Simpl-Resultat/src/hooks/useCompare.ts

import { useReducer, useCallback } from "react";
import { useReportsPeriod } from "./useReportsPeriod";

export type CompareMode = "mom" | "yoy" | "budget";

interface State {
  mode: CompareMode;
  isLoading: boolean;
  error: string | null;
}

type Action =
  | { type: "SET_MODE"; payload: CompareMode }
  | { type: "SET_LOADING"; payload: boolean }
  | { type: "SET_ERROR"; payload: string };

const initialState: State = {
  mode: "mom",
  isLoading: false,
  error: null,
};

function reducer(state: State, action: Action): State {
  switch (action.type) {
    case "SET_MODE":
      return { ...state, mode: action.payload };
    case "SET_LOADING":
      return { ...state, isLoading: action.payload };
    case "SET_ERROR":
      return { ...state, error: action.payload, isLoading: false };
    default:
      return state;
  }
}

export function useCompare() {
  const { from, to } = useReportsPeriod();
  const [state, dispatch] = useReducer(reducer, initialState);

  const setMode = useCallback((m: CompareMode) => {
    dispatch({ type: "SET_MODE", payload: m });
  }, []);

  // Issue #73 will fetch via reportService.getCompareMonthOverMonth / ...YearOverYear
  return { ...state, setMode, from, to };
}