import type npmRegistryFetch from 'npm-registry-fetch';
import npmConfig from '@pnpm/npm-conf';

/**
 * Utility function to load the appropriate configuration for npmRegistryFetch
 * from the .npmrc configuration chain. Essentially, this allows us to use .npmrc
 * files to configure reading from the NPM registry, which is useful when using
 * a custom registry, especially for private packages.
 *
 * This uses the @pnpm/npm-conf library for reading .npmrc files as its both
 * maintained and sane to work with.
 *
 * @param registry The NPM registry to use, if any
 */
export function getNpmRegistryConfiguration(registry?: string | null | undefined): npmRegistryFetch.Options {
  const conf = npmConfig();

  if (!conf) {
    return {};
  }

  if (conf.warnings.length >= 1) {
    throw new Error(`Warnings while loading .npmrc:\n  ${conf.warnings.join('\n  ')}`);
  }

  if (!conf.config) {
    return {};
  }

  // the returned config object uses getters with no list of keys
  // so to convert this to a "normal" object, we combine all the settings
  // found; note this relies on the internal structure of the config
  // object and may not be stable
  const configuration: npmRegistryFetch.Options = Object.assign({}, ...(conf.config.list.slice().reverse() ?? []));

  if (configuration.__source__) {
    delete configuration.__source__;
  }

  if ('strict-ssl' in configuration) {
    configuration.strictSSL = configuration['strict-ssl'];
    delete configuration['strict-ssl'];
  }

  if (registry) {
    configuration.registry = registry;
  }

  return configuration;
}