(
  function(global) {
    // Current interface is these three methods.
    const requiredMethods = [
      'init',
      'serviceRecentSummarySeries',
      'serviceRecentSummaryStats',
      'upstreamRecentSummaryStats',
      'downstreamRecentSummaryStats',
    ];

    // This is a bit gross but we want to support simple extensibility by
    // including JS in the browser without forcing operators to setup a whole
    // transpiling stack. So for now we use a window global as a thin registry for
    // these providers.
    class Consul {
      constructor() {
        this.registry = {};
        this.providers = {};
      }

      registerMetricsProvider(name, provider) {
        // Basic check that it matches the type we expect
        for (var m of requiredMethods) {
          if (typeof provider[m] !== 'function') {
            throw new Error(`Can't register metrics provider '${name}': missing ${m} method.`);
          }
        }
        this.registry[name] = provider;
      }

      getMetricsProvider(name, options) {
        if (!(name in this.registry)) {
          throw new Error(`Metrics Provider '${name}' is not registered.`);
        }
        if (name in this.providers) {
          return this.providers[name];
        }

        this.providers[name] = Object.create(this.registry[name]);
        this.providers[name].init(options);

        return this.providers[name];
      }
    }

    global.consul = new Consul();

  }
)(window);