#include "uv.h"
#include "internal.h"

#define UV_LOOP_WATCHER_DEFINE(name, type)                                    
  int uv_##name##_init(uv_loop_t* loop, uv_##name##_t* handle) {              

    // 初始化handle的類型，所屬loop，打上UV_HANDLE_REF，并且把handle插入loop->handle_queue隊列的隊尾
    uv__handle_init(loop, (uv_handle_t*)handle, UV_##type);                   
    handle->name##_cb = NULL;                                                 
    return 0;                                                                 
  }                                                                           

  int uv_##name##_start(uv_##name##_t* handle, uv_##name##_cb cb) {           

   // 如果已經執行過start函數則直接返回
    if (uv__is_active(handle)) return 0;                                      
    if (cb == NULL) return UV_EINVAL;                                         

    // 把handle插入loop中相應類型的隊列，loop有prepare，idle和check三個隊列
    QUEUE_INSERT_HEAD(&handle->loop->name##_handles, &handle->queue);         

    // 掛載回調，下一輪循環的時候被執行
    handle->name##_cb = cb;                                                   

   // 設置UV_HANDLE_ACTIVE標記位，并且loop中的handle數加一，init的時候只是把handle掛載到loop，start的時候handle才處于激活態
    uv__handle_start(handle);                                                 
    return 0;                                                                 
  }                                                                           

  int uv_##name##_stop(uv_##name##_t* handle) {                               
    if (!uv__is_active(handle)) return 0;                                     

    // 把handle從loop中相應的隊列移除，但是還掛載到handle_queue中
    QUEUE_REMOVE(&handle->queue);                                             

   // 清除active標記位并且減去loop中handle的active數
    uv__handle_stop(handle);                                                  
    return 0;                                                                 
  }                                                                           


  // 在每一輪循環中執行該函數，執行時機見uv_run
  void uv__run_##name(uv_loop_t* loop) {                                      
    uv_##name##_t* h;                                                         
    QUEUE queue;                                                              
    QUEUE* q;                                                                 

    // 把該類型對應的隊列中所有節點摘下來掛載到queue變量
    QUEUE_MOVE(&loop->name##_handles, &queue);                                

   // 遍歷隊列，執行每個節點里面的函數
    while (!QUEUE_EMPTY(&queue)) {                                            

      // 取下當前待處理的節點
      q = QUEUE_HEAD(&queue);                                                 

      // 取得該節點對應的整個結構體的基地址
      h = QUEUE_DATA(q, uv_##name##_t, queue);                                

      // 把該節點移出當前隊列
      QUEUE_REMOVE(q);                                                        

     // 重新插入原來的隊列
      QUEUE_INSERT_TAIL(&loop->name##_handles, q);                            

     // 執行回調函數
      h->name##_cb(h);                                                        
    }                                                                         
  }                                                                           

  void uv__##name##_close(uv_##name##_t* handle) {                            
    uv_##name##_stop(handle);                                                 
  }

UV_LOOP_WATCHER_DEFINE(prepare, PREPARE)
UV_LOOP_WATCHER_DEFINE(check, CHECK)
UV_LOOP_WATCHER_DEFINE(idle, IDLE)

利用宏定義，在預處理階段拓展成三個不同類型，但是處理邏輯一樣的代碼。有三種類型，分別是prepare，check，idle。