import { DraftHandleValue, EditorState, SelectionState } from 'draft-js';
import { PluginFunctions } from '@draft-js-plugins/editor';
import {
  DndUploadPluginConfig,
  PlaceholderBlockType,
  FileToUpload
} from '.';
import modifyBlockData from './modifiers/modifyBlockData';
import removeBlock from './modifiers/removeBlock';
import { readFiles } from './utils/file';
import { insertPlaceholder } from  './components/insertPlaceholder';

let placeholderBlocksList:Array<PlaceholderBlockType> = [];

export default function onDropFile(config: DndUploadPluginConfig) {
  return function onDropFileInner(
    selection: SelectionState,
    files: Blob[],
    { getEditorState, setEditorState }: PluginFunctions
  ): DraftHandleValue {

    // Get upload function from config.
    const { handleUpload } = config;

    if (handleUpload) {

      const formData = new FormData();
      const data: { files: File[]; formData: FormData } = { files: [], formData };

      for (const file of files) {
        // eslint-disable-line no-restricted-syntax
        if (file && file instanceof File) {
          data.formData.append('files', file);
          data.files.push(file);
        }
      }

      setEditorState(EditorState.acceptSelection(getEditorState(), selection));

      // Read files on client side
      readFiles(data.files).then((placeholders) => {

        // Add upload placeholders for each image before uploading
        let _editorState = getEditorState();
        placeholderBlocksList = [];
        placeholders.forEach((placeholder) => {
          const customBlockProps = insertPlaceholder(_editorState, placeholder.name);
          const { state, key, text, blockKey } = customBlockProps;
          placeholderBlocksList.push({key, text, blockKey});
          _editorState = state;
        });
        setEditorState(_editorState);

        handleUpload(data,
          // TODO: what does retainSrc do? Is it useful to keep this option.
          (uploadedFiles:Array<FileToUpload> /*, {  retainSrc }*/):void => {
            /* Success! */

           /*
            * TODO:
            * This removes all placeholders and inserts all uploaded images,
            * Since fail() function removes placeholders for the files that have been marked as failing by the fail()
            * function, those placeholders can be safely removed here, but perhaps it would be useful
            * to modify `placeholderBlocksList` at some point on the fail() function.
           */
           let editorState = getEditorState();
           placeholderBlocksList.forEach(element => {
             editorState = removeBlock(editorState, element.blockKey);
           });
           setEditorState(editorState);

           if(uploadedFiles) {
             uploadedFiles.forEach((file) => {
               if (config.addImage) {
                 editorState = config.addImage(editorState, file.src);
               }
             });
             setEditorState(editorState);
           }

         } , (file: FileToUpload):void => {
           /* On fail */

           // Failed to upload a given file.
           // Remove placeholder for the file.
           // Any other special handling of this use case should be done manually by the user.
           let editorState = getEditorState();
           const blockInList  = placeholderBlocksList.find(p => p.text === file.name);
           if(blockInList !== undefined) {
             editorState = removeBlock(editorState, blockInList.blockKey);
             setEditorState(editorState);
           }
         }, (percent:number, file:FileToUpload):void => {
          /* On progress */
          let newEditorState = getEditorState();
          const block = placeholderBlocksList.find(p => p.text === file.name);
          if(block !== undefined) {
            const blockData = { name: file.name, progress: `${percent}%`};
            newEditorState = modifyBlockData(newEditorState, block.key, blockData);
            setEditorState(newEditorState);
          }
        });

      });

      return 'handled';
   }

    return 'not-handled';
  }
}