Proposal for pg-async transaction stack

pg-async-transactions.js

"use strict";

var values = function(obj){
  var val = []
  Object.keys(obj).forEach(function(key) {
    val.push(obj[key]);
  });
  return val;
};


var transactions_stack = {};

var get_transaction_level = function() {

  var depths = values(transactions_stack);
  var level = depths.length ? Math.max.apply(null, depths ) + 1: 0;
  console.log(depths, level);
  return level;
}


function* begin(lnk) {
  var transaction_hash = `_trans_${Math.random().toString(16).substr(2)}`;

  var level = get_transaction_level();
  transactions_stack[transaction_hash] = level;

  var query = `BEGIN`;
  if(level != 0) 
    query = `SAVEPOINT ${transaction_hash}`;

  yield lnk.query(query);
  return Promise.resolve(transaction_hash);
}


function* commit(lnk, transaction_hash){
  var level = transactions_stack[transaction_hash];

  if(level === undefined)
    throw `Incorrect transaction passed ${transaction_hash}`;

   delete transactions_stack[transaction_hash];
   var max_depth = get_transaction_level();

   if(max_depth > level)
      throw `Incorrect transaction level passed ${level} < ${max_depth}`;

    if(level == 0)
      yield lnk.query(`COMMIT`);

  return Promise.resolve(true);
}

function* rollback(lnk, transaction_hash) {
  var level = transactions_stack[transaction_hash];

  if(level === undefined)
    throw `Incorrect transaction passed ${transaction_hash}`;

  for(var tmp_hash in transactions_stack)
    if(transactions_stack[tmp_hash] >= level)
      delete transactions_stack[tmp_hash];

  var query = `ROLLBACK`;

  if(level > 0)
    query = `ROLLBACK TO SAVEPOINT ${transaction_hash}`;

  yield lnk.query(query);
  return Promise.resolve(true);
}


module.exports = {
  begin,
  commit,
  rollback,
  install : function(pgAsync){
  
    pgAsync.prototype.begin = function(){
      return begin(this);
    };

    pgAsync.prototype.rollback = function(token){
      return rollback(this, token);
    };

    pgAsync.prototype.commit = function(token){
      return commit(this, token);
    };
  }
};