src/hooks/useLogData/index.ts

import { useCallback, useEffect, useMemo, useState } from 'react';
import { apiHttp } from '@/constants';
import { APIError, AsyncStatus, Log } from '@/types';
import { DataModel, defaultError } from '@hooks/useResource';

export type LogItem = Log | 'Loading' | 'Error' | undefined;

export type LogData = {
  logs: Array<LogItem>;
  preloadStatus: AsyncStatus;
  status: AsyncStatus;
  loadMore: (index: number) => void;
  error: APIError | null;
  localSearch: LocalSearchType;
};

export type LogDataSettings = {
  preload: boolean;
  paused: boolean;
  url: string;
  pagesize?: number;
};

type LogSearchResult = {
  line: number;
  char: [number, number];
};

export type SearchState = { active: boolean; result: LogSearchResult[]; current: number; query: string };

export type LocalSearchType = {
  search: (str: string) => void;
  result: SearchState;
  nextResult: () => void;
};

const DEFAULT_PAGE_SIZE = 500;
const PRELOAD_POLL_INTERVALL = 20000;
const POSTLOAD_POLL_INTERVAL = 10000;

const emptyArray: LogItem[] = [];
const emptySearchResult = { active: false, result: [], current: 0, query: '' };

function isOkResult(param: DataModel<Log[]> | APIError): param is DataModel<Log[]> {
  return 'data' in param;
}

/**
 * Currently useLogData does not include websocket support.
 *
 * Log amounts might be massive so we want to load them paginated and on demand depending on user
 * actions. When preload is active (task is on running status) we first load what ever we get and after
 * task completes we need to fetch again.
 */

const useLogData = ({ preload, paused, url, pagesize }: LogDataSettings): LogData => {
  const [status, setStatus] = useState<AsyncStatus>('NotAsked');
  const [preloadStatus, setPreloadStatus] = useState<AsyncStatus>('NotAsked');
  const [error, setError] = useState<APIError | null>(null);
  const [postPoll, setPostPoll] = useState<boolean>(false);
  // Datastore
  const [logs, setLogs] = useState<LogItem[]>(emptyArray);
  const PAGE_SIZE = pagesize || DEFAULT_PAGE_SIZE;

  // generic log fetcher
  const fetchLogs = useCallback(
    (
      page: number,
      order: '+' | '-' = '+',
      isPostPoll = false,
    ): Promise<{ type: 'error'; error: APIError } | { type: 'ok'; data: Log[] }> => {
      const requestUrl = url;
      const fullUrl = `${requestUrl}${requestUrl.indexOf('?') > -1 ? '&' : '?'}_limit=${PAGE_SIZE}${
        page ? `&_page=${page}` : ''
      }&_order=${order}row`;

      return fetch(apiHttp(fullUrl))
        .then((response) => response.json())
        .then((result: DataModel<Log[]> | APIError) => {
          if (isOkResult(result)) {
            // Check if there was any new lines. If there wasn't, let's cancel post finish polling.
            // Or if was postpoll and we didnt get any results
            if (
              (result.data.length > 0 && logs.length > 0 && result.data[0].row === logs.length - 1) ||
              (isPostPoll && result.data.length === 0)
            ) {
              setPostPoll(false);
            }

            setLogs((array) => {
              const newarr = [...array];
              for (const item of result.data) {
                newarr[item.row] = item;
              }
              return newarr;
            });
            return { type: 'ok' as const, data: result.data };
          } else {
            return { type: 'error' as const, error: result };
          }
        })
        .catch((e) => {
          if (e instanceof DOMException) {
            return { type: 'error', error: { ...defaultError, id: 'user-aborted' } };
          }
          return { type: 'error', error: defaultError };
        });
    },
    [PAGE_SIZE, logs.length, url],
  );

  const fetchPreload = useCallback(() => {
    setPreloadStatus('Loading');
    fetchLogs(1, '-').then((result) => {
      if (result.type === 'error') {
        if (result.error.id === 'user-aborted') {
          setPreloadStatus('NotAsked');
          return;
        }
        setPreloadStatus('Error');
        return;
      }
      setPreloadStatus('Ok');
    });
  }, [fetchLogs]);

  // Fetch logs when task gets completed
  useEffect(() => {
    if (status === 'NotAsked' && !paused) {
      setStatus('Loading');

      fetchLogs(1, '-').then((result) => {
        setPostPoll(true);

        if (result.type === 'error') {
          if (result.error.id === 'user-aborted') {
            return;
          }

          setStatus('Error');
          setError(result.error);
          return;
        }
        setStatus('Ok');
      });
    }
  }, [paused, url, status, fetchLogs]);

  useEffect(() => {
    // For preload to happen following rules have to be matched
    // paused        -> Run has to be on running state
    // status        -> This should always be NotAsked if paused is on. Check just in case
    // preload       -> Run has to be runnign
    // preloadStatus -> We havent triggered this yet.
    if (paused && status === 'NotAsked' && preload && preloadStatus === 'NotAsked') {
      fetchPreload();
    }
  }, [paused, preload, preloadStatus, status, url, fetchPreload]);

  // Poller for auto updates when task is running
  useEffect(() => {
    let t: number;
    if (['Ok', 'Error'].includes(preloadStatus) && paused) {
      t = window.setTimeout(() => {
        fetchPreload();
      }, PRELOAD_POLL_INTERVALL);
    }
    return () => {
      clearTimeout(t);
    };
  }, [preloadStatus, paused, fetchPreload]);

  // Post finish polling
  // In some cases all logs might not be there after task finishes. For this, lets poll new logs every 10sec until
  // there are no new lines
  useEffect(() => {
    let t: number;
    if (status === 'Ok' && postPoll) {
      t = window.setTimeout(() => {
        fetchLogs(1, '-', true);
      }, POSTLOAD_POLL_INTERVAL);
    }
    return () => {
      clearTimeout(t);
    };
  }, [status, postPoll, logs, fetchLogs]);

  // loadMore gets triggered on all scrolling events on list.
  function loadMore(index: number) {
    // Get page number. Add one to correct lines starting from index 0
    const page = Math.ceil((index + 1) / PAGE_SIZE);
    // Need to have initial page before any other request.
    if ((status === 'Ok' || preloadStatus === 'Ok') && !logs[index]) {
      setLogs((arr) => {
        // Since we are fetching stuff as pages, find start of page where current line is
        // and fill them as loading so we dont try to fetch same page again.
        const startOfPage = (page - 1) * PAGE_SIZE;
        const endOfPage = startOfPage + PAGE_SIZE;

        for (let i = startOfPage; i < endOfPage; i++) {
          arr[i] = arr[i] || 'Loading';
        }
        return arr;
      });

      fetchLogs(page, '+').then((result) => {
        if (result.type === 'error') {
          return;
        }
      });
    }
  }

  const [searchResult, setSearchResult] = useState<SearchState>(emptySearchResult);

  const search = useCallback(
    (str: string) => {
      if (!str) {
        return setSearchResult(emptySearchResult);
      }
      const query = str.toLowerCase();
      const results = logs
        .filter(filterbySearchTerm)
        .filter((line) => line.line.toLowerCase().indexOf(query) > -1)
        .map((item) => {
          const index = item.line.toLowerCase().indexOf(query);
          return {
            line: item.row,
            char: [index, index + str.length] as [number, number],
          };
        });
      setSearchResult({ active: true, result: results, current: 0, query: str });
    },
    [logs],
  );

  const nextResult = useCallback(() => {
    if (searchResult.current === searchResult.result.length - 1) {
      setSearchResult((cur) => ({ ...cur, current: 0 }));
    } else {
      setSearchResult((cur) => ({ ...cur, current: cur.current + 1 }));
    }
  }, [searchResult]);

  // Clean up on url change
  useEffect(() => {
    return () => {
      setStatus('NotAsked');
      setPreloadStatus('NotAsked');
      setLogs(emptyArray);
      setError(null);
      setPostPoll(false);
      setSearchResult(emptySearchResult);
    };
  }, [url]);

  const localSearch = useMemo(() => ({ search, nextResult, result: searchResult }), [nextResult, search, searchResult]);

  return { logs, status, preloadStatus, error, loadMore, localSearch };
};

function filterbySearchTerm(item: LogItem): item is Log {
  return typeof item === 'object';
}

export default useLogData;