/**
 * @deprecated — legacy monolithic reports hook. Kept during the refonte
 * (Issues #70 → #76) so the pre-existing 4 tabs on `/reports` keep working
 * while the new per-domain hooks (useHighlights / useTrends / useCompare /
 * useCategoryZoom) are wired up. Will be removed in Issue #76 once every
 * report migrates to its own route.
 */
import { useReducer, useCallback, useEffect, useRef } from "react";
import type {
  ReportTab,
  MonthlyTrendItem,
  CategoryBreakdownItem,
  CategoryOverTimeData,
  BudgetVsActualRow,
} from "../shared/types";
import { getMonthlyTrends, getCategoryOverTime } from "../services/reportService";
import { getExpensesByCategory } from "../services/dashboardService";
import { getBudgetVsActualData } from "../services/budgetService";
import { useReportsPeriod } from "./useReportsPeriod";

export type CategoryTypeFilter = "expense" | "income" | "transfer" | null;

interface ReportsState {
  tab: ReportTab;
  sourceId: number | null;
  categoryType: CategoryTypeFilter;
  monthlyTrends: MonthlyTrendItem[];
  categorySpending: CategoryBreakdownItem[];
  categoryOverTime: CategoryOverTimeData;
  budgetYear: number;
  budgetMonth: number;
  budgetVsActual: BudgetVsActualRow[];
  isLoading: boolean;
  error: string | null;
}

type ReportsAction =
  | { type: "SET_TAB"; payload: ReportTab }
  | { type: "SET_LOADING"; payload: boolean }
  | { type: "SET_ERROR"; payload: string | null }
  | { type: "SET_MONTHLY_TRENDS"; payload: MonthlyTrendItem[] }
  | { type: "SET_CATEGORY_SPENDING"; payload: CategoryBreakdownItem[] }
  | { type: "SET_CATEGORY_OVER_TIME"; payload: CategoryOverTimeData }
  | { type: "SET_BUDGET_MONTH"; payload: { year: number; month: number } }
  | { type: "SET_BUDGET_VS_ACTUAL"; payload: BudgetVsActualRow[] }
  | { type: "SET_SOURCE_ID"; payload: number | null }
  | { type: "SET_CATEGORY_TYPE"; payload: CategoryTypeFilter };

const now = new Date();

const initialState: ReportsState = {
  tab: "trends",
  sourceId: null,
  categoryType: "expense",
  monthlyTrends: [],
  categorySpending: [],
  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {} },
  budgetYear: now.getMonth() === 0 ? now.getFullYear() - 1 : now.getFullYear(),
  budgetMonth: now.getMonth() === 0 ? 12 : now.getMonth(),
  budgetVsActual: [],
  isLoading: false,
  error: null,
};

function reducer(state: ReportsState, action: ReportsAction): ReportsState {
  switch (action.type) {
    case "SET_TAB":
      return { ...state, tab: action.payload };
    case "SET_LOADING":
      return { ...state, isLoading: action.payload };
    case "SET_ERROR":
      return { ...state, error: action.payload, isLoading: false };
    case "SET_MONTHLY_TRENDS":
      return { ...state, monthlyTrends: action.payload, isLoading: false };
    case "SET_CATEGORY_SPENDING":
      return { ...state, categorySpending: action.payload, isLoading: false };
    case "SET_CATEGORY_OVER_TIME":
      return { ...state, categoryOverTime: action.payload, isLoading: false };
    case "SET_BUDGET_MONTH":
      return { ...state, budgetYear: action.payload.year, budgetMonth: action.payload.month };
    case "SET_BUDGET_VS_ACTUAL":
      return { ...state, budgetVsActual: action.payload, isLoading: false };
    case "SET_SOURCE_ID":
      return { ...state, sourceId: action.payload };
    case "SET_CATEGORY_TYPE":
      return { ...state, categoryType: action.payload };
    default:
      return state;
  }
}

/** @deprecated — see module-level comment. */
export function useReports() {
  const { from, to, period, setPeriod, setCustomDates } = useReportsPeriod();
  const [innerState, dispatch] = useReducer(reducer, initialState);
  const fetchIdRef = useRef(0);

  const fetchData = useCallback(
    async (
      tab: ReportTab,
      dateFrom: string,
      dateTo: string,
      budgetYear: number,
      budgetMonth: number,
      srcId: number | null,
      catType: CategoryTypeFilter,
    ) => {
      const fetchId = ++fetchIdRef.current;
      dispatch({ type: "SET_LOADING", payload: true });
      dispatch({ type: "SET_ERROR", payload: null });

      try {
        switch (tab) {
          case "trends": {
            const data = await getMonthlyTrends(dateFrom, dateTo, srcId ?? undefined);
            if (fetchId !== fetchIdRef.current) return;
            dispatch({ type: "SET_MONTHLY_TRENDS", payload: data });
            break;
          }
          case "byCategory": {
            const data = await getExpensesByCategory(dateFrom, dateTo, srcId ?? undefined);
            if (fetchId !== fetchIdRef.current) return;
            dispatch({ type: "SET_CATEGORY_SPENDING", payload: data });
            break;
          }
          case "overTime": {
            const data = await getCategoryOverTime(dateFrom, dateTo, undefined, srcId ?? undefined, catType ?? undefined);
            if (fetchId !== fetchIdRef.current) return;
            dispatch({ type: "SET_CATEGORY_OVER_TIME", payload: data });
            break;
          }
          case "budgetVsActual": {
            const data = await getBudgetVsActualData(budgetYear, budgetMonth);
            if (fetchId !== fetchIdRef.current) return;
            dispatch({ type: "SET_BUDGET_VS_ACTUAL", payload: data });
            break;
          }
        }
      } catch (e) {
        if (fetchId !== fetchIdRef.current) return;
        dispatch({
          type: "SET_ERROR",
          payload: e instanceof Error ? e.message : String(e),
        });
      }
    },
    [],
  );

  useEffect(() => {
    fetchData(
      innerState.tab,
      from,
      to,
      innerState.budgetYear,
      innerState.budgetMonth,
      innerState.sourceId,
      innerState.categoryType,
    );
  }, [fetchData, innerState.tab, from, to, innerState.budgetYear, innerState.budgetMonth, innerState.sourceId, innerState.categoryType]);

  const setTab = useCallback((tab: ReportTab) => {
    dispatch({ type: "SET_TAB", payload: tab });
  }, []);

  const setBudgetMonth = useCallback((year: number, month: number) => {
    dispatch({ type: "SET_BUDGET_MONTH", payload: { year, month } });
  }, []);

  const setSourceId = useCallback((id: number | null) => {
    dispatch({ type: "SET_SOURCE_ID", payload: id });
  }, []);

  const setCategoryType = useCallback((catType: CategoryTypeFilter) => {
    dispatch({ type: "SET_CATEGORY_TYPE", payload: catType });
  }, []);

  const state = {
    ...innerState,
    period,
    customDateFrom: from,
    customDateTo: to,
  };

  return { state, setTab, setPeriod, setCustomDates, setBudgetMonth, setSourceId, setCategoryType };
}