New source found from dndbeyond.com

ddb_main/packages/rules-engine/es/engine/Prerequisite/utils.js

@@ -1,3 +1,4 @@
+import sortBy from 'lodash/sortBy';
 import { AbilityAccessors } from '../Ability';
 import { FormatUtils } from '../Format';
 import { getEntityId, getFriendlySubtypeName, getPrerequisites, getSubType, getType, getValue, getShouldExclude, } from './accessors';
@@ -207,3 +208,46 @@ export function getPrerequisiteGroupingFailures(prerequisiteGrouping, prerequisi
     }
     return groupingFailures.filter((group) => group.length);
 }
+// Creates a string that summarizes the prerequisite failures for feats and multiclassing
+export function getPrerequisiteFailuresText(prereqFailures) {
+    //get all the prerequisite failures, sorted so that if every group failure is a missing prereq, they come first
+    const failures = sortBy(prereqFailures, (failureGroup) => (failureGroup.every((f) => !f.shouldExclude) ? 0 : 1));
+    // Create an intro string for the summary
+    let intro = '';
+    // Check if all failures are either missing or prohibited
+    const hasOnlyMissingFailures = failures.every((failureGroup) => failureGroup.every((f) => !f.shouldExclude));
+    const hasOnlyProhibitedFailures = failures.every((failureGroup) => failureGroup.every((f) => f.shouldExclude));
+    // Determine the intro text based on the type of failures
+    if (hasOnlyMissingFailures) {
+        intro = 'Missing: ';
+    }
+    else if (hasOnlyProhibitedFailures) {
+        intro = 'Prohibited by: ';
+    }
+    else {
+        intro = 'Requires: ';
+    }
+    // Each failure is sorted so that prohibited failures come last, and then combined into a single string
+    const combinedStrings = failures
+        .map((failure) => sortBy(failure, (f) => (f.shouldExclude ? 1 : 0))
+        .map((failureAnd) => {
+        if (failureAnd.shouldExclude && !hasOnlyProhibitedFailures && !hasOnlyMissingFailures) {
+            return `Prohibited by: ${failureAnd.data.requiredDescription}`;
+        }
+        return `${failureAnd.data.requiredDescription}`;
+    })
+        .reduce((acc, desc, idx) => {
+        let connector = '';
+        if (idx < failure.length - 2) {
+            connector = ', ';
+        }
+        else if (idx < failure.length - 1) {
+            connector = ' and ';
+        }
+        acc += `${desc}${connector}`;
+        return acc;
+    }, ''))
+        .join(' or ');
+    // return the intro text followed by the combined strings
+    return `${intro}${combinedStrings}`;
+}