md022.mjs

// @ts-check

import { addErrorDetailIf, isBlankLine } from "../helpers/helpers.cjs";
import { getBlockQuotePrefixText, getHeadingLevel } from "../helpers/micromark-helpers.cjs";
import { filterByTypesCached } from "./cache.mjs";

const defaultLines = 1;

const getLinesFunction = (linesParam) => {
  if (Array.isArray(linesParam)) {
    const linesArray = new Array(6).fill(defaultLines);
    for (const [ index, value ] of [ ...linesParam.entries() ].slice(0, 6)) {
      linesArray[index] = value;
    }
    return (heading) => linesArray[getHeadingLevel(heading) - 1];
  }
  // Coerce linesParam to a number
  const lines = (linesParam === undefined) ? defaultLines : Number(linesParam);
  return () => lines;
};

/** @type {import("markdownlint").Rule} */
export default {
  "names": [ "MD022", "blanks-around-headings" ],
  "description": "Headings should be surrounded by blank lines",
  "tags": [ "headings", "blank_lines" ],
  "parser": "micromark",
  "function": function MD022(params, onError) {
    const getLinesAbove = getLinesFunction(params.config.lines_above);
    const getLinesBelow = getLinesFunction(params.config.lines_below);
    const { lines } = params;
    const blockQuotePrefixes = filterByTypesCached([ "blockQuotePrefix", "linePrefix" ]);
    for (const heading of filterByTypesCached([ "atxHeading", "setextHeading" ])) {
      const { startLine, endLine } = heading;
      const line = lines[startLine - 1].trim();

      // Check lines above
      const linesAbove = getLinesAbove(heading);
      if (linesAbove >= 0) {
        let actualAbove = 0;
        for (
          let i = 0;
          (i < linesAbove) && isBlankLine(lines[startLine - 2 - i]);
          i++
        ) {
          actualAbove++;
        }
        addErrorDetailIf(
          onError,
          startLine,
          linesAbove,
          actualAbove,
          "Above",
          line,
          undefined,
          {
            "insertText": getBlockQuotePrefixText(
              blockQuotePrefixes,
              startLine - 1,
              linesAbove - actualAbove
            )
          }
        );
      }

      // Check lines below
      const linesBelow = getLinesBelow(heading);
      if (linesBelow >= 0) {
        let actualBelow = 0;
        for (
          let i = 0;
          (i < linesBelow) && isBlankLine(lines[endLine + i]);
          i++
        ) {
          actualBelow++;
        }
        addErrorDetailIf(
          onError,
          startLine,
          linesBelow,
          actualBelow,
          "Below",
          line,
          undefined,
          {
            "lineNumber": endLine + 1,
            "insertText": getBlockQuotePrefixText(
              blockQuotePrefixes,
              endLine + 1,
              linesBelow - actualBelow
            )
          }
        );
      }
    }
  }
};