/**
 * GitHub API Service
 * Fetches files from a public GitHub repository directly from the browser.
 * No proxy or token required for public repos.
 */

const GITHUB_API  = 'https://api.github.com';
const GITHUB_RAW  = 'https://raw.githubusercontent.com';

/**
 * List markdown/text files in a GitHub repository folder.
 * @param {string} owner  - e.g. "respellion"
 * @param {string} repo   - e.g. "employee-handbook"
 * @param {string} folder - e.g. "docs" or "" for root
 * @param {string} branch - e.g. "main"
 * @returns {Promise<Array<{name, sha, path}>>}
 */
export async function getRepoFolder(owner, repo, folder = '', branch = 'main') {
  // Use the GitHub Git Trees API to fetch all files recursively in one request
  const url = `${GITHUB_API}/repos/${owner}/${repo}/git/trees/${branch}?recursive=1`;

  const res = await fetch(url, {
    headers: { Accept: 'application/vnd.github+json' },
  });

  if (!res.ok) {
    const err = await res.json().catch(() => ({}));
    throw new Error(`GitHub API ${res.status}: ${err.message || 'Could not list folder'}`);
  }

  const data = await res.json();
  
  // If folder is 'docs', we only want paths starting with 'docs/'
  const folderPrefix = folder ? folder.replace(/^\/|\/$/g, '') + '/' : '';

  // Return only files (blobs) that match the folder prefix and file extensions
  return data.tree
    .filter(item => 
      item.type === 'blob' && 
      item.path.startsWith(folderPrefix) && 
      (item.path.endsWith('.md') || item.path.endsWith('.txt'))
    )
    .map(item => ({
      name: item.path.split('/').pop(),
      path: item.path,
      sha: item.sha
    }));
}

/**
 * Fetch the raw text content of a file.
 * Uses raw.githubusercontent.com — no rate limits for public content.
 * @param {string} owner
 * @param {string} repo
 * @param {string} path   - e.g. "docs/ROLES.md"
 * @param {string} branch
 * @returns {Promise<string>}
 */
export async function getFileContent(owner, repo, path, branch = 'main') {
  const url = `${GITHUB_RAW}/${owner}/${repo}/${branch}/${path}`;
  const res = await fetch(url);

  if (!res.ok) {
    throw new Error(`Could not fetch "${path}" from GitHub (${res.status})`);
  }

  return res.text();
}

/**
 * Parse a GitHub tree URL into its parts.
 * e.g. "https://github.com/respellion/employee-handbook/tree/main/docs"
 * → { owner: 'respellion', repo: 'employee-handbook', branch: 'main', folder: 'docs' }
 */
export function parseGitHubUrl(url) {
  try {
    const match = url.match(/github\.com\/([^/]+)\/([^/]+)(?:\/tree\/([^/]+)(?:\/(.+))?)?/);
    if (!match) return null;
    return {
      owner:  match[1],
      repo:   match[2],
      branch: match[3] || 'main',
      folder: match[4] || '',
    };
  } catch {
    return null;
  }
}