import { readFile } from 'fs/promises';
import moment from 'moment';

interface ParseFunc {
  (value: string | null): {[key: string]: string | null}
}

interface SpecialKeysOptions {
  key: string,
  parseFunc: ParseFunc
}

export interface HandleLogRowOptions {
  timeKey?: string;
  keys: string[];
  kvSeparator?: string;
  specialKeys?: SpecialKeysOptions[];
}

export async function readLogFile(filePath: string): Promise<string[]> {
  const fileContent = await readFile(filePath, { encoding: 'utf-8' });
  const content = fileContent.split('\n');

  return Promise.resolve(content);
}

export function parseLogTime(log: string): string | null {
  const time = /:(\d+-\d+-\d+\s\d+:\d+:\d+\.\d+)\s/.exec(log);
  if (time) {
    return moment(time[1]).format('DD/MM/YYYY HH:mm:ss');
  }
  return null;
}

/**
 * 将一行log解析为对象
 * @param log
 * @param keys
 */
export function parseLogKV(
  log: string,
  keys: string[] = [],
  kvSeparator = '=',
): {[key: string]: string} {
  if (keys.length === 0) {
    return {};
  }

  const res:{[key: string]: string} = {};
  const KVList = log.split(' ');
  keys.forEach((key) => {
    const reg = new RegExp(`^${key}${kvSeparator}`);
    const item = KVList.find((KVItem) => reg.test(KVItem));

    if (item) {
      const splitIndex = item.indexOf(kvSeparator);
      const value = item.substring(splitIndex + 1);
      res[key] = value;
    }
  });
  return res;
}

export function parseSpecialKeys(
  row: string,
  options: SpecialKeysOptions[],
  kvSeparator = '=',
):{[key: string]: string | null} {
  const obj = parseLogKV(row, options.map((item) => item.key), kvSeparator);

  let res = {};
  options.forEach((item) => {
    res = { ...res, ...item.parseFunc(obj[item.key]) };
  });
  return res;
}

export function handleLogRow(
  log: string,
  options: HandleLogRowOptions,
): {[key: string]: string | null} {
  let res: {[key: string]: string | null} = {};
  const {
    timeKey = 'create_time',
    kvSeparator = '=',
    keys = [],
    specialKeys = [],
  } = options;

  res[timeKey] = parseLogTime(log);
  res = { ...res, ...parseLogKV(log, keys, kvSeparator) };
  res = { ...res, ...parseSpecialKeys(log, specialKeys, kvSeparator) };

  return res;
}