feat: Add JS experiment client

clients/js/src/index.ts

@@ -1,7 +1,7 @@
 import * as jsonLogic from 'json-logic-js';
 import { deepMerge } from './utils/deepMerge';
 import { compareSemanticIsGreater } from './utils/operations'
-import { IObject, Dimension } from './types'
+import { IObject, Dimension, Experiments, Variant, VariantType, Variants } from './types'
 
 type DataFromCacApi = {
     contexts: Array<Dimension>;
@@ -39,3 +39,55 @@ export class CacReader {
         return deepMerge(targetConfig, ...requiredOverrides);
     }
 }
+
+export class ExperimentReader {
+    experiments: Experiments;
+
+    constructor(experiments: Experiments) {
+        this.experiments = experiments;
+    }
+
+    public getApplicableVariant(data: IObject, toss: number): Array<String> {
+        if (!Number.isInteger(toss)) {
+            throw new Error("Invalid toss, valid range: -1 to 100");
+        }
+        const experiments = this.getSatisfiedExperiments(data);
+        const variants = [];
+        for (const exp of experiments) {
+            const v = this.decideVariant(exp.traffic_percentage, exp.variants, toss);
+            if (v) {
+                variants.push(v.id)
+            }
+        }
+        return variants;
+    };
+
+    getSatisfiedExperiments(data: IObject): Experiments {
+        return this.experiments.filter(exp => jsonLogic.apply(exp.context, data));
+    };
+
+    // decide which variant to return among all applicable experiments
+    decideVariant(
+        traffic: number,
+        applicable_variants: Variants,
+        toss: number,
+    ): Variant | undefined {
+        if (!Number.isInteger(traffic) || !Number.isInteger(toss)) {
+            return undefined;
+        }
+        if (toss < 0) {
+            for (const variant of applicable_variants) {
+                if (variant.variant_type == VariantType.EXPERIMENTAL) {
+                    return variant;
+                }
+            }
+        }
+        const variant_count = applicable_variants.length;
+        const range = traffic * variant_count;
+        if (toss >= range) {
+            return undefined;
+        }
+        const index = Math.floor(toss / traffic);
+        return applicable_variants[index];
+    }
+}

clients/js/src/types.ts

@@ -13,4 +13,34 @@ export type DimensionConfig = {
 
 export type IIsObject = {
     (item: any): boolean;
-}
+}
+
+export enum VariantType {
+    CONTROL = "CONTROL",
+    EXPERIMENTAL = "EXPERIMENTAL",
+}
+
+export type Variant = {
+    id: String,
+    overrides: Object,
+    variant_type: VariantType,
+}
+
+export type Variants = Array<Variant>;
+
+export enum ExperimentStatusType {
+    CREATED = "CREATED",
+    INPROGRESS = "INPROGRESS",
+    CONCLUDED = "CONCLUDED",
+}
+
+export type Experiment = {
+    variants: Variants,
+    name: String,
+    id: String,
+    traffic_percentage: number,
+    context: Object,
+    status: ExperimentStatusType,
+}
+
+export type Experiments = Array<Experiment>;