/*
 * 自然写互动课堂教学管理网关软件 V1.0
 * mqtt_client.c - MQTT通信客户端（TLS加密）
 *
 * 功能说明：
 * 1. MQTT 3.1.1协议实现（基于mosquitto库）
 * 2. TLS/SSL加密通信
 * 3. 自动重连与会话恢复
 * 4. 主题订阅管理（控制指令下发）
 * 5. 笔迹数据批量发布
 * 6. 遗嘱消息（设备离线通知）
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <syslog.h>
#include <errno.h>
#include <time.h>

/* Mosquitto MQTT库 */
#include <mosquitto.h>

/* 模块头文件 */
#include "mqtt_client.h"
#include "gateway_config.h"

/* ========== 常量定义 ========== */

/* MQTT QoS级别 */
#define MQTT_QOS_AT_MOST_ONCE   0
#define MQTT_QOS_AT_LEAST_ONCE  1

/* MQTT保活间隔（秒） */
#define MQTT_KEEPALIVE_SEC      60

/* 重连间隔（秒） */
#define MQTT_RECONNECT_SEC      5

/* 最大重连间隔（秒，指数退避上限） */
#define MQTT_MAX_RECONNECT_SEC  120

/* 消息批量发布缓冲区大小 */
#define PUBLISH_BATCH_SIZE      32

/* 主题前缀 */
#define TOPIC_PREFIX            "writech/gateway/"

/* ========== 数据结构 ========== */

/* MQTT客户端状态 */
typedef struct {
    struct mosquitto *mosq;         /* Mosquitto实例 */
    char gateway_id[64];            /* 网关唯一ID */
    char broker_host[256];          /* 服务器地址 */
    int broker_port;                /* 服务器端口 */
    int is_connected;               /* 是否已连接 */
    int reconnect_count;            /* 重连次数 */
    pthread_mutex_t pub_mutex;      /* 发布锁 */

    /* 主题 */
    char topic_stroke_data[128];    /* 笔迹数据上报主题 */
    char topic_device_status[128];  /* 设备状态上报主题 */
    char topic_cmd_subscribe[128];  /* 命令下发订阅主题 */
    char topic_ota[128];            /* OTA升级通知主题 */

    /* TLS证书路径 */
    char ca_cert_path[256];         /* CA证书 */
    char client_cert_path[256];     /* 客户端证书 */
    char client_key_path[256];      /* 客户端私钥 */

    /* 统计 */
    unsigned long msgs_published;
    unsigned long msgs_received;
    unsigned long bytes_sent;
} MQTTState;

static MQTTState g_mqtt;

/* 命令回调函数 */
static void (*g_cmd_callback)(const char *topic, const uint8_t *payload,
                               int payload_len) = NULL;

/* ========== MQTT回调函数 ========== */

/**
 * 连接成功回调
 */
static void on_connect(struct mosquitto *mosq, void *userdata, int rc) {
    (void)userdata;

    if (rc == 0) {
        g_mqtt.is_connected = 1;
        g_mqtt.reconnect_count = 0;
        syslog(LOG_INFO, "MQTT: 已连接到 %s:%d", g_mqtt.broker_host, g_mqtt.broker_port);

        /* 订阅控制指令主题 */
        mosquitto_subscribe(mosq, NULL, g_mqtt.topic_cmd_subscribe, MQTT_QOS_AT_LEAST_ONCE);

        /* 订阅OTA升级通知主题 */
        mosquitto_subscribe(mosq, NULL, g_mqtt.topic_ota, MQTT_QOS_AT_LEAST_ONCE);

        /* 发布上线状态 */
        publish_status("online");
    } else {
        syslog(LOG_ERR, "MQTT: 连接失败，返回码=%d", rc);
        g_mqtt.is_connected = 0;
    }
}

/**
 * 连接断开回调
 */
static void on_disconnect(struct mosquitto *mosq, void *userdata, int rc) {
    (void)mosq;
    (void)userdata;

    g_mqtt.is_connected = 0;
    syslog(LOG_WARNING, "MQTT: 连接断开，原因=%d", rc);

    /* 非主动断开，将自动重连 */
    if (rc != 0) {
        g_mqtt.reconnect_count++;
    }
}

/**
 * 消息接收回调（订阅的主题收到消息）
 */
static void on_message(struct mosquitto *mosq, void *userdata,
                         const struct mosquitto_message *msg) {
    (void)mosq;
    (void)userdata;

    g_mqtt.msgs_received++;
    syslog(LOG_DEBUG, "MQTT: 收到消息 [%s] 长度=%d", msg->topic, msg->payloadlen);

    /* 分发到命令处理回调 */
    if (g_cmd_callback) {
        g_cmd_callback(msg->topic, (const uint8_t *)msg->payload, msg->payloadlen);
    }
}

/**
 * 发布完成回调
 */
static void on_publish(struct mosquitto *mosq, void *userdata, int mid) {
    (void)mosq;
    (void)userdata;
    (void)mid;
    g_mqtt.msgs_published++;
}

/* ========== 初始化 ========== */

/**
 * 初始化MQTT客户端
 *
 * @param host  MQTT服务器地址
 * @param port  MQTT服务器端口（8883=TLS）
 * @return 0成功, -1失败
 */
int mqtt_client_init(const char *host, int port) {
    memset(&g_mqtt, 0, sizeof(g_mqtt));
    pthread_mutex_init(&g_mqtt.pub_mutex, NULL);

    strncpy(g_mqtt.broker_host, host, sizeof(g_mqtt.broker_host) - 1);
    g_mqtt.broker_port = port;

    /* 生成网关ID */
    snprintf(g_mqtt.gateway_id, sizeof(g_mqtt.gateway_id),
             "writech-gw-%08x", (unsigned int)time(NULL));

    /* 构建主题 */
    snprintf(g_mqtt.topic_stroke_data, sizeof(g_mqtt.topic_stroke_data),
             "%s%s/stroke", TOPIC_PREFIX, g_mqtt.gateway_id);
    snprintf(g_mqtt.topic_device_status, sizeof(g_mqtt.topic_device_status),
             "%s%s/status", TOPIC_PREFIX, g_mqtt.gateway_id);
    snprintf(g_mqtt.topic_cmd_subscribe, sizeof(g_mqtt.topic_cmd_subscribe),
             "%s%s/cmd/#", TOPIC_PREFIX, g_mqtt.gateway_id);
    snprintf(g_mqtt.topic_ota, sizeof(g_mqtt.topic_ota),
             "%s%s/ota", TOPIC_PREFIX, g_mqtt.gateway_id);

    /* 初始化Mosquitto库 */
    mosquitto_lib_init();

    /* 创建Mosquitto客户端实例 */
    g_mqtt.mosq = mosquitto_new(g_mqtt.gateway_id, true, NULL);
    if (g_mqtt.mosq == NULL) {
        syslog(LOG_ERR, "MQTT: 创建客户端失败");
        return -1;
    }

    /* 注册回调 */
    mosquitto_connect_callback_set(g_mqtt.mosq, on_connect);
    mosquitto_disconnect_callback_set(g_mqtt.mosq, on_disconnect);
    mosquitto_message_callback_set(g_mqtt.mosq, on_message);
    mosquitto_publish_callback_set(g_mqtt.mosq, on_publish);

    /* 设置遗嘱消息（设备异常离线时自动发布） */
    char will_payload[128];
    snprintf(will_payload, sizeof(will_payload),
             "{\"gatewayId\":\"%s\",\"status\":\"offline\"}", g_mqtt.gateway_id);
    mosquitto_will_set(g_mqtt.mosq, g_mqtt.topic_device_status,
                       strlen(will_payload), will_payload, MQTT_QOS_AT_LEAST_ONCE, true);

    /* 配置TLS */
    const char *ca_cert = gateway_config_get_string("mqtt.ca_cert", "/etc/writech/ca.pem");
    const char *client_cert = gateway_config_get_string("mqtt.client_cert", "/etc/writech/client.pem");
    const char *client_key = gateway_config_get_string("mqtt.client_key", "/etc/writech/client.key");

    strncpy(g_mqtt.ca_cert_path, ca_cert, sizeof(g_mqtt.ca_cert_path) - 1);
    strncpy(g_mqtt.client_cert_path, client_cert, sizeof(g_mqtt.client_cert_path) - 1);
    strncpy(g_mqtt.client_key_path, client_key, sizeof(g_mqtt.client_key_path) - 1);

    int tls_ret = mosquitto_tls_set(g_mqtt.mosq, ca_cert, NULL,
                                     client_cert, client_key, NULL);
    if (tls_ret != MOSQ_ERR_SUCCESS) {
        syslog(LOG_WARNING, "MQTT: TLS配置失败，将使用非加密连接");
    }

    /* 设置自动重连 */
    mosquitto_reconnect_delay_set(g_mqtt.mosq, MQTT_RECONNECT_SEC,
                                   MQTT_MAX_RECONNECT_SEC, true);

    /* 发起连接 */
    int ret = mosquitto_connect_async(g_mqtt.mosq, host, port, MQTT_KEEPALIVE_SEC);
    if (ret != MOSQ_ERR_SUCCESS) {
        syslog(LOG_ERR, "MQTT: 连接发起失败: %s", mosquitto_strerror(ret));
        return -1;
    }

    /* 启动Mosquitto网络循环线程 */
    mosquitto_loop_start(g_mqtt.mosq);

    syslog(LOG_INFO, "MQTT客户端初始化完成，网关ID=%s", g_mqtt.gateway_id);
    return 0;
}

/* ========== 数据发布 ========== */

/**
 * 发布笔迹数据到MQTT
 *
 * @param pen_mac    笔MAC地址
 * @param data       笔迹二进制数据
 * @param data_len   数据长度
 * @return 0成功, -1未连接, -2发布失败
 */
int mqtt_publish_stroke(const char *pen_mac, const uint8_t *data, int data_len) {
    if (!g_mqtt.is_connected) {
        return -1;
    }

    /* 构建包含笔MAC的完整主题 */
    char topic[256];
    snprintf(topic, sizeof(topic), "%s/%s", g_mqtt.topic_stroke_data, pen_mac);

    pthread_mutex_lock(&g_mqtt.pub_mutex);

    int ret = mosquitto_publish(g_mqtt.mosq, NULL, topic,
                                 data_len, data, MQTT_QOS_AT_MOST_ONCE, false);

    pthread_mutex_unlock(&g_mqtt.pub_mutex);

    if (ret == MOSQ_ERR_SUCCESS) {
        g_mqtt.bytes_sent += data_len;
        return 0;
    }

    syslog(LOG_WARNING, "MQTT: 发布失败: %s", mosquitto_strerror(ret));
    return -2;
}

/**
 * 发布网关/设备状态
 */
static void publish_status(const char *status) {
    char payload[512];
    snprintf(payload, sizeof(payload),
             "{\"gatewayId\":\"%s\",\"status\":\"%s\","
             "\"uptime\":%lu,\"penCount\":%d,"
             "\"msgsSent\":%lu,\"msgsRecv\":%lu}",
             g_mqtt.gateway_id, status,
             (unsigned long)time(NULL),
             0, /* pen count to be filled */
             g_mqtt.msgs_published,
             g_mqtt.msgs_received);

    mosquitto_publish(g_mqtt.mosq, NULL, g_mqtt.topic_device_status,
                       strlen(payload), payload, MQTT_QOS_AT_LEAST_ONCE, true);
}

/* ========== 外部接口 ========== */

int mqtt_client_is_connected(void) { return g_mqtt.is_connected; }

int mqtt_client_get_fd(void) {
    return mosquitto_socket(g_mqtt.mosq);
}

void mqtt_client_process_read(void) {
    mosquitto_loop_read(g_mqtt.mosq, 1);
}

void mqtt_client_process_write(void) {
    mosquitto_loop_write(g_mqtt.mosq, 1);
}

void mqtt_client_set_cmd_callback(void (*cb)(const char *, const uint8_t *, int)) {
    g_cmd_callback = cb;
}

void mqtt_client_cleanup(void) {
    if (g_mqtt.mosq) {
        publish_status("offline");
        mosquitto_disconnect(g_mqtt.mosq);
        mosquitto_loop_stop(g_mqtt.mosq, true);
        mosquitto_destroy(g_mqtt.mosq);
    }
    mosquitto_lib_cleanup();
    pthread_mutex_destroy(&g_mqtt.pub_mutex);
    syslog(LOG_INFO, "MQTT客户端已清理");
}