// This file only applies to use of experiments through https://gitlab.com/gitlab-org/ruby/gems/gitlab-experiment
import { get, mapValues, pick } from 'lodash';
import { DEFAULT_VARIANT, CANDIDATE_VARIANT, TRACKING_CONTEXT_SCHEMA } from './constants';

function getExperimentsData() {
  // Pull from deprecated window.gon.experiment
  const experimentsFromGon = get(window, ['gon', 'experiment'], {});
  // Pull from preferred window.gl.experiments
  const experimentsFromGl = get(window, ['gl', 'experiments'], {});

  // Bandaid to allow-list only the properties which the current gitlab_experiment
  // context schema suppports, since we most often use this data to create that
  // Snowplow context.
  // See TRACKING_CONTEXT_SCHEMA for current version (1-0-0)
  // https://gitlab.com/gitlab-org/iglu/-/blob/master/public/schemas/com.gitlab/gitlab_experiment/jsonschema/1-0-0
  return mapValues({ ...experimentsFromGon, ...experimentsFromGl }, (xp) => {
    return pick(xp, ['experiment', 'key', 'variant', 'migration_keys']);
  });
}

function createGitlabExperimentContext(experimentData) {
  return { schema: TRACKING_CONTEXT_SCHEMA, data: experimentData };
}

export function getExperimentData(experimentName) {
  return getExperimentsData()[experimentName];
}

export function getAllExperimentContexts() {
  return Object.values(getExperimentsData()).map(createGitlabExperimentContext);
}

export function isExperimentVariant(experimentName, variantName = CANDIDATE_VARIANT) {
  return getExperimentData(experimentName)?.variant === variantName;
}

export function getExperimentVariant(experimentName) {
  return getExperimentData(experimentName)?.variant || DEFAULT_VARIANT;
}

export function experiment(experimentName, { use, control, candidate, ...variants }) {
  const variant = getExperimentVariant(experimentName);

  switch (variant) {
    case DEFAULT_VARIANT:
      return (use || control).call();
    case CANDIDATE_VARIANT:
      return (variants.try || candidate).call();
    default:
      return variants[variant].call();
  }
}