import Vue from 'vue';
import DiffMatchPatch from 'diff-match-patch';
import Prism from 'prismjs';
import markdownItPandocRenderer from 'markdown-it-pandoc-renderer';
import cledit from '../libs/cledit';
import pagedown from '../libs/pagedown';
import htmlSanitizer from '../libs/htmlSanitizer';
import markdownConversionSvc from './markdownConversionSvc';
import markdownGrammarSvc from './markdownGrammarSvc';
import sectionUtils from './sectionUtils';
import extensionSvc from './extensionSvc';
import animationSvc from './animationSvc';
import editorEngineSvc from './editorEngineSvc';
import store from '../store';

const debounce = cledit.Utils.debounce;

const allowDebounce = (action, wait) => {
  let timeoutId;
  return (doDebounce = false, ...params) => {
    clearTimeout(timeoutId);
    if (doDebounce) {
      timeoutId = setTimeout(() => action(...params), wait);
    } else {
      action(...params);
    }
  };
};

const diffMatchPatch = new DiffMatchPatch();
let instantPreview = true;
let tokens;
const anchorHash = {};

const editorSvc = Object.assign(new Vue(), { // Use a vue instance as an event bus
  // Elements
  editorElt: null,
  previewElt: null,
  tocElt: null,
  // Other objects
  pagedownEditor: null,
  options: null,
  prismGrammars: null,
  converter: null,
  parsingCtx: null,
  conversionCtx: null,
  sectionList: null,
  sectionDescList: [],
  sectionDescMeasuredList: null,
  sectionDescWithDiffsList: null,
  selectionRange: null,
  previewSelectionRange: null,
  previewSelectionStartOffset: null,
  previewHtml: null,
  previewText: null,

  /**
   * Get element and dimension that handles scrolling.
   */
  getObjectToScroll() {
    let elt = this.editorElt.parentNode;
    let dimensionKey = 'editorDimension';
    if (!store.getters['layout/styles'].showEditor) {
      elt = this.previewElt.parentNode;
      dimensionKey = 'previewDimension';
    }
    return {
      elt,
      dimensionKey,
    };
  },

  /**
   * Get an object describing the position of the scroll bar in the file.
   */
  getScrollPosition() {
    const objToScroll = this.getObjectToScroll();
    const scrollTop = objToScroll.elt.scrollTop;
    let result;
    if (this.sectionDescMeasuredList) {
      this.sectionDescMeasuredList.some((sectionDesc, sectionIdx) => {
        if (scrollTop >= sectionDesc[objToScroll.dimensionKey].endOffset) {
          return false;
        }
        const posInSection = (scrollTop - sectionDesc[objToScroll.dimensionKey].startOffset) /
          (sectionDesc[objToScroll.dimensionKey].height || 1);
        result = {
          sectionIdx,
          posInSection,
        };
        return true;
      });
    }
    return result;
  },

  /**
   * Get the offset in the preview corresponding to the offset of the markdown in the editor
   */
  getPreviewOffset(editorOffset) {
    let previewOffset = 0;
    let offset = editorOffset;
    this.sectionDescList.some((sectionDesc) => {
      if (!sectionDesc.textToPreviewDiffs) {
        previewOffset = undefined;
        return true;
      }
      if (sectionDesc.section.text.length >= offset) {
        previewOffset += diffMatchPatch.diff_xIndex(sectionDesc.textToPreviewDiffs, offset);
        return true;
      }
      offset -= sectionDesc.section.text.length;
      previewOffset += sectionDesc.previewText.length;
      return false;
    });
    return previewOffset;
  },

  /**
   * Get the offset of the markdown in the editor corresponding to the offset in the preview
   */
  getEditorOffset(previewOffset) {
    let offset = previewOffset;
    let editorOffset = 0;
    this.sectionDescList.some((sectionDesc) => {
      if (!sectionDesc.textToPreviewDiffs) {
        editorOffset = undefined;
        return true;
      }
      if (sectionDesc.previewText.length >= offset) {
        const previewToTextDiffs = sectionDesc.textToPreviewDiffs
          .map(diff => [-diff[0], diff[1]]);
        editorOffset += diffMatchPatch.diff_xIndex(previewToTextDiffs, offset);
        return true;
      }
      offset -= sectionDesc.previewText.length;
      editorOffset += sectionDesc.section.text.length;
      return false;
    });
    return editorOffset;
  },

  /**
   * Returns the pandoc AST generated from the file tokens and the converter options
   */
  getPandocAst() {
    return tokens && markdownItPandocRenderer(tokens, this.converter.options);
  },

  /**
   * Initialize the Prism grammar with the options
   */
  initPrism() {
    const options = {
      ...this.options,
      insideFences: markdownConversionSvc.defaultOptions.insideFences,
    };
    this.prismGrammars = markdownGrammarSvc.makeGrammars(options);
  },

  /**
   * Initialize the markdown-it converter with the options
   */
  initConverter() {
    this.converter = markdownConversionSvc.createConverter(this.options, true);
  },

  /**
   * Initialize the cledit editor with markdown-it section parser and Prism highlighter
   */
  initClEditor() {
    const options = {
      sectionHighlighter: section => Prism.highlight(
        section.text, this.prismGrammars[section.data]),
      sectionParser: (text) => {
        this.parsingCtx = markdownConversionSvc.parseSections(this.converter, text);
        return this.parsingCtx.sections;
      },
      getCursorFocusRatio: () => {
        if (store.getters['data/localSettings'].focusMode) {
          return 1;
        }
        return 0.15;
      },
    };
    editorEngineSvc.initClEditor(options);
    this.restoreScrollPosition();
  },

  /**
   * Finish the conversion initiated by the section parser
   */
  convert() {
    this.conversionCtx = markdownConversionSvc.convert(this.parsingCtx, this.conversionCtx);
    this.$emit('conversionCtx', this.conversionCtx);
    tokens = this.parsingCtx.markdownState.tokens;
  },

  /**
   * Refresh the preview with the result of `convert()`
   */
  refreshPreview() {
    const newSectionDescList = [];
    let sectionPreviewElt;
    let sectionTocElt;
    let sectionIdx = 0;
    let sectionDescIdx = 0;
    let insertBeforePreviewElt = this.previewElt.firstChild;
    let insertBeforeTocElt = this.tocElt.firstChild;
    let previewHtml = '';
    this.conversionCtx.htmlSectionDiff.forEach((item) => {
      for (let i = 0; i < item[1].length; i += 1) {
        const section = this.conversionCtx.sectionList[sectionIdx];
        if (item[0] === 0) {
          const sectionDesc = this.sectionDescList[sectionDescIdx];
          sectionDescIdx += 1;
          sectionDesc.editorElt = section.elt;
          newSectionDescList.push(sectionDesc);
          previewHtml += sectionDesc.html;
          sectionIdx += 1;
          insertBeforePreviewElt.classList.remove('modified');
          insertBeforePreviewElt = insertBeforePreviewElt.nextSibling;
          insertBeforeTocElt.classList.remove('modified');
          insertBeforeTocElt = insertBeforeTocElt.nextSibling;
        } else if (item[0] === -1) {
          sectionDescIdx += 1;
          sectionPreviewElt = insertBeforePreviewElt;
          insertBeforePreviewElt = insertBeforePreviewElt.nextSibling;
          this.previewElt.removeChild(sectionPreviewElt);
          sectionTocElt = insertBeforeTocElt;
          insertBeforeTocElt = insertBeforeTocElt.nextSibling;
          this.tocElt.removeChild(sectionTocElt);
        } else if (item[0] === 1) {
          const html = htmlSanitizer.sanitizeHtml(this.conversionCtx.htmlSectionList[sectionIdx]);
          sectionIdx += 1;

          // Create preview section element
          sectionPreviewElt = document.createElement('div');
          sectionPreviewElt.className = 'cl-preview-section modified';
          sectionPreviewElt.innerHTML = html;
          if (insertBeforePreviewElt) {
            this.previewElt.insertBefore(sectionPreviewElt, insertBeforePreviewElt);
          } else {
            this.previewElt.appendChild(sectionPreviewElt);
          }
          extensionSvc.sectionPreview(sectionPreviewElt, this.options);

          // Create TOC section element
          sectionTocElt = document.createElement('div');
          sectionTocElt.className = 'cl-toc-section modified';
          const headingElt = sectionPreviewElt.querySelector('h1, h2, h3, h4, h5, h6');
          if (headingElt) {
            const clonedElt = headingElt.cloneNode(true);
            clonedElt.removeAttribute('id');
            sectionTocElt.appendChild(clonedElt);
          }
          if (insertBeforeTocElt) {
            this.tocElt.insertBefore(sectionTocElt, insertBeforeTocElt);
          } else {
            this.tocElt.appendChild(sectionTocElt);
          }

          previewHtml += html;
          newSectionDescList.push({
            section,
            editorElt: section.elt,
            previewElt: sectionPreviewElt,
            tocElt: sectionTocElt,
            html,
          });
        }
      }
    });
    this.sectionDescList = newSectionDescList;
    this.previewHtml = previewHtml.replace(/^\s+|\s+$/g, '');
    this.tocElt.classList[
      this.tocElt.querySelector('.cl-toc-section *') ? 'remove' : 'add'
    ]('toc-tab--empty');

    // Run preview async operations (image loading, mathjax...)
    const loadingImages = this.previewElt.querySelectorAll('.cl-preview-section.modified img');
    const loadedPromises = loadingImages.cl_map(imgElt => new Promise((resolve) => {
      if (!imgElt.src) {
        resolve();
        return;
      }
      const img = new window.Image();
      img.onload = resolve;
      img.onerror = resolve;
      img.src = imgElt.src;
    }));

    Promise.all(loadedPromises.concat(extensionSvc.asyncPreview(this.options)))
      .then(() => {
        this.previewText = this.previewElt.textContent;
        this.$emit('previewText', this.previewText);
        // Debounce if sections have already been mesured
        this.measureSectionDimensions(!!this.sectionDescMeasuredList);
        this.makeTextToPreviewDiffs(true);
      });
  },

  /**
   * Measure the height of each section in editor, preview and toc.
   */
  measureSectionDimensions: allowDebounce((restoreScrollPosition) => {
    if (editorSvc.sectionDescList && this.sectionDescList !== editorSvc.sectionDescMeasuredList) {
      sectionUtils.measureSectionDimensions(editorSvc);
      editorSvc.sectionDescMeasuredList = editorSvc.sectionDescList;
      if (restoreScrollPosition) {
        editorSvc.restoreScrollPosition();
      }
      editorSvc.$emit('sectionDescMeasuredList', editorSvc.sectionDescMeasuredList);
    }
  }, 500),

  /**
   * Make the diff between editor's markdown and preview's html.
   */
  makeTextToPreviewDiffs: allowDebounce(() => {
    if (editorSvc.sectionDescList &&
      editorSvc.sectionDescList !== editorSvc.sectionDescMeasuredList) {
      editorSvc.sectionDescList
        .forEach((sectionDesc) => {
          if (!sectionDesc.textToPreviewDiffs) {
            sectionDesc.previewText = sectionDesc.previewElt.textContent;
            sectionDesc.textToPreviewDiffs = diffMatchPatch.diff_main(
              sectionDesc.section.text, sectionDesc.previewText);
          }
        });
      editorSvc.sectionDescWithDiffsList = editorSvc.sectionDescList;
    }
  }, 50),

  /**
   * Save editor selection/scroll state into the current file content.
   */
  saveContentState: allowDebounce(() => {
    const scrollPosition = editorSvc.getScrollPosition() ||
      store.getters['contentState/current'].scrollPosition;
    store.dispatch('contentState/patchCurrent', {
      selectionStart: editorEngineSvc.clEditor.selectionMgr.selectionStart,
      selectionEnd: editorEngineSvc.clEditor.selectionMgr.selectionEnd,
      scrollPosition,
    });
  }, 100),

  /**
   * Restore the scroll position from the current file content state.
   */
  restoreScrollPosition() {
    const scrollPosition = store.getters['contentState/current'].scrollPosition;
    if (scrollPosition && this.sectionDescMeasuredList) {
      const objectToScroll = this.getObjectToScroll();
      const sectionDesc = this.sectionDescMeasuredList[scrollPosition.sectionIdx];
      if (sectionDesc) {
        const scrollTop = sectionDesc[objectToScroll.dimensionKey].startOffset +
          (sectionDesc[objectToScroll.dimensionKey].height * scrollPosition.posInSection);
        objectToScroll.elt.scrollTop = Math.floor(scrollTop);
      }
    }
  },

  /**
   * Report selection from the preview to the editor.
   */
  saveSelection: allowDebounce(() => {
    const selection = window.getSelection();
    let range = selection.rangeCount && selection.getRangeAt(0);
    if (range) {
      if (
        /* eslint-disable no-bitwise */
        !(editorSvc.previewElt.compareDocumentPosition(range.startContainer) &
          window.Node.DOCUMENT_POSITION_CONTAINED_BY) ||
        !(editorSvc.previewElt.compareDocumentPosition(range.endContainer) &
          window.Node.DOCUMENT_POSITION_CONTAINED_BY)
        /* eslint-enable no-bitwise */
      ) {
        range = null;
      }
    }
    if (editorSvc.previewSelectionRange !== range) {
      let previewSelectionStartOffset;
      let previewSelectionEndOffset;
      if (range) {
        const startRange = document.createRange();
        startRange.setStart(editorSvc.previewElt, 0);
        startRange.setEnd(range.startContainer, range.startOffset);
        previewSelectionStartOffset = `${startRange}`.length;
        previewSelectionEndOffset = previewSelectionStartOffset + `${range}`.length;
        const editorStartOffset = editorSvc.getEditorOffset(previewSelectionStartOffset);
        const editorEndOffset = editorSvc.getEditorOffset(previewSelectionEndOffset);
        if (editorStartOffset !== undefined && editorEndOffset !== undefined) {
          editorEngineSvc.clEditor.selectionMgr.setSelectionStartEnd(
            editorStartOffset, editorEndOffset, false);
        }
      }
      editorSvc.previewSelectionRange = range;
      editorSvc.$emit('previewSelectionRange', editorSvc.previewSelectionRange);
    }
  }, 50),

  /**
   * Scroll the preview (or the editor if preview is hidden) to the specified anchor
   */
  scrollToAnchor(anchor) {
    let scrollTop = 0;
    let scrollerElt = this.previewElt.parentNode;
    const sectionDesc = anchorHash[anchor];
    if (sectionDesc) {
      if (store.getters['layout/styles'].showPreview) {
        scrollTop = sectionDesc.previewDimension.startOffset;
      } else {
        scrollTop = sectionDesc.editorDimension.startOffset;
        scrollerElt = this.editorElt.parentNode;
      }
    } else {
      const elt = document.getElementById(anchor);
      if (elt) {
        scrollTop = elt.offsetTop;
      }
    }
    const maxScrollTop = scrollerElt.scrollHeight - scrollerElt.offsetHeight;
    if (scrollTop < 0) {
      scrollTop = 0;
    } else if (scrollTop > maxScrollTop) {
      scrollTop = maxScrollTop;
    }
    animationSvc.animate(scrollerElt)
      .scrollTop(scrollTop)
      .duration(360)
      .start();
  },

  /**
   * Pass the elements to the store and initialize the editor.
   */
  init(editorElt, previewElt, tocElt) {
    this.editorElt = editorElt;
    this.previewElt = previewElt;
    this.tocElt = tocElt;

    editorEngineSvc.createClEditor(editorElt);
    editorEngineSvc.clEditor.on('contentChanged', (content, diffs, sectionList) => {
      const parsingCtx = {
        ...this.parsingCtx,
        sectionList,
      };
      this.parsingCtx = parsingCtx;
    });
    this.pagedownEditor = pagedown({
      input: Object.create(editorEngineSvc.clEditor),
    });
    this.pagedownEditor.run();
    this.pagedownEditor.hooks.set('insertLinkDialog', (callback) => {
      store.dispatch('modal/open', {
        type: 'link',
        callback,
      });
      return true;
    });
    this.pagedownEditor.hooks.set('insertImageDialog', (callback) => {
      store.dispatch('modal/open', {
        type: 'image',
        callback,
      });
      return true;
    });

    this.editorElt.parentNode.addEventListener('scroll', () => this.saveContentState(true));
    this.previewElt.parentNode.addEventListener('scroll', () => this.saveContentState(true));

    const refreshPreview = () => {
      this.convert();
      if (instantPreview) {
        this.refreshPreview();
        this.measureSectionDimensions(false, true);
      } else {
        setTimeout(() => this.refreshPreview(), 10);
      }
      instantPreview = false;
    };

    const debouncedRefreshPreview = debounce(refreshPreview, 20);

    const onEditorChanged =
      (sectionList = this.sectionList, selectionRange = this.selectionRange) => {
        if (this.sectionList !== sectionList) {
          this.sectionList = sectionList;
          this.$emit('sectionList', this.sectionList);
          if (instantPreview) {
            refreshPreview();
          } else {
            debouncedRefreshPreview();
          }
        }
        if (this.selectionRange !== selectionRange) {
          this.selectionRange = selectionRange;
          this.$emit('selectionRange', this.selectionRange);
        }
        this.saveContentState();
      };

    editorEngineSvc.clEditor.selectionMgr.on('selectionChanged',
      (start, end, selectionRange) => onEditorChanged(undefined, selectionRange));

    /* -----------------------------
     * Inline images
     */

    const imgCache = Object.create(null);

    const addToImgCache = (imgElt) => {
      let entries = imgCache[imgElt.src];
      if (!entries) {
        entries = [];
        imgCache[imgElt.src] = entries;
      }
      entries.push(imgElt);
    };

    const getFromImgCache = (src) => {
      const entries = imgCache[src];
      if (!entries) {
        return null;
      }
      let imgElt;
      return entries
        .some((entry) => {
          if (this.editorElt.contains(entry)) {
            return false;
          }
          imgElt = entry;
          return true;
        }) && imgElt;
    };

    const triggerImgCacheGc = debounce(() => {
      Object.keys(imgCache).forEach((src) => {
        const entries = imgCache[src]
          .filter(imgElt => this.editorElt.contains(imgElt));
        if (entries.length) {
          imgCache[src] = entries;
        } else {
          delete imgCache[src];
        }
      });
    }, 100);

    let imgEltsToCache = [];
    if (store.getters['data/computedSettings'].editor.inlineImages) {
      editorEngineSvc.clEditor.highlighter.on('sectionHighlighted', (section) => {
        section.elt.getElementsByClassName('token img').cl_each((imgTokenElt) => {
          const srcElt = imgTokenElt.querySelector('.token.cl-src');
          if (srcElt) {
            // Create an img element before the .img.token and wrap both elements
            // into a .token.img-wrapper
            const imgElt = document.createElement('img');
            imgElt.style.display = 'none';
            const uri = srcElt.textContent;
            if (!/^unsafe/.test(htmlSanitizer.sanitizeUri(uri, true))) {
              imgElt.onload = () => {
                imgElt.style.display = '';
              };
              imgElt.src = uri;
              imgEltsToCache.push(imgElt);
            }
            const imgTokenWrapper = document.createElement('span');
            imgTokenWrapper.className = 'token img-wrapper';
            imgTokenElt.parentNode.insertBefore(imgTokenWrapper, imgTokenElt);
            imgTokenWrapper.appendChild(imgElt);
            imgTokenWrapper.appendChild(imgTokenElt);
          }
        });
      });
    }

    editorEngineSvc.clEditor.highlighter.on('highlighted', () => {
      imgEltsToCache.forEach((imgElt) => {
        const cachedImgElt = getFromImgCache(imgElt.src);
        if (cachedImgElt) {
          // Found a previously loaded image that has just been released
          imgElt.parentNode.replaceChild(cachedImgElt, imgElt);
        } else {
          addToImgCache(imgElt);
        }
      });
      imgEltsToCache = [];
      // Eject released images from cache
      triggerImgCacheGc();
    });

    editorEngineSvc.clEditor.on('contentChanged',
      (content, diffs, sectionList) => onEditorChanged(sectionList));

    this.$emit('inited');

    // clEditorSvc.setPreviewElt(element[0].querySelector('.preview__inner-2'))
    // var previewElt = element[0].querySelector('.preview')
    // clEditorSvc.isPreviewTop = previewElt.scrollTop < 10
    // previewElt.addEventListener('scroll', function () {
    //   var isPreviewTop = previewElt.scrollTop < 10
    //   if (isPreviewTop !== clEditorSvc.isPreviewTop) {
    //     clEditorSvc.isPreviewTop = isPreviewTop
    //     scope.$apply()
    //   }
    // })

    // Watch file content changes
    let lastContentId = null;
    let lastProperties;
    store.watch(
      () => store.getters['content/current'].hash,
      () => {
        const content = store.getters['content/current'];
        // Track ID changes
        let initClEditor = false;
        if (content.id !== lastContentId) {
          instantPreview = true;
          lastContentId = content.id;
          initClEditor = true;
        }
        // Track properties changes
        if (content.properties !== lastProperties) {
          lastProperties = content.properties;
          const options = extensionSvc.getOptions(store.getters['content/currentProperties']);
          if (JSON.stringify(options) !== JSON.stringify(editorSvc.options)) {
            editorSvc.options = options;
            editorSvc.initPrism();
            editorSvc.initConverter();
            initClEditor = true;
          }
        }
        if (initClEditor) {
          editorSvc.initClEditor();
        }
        // Apply possible text and discussion changes
        editorEngineSvc.applyContent();
      }, {
        immediate: true,
      });

    // Disable editor if hidden or if no content is loaded
    store.watch(
      () => store.getters['content/current'].id && store.getters['layout/styles'].showEditor,
      editable => editorEngineSvc.clEditor.toggleEditable(!!editable), {
        immediate: true,
      });

    store.watch(() => store.getters['layout/styles'],
      () => editorSvc.measureSectionDimensions(false, true));
  },
});

export default editorSvc;