import { readFileSync } from 'node:fs';
import { THREADS } from '../../src/constants/threads.ts';

export interface ThreadsConfig {
  accessToken: string;
  siteUrl: string;
  stateDir: string;
  imageDir: string;
  imageBaseUrl: string;
}

export function loadThreadsConfig(path: string | URL = new URL('../../.env.threads.json', import.meta.url), optional = false): ThreadsConfig {
  const defaults: ThreadsConfig = {
    accessToken: '', siteUrl: THREADS.siteUrl, stateDir: 'data/threads',
    imageDir: 'dist/threads-captures', imageBaseUrl: `${THREADS.siteUrl}/threads-captures/`,
  };
  let contents: string;
  try { contents = readFileSync(path, 'utf8'); }
  catch (error) {
    if (optional && (error as NodeJS.ErrnoException).code === 'ENOENT') return defaults;
    throw new Error('Cannot read .env.threads.json; copy .env.threads.sample.json and configure it.');
  }
  let value: unknown;
  try { value = JSON.parse(contents); }
  catch { throw new Error('Invalid JSON in .env.threads.json'); }
  if (!value || typeof value !== 'object' || Array.isArray(value)) throw new Error('Invalid .env.threads.json: expected an object');
  const config = { ...defaults, ...value } as ThreadsConfig;
  for (const field of Object.keys(defaults) as (keyof ThreadsConfig)[]) {
    if (typeof config[field] !== 'string' || (field !== 'accessToken' && !config[field].trim())) {
      throw new Error(`Invalid .env.threads.json field: ${field}`);
    }
  }
  for (const field of ['siteUrl', 'imageBaseUrl'] as const) {
    try {
      if (!['http:', 'https:'].includes(new URL(config[field]).protocol)) throw new Error();
    } catch { throw new Error(`Invalid .env.threads.json field: ${field}`); }
  }
  return config;
}