Weight WTD/MTD budget split by PY DOW-matched sales instead of flat day count

Distributes the monthly wage budget across days proportionally to each
day's share of last year's same-day-of-week sales, so pacing on Weekly/
Monthly views reflects real demand shape (e.g. weekend-heavy) rather than
an even calendar split. Falls back to the old flat day-count split when
PY sales data is unavailable. Weekly also now sources each day's budget
from its own calendar month, so weeks spanning a month boundary split
correctly across both months' budgets.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/Monthly.tsx

@@ -51,6 +51,7 @@ export default function Monthly() {
   const [pyTableOpen,    setPyTableOpen]    = useState(false)
   const [prevMonthDepts, setPrevMonthDepts] = useState<{id: string; cost: number}[]>([])
   const [budget,         setBudget]         = useState<number | null>(null)
+  const [pySalesByDay,   setPySalesByDay]   = useState<Record<string, number>>({})
   const [deptPcts,     setDeptPcts]     = useState<Record<string, number>>({})
   const [showOncosts,  setShowOncosts]  = useState(true)
   const [loading,      setLoading]      = useState(true)
@@ -100,6 +101,10 @@ export default function Monthly() {
       setPySalesMTD(salesRes.days.filter(d => d.date <= cutoff).reduce((s, d) => s + d.py_sales, 0))
       setPySalesFull(salesRes.days.reduce((s, d) => s + d.py_sales, 0))
 
+      const pyMap: Record<string, number> = {}
+      for (const d of salesRes.days) pyMap[d.date] = d.py_sales
+      setPySalesByDay(pyMap)
+
       // PY MTD: same day number as yesterday in PY (or full month for past months)
       const yDay       = parseInt(yesterdayStr.slice(8))
       const pyMtdLimit = isCurrentMonth
@@ -179,9 +184,16 @@ export default function Monthly() {
   const pyTotalWagesFull = pyDepts.reduce((s, d) => s + d.costFull, 0)
   const prevMonthTotal   = prevMonthDepts.reduce((s, d) => s + d.cost, 0)
 
-  // MTD row: pro-rata budget to yesterday
+  // MTD row: budget split across the month by each day's share of PY (DOW-matched) sales,
-  const yDay         = isCurrentMonth ? parseInt(yesterdayStr.slice(8)) : dim
+  // so a weekend-heavy budget lands more on weekends rather than an even calendar split.
-  const budgetMTD    = budget != null ? budget * yDay / dim : null
+  // Falls back to flat day-count proration when PY sales data isn't available.
+  const yDay          = isCurrentMonth ? parseInt(yesterdayStr.slice(8)) : dim
+  const monthPyTotal  = Object.values(pySalesByDay).reduce((s, v) => s + v, 0)
+  const isBudgetWeighted = monthPyTotal > 0
+  const mtdFrac = isBudgetWeighted
+    ? Object.entries(pySalesByDay).filter(([d]) => d <= cutoff).reduce((s, [, v]) => s + v, 0) / monthPyTotal
+    : yDay / dim
+  const budgetMTD    = budget != null ? budget * mtdFrac : null
   const varianceMTD  = budgetMTD != null ? totalActual - budgetMTD : null
   const pctBudgMTD   = budgetMTD != null && budgetMTD > 0 ? (totalActual / budgetMTD) * 100 : null
   const pctSalesMTD  = netSalesMTD > 0 ? (totalActual / netSalesMTD) * 100 : null
@@ -253,7 +265,7 @@ export default function Monthly() {
             <div className="summary-card">
               <div className="label">Budget MTD</div>
               <div className="value">{budgetMTD != null ? fmtMoney(budgetMTD) : '—'}</div>
-              <div className="sub">pro-rata {yDay}/{dim} days</div>
+              <div className="sub">{isBudgetWeighted ? 'sales-weighted (PY DOW)' : `pro-rata ${yDay}/${dim} days`}</div>
             </div>
             <div className="summary-card">
               <div className="label">% Budget MTD</div>

frontend/src/pages/Weekly.tsx

@@ -23,6 +23,13 @@ function daysInMonthFor(dateStr: string): number {
   const d = new Date(dateStr + 'T00:00:00')
   return new Date(d.getFullYear(), d.getMonth() + 1, 0).getDate()
 }
+function monthKeyOf(dateStr: string): string {
+  return dateStr.slice(0, 7)
+}
+function monthRangeOf(monthKey: string): { from: string; to: string } {
+  const from = `${monthKey}-01`
+  return { from, to: `${monthKey}-${String(daysInMonthFor(from)).padStart(2, '0')}` }
+}
 function fmtDisplay(dateStr: string): string {
   return new Date(dateStr + 'T00:00:00').toLocaleDateString('en-GB', { day: 'numeric', month: 'short' })
 }
@@ -67,7 +74,9 @@ export default function Weekly() {
   const [pySalesFull,  setPySalesFull]  = useState(0)
   const [pyWages,      setPyWages]      = useState<number | null>(null)
   const [pyDepts,      setPyDepts]      = useState<{id: string; name: string; cost: number}[]>([])
-  const [monthlyBudg,  setMonthlyBudg]  = useState<number | null>(null)
+  const [budgetsByMonth, setBudgetsByMonth] = useState<Record<string, number>>({}) // monthKey (YYYY-MM) -> amount
+  const [pySalesByDay,   setPySalesByDay]   = useState<Record<string, number>>({}) // date -> PY (DOW-matched) sales
+  const [monthPyTotals,  setMonthPyTotals]  = useState<Record<string, number>>({}) // monthKey -> total PY sales
   const [deptPcts,     setDeptPcts]     = useState<Record<string, number>>({})
   const [showOncosts,  setShowOncosts]  = useState(true)
   const [loading,      setLoading]      = useState(true)
@@ -76,17 +85,40 @@ export default function Weekly() {
   const [modalEmps,    setModalEmps]    = useState<EmployeeDetail[] | null>(null)
   const [modalLoad,    setModalLoad]    = useState(false)
 
+  // A week can span two calendar months (e.g. Mon 26 – Sun 1) — budget/PY-sales weighting
+  // must be sourced per-day from whichever month that day actually belongs to.
+  const weekMonthKeys = Array.from(new Set([monthKeyOf(fromStr), monthKeyOf(toStr)]))
+
   const load = useCallback(async () => {
     setLoading(true); setError(null)
     try {
       const isCurrentWk = fromStr === mondayOf(new Date())
-      const [actRes, salesRes, budgetRes, pyActRes] = await Promise.all([
+      const monthKeys = Array.from(new Set([monthKeyOf(fromStr), monthKeyOf(toStr)]))
+      const monthRanges = monthKeys.map(monthRangeOf)
+
+      const [actRes, salesRes, budgetRes, pyActRes, monthSalesResList] = await Promise.all([
         // 14-day fetch: prev week + current week so prev-week data is in dep.days for forecast + comparison
         getActuals(prevWeekFrom, toStr),
         getNetSales(fromStr, toStr),
         getBudgets(),
         getActuals(pyFromStr, pyToStr),
+        Promise.all(monthRanges.map(r => getNetSales(r.from, r.to))),
       ])
+
+      const pyMap: Record<string, number> = {}
+      const monthTotals: Record<string, number> = {}
+      monthKeys.forEach((key, i) => {
+        let total = 0
+        for (const d of monthSalesResList[i].days) { pyMap[d.date] = d.py_sales; total += d.py_sales }
+        monthTotals[key] = total
+      })
+      setPySalesByDay(pyMap)
+      setMonthPyTotals(monthTotals)
+
+      const budgMap: Record<string, number> = {}
+      for (const b of (budgetRes.budgets as WageBudget[])) budgMap[b.month.slice(0, 7)] = b.budget_amount
+      setBudgetsByMonth(budgMap)
+
       setDepts(actRes.departments)
       setShowOncosts(actRes.show_oncosts)
       setDeptPcts(actRes.dept_pcts)
@@ -107,12 +139,6 @@ export default function Weekly() {
       setPyDepts(pyDeptList)
       const pyTotal = pyDeptList.reduce((s, d) => s + d.cost, 0)
       setPyWages(pyTotal > 0 ? pyTotal : null)
-
-      // Budget: WTD pro-rata (to yesterday) stored; full-week derived in component body
-      const d0 = new Date(fromStr + 'T00:00:00')
-      const monthKey = `${d0.getFullYear()}-${String(d0.getMonth() + 1).padStart(2, '0')}-01`
-      const bRow = (budgetRes.budgets as WageBudget[]).find(b => b.month === monthKey)
-      setMonthlyBudg(bRow ? bRow.budget_amount : null)
     } catch (e: unknown) {
       setError(e instanceof Error ? e.message : 'Failed to load')
     } finally {
@@ -134,17 +160,32 @@ export default function Weekly() {
   const prev = () => setFromStr(s => addDaysStr(s, -7))
   const next = () => setFromStr(s => addDaysStr(s, 7))
 
-  // Budget derived from monthlyBudg
-  const dim         = daysInMonthFor(fromStr)
-  const weekDaysWTD = daysElapsed + 1  // Mon to yesterday inclusive (or 7 for past weeks)
-  const budgetWTD   = monthlyBudg != null ? monthlyBudg * weekDaysWTD / dim : null
-  const budgetFull  = monthlyBudg != null ? monthlyBudg * 7 / dim : null
-
   // Per-dept rows computed from 14-day actuals
   const wtdCutoff  = isCurrentWeek ? yesterdayStr : toStr
   // Prev week comparison cutoff: same elapsed days as WTD (Mon-N of prev week)
   const prevCutoff = isCurrentWeek ? addDaysStr(yesterdayStr, -7) : prevWeekTo
 
+  // Budget for a single day: sourced from THAT day's own calendar month (a week can span two
+  // months), weighted by its share of that month's PY (DOW-matched) sales. Falls back to a flat
+  // day-count split within that month when PY sales data isn't available.
+  const dayBudget = (dateStr: string): number => {
+    const mKey = monthKeyOf(dateStr)
+    const monthBudget = budgetsByMonth[mKey]
+    if (monthBudget == null) return 0
+    const monthTotal = monthPyTotals[mKey] ?? 0
+    if (monthTotal > 0) return monthBudget * ((pySalesByDay[dateStr] ?? 0) / monthTotal)
+    return monthBudget / daysInMonthFor(`${mKey}-01`)
+  }
+  const sumBudget = (fromD: string, toD: string): number => {
+    let s = 0
+    for (let d = fromD; d <= toD; d = addDaysStr(d, 1)) s += dayBudget(d)
+    return s
+  }
+  const hasBudget        = weekMonthKeys.some(k => budgetsByMonth[k] != null)
+  const isBudgetWeighted = weekMonthKeys.every(k => (monthPyTotals[k] ?? 0) > 0)
+  const budgetWTD  = hasBudget ? sumBudget(fromStr, wtdCutoff) : null
+  const budgetFull = hasBudget ? sumBudget(fromStr, toStr) : null
+
   type DeptRow = {
     department_id: string
     department_name: string
@@ -231,7 +272,7 @@ export default function Weekly() {
             <div className="summary-card">
               <div className="label">Budget WTD</div>
               <div className="value">{budgetWTD != null ? fmtMoney(budgetWTD) : '—'}</div>
-              <div className="sub">proportion of monthly</div>
+              <div className="sub">{isBudgetWeighted ? 'sales-weighted (PY DOW)' : 'proportion of monthly'}</div>
             </div>
             <div className="summary-card">
               <div className="label">% Budget WTD</div>
@@ -263,7 +304,7 @@ export default function Weekly() {
             <div className="summary-card">
               <div className="label">Budget Full Week</div>
               <div className="value">{budgetFull != null ? fmtMoney(budgetFull) : '—'}</div>
-              <div className="sub">7-day proportion</div>
+              <div className="sub">{isBudgetWeighted ? 'sales-weighted (PY DOW)' : '7-day proportion'}</div>
             </div>
             <div className="summary-card">
               <div className="label">% Budget (Forecast)</div>