//npm install mysql
var mysql = await import('mysql');


const db = function ({host, port, user, password, database}) {
  var t= this;
  var con = mysql.createConnection({
    host: host,
    port: port,
    user: user,
    password: password,
    database: database,
    multipleStatements: true
  });
  var connected = false;
  t.connect = function(){
    return new Promise((res,rej)=>{
      con.connect(function(err) {
        if (err) {
          rej(err);
        }else{
          connected = true;
          res();
        };
      });
    });
  };

  t.isconnected = function(){
    return connected;
  };
  t.check = function(structure){
    return new Promise((res,rej)=>{
      if(!connected) return false;

      var sqlcode1 = "";
      var sqlcode2 = "";    //ALTER TABLE `cars` ADD IF NOT EXISTS `test` INT NOT NULL;
      var sqlcode3 = "";    //ALTER TABLE `cars` CHANGE `test` `test` TEXT NOT NULL;

      var tablenames = Object.keys(structure);
      for (var i = 0; i < tablenames.length; i++) {
        let tablename = tablenames[i];
        let table = structure[tablename];
        let attributes = Object.keys(table);
        if(attributes.length>1){
          sqlcode1 += `CREATE TABLE IF NOT EXISTS ${con.escapeId(tablename)} (`;
          for (var j = 0; j < attributes.length; j++) {
            var attributename = attributes[j];
            var attribute = table[attributename];
            sqlcode1+=`${con.escapeId(attributename)} ${attribute.type||"text"}`;
            sqlcode2+=`ALTER TABLE ${con.escapeId(tablename)} ADD IF NOT EXISTS ${con.escapeId(attributename)} ${attribute.type||"text"}`;
            sqlcode3+=`ALTER TABLE ${con.escapeId(tablename)} CHANGE ${con.escapeId(attributename)} ${con.escapeId(attributename)} ${attribute.type||"text"}`;
            if(!!attribute.A_I){
              sqlcode1+=` AUTO_INCREMENT PRIMARY KEY`;
              sqlcode2+=` AUTO_INCREMENT PRIMARY KEY`;
              sqlcode3+=` AUTO_INCREMENT`;
            }else if(!!attribute.default){
              sqlcode1+=` DEFAULT ${con.escape(attribute.default)}`;
              sqlcode2+=` DEFAULT ${con.escape(attribute.default)}`;
              sqlcode3+=` DEFAULT ${con.escape(attribute.default)}`;
            }
            sqlcode1+=", ";
            sqlcode2+="; ";
            sqlcode3+="; ";
          }
          sqlcode1 = sqlcode1.slice(0,-2);
          sqlcode1+=`); `;
        }
      }
      con.query(sqlcode1+sqlcode2+sqlcode3,[],function(err,result){
        if(err){
          rej(err);
        }else{
          res();
        }
      });
    });
  };
  t.query = function(sql,insert = []){
    return new Promise((res,rej)=>{
      if(!connected) return rej("Not Connected to DB!");
      con.query(sql,insert,function(err,result){
        if(!err){
          res(result);
        }else{
          rej(err);
        }
      });
    });
  };
  t.disconnect = function(){
    connected = false;
    return new Promise((res,rej)=>{
      con.end((err)=>{
        if(err){
          rej();
        }else{
          res();
        }
      });
    });
  };
}
export default db;
//CREATE TABLE customers (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(255), address VARCHAR(255))