var fileInputImageUploader = fileInputImageUploader || {};

Object.assign( fileInputImageUploader, {
  options: {
    inputSelector: 'form input[type=file]',
    placeholderSelector: 'label[for="{{inputID}}"]'
  },

  removeStyles: function(){
    document.querySelectorAll('style.post-image-upload-preview').forEach( e => {
       e.parentNode.removeChild(e); 
    });
  },

  addStyles: function(inputID, imageURL ){
      let styleID = `post-image-upload-preview-${inputID}`
      let styles = document.querySelector(`style#${styleID}`);
      if( styles ){
          styles.parentNode.removeChild(styles);
      }

      styles = document.body.appendChild(document.createElement('style'));
      styles.setAttribute('id', styleID);
      styles.setAttribute('class','post-image-upload-preview');
      styles.innerHTML = `
      label[for=${inputID}].gfield_label:after {
        content: "";
        display:block;
        width: 100px;
        height:100px;
        background-size: contain;
        background-repeat: no-repeat;
        background-position: center;
        border: 1px solid #0c0c0c;
        background-image: url(${imageURL});
      }`;
  },

  preview: function(){

    if( !(this instanceof HTMLInputElement) || 'file' !== this.type ){
      alert( 'Invalid input received...' );
      fileInputImageUploader.removeStyles()
      return;
    }

    if( !this.files || this.files.length < 1 ){
      alert( 'No files received' );
      fileInputImageUploader.removeStyles()
      return;
    }

    let reader = new FileReader();
    reader.inputElement = this;

    reader.onload = function (e) {
      fileInputImageUploader.addStyles(`${this.inputElement.id}`, e.target.result);
    };

    reader.readAsDataURL(this.files[0]);
  },

  init: function(){
    jQuery(fileInputImageUploader.options.inputSelector).each(function(i){
      jQuery(this).on('change', fileInputImageUploader.preview.bind(this) );
    })
  }
});

jQuery(document).ready(fileInputImageUploader.init);