index.ts

import { getTreatment, shouldApplyRollout } from './engineUtils';
import { thenable } from '../../utils/promise/thenable';
import { NOT_IN_SPLIT } from '../../utils/labels';
import { MaybeThenable } from '../../dtos/types';
import { IEvaluation, IEvaluator, ISplitEvaluator } from '../types';
import SplitIO from '../../../types/splitio';
import { ILogger } from '../../logger/types';

// Build Evaluation object if and only if matchingResult is true
function match(log: ILogger, matchingResult: boolean, bucketingKey: string | undefined, seed?: number, treatments?: { getTreatmentFor: (x: number) => string }, label?: string): IEvaluation | boolean | undefined {
  if (matchingResult) {
    return treatments ? // Feature flag
      {
        treatment: getTreatment(log, bucketingKey as string, seed, treatments),
        label: label!
      } : // Rule-based segment
      true;
  }

  // else we should notify the engine to continue evaluating
  return undefined;
}

// Condition factory
export function conditionContext(log: ILogger, matcherEvaluator: (key: SplitIO.SplitKeyObject, attributes?: SplitIO.Attributes, splitEvaluator?: ISplitEvaluator) => MaybeThenable<boolean>, treatments?: { getTreatmentFor: (x: number) => string }, label?: string, conditionType?: 'ROLLOUT' | 'WHITELIST'): IEvaluator {

  return function conditionEvaluator(key?: SplitIO.SplitKeyObject, seed?: number, trafficAllocation?: number, trafficAllocationSeed?: number, attributes?: SplitIO.Attributes, splitEvaluator?: ISplitEvaluator) {

    // Whitelisting has more priority than traffic allocation, so we don't apply this filtering to those conditions.
    if (!key || (conditionType === 'ROLLOUT' && !shouldApplyRollout(trafficAllocation!, key.bucketingKey, trafficAllocationSeed!))) {
      return {
        treatment: undefined, // treatment value is assigned later
        label: NOT_IN_SPLIT
      };
    }

    // matcherEvaluator could be Async, this relays on matchers return value, so we need
    // to verify for thenable before play with the result.
    // Also, we pass splitEvaluator function in case we have a matcher that needs to evaluate another split,
    // as well as the entire key object for the same reason.
    const matches = matcherEvaluator(key, attributes, splitEvaluator);

    if (thenable(matches)) {
      return matches.then(result => match(log, result, key.bucketingKey, seed, treatments, label));
    }

    return match(log, matches, key.bucketingKey, seed, treatments, label);
  };

}