fh-fhc/lib/utils/promise-chain.js

A Command Line Interface for FeedHenry

module.exports = promiseChain;

// usage:
//
// promiseChain(cb) <-- this is the callback for eventual success or error
//  ( fn, [arg, arg, arg], function(a,b,c) { success(a,b,c) })
//  ( fn2, [args] )
//  () <-- this kicks it off.
//
// promiseChain.call(someObj, cb) <-- bind this-context for all functions

function promiseChain(cb) {
  var steps = []
    , context = this;

  function go() {
    var step = steps.shift();
    if (!step) {
      return cb();
    }
    try {
      step[0].apply(context, step[1]);
    } catch (ex) {
      cb(ex);
    }
  }

  return function pc(fn, args, success) {
    if (arguments.length === 0) {
      return go();
    }
    // add the step
    steps.push([fn,
      (args || []).concat([function(er) {
        if (er) {
          return cb(er);
        }
        var a = Array.prototype.slice.call(arguments, 1);
        try {
          if (success) {
            success.apply(context, a);
          }
        } catch (ex) {
          return cb(ex);
        }
        go();
      }])
    ]);
    return pc;
  };
}