Let students waive a prerequisite for units

packages/db/src/planner-state.ts

@@ -102,6 +102,11 @@ export interface PlannerState {
    * away!!!").
    */
   credit?: PlannerCreditEntry[]
+  /**
+   * Prerequisites the student has waived, per unit. Cleared when the
+   * course or start year changes, since they belong to this course map.
+   */
+  waivers?: PlannerPrerequisiteWaiver[]
   /**
    * Campus the student is planning at, e.g. "Clayton" or "Malaysia".
    * Filters campus-scoped area-of-study options and requirement groups
@@ -120,6 +125,15 @@ export interface PlannerState {
   campus?: string
 }
 
+/**
+ * `prerequisiteCode` counts as met for `unitCode`'s prerequisites only.
+ * It earns no credit and doesn't touch any other rule or unit.
+ */
+export interface PlannerPrerequisiteWaiver {
+  unitCode: string
+  prerequisiteCode: string
+}
+
 /**
  * One piece of advanced standing. Two flavours in one shape:
  *

packages/webapp/components/planner/left-sidebar.tsx

@@ -10,6 +10,7 @@ import {
   PrinterIcon,
   Redo2Icon,
   RotateCcwIcon,
+  ShieldCheckIcon,
   Undo2Icon,
 } from "lucide-react"
 import { useCallback, useEffect, useMemo, useState } from "react"
@@ -24,16 +25,19 @@ import {
   DropdownMenuTrigger,
 } from "@/components/ui/dropdown-menu"
 import { buildCsv, downloadBlob, planFileName } from "@/lib/planner/plan-export"
+import { cn } from "@/lib/utils"
 
 import { CreditDialog } from "./credit-dialog"
 import { PlanStartControl } from "./plan-basics"
 import { usePlanner, usePlannerSync } from "./planner-context"
+import { TOUCH_HIT_ROW } from "./touch-target"
 import { useWam } from "./wam-context"
+import { WaiverDialog } from "./waiver-dialog"
 
 /**
  * Plan header above the grid: the plan's name (click to rename) and
  * its start ("Starts Semester 1, 2027") and validation status on the
- * left; undo/redo, Results, Credit and Print on the right, with
+ * left; undo/redo, Results, Credit, Waivers and Print on the right, with
  * Export to CSV and Reset under More. State-only operations
  * (no server round-trip).
  */
@@ -80,15 +84,29 @@ export function LeftSidebar() {
   const { showResults, toggleShowResults, grades } = useWam()
   const [creditOpen, setCreditOpen] = useState(false)
   const creditCount = state.credit?.length ?? 0
+  const [waiversOpen, setWaiversOpen] = useState(false)
+  const waiverCount = state.waivers?.length ?? 0
 
   const errorCount = useMemo(() => {
     let n = 0
     for (const v of validations.values()) n += v.errors.length
     return n
   }, [validations])
 
+  const validText = useMemo(
+    () =>
+      [...validations.values()].some((v) => v.reliesOnWaiver)
+        ? "Every unit meets its prereqs or has them waived, and is offered in its slot"
+        : "Every unit meets its prereqs and is offered in its slot",
+    [validations]
+  )
+
   const onReset = useCallback(() => {
-    if (!confirm("Reset the whole plan? This clears every unit you've placed."))
+    if (
+      !confirm(
+        "Reset the whole plan? This clears every unit you've placed and any waivers."
+      )
+    )
       return
     dispatch({ type: "reset" })
   }, [dispatch])
@@ -149,17 +167,14 @@ export function LeftSidebar() {
           onClick={() => {
             if (errorCount === 0) {
               toast.success("Plan validates cleanly", {
-                description:
-                  "Every unit meets its prereqs and is offered in its slot.",
+                description: `${validText}.`,
               })
               return
             }
             flashErrors()
           }}
           title={
-            errorCount === 0
-              ? "Every unit meets its prereqs and is offered in its slot"
-              : "Highlight the units with problems"
+            errorCount === 0 ? validText : "Highlight the units with problems"
           }
           className="ml-1.5 shrink-0 self-center"
         >
@@ -211,6 +226,14 @@ export function LeftSidebar() {
           onClick={() => setCreditOpen(true)}
           count={creditCount}
         />
+        <ToolbarButton
+          icon={<ShieldCheckIcon />}
+          label="Waivers"
+          title="Prerequisites waived on this plan"
+          onClick={() => setWaiversOpen(true)}
+          count={waiverCount}
+          className={TOUCH_HIT_ROW}
+        />
         <ToolbarButton
           icon={<PrinterIcon />}
           label="Print"
@@ -248,6 +271,7 @@ export function LeftSidebar() {
       </div>
 
       <CreditDialog open={creditOpen} onOpenChangeAction={setCreditOpen} />
+      <WaiverDialog open={waiversOpen} onOpenChangeAction={setWaiversOpen} />
     </div>
   )
 }
@@ -262,12 +286,14 @@ function ToolbarButton({
   title,
   onClick,
   count = 0,
+  className,
 }: {
   icon: React.ReactNode
   label: string
   title: string
   onClick: () => void
   count?: number
+  className?: string
 }) {
   return (
     <Button
@@ -276,7 +302,7 @@ function ToolbarButton({
       onClick={onClick}
       title={title}
       aria-label={count > 0 ? `${label} (${count})` : label}
-      className="text-muted-foreground"
+      className={cn("text-muted-foreground", className)}
     >
       {icon}
       <span className="hidden lg:inline">{label}</span>

packages/webapp/components/planner/plan-basics.tsx

@@ -41,18 +41,20 @@ import { usePlanner } from "./planner-context"
  * When the student starts: intake (Semester 1 or 2) and starting year.
  * One set of controls, used by the first-run setup card and by the
  * "Starts …" control beside the plan title. Changing the year on a plan
- * with units asks first, because each year has its own handbook.
+ * with units or waivers asks first, because each year has its own handbook.
  */
 function StartFields() {
   const { state, dispatch, availableYears, switchYear } = usePlanner()
   const [pendingYear, setPendingYear] = useState<string | null>(null)
   const hasUnits = state.years.some((y) =>
     y.slots.some((s) => s.unitCodes.length > 0)
   )
+  const hasWaivers = (state.waivers?.length ?? 0) > 0
 
   function chooseYear(y: string) {
     if (y === state.courseYear) return
-    if (hasUnits) setPendingYear(y)
+
+    if (hasUnits || hasWaivers) setPendingYear(y)
     else void switchYear(y)
   }
 
@@ -68,8 +70,13 @@ function StartFields() {
           <AlertDialogHeader>
             <AlertDialogTitle>Start in {pendingYear}?</AlertDialogTitle>
             <AlertDialogDescription>
-              Each starting year has its own handbook, so changing it clears the
-              units in your plan. You can undo this.
+              Each starting year has its own handbook, so changing it clears the{" "}
+              {hasUnits && hasWaivers
+                ? "units and waivers"
+                : hasWaivers
+                  ? "waivers"
+                  : "units"}{" "}
+              in your plan. You can undo this.
             </AlertDialogDescription>
           </AlertDialogHeader>
           <AlertDialogFooter>

packages/webapp/components/planner/planner-context.tsx

@@ -45,6 +45,7 @@ import {
   defaultState,
   historyReducer,
   initialHistory,
+  withKnownYear,
   type PlannerAction,
 } from "@/lib/planner/state"
 import type {
@@ -255,19 +256,6 @@ export function UnitDataOverlay({
   return <PlannerCtx.Provider value={value}>{children}</PlannerCtx.Provider>
 }
 
-/** The plan with its year moved to `fallback` when the database lacks it. */
-function withKnownYear(
-  plan: PlannerState,
-  availableYears: readonly string[],
-  fallback: string
-): PlannerState {
-  const year =
-    plan.courseYear && availableYears.includes(plan.courseYear)
-      ? plan.courseYear
-      : fallback
-  return { ...plan, courseYear: year }
-}
-
 export function PlannerProvider({
   children,
   initialYear,
@@ -763,6 +751,12 @@ export function PlannerProvider({
         try {
           // Same year, so the units already cached stay valid: merge.
           const c = await loadYearData(year, code, false)
+
+          const { courseCode, waivers } = lastSnapshotRef.current
+
+          const clearsWaivers =
+            courseCode !== code && (waivers?.length ?? 0) > 0
+
           // One undo step reverts the whole switch.
           dispatch({
             type: "batch",
@@ -778,14 +772,19 @@ export function PlannerProvider({
                 : []),
             ],
           })
+
+          if (clearsWaivers)
+            toast("Waivers cleared", {
+              action: { label: "Undo", onClick: undo },
+            })
         } catch (err) {
           toast.error("Couldn't load course", {
             description: err instanceof Error ? err.message : "Unknown error",
           })
         }
       })
     },
-    [state.courseYear, loadYearData]
+    [state.courseYear, loadYearData, undo]
   )
 
   // A "Plan this course" link landed on a saved plan for another

packages/webapp/components/planner/print-sheet.tsx

@@ -31,6 +31,7 @@ import {
   type PlannerState,
   type PlannerUnit,
 } from "@/lib/planner/types"
+import { placedWaivers } from "@/lib/planner/waivers"
 import { cn } from "@/lib/utils"
 
 import { usePlanner, usePlannerSync } from "./planner-context"
@@ -145,6 +146,7 @@ export function PrintSheetView({
   )
 
   const credit = state.credit ?? []
+  const waivers = placedWaivers(state)
   // A code credited twice, or credited and placed, counts once.
   const creditTotal = creditPointsFromCredit(state, placedUnitCodes(state))
 
@@ -260,6 +262,15 @@ export function PrintSheetView({
             {summary.duplicateUnitCodes.join(", ")}.
           </p>
         ) : null}
+        {waivers.length > 0 ? (
+          <p>
+            Prerequisites waived:{" "}
+            {waivers
+              .map((w) => `${w.prerequisiteCode} for ${w.unitCode}`)
+              .join(", ")}
+            .
+          </p>
+        ) : null}
         <p>
           Made with MonMap (monmap.monashcoding.com) by the Monash Association
           of Coding. This is not an official Monash document: check your plan