Add predictions and forecasting analytics

Introduces a new PredictionsChart component and integrates it into the AnalyticsDashboard with a new tab for AI-powered sales, demand, and stock forecasting. Expands analytics-service with types and service functions for predictions, enabling comprehensive future insights for revenue, demand, and inventory.

lib/services/analytics-service.ts

@@ -298,3 +298,202 @@ export function formatGBP(value: number) {
     maximumFractionDigits: 2,
   });
 }
+
+// Prediction Types
+export interface SalesPrediction {
+  predicted: number | null;
+  predictedOrders: number | null;
+  dailyPredictions?: Array<{
+    day: number;
+    predicted: number;
+    date: string;
+  }>;
+  confidence: "high" | "medium" | "low";
+  method: string;
+  methods?: {
+    movingAverage?: number | null;
+    exponentialAverage?: number | null;
+    linearRegression?: number | null;
+    trendAverage?: number | null;
+  };
+  variance?: number;
+  minPrediction?: number;
+  maxPrediction?: number;
+  seasonality?: {
+    dayOfWeek: Record<string, number>;
+    month: Record<string, number>;
+    confidence: string;
+  };
+  historicalPeriod: number;
+  predictionPeriod: number;
+  message?: string;
+}
+
+export interface DemandPrediction {
+  predictedDaily: number | null;
+  predictedWeekly: number | null;
+  predictedMonthly: number | null;
+  confidence: "high" | "medium" | "low";
+  averageDaily?: number;
+  trendFactor?: number;
+  stdDev?: number;
+  historicalPeriod: number;
+  predictionPeriod: number;
+  productId?: string | null;
+  message?: string;
+}
+
+export interface StockPrediction {
+  productId: string;
+  productName: string;
+  currentStock: number;
+  lowStockThreshold: number;
+  unitType: string;
+  prediction: {
+    daysUntilOutOfStock: number | null;
+    estimatedDate: string | null;
+    confidence: "high" | "medium" | "low";
+    averageDailySales?: number;
+    stdDev?: number;
+    message?: string;
+  };
+  needsRestock: boolean;
+}
+
+export interface StockPredictionsResponse {
+  predictions: StockPrediction[];
+  historicalPeriod: number;
+  totalProducts: number;
+  productsNeedingRestock: number;
+}
+
+export interface PredictionsOverview {
+  sales: SalesPrediction;
+  demand: DemandPrediction;
+  stock: {
+    totalProducts: number;
+    message?: string;
+  };
+  historicalPeriod: number;
+  predictionPeriod: number;
+  message?: string;
+}
+
+// Prediction Service Functions
+
+/**
+ * Get sales/revenue predictions
+ * @param daysAhead Number of days to predict ahead (default: 7)
+ * @param period Historical period in days (default: 30)
+ * @param storeId Optional storeId for staff users
+ */
+export const getSalesPredictions = async (
+  daysAhead: number = 7,
+  period: number = 30,
+  storeId?: string,
+): Promise<SalesPrediction> => {
+  const params = new URLSearchParams({
+    daysAhead: daysAhead.toString(),
+    period: period.toString(),
+  });
+  if (storeId) params.append("storeId", storeId);
+
+  const url = `/analytics/predictions/sales?${params.toString()}`;
+  return clientFetch<SalesPrediction>(url);
+};
+
+/**
+ * Get product demand predictions
+ * @param productId Optional product ID for specific product prediction
+ * @param daysAhead Number of days to predict ahead (default: 7)
+ * @param period Historical period in days (default: 30)
+ * @param storeId Optional storeId for staff users
+ */
+export const getDemandPredictions = async (
+  productId?: string,
+  daysAhead: number = 7,
+  period: number = 30,
+  storeId?: string,
+): Promise<DemandPrediction> => {
+  const params = new URLSearchParams({
+    daysAhead: daysAhead.toString(),
+    period: period.toString(),
+  });
+  if (productId) params.append("productId", productId);
+  if (storeId) params.append("storeId", storeId);
+
+  const url = `/analytics/predictions/demand?${params.toString()}`;
+  return clientFetch<DemandPrediction>(url);
+};
+
+/**
+ * Get stock depletion predictions
+ * @param period Historical period in days (default: 30)
+ * @param storeId Optional storeId for staff users
+ */
+export const getStockPredictions = async (
+  period: number = 30,
+  storeId?: string,
+): Promise<StockPredictionsResponse> => {
+  const params = new URLSearchParams({
+    period: period.toString(),
+  });
+  if (storeId) params.append("storeId", storeId);
+
+  const url = `/analytics/predictions/stock?${params.toString()}`;
+  return clientFetch<StockPredictionsResponse>(url);
+};
+
+/**
+ * Get comprehensive predictions overview
+ * @param daysAhead Number of days to predict ahead (default: 7)
+ * @param period Historical period in days (default: 30)
+ * @param storeId Optional storeId for staff users
+ */
+export const getPredictionsOverview = async (
+  daysAhead: number = 7,
+  period: number = 30,
+  storeId?: string,
+): Promise<PredictionsOverview> => {
+  const params = new URLSearchParams({
+    daysAhead: daysAhead.toString(),
+    period: period.toString(),
+  });
+  if (storeId) params.append("storeId", storeId);
+
+  const url = `/analytics/predictions/overview?${params.toString()}`;
+  return clientFetch<PredictionsOverview>(url);
+};
+
+// Helper functions with automatic storeId handling
+export const getSalesPredictionsWithStore = async (
+  daysAhead: number = 7,
+  period: number = 30,
+): Promise<SalesPrediction> => {
+  const storeId = getStoreIdForUser();
+  return getSalesPredictions(daysAhead, period, storeId);
+};
+
+export const getDemandPredictionsWithStore = async (
+  productId?: string,
+  daysAhead: number = 7,
+  period: number = 30,
+): Promise<DemandPrediction> => {
+  const storeId = getStoreIdForUser();
+  return getDemandPredictions(productId, daysAhead, period, storeId);
+};
+
+export const getStockPredictionsWithStore = async (
+  period: number = 30,
+): Promise<StockPredictionsResponse> => {
+  const storeId = getStoreIdForUser();
+  return getStockPredictions(period, storeId);
+};
+
+export const getPredictionsOverviewWithStore = async (
+  daysAhead: number = 7,
+  period: number = 30,
+): Promise<PredictionsOverview> => {
+  const storeId = getStoreIdForUser();
+  return getPredictionsOverview(daysAhead, period, storeId);
+};