PLU-591: [show-multiple-rows-2]: modified step regex and add table variable marker

packages/backend/src/helpers/compute-parameters.ts

@@ -6,13 +6,33 @@ import {
   computeForEachParameters,
   ForEachContext,
 } from '@/helpers/compute-for-each-parameters'
+import { hexDecode } from '@/helpers/hex-encoding'
 import logger from '@/helpers/logger'
 import ExecutionStep from '@/models/execution-step'
 
 import Step from '../models/step'
 
+/**
+ * Regex to match step variables with optional hex-encoded modifier
+ *
+ * Format: {{step.<uuid>.<path>}} or {{step.<uuid>.<path>|<hexModifier>}}
+ *
+ * Examples:
+ * - {{step.abc-123-def.data}}
+ * - {{step.abc-123-def.data|7461626c653a636f6c31}} (with hex-encoded "table:col1")
+ */
 const variableRegExp =
-  /({{step\.[\da-f]{8}-(?:[\da-f]{4}-){3}[\da-f]{12}(?:\.[\da-zA-Z-_ ]+)+}})/g
+  /({{step\.[\da-f]{8}-(?:[\da-f]{4}-){3}[\da-f]{12}(?:\.[\da-zA-Z-_ ]+)+(?:\|[a-fA-F0-9]+)?}})/g
+
+/**
+ * Marker object returned when a table modifier is detected.
+ * This is processed by the action's preprocessVariable function.
+ */
+export interface TableVariableMarker {
+  __type: 'table'
+  data: unknown
+  selectedColumnIds: string[]
+}
 
 function findAndSubstituteVariables(
   // i.e. the `key` corresponding to this variable's form field in defineAction
@@ -76,7 +96,14 @@ function findAndSubstituteVariables(
     const isVariable = part.match(variableRegExp)
     if (isVariable) {
       const stepIdAndKeyPath = part.replace(/{{step.|}}/g, '') as string
-      const [stepId, ...keyPaths] = stepIdAndKeyPath.split('.')
+
+      // Check for hex-encoded modifier (e.g., "|7461626c653a636f6c31")
+      const modifierMatch = stepIdAndKeyPath.match(/\|([a-fA-F0-9]+)$/)
+      const cleanStepIdAndKeyPath = modifierMatch
+        ? stepIdAndKeyPath.replace(/\|[a-fA-F0-9]+$/, '')
+        : stepIdAndKeyPath
+
+      const [stepId, ...keyPaths] = cleanStepIdAndKeyPath.split('.')
       const executionStep = executionSteps.find((executionStep) => {
         return executionStep.stepId === stepId
       })
@@ -98,6 +125,56 @@ function findAndSubstituteVariables(
         })
       }
 
+      // Handle hex-encoded modifier (e.g., table:col1,col2)
+      if (modifierMatch) {
+        try {
+          const decodedModifier = hexDecode(modifierMatch[1])
+          const [modifierType, ...modifierArgs] = decodedModifier.split(':')
+
+          if (modifierType === 'table') {
+            // Parse column IDs from modifier args (e.g., "col1,col2,col3")
+            const selectedColumnIds = modifierArgs[0]
+              ? modifierArgs[0].split(',').filter(Boolean)
+              : []
+
+            // Handle FormSG tables where dataValue is a stringified JSON
+            let tableData = dataValue
+            if (typeof dataValue === 'string') {
+              try {
+                tableData = JSON.parse(dataValue)
+              } catch {
+                // Not valid JSON, keep as-is (will fail validation in formatTable)
+              }
+            }
+
+            // Return marker object for preprocessVariable to handle
+            const marker: TableVariableMarker = {
+              __type: 'table',
+              data: tableData,
+              selectedColumnIds,
+            }
+
+            if (preprocessVariable) {
+              return preprocessVariable(parameterKey, marker)
+            }
+
+            // If no preprocessVariable, return original variable string
+            // to avoid [object Object] in string context
+            return part
+          }
+
+          // Unknown modifier type - return original variable string
+          return part
+        } catch {
+          // Invalid hex encoding - return original variable string
+          logger.warn('Invalid hex-encoded modifier in variable', {
+            event: 'invalid-variable-modifier',
+            modifier: modifierMatch[1],
+          })
+          return part
+        }
+      }
+
       // NOTE: dataValue could be an array if it is not processed on variables.ts
       // which is the case for formSG checkbox only, this is to deal with forEach next time
       if (preprocessVariable) {