/**
 * Shared frontmatter utilities — used by read-frontmatter, write-frontmatter,
 * card-crud, preview-deck, and generate-card-deck.
 */

import yaml from "js-yaml";
import type { DeckFrontmatter } from "./read-frontmatter.js";

/**
 * Parse YAML frontmatter from a CSV file's raw content.
 * Expects `---\n...\n---\n` delimited frontmatter at the top of the file.
 */
export function parseFrontMatter(content: string): {
  frontmatter?: DeckFrontmatter;
  csvContent: string;
} {
  const parts = content.trim().split(/(?:^|\n)---\s*\n/g);

  if (parts.length !== 3 || parts[0] !== "") {
    return { csvContent: content };
  }

  try {
    const frontmatterStr = parts[1].trim();
    const frontmatter = yaml.load(frontmatterStr) as
      | DeckFrontmatter
      | undefined;
    const csvContent = parts.slice(2).join("---\n").trimStart();
    return { frontmatter, csvContent };
  } catch (error) {
    console.warn("Failed to parse front matter:", error);
    return { csvContent: content };
  }
}

/**
 * Serialize a DeckFrontmatter object to YAML frontmatter string.
 */
export function serializeFrontMatter(frontmatter: DeckFrontmatter): string {
  const yamlStr = yaml.dump(frontmatter, {
    indent: 2,
    lineWidth: -1,
    noRefs: true,
    quotingType: '"',
    forceQuotes: false,
  });
  return `---\n${yamlStr}---\n`;
}