数据段
    memcpy(send_buffer + HEADER_SIZE + 2, data, length - 2);

    // 计算 CRC32 校验和
    unsigned long crc = calculate_crc32(send_buffer, HEADER_SIZE + DATA_SIZE + FEC_SIZE);
    memcpy(send_buffer + HEADER_SIZE + DATA_SIZE + FEC_SIZE, &crc, CHECKSUM_SIZE);

    unsigned short tail = FRAME_TAIL;
    memcpy(send_buffer + HEADER_SIZE + DATA_SIZE + FEC_SIZE + CHECKSUM_SIZE, &tail, TAIL_SIZE);

    // 发送响应帧
    if (by_serial_write(&serial_port, send_buffer, FRAME_SIZE) != 0)
    {
        return -2; // 发送失败
    }

    return 0;
}

// 初始化串口
static PyObject *serial_init(PyObject *self, PyObject *args)
{
    const char *dev_name;
    if (!PyArg_ParseTuple(args, "s", &dev_name))
    {
        return NULL;
    }
    if (by_serial_init(&serial_port, dev_name) != 0)
    {
        PyErr_SetString(PyExc_IOError, "Failed to initialize serial port");
        return NULL;
    }
    // 初始化环形缓冲区
    if (by_ringbuf_init(&ring_buffer, RING_BUFFER_SIZE) != 0)
    {
        PyErr_SetString(PyExc_IOError, "Failed to initialize ring buffer");
        return NULL;
    }
    // 启动接收线程
    pthread_t receive_thread;
    stop_receiving = false;
    if (pthread_create(&receive_thread, NULL, receive_thread_func, NULL) != 0)
    {
        PyErr_SetString(PyExc_RuntimeError, "Failed to start receive thread");
        return NULL;
    }
    Py_RETURN_TRUE;
}

// 发送数据
static PyObject *serial_send(PyObject *self, PyObject *args)
{
    const char *data;
    Py_ssize_t length;
    if (!PyArg_ParseTuple(args, "s#", &data, &length))
    {
        return NULL;
    }
    size_t offset = 0;
    while (offset < length)
    {
        memset(send_buffer, 0, FRAME_SIZE);
        // 构造帧头
        unsigned short header = FRAME_HEADER;
        memcpy(send_buffer, &header, 2);
        // 构造帧序号和数据长度
        memcpy(send_buffer + 2, &frame_counter, 1);
        if (length - offset > DATA_SIZE)
        {
            data_len = DATA_SIZE;
        }
        else
        {
            data_len = length - offset;
        }
        memcpy(send_buffer + 3, &data_len, 1);
        // 拷贝该帧对应数据段
        memcpy(send_buffer + HEADER_SIZE, data + offset, data_len);
        printf("Received frame: seq=%d, len=%d\r\n", frame_counter, data_len);
        // 计算 CRC32 校验和
        unsigned long crc = calculate_crc32(send_buffer, HEADER_SIZE + DATA_SIZE + FEC_SIZE);
        memcpy(send_buffer + HEADER_SIZE + DATA_SIZE + FEC_SIZE, &crc, CHECKSUM_SIZE);
        unsigned short tail = FRAME_TAIL;
        memcpy(send_buffer + HEADER_SIZE + DATA_SIZE + FEC_SIZE + CHECKSUM_SIZE, &tail, TAIL_SIZE);
        // 发送帧
        if (by_serial_write(&serial_port, (const char *)send_buffer, FRAME_SIZE) != 0)
        {
            PyErr_SetString(PyExc_IOError, "Failed to send data over serial port");
            return NULL;
        }
        offset += DATA_SIZE;
        frame_counter++;
        usleep(80000);
    }

    unsigned short ack_timeout = 10;
    // 等待 ACK 响应
    while (!ack_flag)
    {
        usleep(100000);
        if (ack_timeout-- == 0)
        {
            ack_flag = 0;
            frame_counter = 0;
            printf("ACK timeout\r\n");
            Py_RETURN_FALSE;
        }
    }
    ack_flag = 0;
    frame_counter = 0;
    // Py_RETURN_TRUE;
    // 返回 ACK 响应
    PyObject *result = Py_BuildValue("y#", recv_ack_data_buffer, ack_data_len);
    ack_data_len = 0;
    return result;
}

// 接收数据
static PyObject *serial_receive(PyObject *self, PyObject *args)
{
    pthread_mutex_lock(&queue_mutex);
    if (queue_head == queue_tail)
    {
        pthread_mutex_unlock(&queue_mutex);
        PyErr_SetString(PyExc_IOError, "No data available in the queue");
        return NULL;
    }
    // 获取队列中最早的数据包
    FrameData frame = frame_queue[queue_head];
    queue_head = (queue_head + 1) % QUEUE_MAX_SIZE;
    pthread_mutex_unlock(&queue_mutex);
    // 返回解析后的数据
    PyObject *result = Py_BuildValue("y#", frame.data, frame.length);
    free(frame.data); // 释放内存
    return result;
}

static PyObject *serial_set_ack_data(PyObject *self, PyObject *args)
{
    const char *input_data;  // 用于存储输入的二进制数据
    Py_ssize_t input_length; // 用于存储输入数据的长度

    // 解析参数，期望接收到一个 bytes 对象
    if (!PyArg_ParseTuple(args, "y#", &input_data, &input_length))
    {
        PyErr_SetString(PyExc_TypeError, "Expected a bytes object");
        return NULL;
    }

    // 检查输入数据是否为空
    if (input_length == 0)
    {
        PyErr_SetString(PyExc_ValueError, "Input data cannot be empty");
        return NULL;
    }

    // 检查输入数据是否为空
    if (input_length > (DATA_SIZE - 2))
    {
        PyErr_SetString(PyExc_ValueError, "Input data is too long");
        return NULL;
    }

    // // 创建一个缓冲区用于存储处理后的数据
    // char *processed_data = (char *)malloc(input_length);
    // if (processed_data == NULL) {
    //     PyErr_SetString(PyExc_MemoryError, "Failed to allocate memory");
    //     return NULL;
    // }

    // // 将处理后的数据封装为 Python 的 bytes 对象
    // PyObject *result = PyBytes_FromStringAndSize(processed_data, input_length);

    // // 释放分配的内存
    // free(processed_data);

    // // 返回结果
    // return result;

    memcpy(ack_data, input_data, input_length);
    ack_data_len = input_length;

    Py_RETURN_NONE;
}

// 模块方法表
static PyMethodDef SerialMethods[] = {
    {"init", serial_init, METH_VARARGS, "Initialize serial port"},
    {"send", serial_send, METH_VARARGS, "Send data over serial port"},
    {"receive", serial_receive, METH_VARARGS, "Receive data from serial port"},
    {"set_ack_data", serial_set_ack_data, METH_VARARGS, "Set ACK data"},
    {NULL, NULL, 0, NULL}};

// 模块定义
static struct PyModuleDef serialmodule = {
    PyModuleDef_HEAD_INIT,
    "serial_module",
    "A module to transfer serializable data over serial port",
    -1,
    SerialMethods};

// 模块初始化函数
PyMODINIT_FUNC PyInit_serial_module(void)
{
    return PyModule_Create(&serialmodule);
}