import createLoaders from './loaders.js';
import createDebug from 'debug';

const debug = createDebug('graphbrainz:context');

export function extendContext(extension, context, options) {
  if (extension.extendContext) {
    if (typeof extension.extendContext === 'function') {
      debug(
        `Extending context via a function from the “${extension.name}” extension.`
      );
      context = extension.extendContext(context, options);
    } else {
      throw new Error(
        `Extension “${extension.name}” contains an invalid \`extendContext\` ` +
          `value: ${extension.extendContext}`
      );
    }
  }
  return context;
}

export function createContext(options = {}) {
  const { client, extensions = [] } = options;
  const loaders = createLoaders(client);
  let context = { client, loaders };
  return extensions.reduce((context, extension) => {
    return extendContext(extension, context, options);
  }, context);
}