feat: obfuscated precomputed assignments (#164)

* make getMD5HashWithSalt

* add tests

* Export saltedHasher

* Fix tests

* Alter test to use obfuscated file

* Change branch name for test data

* Get all the tests to pass

* Make more obvious that the salt was decoded

* Switch to using appendBinary for the salt

* Clean up

* Include salt in convenience method for setting precomputed flag store

* Add a helper to convert context attributes to subject attributes

* Change default to isObfuscated since we expect the precomputed api to mainly be used by clients

* v4.7.1-alpha.0

* Revert "v4.7.1-alpha.0"

This reverts commit b81175f.

* v4.7.0-alpha.0

* Switch to initializing the client with an options object

* Make response data not optional

* precomputedFlag variable casing

* update hashing

* fix lint

* handoff and address comments

* bump version

* Inf is a numeric attribute too

* Remove unnecessary public methods

* Remove more unnecessary functions

* Add to exported interfaces

* Update src/interfaces.ts

Co-authored-by: Oleksii Shmalko <[email protected]>

* Update src/attributes.ts attributes is ContextAttributes

Co-authored-by: Oleksii Shmalko <[email protected]>

* Remove redundant 'subjectAttributes as ContextAttributes'

* Also print error if store is missing salt

* Remove buildContextAttributes

* v4.8.0-alpha.0

---------

Co-authored-by: Ty Potter <[email protected]>
Co-authored-by: Leo Romanovsky <[email protected]>
Co-authored-by: Oleksii Shmalko <[email protected]>

Author: 4 people

Makefile

@@ -36,6 +36,7 @@ test-data:
 	mkdir -p $(tempDir)
 	git clone -b ${branchName} --depth 1 --single-branch ${githubRepoLink} ${gitDataDir}
 	cp -r ${gitDataDir}ufc ${testDataDir}
+	cp -r ${gitDataDir}configuration-wire ${testDataDir}
 	rm -rf ${tempDir}
 
 ## prepare

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@eppo/js-client-sdk-common",
-  "version": "4.7.1",
+  "version": "4.8.0-alpha.0",
   "description": "Common library for Eppo JavaScript SDKs (web, react native, and node)",
   "main": "dist/index.js",
   "files": [

src/attributes.ts

@@ -0,0 +1,76 @@
+import { Attributes, BanditActions, BanditSubjectAttributes, ContextAttributes } from './types';
+
+export function isInstanceOfContextualAttributes(
+  attributes: unknown,
+): attributes is ContextAttributes {
+  return Boolean(
+    typeof attributes === 'object' &&
+      attributes && // exclude null
+      'numericAttributes' in attributes &&
+      'categoricalAttributes' in attributes,
+  );
+}
+
+export function ensureNonContextualSubjectAttributes(
+  subjectAttributes: BanditSubjectAttributes,
+): Attributes {
+  let result: Attributes;
+  if (isInstanceOfContextualAttributes(subjectAttributes)) {
+    const contextualSubjectAttributes = subjectAttributes;
+    result = {
+      ...contextualSubjectAttributes.numericAttributes,
+      ...contextualSubjectAttributes.categoricalAttributes,
+    };
+  } else {
+    // Attributes are non-contextual
+    result = subjectAttributes as Attributes;
+  }
+  return result;
+}
+
+export function ensureContextualSubjectAttributes(
+  subjectAttributes: BanditSubjectAttributes,
+): ContextAttributes {
+  if (isInstanceOfContextualAttributes(subjectAttributes)) {
+    return subjectAttributes;
+  } else {
+    return deduceAttributeContext(subjectAttributes as Attributes);
+  }
+}
+
+export function deduceAttributeContext(attributes: Attributes): ContextAttributes {
+  const contextualAttributes: ContextAttributes = {
+    numericAttributes: {},
+    categoricalAttributes: {},
+  };
+  Object.entries(attributes).forEach(([attribute, value]) => {
+    const isNumeric = typeof value === 'number';
+    if (isNumeric) {
+      contextualAttributes.numericAttributes[attribute] = value;
+    } else {
+      contextualAttributes.categoricalAttributes[attribute] = value;
+    }
+  });
+  return contextualAttributes;
+}
+
+export function ensureActionsWithContextualAttributes(
+  actions: BanditActions,
+): Record<string, ContextAttributes> {
+  let result: Record<string, ContextAttributes> = {};
+  if (Array.isArray(actions)) {
+    // no context
+    actions.forEach((action) => {
+      result[action] = { numericAttributes: {}, categoricalAttributes: {} };
+    });
+  } else if (!Object.values(actions).every(isInstanceOfContextualAttributes)) {
+    // Actions have non-contextual attributes; bucket based on number or not
+    Object.entries(actions).forEach(([action, attributes]) => {
+      result[action] = deduceAttributeContext(attributes);
+    });
+  } else {
+    // Actions already have contextual attributes
+    result = actions as Record<string, ContextAttributes>;
+  }
+  return result;
+}

src/client/eppo-client.ts

@@ -3,6 +3,11 @@ import { v4 as randomUUID } from 'uuid';
 import ApiEndpoints from '../api-endpoints';
 import { logger } from '../application-logger';
 import { IAssignmentEvent, IAssignmentLogger } from '../assignment-logger';
+import {
+  ensureActionsWithContextualAttributes,
+  ensureContextualSubjectAttributes,
+  ensureNonContextualSubjectAttributes,
+} from '../attributes';
 import { BanditEvaluator } from '../bandit-evaluator';
 import { IBanditEvent, IBanditLogger } from '../bandit-logger';
 import { AssignmentCache } from '../cache/abstract-assignment-cache';
@@ -535,9 +540,8 @@ export default class EppoClient {
     if (banditKey) {
       const banditParameters = this.banditModelConfigurationStore?.get(banditKey);
       if (banditParameters) {
-        const contextualSubjectAttributes =
-          this.ensureContextualSubjectAttributes(subjectAttributes);
-        const actionsWithContextualAttributes = this.ensureActionsWithContextualAttributes(actions);
+        const contextualSubjectAttributes = ensureContextualSubjectAttributes(subjectAttributes);
+        const actionsWithContextualAttributes = ensureActionsWithContextualAttributes(actions);
 
         result = this.banditEvaluator.evaluateBestBanditAction(
           contextualSubjectAttributes,
@@ -571,7 +575,7 @@ export default class EppoClient {
       // Get the assigned variation for the flag with a possible bandit
       // Note for getting assignments, we don't care about context
       const nonContextualSubjectAttributes =
-        this.ensureNonContextualSubjectAttributes(subjectAttributes);
+        ensureNonContextualSubjectAttributes(subjectAttributes);
       const { variation: assignedVariation, evaluationDetails: assignmentEvaluationDetails } =
         this.getStringAssignmentDetails(
           flagKey,
@@ -683,8 +687,8 @@ export default class EppoClient {
     }
 
     const banditModelData = banditParameters.modelData;
-    const contextualSubjectAttributes = this.ensureContextualSubjectAttributes(subjectAttributes);
-    const actionsWithContextualAttributes = this.ensureActionsWithContextualAttributes(actions);
+    const contextualSubjectAttributes = ensureContextualSubjectAttributes(subjectAttributes);
+    const actionsWithContextualAttributes = ensureActionsWithContextualAttributes(actions);
     const banditEvaluation = this.banditEvaluator.evaluateBandit(
       flagKey,
       subjectKey,
@@ -715,79 +719,6 @@ export default class EppoClient {
     return action;
   }
 
-  private ensureNonContextualSubjectAttributes(
-    subjectAttributes: BanditSubjectAttributes,
-  ): Attributes {
-    let result: Attributes;
-    if (this.isInstanceOfContextualAttributes(subjectAttributes)) {
-      const contextualSubjectAttributes = subjectAttributes as ContextAttributes;
-      result = {
-        ...contextualSubjectAttributes.numericAttributes,
-        ...contextualSubjectAttributes.categoricalAttributes,
-      };
-    } else {
-      // Attributes are non-contextual
-      result = subjectAttributes as Attributes;
-    }
-    return result;
-  }
-
-  private ensureContextualSubjectAttributes(
-    subjectAttributes: BanditSubjectAttributes,
-  ): ContextAttributes {
-    if (this.isInstanceOfContextualAttributes(subjectAttributes)) {
-      return subjectAttributes as ContextAttributes;
-    } else {
-      return this.deduceAttributeContext(subjectAttributes as Attributes);
-    }
-  }
-
-  private ensureActionsWithContextualAttributes(
-    actions: BanditActions,
-  ): Record<string, ContextAttributes> {
-    let result: Record<string, ContextAttributes> = {};
-    if (Array.isArray(actions)) {
-      // no context
-      actions.forEach((action) => {
-        result[action] = { numericAttributes: {}, categoricalAttributes: {} };
-      });
-    } else if (!Object.values(actions).every(this.isInstanceOfContextualAttributes)) {
-      // Actions have non-contextual attributes; bucket based on number or not
-      Object.entries(actions).forEach(([action, attributes]) => {
-        result[action] = this.deduceAttributeContext(attributes);
-      });
-    } else {
-      // Actions already have contextual attributes
-      result = actions as Record<string, ContextAttributes>;
-    }
-    return result;
-  }
-
-  private isInstanceOfContextualAttributes(attributes: unknown): boolean {
-    return Boolean(
-      typeof attributes === 'object' &&
-        attributes && // exclude null
-        'numericAttributes' in attributes &&
-        'categoricalAttributes' in attributes,
-    );
-  }
-
-  private deduceAttributeContext(attributes: Attributes): ContextAttributes {
-    const contextualAttributes: ContextAttributes = {
-      numericAttributes: {},
-      categoricalAttributes: {},
-    };
-    Object.entries(attributes).forEach(([attribute, value]) => {
-      const isNumeric = typeof value === 'number' && isFinite(value);
-      if (isNumeric) {
-        contextualAttributes.numericAttributes[attribute] = value;
-      } else {
-        contextualAttributes.categoricalAttributes[attribute] = value as AttributeType;
-      }
-    });
-    return contextualAttributes;
-  }
-
   private logBanditAction(banditEvent: IBanditEvent): void {
     // First we check if this bandit action has been logged before
     const subjectKey = banditEvent.subject;
@@ -944,8 +875,8 @@ export default class EppoClient {
   ): string {
     const configDetails = this.getConfigDetails();
 
-    const subjectContextualAttributes = this.ensureContextualSubjectAttributes(subjectAttributes);
-    const subjectFlatAttributes = this.ensureNonContextualSubjectAttributes(subjectAttributes);
+    const subjectContextualAttributes = ensureContextualSubjectAttributes(subjectAttributes);
+    const subjectFlatAttributes = ensureNonContextualSubjectAttributes(subjectAttributes);
     const flags = this.getAllAssignments(subjectKey, subjectFlatAttributes);
 
     const precomputedConfig: IPrecomputedConfiguration = obfuscated
@@ -1095,6 +1026,7 @@ export default class EppoClient {
       configPublishedAt: this.flagConfigurationStore.getConfigPublishedAt() ?? '',
       configEnvironment: this.flagConfigurationStore.getEnvironment() ?? { name: '' },
       configFormat: this.flagConfigurationStore.getFormat() ?? '',
+      salt: this.flagConfigurationStore.salt,
     };
   }