import React, {
  useCallback, useEffect, useMemo, useRef, useState,
} from 'react';

import EventEmitter from 'events';
import nodePath from 'path';

import type { IPageHasId } from '@growi/core';
import { pathUtils } from '@growi/core/dist/utils';
import detectIndent from 'detect-indent';
import { useTranslation } from 'next-i18next';
import { useRouter } from 'next/router';
import { throttle, debounce } from 'throttle-debounce';

import { useUpdateStateAfterSave, useSaveOrUpdate } from '~/client/services/page-operation';
import { apiGet, apiPostForm } from '~/client/util/apiv1-client';
import { toastError, toastSuccess } from '~/client/util/toastr';
import { IEditorMethods } from '~/interfaces/editor-methods';
import { OptionsToSave } from '~/interfaces/page-operation';
import { SocketEventName } from '~/interfaces/websocket';
import {
  useCurrentPathname, useIsEnabledAttachTitleHeader,
  useIsEditable, useIsUploadableFile, useIsUploadableImage, useIsIndentSizeForced,
} from '~/stores/context';
import {
  useCurrentIndentSize, useIsSlackEnabled, usePageTagsForEditors,
  useIsEnabledUnsavedWarning,
  useIsConflict,
  useEditingMarkdown,
  useWaitingSaveProcessing,
} from '~/stores/editor';
import { useConflictDiffModal } from '~/stores/modal';
import {
  useCurrentPagePath, useSWRMUTxCurrentPage, useSWRxCurrentPage, useSWRxTagsInfo, useCurrentPageId, useIsNotFound, useIsLatestRevision, useTemplateBodyData,
} from '~/stores/page';
import { mutatePageTree } from '~/stores/page-listing';
import {
  useRemoteRevisionId,
  useRemoteRevisionBody,
  useRemoteRevisionLastUpdatedAt,
  useRemoteRevisionLastUpdateUser,
} from '~/stores/remote-latest-page';
import { usePreviewOptions } from '~/stores/renderer';
import {
  EditorMode,
  useEditorMode, useSelectedGrant,
} from '~/stores/ui';
import { useGlobalSocket } from '~/stores/websocket';
import loggerFactory from '~/utils/logger';


// import { ConflictDiffModal } from './PageEditor/ConflictDiffModal';
import { ConflictDiffModal } from './PageEditor/ConflictDiffModal';
import Editor from './PageEditor/Editor';
import Preview from './PageEditor/Preview';
import scrollSyncHelper from './PageEditor/ScrollSyncHelper';


const logger = loggerFactory('growi:PageEditor');


declare global {
  // eslint-disable-next-line vars-on-top, no-var
  var globalEmitter: EventEmitter;
}


// for scrolling
let lastScrolledDateWithCursor: Date | null = null;
let isOriginOfScrollSyncEditor = false;
let isOriginOfScrollSyncPreview = false;

const PageEditor = React.memo((): JSX.Element => {

  const { t } = useTranslation();
  const router = useRouter();

  const { data: isNotFound } = useIsNotFound();
  const { data: pageId, mutate: mutateCurrentPageId } = useCurrentPageId();
  const { data: currentPagePath } = useCurrentPagePath();
  const { data: currentPathname } = useCurrentPathname();
  const { data: currentPage } = useSWRxCurrentPage();
  const { trigger: mutateCurrentPage } = useSWRMUTxCurrentPage();
  const { data: grantData } = useSelectedGrant();
  const { data: pageTags, sync: syncTagsInfoForEditor } = usePageTagsForEditors(pageId);
  const { mutate: mutateTagsInfo } = useSWRxTagsInfo(pageId);
  const { data: editingMarkdown, mutate: mutateEditingMarkdown } = useEditingMarkdown();
  const { data: isEnabledAttachTitleHeader } = useIsEnabledAttachTitleHeader();
  const { data: templateBodyData } = useTemplateBodyData();
  const { data: isEditable } = useIsEditable();
  const { mutate: mutateWaitingSaveProcessing } = useWaitingSaveProcessing();
  const { data: editorMode, mutate: mutateEditorMode } = useEditorMode();
  const { data: isSlackEnabled } = useIsSlackEnabled();
  const { data: isIndentSizeForced } = useIsIndentSizeForced();
  const { data: currentIndentSize, mutate: mutateCurrentIndentSize } = useCurrentIndentSize();
  const { data: isUploadableFile } = useIsUploadableFile();
  const { data: isUploadableImage } = useIsUploadableImage();
  const { data: conflictDiffModalStatus, close: closeConflictDiffModal } = useConflictDiffModal();
  const { mutate: mutateIsLatestRevision } = useIsLatestRevision();
  const { mutate: mutateRemotePageId } = useRemoteRevisionId();
  const { mutate: mutateRemoteRevisionId } = useRemoteRevisionBody();
  const { mutate: mutateRemoteRevisionLastUpdatedAt } = useRemoteRevisionLastUpdatedAt();
  const { mutate: mutateRemoteRevisionLastUpdateUser } = useRemoteRevisionLastUpdateUser();

  const { data: rendererOptions } = usePreviewOptions();
  const { mutate: mutateIsEnabledUnsavedWarning } = useIsEnabledUnsavedWarning();
  const saveOrUpdate = useSaveOrUpdate();

  const updateStateAfterSave = useUpdateStateAfterSave(pageId, { supressEditingMarkdownMutation: true });

  // TODO: remove workaround
  // for https://redmine.weseek.co.jp/issues/125923
  const [createdPageRevisionIdWithAttachment, setCreatedPageRevisionIdWithAttachment] = useState();

  // TODO: remove workaround
  // for https://redmine.weseek.co.jp/issues/125923
  const currentRevisionId = currentPage?.revision?._id ?? createdPageRevisionIdWithAttachment;

  const initialValue = useMemo(() => {
    if (!isNotFound) {
      return editingMarkdown ?? '';
    }

    let initialValue = '';
    if (isEnabledAttachTitleHeader && currentPathname != null) {
      const pageTitle = nodePath.basename(currentPathname);
      initialValue += `${pathUtils.attachTitleHeader(pageTitle)}\n`;
    }
    if (templateBodyData != null) {
      initialValue += `${templateBodyData}\n`;
    }
    return initialValue;

  }, [isNotFound, currentPathname, editingMarkdown, isEnabledAttachTitleHeader, templateBodyData]);

  const markdownToSave = useRef<string>(initialValue);
  const [markdownToPreview, setMarkdownToPreview] = useState<string>(initialValue);

  const { data: socket } = useGlobalSocket();

  const { mutate: mutateIsConflict } = useIsConflict();


  const editorRef = useRef<IEditorMethods>(null);
  const previewRef = useRef<HTMLDivElement>(null);

  const checkIsConflict = useCallback((data) => {
    const { s2cMessagePageUpdated } = data;

    const isConflict = markdownToPreview !== s2cMessagePageUpdated.revisionBody;

    mutateIsConflict(isConflict);

  }, [markdownToPreview, mutateIsConflict]);

  // TODO: remove workaround
  // for https://redmine.weseek.co.jp/issues/125923
  useEffect(() => {
    setCreatedPageRevisionIdWithAttachment(undefined);
  }, [router]);

  useEffect(() => {
    markdownToSave.current = initialValue;
    setMarkdownToPreview(initialValue);
  }, [initialValue]);

  useEffect(() => {
    if (socket == null) { return }

    socket.on(SocketEventName.PageUpdated, checkIsConflict);

    return () => {
      socket.off(SocketEventName.PageUpdated, checkIsConflict);
    };

  }, [socket, checkIsConflict]);

  const optionsToSave = useMemo((): OptionsToSave | undefined => {
    if (grantData == null) {
      return;
    }
    const grantedGroups = grantData.grantedGroups?.map((group) => {
      return { item: group.id, type: group.type };
    });
    const optionsToSave = {
      isSlackEnabled: isSlackEnabled ?? false,
      slackChannels: '', // set in save method by opts in SavePageControlls.tsx
      grant: grantData.grant,
      pageTags: pageTags ?? [],
      grantUserGroupIds: grantedGroups,
    };
    return optionsToSave;
  }, [grantData, isSlackEnabled, pageTags]);

  const setMarkdownWithDebounce = useMemo(() => debounce(100, throttle(150, (value: string, isClean: boolean) => {
    markdownToSave.current = value;
    setMarkdownToPreview(value);

    // Displays an unsaved warning alert
    mutateIsEnabledUnsavedWarning(!isClean);
  })), [mutateIsEnabledUnsavedWarning]);


  const markdownChangedHandler = useCallback((value: string, isClean: boolean): void => {
    setMarkdownWithDebounce(value, isClean);
  }, [setMarkdownWithDebounce]);

  const save = useCallback(async(opts?: {slackChannels: string, overwriteScopesOfDescendants?: boolean}): Promise<IPageHasId | null> => {
    if (currentPathname == null || optionsToSave == null) {
      logger.error('Some materials to save are invalid', { grantData, isSlackEnabled, currentPathname });
      throw new Error('Some materials to save are invalid');
    }

    const options = Object.assign(optionsToSave, opts);

    try {
      mutateWaitingSaveProcessing(true);

      const { page } = await saveOrUpdate(
        markdownToSave.current,
        { pageId, path: currentPagePath || currentPathname, revisionId: currentRevisionId },
        options,
      );

      // to sync revision id with page tree: https://github.com/weseek/growi/pull/7227
      mutatePageTree();

      return page;
    }
    catch (error) {
      logger.error('failed to save', error);
      toastError(error);
      if (error.code === 'conflict') {
        mutateRemotePageId(error.data.revisionId);
        mutateRemoteRevisionId(error.data.revisionBody);
        mutateRemoteRevisionLastUpdatedAt(error.data.createdAt);
        mutateRemoteRevisionLastUpdateUser(error.data.user);
      }
      return null;
    }
    finally {
      mutateWaitingSaveProcessing(false);
    }

  }, [
    currentPathname, optionsToSave, grantData, isSlackEnabled, saveOrUpdate, pageId,
    currentPagePath, currentRevisionId,
    mutateWaitingSaveProcessing, mutateRemotePageId, mutateRemoteRevisionId, mutateRemoteRevisionLastUpdatedAt, mutateRemoteRevisionLastUpdateUser,
  ]);

  const saveAndReturnToViewHandler = useCallback(async(opts: {slackChannels: string, overwriteScopesOfDescendants?: boolean}) => {
    if (editorMode !== EditorMode.Editor) {
      return;
    }

    const page = await save(opts);
    if (page == null) {
      return;
    }

    if (isNotFound) {
      await router.push(`/${page._id}`);
    }
    else {
      updateStateAfterSave?.();
    }
    mutateEditorMode(EditorMode.View);
  }, [editorMode, save, isNotFound, mutateEditorMode, router, updateStateAfterSave]);

  const saveWithShortcut = useCallback(async() => {
    if (editorMode !== EditorMode.Editor) {
      return;
    }

    const page = await save();
    if (page == null) {
      return;
    }

    if (isNotFound) {
      await router.push(`/${page._id}#edit`);
    }
    else {
      updateStateAfterSave?.();
    }
    toastSuccess(t('toaster.save_succeeded'));
    mutateEditorMode(EditorMode.Editor);

  }, [editorMode, isNotFound, mutateEditorMode, router, save, t, updateStateAfterSave]);


  /**
   * the upload event handler
   * @param {any} file
   */
  const uploadHandler = useCallback(async(file) => {
    if (editorRef.current == null) {
      return;
    }

    try {
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      let res: any = await apiGet('/attachments.limit', {
        fileSize: file.size,
      });

      if (!res.isUploadable) {
        throw new Error(res.errorMessage);
      }

      const formData = new FormData();
      // const { pageId, path } = pageContainer.state;
      formData.append('file', file);
      if (currentPagePath != null) {
        formData.append('path', currentPagePath);
      }
      if (pageId != null) {
        formData.append('page_id', pageId);
      }
      if (pageId == null && markdownToSave.current != null) {
        formData.append('page_body', markdownToSave.current);
      }

      res = await apiPostForm('/attachments.add', formData);
      const attachment = res.attachment;
      const fileName = attachment.originalName;

      let insertText = `[${fileName}](${attachment.filePathProxied})`;
      // when image
      if (attachment.fileFormat.startsWith('image/')) {
        // modify to "![fileName](url)" syntax
        insertText = `!${insertText}`;
      }
      editorRef.current.insertText(insertText);

      // when if created newly
      // Not using 'mutateGrant' to inherit the grant of the parent page
      if (res.pageCreated) {
        logger.info('Page is created', res.page._id);
        globalEmitter.emit('resetInitializedHackMdStatus');
        mutateIsLatestRevision(true);
        setCreatedPageRevisionIdWithAttachment(res.page.revision);
        await mutateCurrentPageId(res.page._id);
        await mutateCurrentPage();
      }
    }
    catch (e) {
      logger.error('failed to upload', e);
      toastError(e);
    }
    finally {
      editorRef.current.terminateUploadingState();
    }
  }, [currentPagePath, mutateCurrentPage, mutateCurrentPageId, mutateIsLatestRevision, pageId]);


  const scrollPreviewByEditorLine = useCallback((line: number) => {
    if (previewRef.current == null) {
      return;
    }

    // prevent circular invocation
    if (isOriginOfScrollSyncPreview) {
      isOriginOfScrollSyncPreview = false; // turn off the flag
      return;
    }

    // turn on the flag
    isOriginOfScrollSyncEditor = true;
    scrollSyncHelper.scrollPreview(previewRef.current, line);
  }, []);
  const scrollPreviewByEditorLineWithThrottle = useMemo(() => throttle(20, scrollPreviewByEditorLine), [scrollPreviewByEditorLine]);

  /**
   * the scroll event handler from codemirror
   * @param {any} data {left, top, width, height, clientWidth, clientHeight} object that represents the current scroll position,
   *                    the size of the scrollable area, and the size of the visible area (minus scrollbars).
   *                    And data.line is also available that is added by Editor component
   * @see https://codemirror.net/doc/manual.html#events
   */
  const editorScrolledHandler = useCallback(({ line }: { line: number }) => {
    // prevent scrolling
    //   if the elapsed time from last scroll with cursor is shorter than 40ms
    const now = new Date();
    if (lastScrolledDateWithCursor != null && now.getTime() - lastScrolledDateWithCursor.getTime() < 40) {
      return;
    }

    scrollPreviewByEditorLineWithThrottle(line);
  }, [scrollPreviewByEditorLineWithThrottle]);

  /**
   * scroll Preview element by cursor moving
   * @param {number} line
   */
  const scrollPreviewByCursorMoving = useCallback((line: number) => {
    if (previewRef.current == null) {
      return;
    }

    // prevent circular invocation
    if (isOriginOfScrollSyncPreview) {
      isOriginOfScrollSyncPreview = false; // turn off the flag
      return;
    }

    // turn on the flag
    isOriginOfScrollSyncEditor = true;
    if (previewRef.current != null) {
      scrollSyncHelper.scrollPreviewToRevealOverflowing(previewRef.current, line);
    }
  }, []);
  const scrollPreviewByCursorMovingWithThrottle = useMemo(() => throttle(20, scrollPreviewByCursorMoving), [scrollPreviewByCursorMoving]);

  /**
   * the scroll event handler from codemirror
   * @param {number} line
   * @see https://codemirror.net/doc/manual.html#events
   */
  const editorScrollCursorIntoViewHandler = useCallback((line: number) => {
    // record date
    lastScrolledDateWithCursor = new Date();
    scrollPreviewByCursorMovingWithThrottle(line);
  }, [scrollPreviewByCursorMovingWithThrottle]);

  /**
   * scroll Editor component by scroll event of Preview component
   * @param {number} offset
   */
  const scrollEditorByPreviewScroll = useCallback((offset: number) => {
    if (editorRef.current == null || previewRef.current == null) {
      return;
    }

    // prevent circular invocation
    if (isOriginOfScrollSyncEditor) {
      isOriginOfScrollSyncEditor = false; // turn off the flag
      return;
    }

    // turn on the flag
    // eslint-disable-next-line @typescript-eslint/no-unused-vars
    isOriginOfScrollSyncPreview = true;

    scrollSyncHelper.scrollEditor(editorRef.current, previewRef.current, offset);
  }, []);
  const scrollEditorByPreviewScrollWithThrottle = useMemo(() => throttle(20, scrollEditorByPreviewScroll), [scrollEditorByPreviewScroll]);

  const afterResolvedHandler = useCallback(async() => {
    // get page data from db
    const pageData = await mutateCurrentPage();

    // update tag
    await mutateTagsInfo(); // get from DB
    syncTagsInfoForEditor(); // sync global state for client

    // clear isConflict
    mutateIsConflict(false);

    // set resolved markdown in editing markdown
    const markdown = pageData?.revision.body ?? '';
    mutateEditingMarkdown(markdown);

  }, [mutateCurrentPage, mutateEditingMarkdown, mutateIsConflict, mutateTagsInfo, syncTagsInfoForEditor]);


  // initialize
  useEffect(() => {
    if (initialValue == null) {
      return;
    }
    markdownToSave.current = initialValue;
    setMarkdownToPreview(initialValue);
    mutateIsEnabledUnsavedWarning(false);
  }, [initialValue, mutateIsEnabledUnsavedWarning]);

  // initial caret line
  useEffect(() => {
    if (editorRef.current != null) {
      editorRef.current.setCaretLine(0);
    }
  }, []);

  // set handler to set caret line
  useEffect(() => {
    const handler = (line) => {
      if (editorRef.current != null) {
        editorRef.current.setCaretLine(line);
      }
      if (previewRef.current != null) {
        scrollSyncHelper.scrollPreview(previewRef.current, line);
      }
    };
    globalEmitter.on('setCaretLine', handler);

    return function cleanup() {
      globalEmitter.removeListener('setCaretLine', handler);
    };
  }, []);

  // set handler to save and return to View
  useEffect(() => {
    globalEmitter.on('saveAndReturnToView', saveAndReturnToViewHandler);

    return function cleanup() {
      globalEmitter.removeListener('saveAndReturnToView', saveAndReturnToViewHandler);
    };
  }, [saveAndReturnToViewHandler]);

  // set handler to focus
  useEffect(() => {
    if (editorRef.current != null && editorMode === EditorMode.Editor) {
      editorRef.current.forceToFocus();
    }
  }, [editorMode]);

  // Detect indent size from contents (only when users are allowed to change it)
  useEffect(() => {
    // do nothing if the indent size fixed
    if (isIndentSizeForced == null || isIndentSizeForced) {
      return;
    }

    // detect from markdown
    if (initialValue != null) {
      const detectedIndent = detectIndent(initialValue);
      if (detectedIndent.type === 'space' && new Set([2, 4]).has(detectedIndent.amount)) {
        mutateCurrentIndentSize(detectedIndent.amount);
      }
    }
  }, [initialValue, isIndentSizeForced, mutateCurrentIndentSize]);

  // when transitioning to a different page, if the initialValue is the same,
  // UnControlled CodeMirror value does not reset, so explicitly set the value to initialValue
  const onRouterChangeComplete = useCallback(() => {
    editorRef.current?.setValue(initialValue);
    editorRef.current?.setCaretLine(0);
  }, [initialValue]);

  useEffect(() => {
    router.events.on('routeChangeComplete', onRouterChangeComplete);
    return () => {
      router.events.off('routeChangeComplete', onRouterChangeComplete);
    };
  }, [onRouterChangeComplete, router.events]);

  if (!isEditable) {
    return <></>;
  }

  if (rendererOptions == null) {
    return <></>;
  }

  const isUploadable = isUploadableImage || isUploadableFile;

  return (
    <div className="d-flex flex-wrap">
      <div className="page-editor-editor-container flex-grow-1 flex-basis-0 mw-0">
        <Editor
          ref={editorRef}
          value={initialValue}
          isUploadable={isUploadable}
          isUploadableFile={isUploadableFile}
          indentSize={currentIndentSize}
          onScroll={editorScrolledHandler}
          onScrollCursorIntoView={editorScrollCursorIntoViewHandler}
          onChange={markdownChangedHandler}
          onUpload={uploadHandler}
          onSave={saveWithShortcut}
        />
      </div>
      <div className="d-none d-lg-block page-editor-preview-container flex-grow-1 flex-basis-0 mw-0">
        <Preview
          ref={previewRef}
          rendererOptions={rendererOptions}
          markdown={markdownToPreview}
          pagePath={currentPagePath}
          onScroll={offset => scrollEditorByPreviewScrollWithThrottle(offset)}
        />
      </div>
      <ConflictDiffModal
        isOpen={conflictDiffModalStatus?.isOpened}
        onClose={() => closeConflictDiffModal()}
        markdownOnEdit={markdownToPreview}
        optionsToSave={optionsToSave}
        afterResolvedHandler={afterResolvedHandler}
      />
    </div>
  );
});
PageEditor.displayName = 'PageEditor';

export default PageEditor;