import { createContext, useContext, useState, useCallback, useMemo } from 'react';

// ==============================|| OPS STORE — SESSION PERSISTENCE ||============================== //
// A lightweight in-memory store so operational actions actually COMMIT during a session (no backend).
// Holds: dispatch assignments (order → rider), reroutes, and exceptions. Future workflows (status
// advance, payments) hang off the same provider. State resets on full reload — intentional for a demo.

const OpsContext = createContext(null);

export function OpsProvider({ children }) {
  // assignments: { [orderId]: { riderId, riderName, vehicle, at } }
  const [assignments, setAssignments] = useState({});
  // reroutes: { [orderId]: at }
  const [reroutes, setReroutes] = useState({});
  // exceptions: { [orderId]: { reason, at } }
  const [exceptions, setExceptions] = useState({});

  const assignOrder = useCallback((orderId, rider) => {
    setAssignments((prev) => ({
      ...prev,
      [orderId]: { riderId: rider.id, riderName: rider.name, vehicle: rider.vehicle, at: Date.now() }
    }));
  }, []);

  const unassignOrder = useCallback((orderId) => {
    setAssignments((prev) => {
      const next = { ...prev };
      delete next[orderId];
      return next;
    });
  }, []);

  const rerouteOrder = useCallback((orderId) => {
    setReroutes((prev) => ({ ...prev, [orderId]: Date.now() }));
  }, []);

  const raiseException = useCallback((orderId, reason) => {
    setExceptions((prev) => ({ ...prev, [orderId]: { reason, at: Date.now() } }));
  }, []);

  const clearException = useCallback((orderId) => {
    setExceptions((prev) => {
      const next = { ...prev };
      delete next[orderId];
      return next;
    });
  }, []);

  const assignmentOf = useCallback((orderId) => assignments[orderId] || null, [assignments]);
  const exceptionOf = useCallback((orderId) => exceptions[orderId] || null, [exceptions]);
  const isRerouted = useCallback((orderId) => Boolean(reroutes[orderId]), [reroutes]);
  const riderLoad = useCallback(
    (riderId) => Object.values(assignments).filter((a) => a.riderId === riderId).length,
    [assignments]
  );

  const value = useMemo(
    () => ({
      assignments, reroutes, exceptions,
      assignOrder, unassignOrder, rerouteOrder, raiseException, clearException,
      assignmentOf, exceptionOf, isRerouted, riderLoad,
      assignedCount: Object.keys(assignments).length,
      exceptionCount: Object.keys(exceptions).length
    }),
    [assignments, reroutes, exceptions, assignOrder, unassignOrder, rerouteOrder, raiseException, clearException, assignmentOf, exceptionOf, isRerouted, riderLoad]
  );

  return <OpsContext.Provider value={value}>{children}</OpsContext.Provider>;
}

export function useOps() {
  const ctx = useContext(OpsContext);
  if (!ctx) throw new Error('useOps must be used within an OpsProvider');
  return ctx;
}