利用IPFS構建短視頻應用開發經歷（二）

本系列文章是針對 https://blog.csdn.net/weixin_43668031/article/details/83962959 內容的實現所編寫的。開發經歷包括思考過程、重構和推翻重來。

在上一節中Video表（結構體）中含有 uint gratuitySum;字段，此字段冗餘，可以通過實時計算獲得，可以在結構體中刪除。Video 設計如下

     struct Video {
        string title;
        string cover;
        string videoinfo;
        string info;
        uint duration;
        uint timestamp;
        address payable author;
        uint commentsNum;
        uint gratuityNum;
        uint lableNum;
        uint fileNum;
        uint8 permission;
        mapping (uint => Videofile) videofiles;
        mapping (uint => Lable) lables;
        mapping (uint => Gratuity) gratuitys;
        mapping (uint => Comment) comments;
    }
    uint public videoNum;
    mapping(uint => Video) videos;

0x3.智能合約

區塊鏈的智能合約的操作方法更像是mysql dba編寫的過程和函數，但是這是遠遠不夠的，我們連傳統數據庫的insert、delete、update、select都還沒有提供，就連最基本的crud也需要自己去實現。這裏只要考慮像C語言那樣去操作結構體即可，不需要考慮數據同步、分佈式等技術，那是以太坊已經給我做好的鋪墊。也因爲如此，會在我的代碼上看到大量set、get方法。

1.用戶表

    function setMyInfo (string memory _nickname, string memory _profile, string memory _avatar) public {
        users[msg.sender] = User(_nickname, _profile, _avatar, 0);
    }
    function setMyNickname (string memory _nickname) public {
        users[msg.sender].nickname = _nickname;
    }
    function setMyProfile (string memory _profile) public {
        users[msg.sender].profile = _profile;
    }
    function setMyAvatar (string memory _avatar) public {
        users[msg.sender].avatar = _avatar;
    }
    function getUserInfo (address _userAdd) view public returns (string memory nickname, string memory profile, string memory avatar, uint videoNums) {
        return (users[_userAdd].nickname, users[_userAdd].profile, users[_userAdd].avatar, users[_userAdd].videoNums);
    }

2.視頻存儲方法

 function publish (string memory _title, string memory _cover, string memory _videoinfo, string memory _info, uint _duration, string memory _filename, string memory _fileinfo, uint _size, uint32 _width, uint32 _height, uint32 _fps) public returns (uint articleId) {
        videos[videoNum++] = Video(_title, _cover, _videoinfo, _info, _duration, now, msg.sender, 0, 0, 0, 0, 0);
        videos[videoNum].videofiles[videos[videoNum].fileNum++] = Videofile(_filename, _fileinfo, _size, _width, _height, _fps, 0);
        return videoNum-1;
	}
	function setVideoPermission(uint _videoId, uint8 _value) public {
	    if( msg.sender != videos[_videoId].author) return;
	    videos[_videoId].permission = _value;
	}
	function setVideo(uint _videoId, string memory _cover, string memory _videoinfo) public {
	    if( msg.sender != videos[_videoId].author) return;
	    videos[_videoId].cover = _cover;
	    videos[_videoId].videoinfo = _videoinfo;
	}
	function setVideoInfo(uint _videoId, string memory _title, string memory _info) public {
	    if( msg.sender != videos[_videoId].author) return;
    	videos[_videoId].title = _title;
    	videos[_videoId].info = _info;
	}
	function addVideofile(uint _videoId, string memory _filename, string memory _fileinfo, uint _size, uint32 _width, uint32 _height, uint32 _fps) public {
	    if( msg.sender != videos[_videoId].author){
	        videos[_videoId].videofiles[videos[_videoId].fileNum++] = Videofile(_filename, _fileinfo, _size, _width, _height, _fps, 1);
	    }else{
	        videos[_videoId].videofiles[videos[_videoId].fileNum++] = Videofile(_filename, _fileinfo, _size, _width, _height, _fps, 0);
	    }
	}
	function setFilePermission(uint _videoId, uint _fileId, uint8 _value) public {
	     if( msg.sender == videos[_videoId].author ){
	         videos[_videoId].videofiles[_fileId].filePermission = _value;
	     }
	}
	function getVideo (uint _videoId) view public returns (string memory title, string memory cover, string memory videoinfo,string memory info, uint timestamp, address author, uint commentsNum, uint videofiles, uint gratuitySum) {
	    if( videos[_videoId].permission != 0 && msg.sender != videos[_videoId].author ){
	         Video storage _video = videos[_videoId];
	         for (uint i = 0; i < _video.gratuityNum; i++)
	            gratuitySum += _video.gratuitys[i].gratuity;
	         return (_video.title, _video.cover,_video.videoinfo,_video.info, _video.timestamp, _video.author,_video.commentsNum, _video.fileNum, gratuitySum);
	    }
	}
	function getVideoFile (uint _videoId, uint _fileId) view public returns (string memory filename, string memory fileinfo,uint size, uint32 width, uint32 height, uint32 fps, uint fileNum){
	    if(videos[_videoId].permission != 0 && msg.sender == videos[_videoId].author || videos[_videoId].permission == 0 && videos[_videoId].videofiles[_fileId].filePermission ==0){
	        Video storage _video = videos[_videoId];
	        Videofile storage _videofile = _video.videofiles[_fileId];
	        return (_videofile.filename, _videofile.fileinfo, _videofile.size, _videofile.width, _videofile.height, _videofile.fps, _video.fileNum);
	    }else{
	         return ("", "", 0, 0, 0, 0, videos[_videoId].fileNum);
	    }
	}

這裏會詳細說明一下：
getVideoFile 方法中的判斷，如果多視頻資源有訪問權限，並視頻的文件也有訪問權限，那就是可以訪問的，如果視頻無訪問權限，但是是作者自己上傳的視頻，也可以訪問，還要用於覈審呢！

addVideofile方法中如果是作者本人再向視頻資源中添加視頻文件，那麼默認是直接允許訪問的，如果是他人向我的視頻資源中添加視頻文件，默認是不可以訪問的，我需要去核審視頻並再開放權限，允許這個資源訪問。