/*
 * Beamer Viewer, a web-based PDF presentation viewer
 * Copyright (C) 2018-2023 Pacien TRAN-GIRARD
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

"use strict";

class Viewer {
  constructor() {
    this.fileInput = document.getElementById("fileInput");
    this.startButton = document.getElementById("startButton");

    this.fileReader = new FileReader();
    this.presentation = null;

    document.addEventListener("DOMContentLoaded", () => this._unlockUi());
    this._listenForInput();
  }

  _unlockUi() {
    this.fileInput.disabled = false;
  }

  _preparePresentation(source) {
    pdfjsLib.getDocument(source).then(pdf => {
      this.presentation = new Presentation(pdf);
    }).catch(error => {
      console.error(error);
      window.alert("Error while loading presentation:\n\n" + error.message);
      window.location.href = window.location.pathname; // reload without "?file=..."
    });
  }

  _readFile(file) {
    this.fileReader.onload = () => {
      this._setPresentation(new Uint8Array(this.result));
    }

    this.fileReader.abort();
    this.fileReader.readAsArrayBuffer(file);
  }

  _setPresentation(presentation) {
    this._preparePresentation(presentation);
    this.startButton.disabled = false;
  }

  _setFileName(name) {
    const dummy = new DataTransfer();
    dummy.items.add(new File([], name));
    this.fileInput.files = dummy.files;
  }

  _loadFromUrl(url) {
    this._setFileName(url);
    this._setPresentation(url);
  }

  _listenForInput() {
    fileInput.addEventListener("change", event => {
      this._readFile(event.target.files[0]);
    });

    startButton.addEventListener("click", event => {
      event.preventDefault();
      event.stopPropagation();
      this.presentation.start();
    });

    document.body.addEventListener("drop", event => {
      event.preventDefault();
      event.stopPropagation();
      this.fileInput.files = event.dataTransfer.files;
      this._readFile(event.dataTransfer.files[0]);
    });

    document.body.addEventListener("dragover", event => {
      event.preventDefault();
      event.stopPropagation();
    });

    window.addEventListener('load', () => this._on_hash_change());
    window.addEventListener('hashchange', () => this._on_hash_change());
  }

  _on_hash_change() {
    const params = this._hash_params();
    if ("file" in params)
      this._loadFromUrl(params["file"]);
  }

  _hash_params() {
    return Object.fromEntries(
      location.hash
        .slice(1)  // skip #
        .split("&")
        .map(item => item.split("="))
    );
  }
}