/**
 * @file protocol.h
 * @brief 简化的ASCII文本指令协议
 *
 * 协议格式: $SN,CMD,param1,param2*CS\r\n
 * - SN: 序列号(0-255)，用于防丢包和重复
 * - CMD: 指令名称
 * - CS: CRC8校验(从$到*之间所有字符的CRC8值)
 *
 * 抗干扰/防丢失机制:
 * 1. CRC8校验 - 比XOR更强的检错能力
 * 2. 序列号 - 接收方可检测丢包和重复
 * 3. 应答机制 - 重要指令需要确认
 */

#ifndef __PROTOCOL_H
#define __PROTOCOL_H

#include <stdint.h>
#include <stdbool.h>

#ifdef __cplusplus
extern "C" {
#endif

/* 协议配置 */
#define PROTOCOL_MAX_CMD_LEN     8
#define PROTOCOL_MAX_PARAM_LEN  32
#define PROTOCOL_MAX_PARAMS     4
#define PROTOCOL_FRAME_TIMEOUT  1000  /* 帧超时/ms */

typedef struct {
    uint8_t sn;                       /* 序列号 */
    char cmd[PROTOCOL_MAX_CMD_LEN];   /* 指令名 */
    char params[PROTOCOL_MAX_PARAMS][PROTOCOL_MAX_PARAM_LEN];
    uint8_t param_count;              /* 参数数量 */
    uint8_t checksum;                 /* CRC8校验和 */
    bool valid;                       /* 解析是否成功 */
} protocol_frame_t;

typedef enum {
    PROTOCOL_OK = 0,
    PROTOCOL_ERROR_INVALID_FRAME,
    PROTOCOL_ERROR_CHECKSUM_FAIL,
    PROTOCOL_ERROR_TIMEOUT,
    PROTOCOL_ERROR_UNKNOWN_CMD,
    PROTOCOL_ERROR_PARAM_COUNT,
    PROTOCOL_ERROR_BUFFER_FULL
} protocol_error_t;

typedef enum {
    PROTOCOL_CMD_RL,      /* 继电器控制: RL,id,ON/OFF */
    PROTOCOL_CMD_DI,      /* 查询IO: DI,id */
    PROTOCOL_CMD_DIA,     /* 查询所有IO: DIA */
    PROTOCOL_CMD_FWD,     /* 数据转发: FWD,port,data */
    PROTOCOL_CMD_ECHO,    /* 心跳: ECHO */
    PROTOCOL_CMD_ACK,     /* 应答: ACK,sn,result */
    PROTOCOL_CMD_STATUS,  /* 状态查询: STATUS */
    PROTOCOL_CMD_UNKNOWN
} protocol_cmd_t;

typedef struct {
    protocol_cmd_t cmd;
    uint8_t sn;
    bool need_ack;       /* 是否需要应答 */
    uint32_t send_time;  /* 发送时间 */
    uint8_t retry_count; /* 重试次数 */
} protocol_pending_t;

#define PROTOCOL_MAX_PENDING 4

typedef struct {
    protocol_pending_t pending[PROTOCOL_MAX_PENDING];
    uint8_t pending_count;
    uint8_t next_sn;
    uint8_t last_rx_sn;
} protocol_context_t;

/* 协议初始化 */
void protocol_init(void);

/* 解析收到的指令 */
protocol_error_t protocol_parse(const char *data, uint16_t length, protocol_frame_t *frame);

/* 构造发送帧 */
protocol_error_t protocol_build(char *buffer, uint16_t buffer_size, uint16_t *out_length,
                                protocol_cmd_t cmd, uint8_t sn,
                                const char *params[], uint8_t param_count);

/* 构造应答帧 */
protocol_error_t protocol_build_ack(char *buffer, uint16_t buffer_size, uint16_t *out_length,
                                     uint8_t sn, bool success, const char *msg);

/* 发送命令并等待应答 */
protocol_error_t protocol_send_with_ack(protocol_cmd_t cmd, const char *params[], uint8_t param_count,
                                         uint32_t timeout_ms, uint8_t max_retries);

/* 协议任务处理(处理超时和重试) */
void protocol_task(void);

/* CRC8计算 */
uint8_t protocol_crc8(const uint8_t *data, uint16_t length);

/* 指令名转枚举 */
protocol_cmd_t protocol_cmd_from_string(const char *cmd_str);

/* 枚举转指令名 */
const char* protocol_cmd_to_string(protocol_cmd_t cmd);

/* 获取上一个错误 */
protocol_error_t protocol_get_last_error(void);

#ifdef __cplusplus
}
#endif

#endif /* __PROTOCOL_H */