command-validator

import { load as parseYaml } from "js-yaml";
import type { CommandFile } from "./types.js";

const FRONTMATTER_DELIMITER = "---";

export function parseCommandFile(
  filePath: string,
  content: string,
): CommandFile {
  const lines = content.split(/\r?\n/);
  const lineCount = lines.length;
  const filename =
    filePath.split(/[\\/]/).pop()?.replace(/\.md$/i, "") || "unknown";

  // Must start with '---'
  const trimmedLeft = content.trimStart();
  const leadingWhitespace = content.length - trimmedLeft.length;
  const firstLineEnd = content.indexOf("\n");
  const firstLine =
    firstLineEnd === -1 ? content : content.slice(0, firstLineEnd);

  if (leadingWhitespace > 0 || firstLine.trim() !== FRONTMATTER_DELIMITER) {
    return {
      path: filePath,
      filename,
      raw: content,
      frontmatter: null,
      body: content,
      parseError:
        'File must start with "---" on the first line (no leading whitespace)',
      lineCount,
    };
  }

  // Find the closing '---'
  const afterFirstDelim = content.indexOf("\n", firstLineEnd + 1);
  if (afterFirstDelim === -1) {
    return {
      path: filePath,
      filename,
      raw: content,
      frontmatter: null,
      body: "",
      parseError: 'Unclosed frontmatter: expected closing "---"',
      lineCount,
    };
  }

  const closingDelimIndex = content.indexOf(
    `\n${FRONTMATTER_DELIMITER}`,
    afterFirstDelim,
  );

  if (closingDelimIndex === -1) {
    return {
      path: filePath,
      filename,
      raw: content,
      frontmatter: null,
      body: "",
      parseError: 'Unclosed frontmatter: expected closing "---"',
      lineCount,
    };
  }

  // Extract frontmatter YAML (between the two --- delimiters)
  const yamlStart = firstLineEnd + 1;
  const yamlEnd = closingDelimIndex;
  const yamlContent = content.slice(yamlStart, yamlEnd);

  // Body is everything after the closing --- and its trailing newline
  let bodyStart = closingDelimIndex + FRONTMATTER_DELIMITER.length + 1;
  // Skip the newline after closing ---
  if (bodyStart < content.length && content[bodyStart] === "\n") {
    bodyStart++;
  } else if (bodyStart < content.length && content[bodyStart] === "\r") {
    bodyStart += 2;
  }
  const body = content.slice(bodyStart);

  // Parse YAML
  let frontmatter: Record<string, unknown> | null = null;
  let parseError: string | undefined;

  if (yamlContent.trim().length === 0) {
    parseError = "Empty frontmatter block";
  } else {
    try {
      const parsed = parseYaml(yamlContent);
      if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) {
        frontmatter = parsed as Record<string, unknown>;
      } else if (parsed === undefined || parsed === null) {
        frontmatter = {};
      } else {
        parseError =
          "Frontmatter must be a YAML mapping (key-value pairs), got: " +
          typeof parsed;
      }
    } catch (err: unknown) {
      const msg = err instanceof Error ? err.message : String(err);
      parseError = `YAML parse error: ${msg}`;
    }
  }

  return {
    path: filePath,
    filename,
    raw: content,
    frontmatter,
    body,
    parseError,
    lineCount,
  };
}