import messages from 'shared/messages';
import Hint from './hint';

const TARGET_SELECTOR = [
  'a', 'button', 'input', 'textarea',
  '[contenteditable=true]', '[contenteditable=""]'
].join(',');

const inWindow = (win, element) => {
  let {
    top, left, bottom, right
  } = element.getBoundingClientRect();
  let doc = win.doc;
  return (
    top >= 0 && left >= 0 &&
    bottom <= (win.innerHeight || doc.documentElement.clientHeight) &&
    right <= (win.innerWidth || doc.documentElement.clientWidth)
  );
};

export default class Follow {
  constructor(win, store) {
    this.win = win;
    this.store = store;
    this.newTab = false;
    this.hints = {};
    this.targets = [];
  }

  update() {
  }

  key(key) {
    if (Object.keys(this.hints).length === 0) {
      return false;
    }
    this.win.parent.postMessage(JSON.stringify({
      type: messages.FOLLOW_KEY_PRESS,
      key,
    }), '*');
    return true;
  }

  openLink(element) {
    if (!this.newTab) {
      element.click();
      return;
    }

    let href = element.getAttribute('href');

    // eslint-disable-next-line no-script-url
    if (!href || href === '#' || href.toLowerCase().startsWith('javascript:')) {
      return;
    }
    return browser.runtime.sendMessage({
      type: messages.OPEN_URL,
      url: element.href,
      newTab: this.newTab,
    });
  }

  countHints(sender) {
    this.targets = Follow.getTargetElements(this.win);
    sender.postMessage(JSON.stringify({
      type: messages.FOLLOW_RESPONSE_COUNT_TARGETS,
      count: this.targets.length,
    }), '*');
  }

  createHints(keysArray, newTab) {
    if (keysArray.length !== this.targets.length) {
      throw new Error('illegal hint count');
    }

    this.newTab = newTab;
    this.hints = {};
    for (let i = 0; i < keysArray.length; ++i) {
      let keys = keysArray[i];
      let hint = new Hint(this.targets[i], keys);
      this.hints[keys] = hint;
    }
  }

  showHints(keys) {
    Object.keys(this.hints).filter(key => key.startsWith(keys))
      .forEach(key => this.hints[key].show());
    Object.keys(this.hints).filter(key => !key.startsWith(keys))
      .forEach(key => this.hints[key].hide());
  }

  removeHints() {
    Object.keys(this.hints).forEach((key) => {
      this.hints[key].remove();
    });
    this.hints = {};
    this.targets = [];
  }

  activateHints(keys) {
    let hint = this.hints[keys];
    if (!hint) {
      return;
    }
    let element = hint.target;
    switch (element.tagName.toLowerCase()) {
    case 'a':
      return this.openLink(element, this.newTab);
    case 'input':
      switch (element.type) {
      case 'file':
      case 'checkbox':
      case 'radio':
      case 'submit':
      case 'reset':
      case 'button':
      case 'image':
      case 'color':
        return element.click();
      default:
        return element.focus();
      }
    case 'textarea':
      return element.focus();
    case 'button':
      return element.click();
    default:
      // it may contenteditable
      return element.focus();
    }
  }

  onMessage(message, sender) {
    switch (message.type) {
    case messages.FOLLOW_REQUEST_COUNT_TARGETS:
      return this.countHints(sender);
    case messages.FOLLOW_CREATE_HINTS:
      return this.createHints(message.keysArray, message.newTab);
    case messages.FOLLOW_SHOW_HINTS:
      return this.showHints(message.keys);
    case messages.FOLLOW_ACTIVATE:
      return this.activateHints(message.keys);
    case messages.FOLLOW_REMOVE_HINTS:
      return this.removeHints(message.keys);
    }
  }

  static getTargetElements(win) {
    let all = win.document.querySelectorAll(TARGET_SELECTOR);
    let filtered = Array.prototype.filter.call(all, (element) => {
      let style = win.getComputedStyle(element);
      return style.display !== 'none' &&
        style.visibility !== 'hidden' &&
        element.type !== 'hidden' &&
        element.offsetHeight > 0 &&
        inWindow(win, element);
    });
    return filtered;
  }
}