type StackNode = { indent: number; target: Record<string, unknown> };

export function parseSimpleYamlMap(input: string): Record<string, unknown> {
  const root: Record<string, unknown> = {};
  const stack: StackNode[] = [{ indent: -1, target: root }];

  const lines = input.split(/\r?\n/);
  for (const rawLine of lines) {
    if (!rawLine.trim() || rawLine.trimStart().startsWith("#")) {
      continue;
    }

    const indent = rawLine.length - rawLine.trimStart().length;
    const line = rawLine.trim();
    const separatorIndex = line.indexOf(":");
    if (separatorIndex <= 0) {
      continue;
    }

    const key = line
      .slice(0, separatorIndex)
      .trim()
      .replace(/^['"]|['"]$/g, "");
    const rawValue = line.slice(separatorIndex + 1).trim();

    while (stack.length > 1 && indent <= stack[stack.length - 1].indent) {
      stack.pop();
    }

    const current = stack[stack.length - 1].target;

    if (!rawValue) {
      const child: Record<string, unknown> = {};
      current[key] = child;
      stack.push({ indent, target: child });
      continue;
    }

    let scalar = rawValue;
    if (
      (scalar.startsWith('"') && scalar.endsWith('"')) ||
      (scalar.startsWith("'") && scalar.endsWith("'"))
    ) {
      scalar = scalar.slice(1, -1);
    }

    current[key] = scalar;
  }

  return root;
}

export function extractFrontmatter(markdown: string): string {
  const normalized = markdown.replace(/\r\n/g, "\n");
  if (!normalized.startsWith("---\n")) {
    return "";
  }

  const end = normalized.indexOf("\n---", 4);
  if (end === -1) {
    return "";
  }

  return normalized.slice(4, end);
}