//     Backbone.Model File Upload v1.0.0
//     by Joe Vu - joe.vu@homeslicesolutions.com
//     For all details and documentation:
//     https://github.com/homeslicesolutions/backbone-model-file-upload
//     Contributors:
//       lutherism - Alex Jansen - alex.openrobot.net
//       bildja - Dima Bildin - github.com/bildja
//       Minjung - Alejandro - github.com/Minjung
//       XemsDoom - Luca Moser - https://github.com/XemsDoom
//       DanilloCorvalan  - Danillo Corvalan - https://github.com/DanilloCorvalan

(function(root, factory) {

  // AMD
  if (typeof define === 'function' && define.amd) {
    define(['underscore', 'backbone'], function(_, Backbone){
      factory(root, Backbone, _);
    });

  // NodeJS/CommonJS
  } else if (typeof exports !== 'undefined') {
    var _ = require('underscore'), Backbone = require('backbone');
    factory(root, Backbone, _);

  // Browser global
  } else {
    factory(root, root.Backbone, root._);
  }

}(this, function(root, Backbone, _) {
  'use strict';

  // Clone the original Backbone.Model.prototype as superClass
  var _superClass = _.clone( Backbone.Model.prototype );

  // Extending out
  var BackboneModelFileUpload = Backbone.Model.extend({

    // ! Default file attribute - can be overwritten
    fileAttribute: 'file',

    // @ Save - overwritten
    save: function(key, val, options) {

      // Variables
      var attrs, attributes = this.attributes;

      // Signature parsing - taken directly from original Backbone.Model.save
      // and it states: 'Handle both "key", value and {key: value} -style arguments.'
      if (key == null || typeof key === 'object') {
        attrs = key;
        options = val;
      } else {
        (attrs = {})[key] = val;
      }

      // Validate & wait options - taken directly from original Backbone.Model.save
      options = _.extend({validate: true}, options);
      if (attrs && !options.wait) {
        if (!this.set(attrs, options)) return false;
      } else {
        if (!this._validate(attrs, options)) return false;
      }

      // Merge data temporarily for formdata
      var mergedAttrs = _.extend({}, attributes, attrs);

      if (attrs && options.wait) {
        this.attributes = mergedAttrs;
      }

      // Check for "formData" flag and check for if file exist.
      if ( options.formData === true
        || options.formData !== false
        && mergedAttrs[ this.fileAttribute ]
        && mergedAttrs[ this.fileAttribute ] instanceof File
        || mergedAttrs[ this.fileAttribute ] instanceof FileList
        || mergedAttrs[ this.fileAttribute ] instanceof Blob ) {

        // Flatten Attributes reapplying File Object
        var formAttrs = _.clone( mergedAttrs ),
          fileAttr = mergedAttrs[ this.fileAttribute ];
        formAttrs = this._flatten( formAttrs );
        formAttrs[ this.fileAttribute ] = fileAttr;

        // Converting Attributes to Form Data
        var formData = new FormData();
        _.each( formAttrs, function( value, key ){
          if (value instanceof FileList) {
            _.each(value, function(file) {
              formData.append( key, file );
            });
            return;
          }
          formData.append( key, value );
        });

        // Set options for AJAX call
        options.data = formData;
        options.processData = false;
        options.contentType = false;

        // Handle "progress" events
        var that = this;
        var beforeSend = options.beforeSend;
        options.beforeSend = function(xhr){
          xhr.upload.addEventListener('progress', that._progressHandler.bind(that), false);
          if(beforeSend) {
            return beforeSend.apply(this, arguments);
          }
        }
      }

      // Resume back to original state
      if (attrs && options.wait) this.attributes = attributes;

      // Continue to call the existing "save" method
      return _superClass.save.call(this, attrs, options);

    },

    // _ FlattenObject gist by "penguinboy".  Thank You!
    // https://gist.github.com/penguinboy/762197
    // NOTE for those who use "<1.0.0".  The notation changed to nested brackets
    _flatten: function flatten( obj ) {
      var output = {};
      for (var i in obj) {
        if (!obj.hasOwnProperty(i)) continue;
        if (typeof obj[i] == 'object') {
          var flatObject = flatten(obj[i]);
          for (var x in flatObject) {
            if (!flatObject.hasOwnProperty(x)) continue;
            output[i + '[' + x + ']'] = flatObject[x];
          }
        } else {
          output[i] = obj[i];
        }
      }
      return output;

    },

    // An "Unflatten" tool which is something normally should be on the backend
    // But this is a guide to how you would unflatten the object
    _unflatten: function unflatten(obj, output) {
      var re = /^([^\[\]]+)\[(.+)\]$/g;
      output = output || {};
      for (var key in obj) {
        var value = obj[key];
        if (!key.toString().match(re)) {
          var tempOut = {};
          tempOut[key] = value;
          _.extend(output, tempOut);
        } else {
          var keys = _.compact(key.split(re)), tempOut = {};
          tempOut[keys[1]] = value;
          output[keys[0]] = unflatten( tempOut, output[keys[0]] )
        }
      }
      return output;
    },

    // _ Get the Progress of the uploading file
    _progressHandler: function( event ) {
      if (event.lengthComputable) {
        var percentComplete = event.loaded / event.total;
        this.trigger( 'progress', percentComplete );
      }
    }
  });

  // Export out to override Backbone Model
  Backbone.Model = BackboneModelFileUpload;

}));