datemapper/src/convert-date-format.ts

A lightweight date utility for format conversion, validation, and date manipulation.

/**
 * Converts date format placeholders between Unix-style (`%Y-%m-%d`) and Moment.js (`YYYY-MM-DD`).
 *
 * - If `toNewFormat` is `true`, it converts from Unix-style (`%Y`, `%m`, etc.) to Moment.js format (`YYYY`, `MM`, etc.).
 * - If `toNewFormat` is `false`, it converts from Moment.js format back to Unix-style.
 * - Ensures that only valid placeholders are present before conversion.
 *
 * @param format - The date format string containing placeholders.
 * @param toNewFormat - Boolean flag to control conversion direction.
 *                      - `true` (default): Convert Unix-style (`%Y-%m-%d`) to Moment.js (`YYYY-MM-DD`).
 *                      - `false`: Convert Moment.js (`YYYY-MM-DD`) back to Unix-style (`%Y-%m-%d`).
 * @returns The reformatted date format string.
 * @throws {Error} If the format contains unrecognized placeholders.
 */
const convertDateFormat = (format: string, toNewFormat: boolean = true): string => {
  // Define mappings for valid conversions
  const formatMap: Record<string, string> = toNewFormat
    ? {
        "%Y": "YYYY", // Year
        "%m": "MM", // Month
        "%d": "DD", // Day
        "%U": "ww", // Week of the year
        "%H": "HH", // Hour (24-hour format)
        "%M": "mm", // Minute
        "%S": "ss" // Second
      }
    : {
        YYYY: "%Y",
        MM: "%m",
        DD: "%d",
        ww: "%U",
        HH: "%H",
        mm: "%M",
        ss: "%S"
      };

  // Extract valid keys for validation
  const validKeys = Object.keys(formatMap);

  // Validate format: Ensure all placeholders are known
  const regex = toNewFormat ? /%[YmdUHMS]/g : /\b(?:YYYY|MM|DD|ww|HH|mm|ss)\b/g;
  const foundTokens = format.match(regex);

  if (foundTokens) {
    for (const token of foundTokens) {
      if (!validKeys.includes(token)) {
        throw new Error(`Invalid date format token detected: ${token}`);
      }
    }
  }

  // Replace placeholders in the format string using the mapping
  Object.keys(formatMap).forEach(key => {
    format = format.replace(new RegExp(key, "g"), formatMap[key]);
  });

  return format;
};

export default convertDateFormat;