jsc3l_connection.js

'use strict';


var jsc3l_connection = function() {}
///
// [High level] Look for an available IPFS/IPNS node and store it in the localstorage under 'ComChainRepo'
///
jsc3l_connection.ensureComChainRepo = function(callback) {
    // 1. Check if a list of end-point is stored locally (avoid a IPNS slow call)
    var storedEndPoints=[];
    try{
          storedEndPoints = JSON.parse(localStorage.getItem('ComChainApiNodes')); 
    } catch(e){
        storedEndPoints=[];
    }
     
    checkRepo(storedEndPoints, function (result_stored){
         if (result_stored){
             callback(true);
         } else {
             // 2. No locally stored nodes available, try the hard-coded Com-Chain list
             checkRepo(jsc3l_config.confEndPointsOur,function (result){
                 if (result){
                     callback(true);
                 } else {
                     // 3. As a backup try standard ipfs servers
                     checkRepo(jsc3l_config.confEndPointsOther, callback);
                 }
             });
         }
     });
 }

///
// [High level] Get the list of end-points and randomly select a up and running one
///
jsc3l_connection.acquireEndPoint = function(callback) {
    jsc3l_connection.getCCEndPointList(function(list_success) {
        if (list_success) {
            var endpoint_list = JSON.parse(localStorage.getItem('ComChainApiNodes')); 
            jsc3l_connection.selectEndPoint(endpoint_list, callback);
        } else {
            callback(false);
        }
    });
}
 
///
// [Lower level] Get from the IPFS/IPNS node stored it in the localstorage under 'ComChainRepo' the list of ComChain end-points
/// 
jsc3l_connection.getCCEndPointList = function(callback){
    var xhr = new XMLHttpRequest();
    xhr.open('GET', localStorage.getItem('ComChainRepo') + jsc3l_config.nodesRepo+'?_=' + new Date().getTime(), true); 
    xhr.responseType = 'json';
    xhr.onreadystatechange = function (oEvent) {  
      if (xhr.readyState === 4) {  
        if (xhr.status === 200) { 
            try{
                var to_push = xhr.response;
                if(typeof to_push =='object')
                {
                    to_push = JSON.stringify(xhr.response);
                }
                
                localStorage.setItem('ComChainApiNodes',to_push); 
                callback(true);
            } catch(e){
                callback(false);  
            }  
     
        } else {  
            callback(false);
        }  
      }  
    }; 
    xhr.send();
}

///
// [Lower level] Select a ComChain end-point with up and running APIs
///
jsc3l_connection.selectEndPoint = function(nodes, callback){
    if (nodes.length==0){
        localStorage.removeItem('ComChainApiNodes');
        callback(false);
    } else {
        //randomly select a node (poor man's load balancing)
        var id = Math.floor((Math.random() * nodes.length));
        var node = nodes[id];
        
        // check the node is up and running
        jsc3l_connection.testNode(node,function(success){
            if (success){
                // store the node 
                localStorage.setItem('ComChainAPI', node);
                callback(true);
            }else{
                nodes.splice(id,1);
                jsc3l_connection.selectEndPoint(nodes,callback);      
            }
        });
    }
}

///
// [Lower level] Test if a end-point has up and running APIs
///
jsc3l_connection.testNode = function(api_address,callback) {
    testDbApi(api_address, function(result){
        if (result){
            testApi(api_address, callback);
        } else {
            callback(false);
        }
    });
}

jsc3l_connection.getCurrentBlock = function(api_address, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', api_address + '/api.php', true); 
    xhr.responseType = 'json';
    xhr.timeout = 5000;
    xhr.onreadystatechange = function (oEvent) {  
    if (xhr.readyState === 4) {  
        if (xhr.status === 200) { 
          try{
              var answer = xhr.response;
              if(typeof answer =='object'){
                        answer = JSON.stringify(xhr.response);
               }  
               callback(answer);
          } catch(e){
          }  
         
        }
      }  
    }; 
    xhr.send();
}


////////////////////////////////////////////////////////////////////////////////
var checkRepo = function(repoList, callback){
    if (!repoList || repoList.length==0){
        callback(false);
    } else {
         var id = Math.floor((Math.random() * repoList.length));
         var repo = repoList[id];
         var xhr = new XMLHttpRequest();
         xhr.open('GET',repo + jsc3l_config.ping, true); 
         xhr.responseType = 'json';
         xhr.timeout = 3000;
         xhr.onreadystatechange = function (oEvent) {  
           if (xhr.readyState === 4) {  
             if (xhr.status === 200) { 
                    localStorage.setItem('ComChainRepo', repo);
                    callback(true);
             } else {  
                 repoList.splice(id,1);
                 checkRepo(repoList, callback); 
            }  
          }  
       }; 

    xhr.send();
    }
}


var testApi = function(api_address, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', api_address + '/api.php', true); 
    xhr.responseType = 'json';
    xhr.timeout = 5000;
    xhr.onreadystatechange = function (oEvent) {  
    if (xhr.readyState === 4) {  
        if (xhr.status === 200) { 
          try{
              var answer = xhr.response;
              if(typeof answer =='object'){
                        answer = JSON.stringify(xhr.response);
               }  
               callback(answer && answer!="null" && !answer.error);
          } catch(e){
            callback(false);  
          }  
         
        } else {  
           callback(false);
        }  
        }  
    }; 
    xhr.send();
}

var testDbApi = function(api_address, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', api_address + '/dbcheck.php', true); 
    xhr.timeout = 5000;
    xhr.onreadystatechange = function (oEvent) {  
    if (xhr.readyState === 4) {  
        if (xhr.status === 200 ) { 
          try{
            callback(xhr.response==='pong');
          } catch(e){
            callback(false);  
          }  
         
        } else {  
           callback(false);
        }  
        }  
    }; 
    xhr.send();
}



////////////////////////////////////////////////////////////////////////////////

module.exports = jsc3l_connection;