/*
 * outliner
 * (c) 2020 dragonwocky <thedragonring.bod@gmail.com> (https://dragonwocky.me/)
 * (c) 2020 CloudHill
 * under the MIT license
 */

'use strict';

const { createElement } = require("../../pkg/helpers");

module.exports = (store, __exports) => {   
  // Observe for page changes
  const pageObserver = new MutationObserver((list, observer) => {
    for ( let { addedNodes } of list) {
      if (addedNodes[0]) {
        if (addedNodes[0].className === 'notion-page-content') {
          startContentObserver();
        }
        // Clear outline on database pages
        else if (addedNodes[0].className === 'notion-scroller') {
          contentObserver.disconnect();
          const outline = document.querySelector('.outliner');
          if (outline) outline.textContent = '';
        }
      } 
    }
  });

  // Observe for header changes
  const contentObserver = new MutationObserver((list, observer) => {
    list.forEach(m => {
      if (
        (
          m.type === 'childList' &&
          (
            isHeaderElement(m.target) ||
            isHeaderElement(m.addedNodes[0]) ||
            isHeaderElement(m.removedNodes[0])
          )
        ) ||
        (
          m.type === 'characterData' &&
          isHeaderElement(m.target.parentElement)
        )
      ) findHeaders();
    })
  });

  function startContentObserver() {
    findHeaders();
    contentObserver.disconnect();
    contentObserver.observe(
      document.querySelector('.notion-page-content'),
      {
        childList: true,
        subtree: true,
        characterData: true,
      }
    );
  }

  function findHeaders() {
    const outline = document.querySelector('.outliner');
    if (!outline) return;
    outline.textContent = '';
    if (store().lined) outline.setAttribute('lined', '');

    const pageContent = document.querySelector('.notion-page-content');
    const headerBlocks = pageContent.querySelectorAll('[class*="header-block"]');
    
    headerBlocks.forEach(block => {
      const blockId = block.dataset.blockId.replace(/-/g, '');
      const placeholder = block.querySelector('[placeholder]').getAttribute('placeholder');
      const header = createElement(`
        <div class="outline-header" header-level="${placeholder.slice(-1)}">
          <a href="${window.location.pathname}#${blockId}"
            outline-placeholder="${placeholder}">${block.innerText}</a>
        </div>
      `);
      outline.append(header);
    })
  }

  function isHeaderElement(el) {
    let placeholder;
    if (el) {
      if (
        el.querySelector && 
        el.querySelector('[placeholder]')
      ) {
        placeholder = el.querySelector('[placeholder]').getAttribute('placeholder')
      } else if (el.getAttribute) {
        placeholder = el.getAttribute('placeholder');
      } 
    }
    if (!placeholder) placeholder = '';
    return placeholder.includes('Heading');
  }

  return {
    onLoad() {
      // Find headers when switching panels
      if (document.querySelector('.notion-page-content')) {
        startContentObserver();
      };    
      pageObserver.observe(document.body, {
        childList: true,
        subtree: true,
      });
    },
    onSwitch() {
      pageObserver.disconnect();
      contentObserver.disconnect();
    }
  }
}