/*
 * @file example_plugin.cpp
 * @brief Example plugin demonstrating the dstalk plugin API contract.
 * 示例插件：演示 dstalk 插件 API 契约。
 * Copyright (c) 2026 dstalk contributors. GPLv3.
 *
 * Build instructions (conceptual) / 构建说明（概念性）:
 *
 *   Linux / macOS:
 *     g++ -std=c++20 -shared -fPIC -fvisibility=hidden \
 *         -I<dstalk-include-dir> \
 *         -o example_plugin.so example_plugin.cpp
 *
 *   Windows (MSVC):
 *     cl /std:c++20 /LD /EHsc \
 *        /I<dstalk-include-dir> \
 *        /Fe:example_plugin.dll example_plugin.cpp
 *
 * The resulting `.so` / `.dylib` / `.dll` can be loaded with:
 * 生成的 .so / .dylib / .dll 可通过以下方式加载：
 *
 *     int id = dstalk_plugin_load("./example_plugin.so");
 */

#include "dstalk/dstalk_host.h"

#include <cstdio>   /* fprintf */
#include <cstdlib>  /* malloc, free */
#include <cstring>  /* strlen, strcmp */

/* ------------------------------------------------------------------
 * 私有状态（每个插件加载实例一份） / Private state (one instance per plugin load)
 * ------------------------------------------------------------------
 *
 * In a more complex plugin this struct would hold open database
 * connections, configuration, etc.
 * 在更复杂的插件中，此结构体可包含打开的数据库连接、配置等。
 */

struct ExampleState {
    int  call_count;
};

/* ------------------------------------------------------------------
 * 保存主机 API 表，以便回调函数使用主机服务 / Stored host API table so callbacks can use host services.
 * ------------------------------------------------------------------ */

static const dstalk_host_api_t* g_host = nullptr;

static ExampleState g_state;   /* 非堆分配：在库映射期间持续有效 / not heap-allocated: stays valid
                                  while the library is mapped */

/* ------------------------------------------------------------------
 * on_init（原 on_load） / on_init (was on_load)
 * ------------------------------------------------------------------ */

// 插件初始化：保存主机指针，重置调用计数，记录加载消息 / Plugin init: store host pointer, reset call count, log loaded message.
static int my_on_init(const dstalk_host_api_t* host)
{
    g_host = host;
    g_state.call_count = 0;

    /* TODO: 真实插件应在此处初始化资源 / real plugins would initialise resources here:
     *  - 通过 host->config_get 解析插件专属配置文件 / parse a plugin-specific config file via host->config_get
     *  - 打开日志文件 / open a log file
     *  - 连接到本地服务 / connect to a local service
     *  - 通过 host->register_service 注册服务 / register services via host->register_service
     *
     * Return non-zero to signal a fatal initialisation error to the
     * host, which will then unload the plugin immediately.
     * 返回非零值以向主机报告致命初始化错误，主机将立即卸载该插件。
     */

    if (host) {
        host->log(DSTALK_LOG_INFO, "[example-plugin] loaded (v1.0.0)");
    } else {
        std::fprintf(stderr, "[example-plugin] loaded (v1.0.0)\n");
    }
    return 0;
}

/* ------------------------------------------------------------------
 * on_shutdown（原 on_unload） / on_shutdown (was on_unload)
 * ------------------------------------------------------------------ */

// 插件关闭：记录调用次数，释放资源 / Plugin shutdown: log call count, release any resources.
static void my_on_shutdown(void)
{
    /* TODO: 释放 on_init 中分配的所有资源。此函数返回后主机将卸载共享库。 / release any resources allocated in on_init.  After this
     * function returns the host will unmap the shared library. */

    if (g_host) {
        g_host->log(DSTALK_LOG_INFO, "[example-plugin] unloaded (%d events processed)",
                    g_state.call_count);
    } else {
        std::fprintf(stderr,
            "[example-plugin] unloaded (%d callbacks processed)\n",
            g_state.call_count);
    }
}

/* ------------------------------------------------------------------
 * on_event（原 on_message） / on_event (was on_message)
 * ------------------------------------------------------------------ */

// 插件事件处理：记录消息事件，忽略其他事件类型 / Plugin event handler: log message events, ignore other event types.
static void my_on_event(int event_type, const void* data)
{
    if (event_type == DSTALK_EVENT_MESSAGE && data) {
        const auto* msg = static_cast<const dstalk_message_t*>(data);
        g_state.call_count++;

        /* 真实插件可能： / A real plugin might:
         *  - 将对话记录到文件 / log the conversation to a file
         *  - 实施内容审核 / apply content moderation
         *  - 实时翻译消息 / translate messages on the fly
         *  - 用外部数据丰富消息 / enrich messages with external data
         */

        if (g_host) {
            g_host->log(DSTALK_LOG_DEBUG, "[example-plugin] message | role=%-9s len=%zu",
                        msg->role, std::strlen(msg->content));
        } else {
            std::fprintf(stderr,
                "[example-plugin] message | role=%-9s len=%zu\n",
                msg->role, std::strlen(msg->content));
        }
    }
    /* 其他事件类型 / Other event types (DSTALK_EVENT_SESSION_CLEAR, DSTALK_EVENT_CONFIG_CHANGED,
       DSTALK_EVENT_PLUGIN_LOADED, DSTALK_EVENT_PLUGIN_UNLOADED, DSTALK_EVENT_CUSTOM+)
       此最小化插件静默忽略 / are silently ignored by this minimal plugin. */
}

/* ------------------------------------------------------------------
 * 插件描述符（静态 —— 在 .so 的生命周期内有效） / Plugin descriptor (static -- lives for the lifetime of the .so)
 * ------------------------------------------------------------------ */

static dstalk_plugin_info_t g_info = {
    /* .name         = */ "example-plugin",
    /* .version      = */ "1.0.0",
    /* .description  = */ "An example plugin for dstalk    / dstalk 示例插件",
    /* .api_version  = */ DSTALK_API_VERSION,
    /* .dependencies = */ {nullptr},
    /* .on_init      = */ my_on_init,
    /* .on_shutdown  = */ my_on_shutdown,
    /* .on_event     = */ my_on_event,
};

/* ------------------------------------------------------------------
 * 必须入口点 / Mandatory entry point
 * ------------------------------------------------------------------
 *
 * The host looks for this symbol via dlsym / GetProcAddress.
 * 主机通过 dlsym / GetProcAddress 查找此符号。
 * It MUST be declared extern "C" so the name is not mangled.
 * 必须声明为 extern "C" 以避免名称修饰。
 */

// 返回插件描述符给主机加载器 / Returns the plugin descriptor to the host loader.
extern "C" DSTALK_PLUGIN_EXPORT dstalk_plugin_info_t* dstalk_plugin_init(void)
{
    return &g_info;
}