import { useReducer, useCallback, useEffect, useRef } from "react";
import type {
  DashboardPeriod,
  DashboardSummary,
  CategoryBreakdownItem,
  CategoryOverTimeData,
  BudgetVsActualRow,
} from "../shared/types";
import {
  getDashboardSummary,
  getExpensesByCategory,
} from "../services/dashboardService";
import { getCategoryOverTime } from "../services/reportService";
import { getBudgetVsActualData } from "../services/budgetService";
import { computeDateRange } from "../utils/dateRange";

interface DashboardState {
  summary: DashboardSummary;
  categoryBreakdown: CategoryBreakdownItem[];
  categoryOverTime: CategoryOverTimeData;
  budgetVsActual: BudgetVsActualRow[];
  period: DashboardPeriod;
  budgetYear: number;
  budgetMonth: number;
  customDateFrom: string;
  customDateTo: string;
  isLoading: boolean;
  error: string | null;
}

type DashboardAction =
  | { type: "SET_LOADING"; payload: boolean }
  | { type: "SET_ERROR"; payload: string | null }
  | {
      type: "SET_DATA";
      payload: {
        summary: DashboardSummary;
        categoryBreakdown: CategoryBreakdownItem[];
        categoryOverTime: CategoryOverTimeData;
        budgetVsActual: BudgetVsActualRow[];
      };
    }
  | { type: "SET_PERIOD"; payload: DashboardPeriod }
  | { type: "SET_BUDGET_MONTH"; payload: { year: number; month: number } }
  | { type: "SET_CUSTOM_DATES"; payload: { dateFrom: string; dateTo: string } };

const now = new Date();
const todayStr = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}-${String(now.getDate()).padStart(2, "0")}`;
const yearStartStr = `${now.getFullYear()}-01-01`;

const initialState: DashboardState = {
  summary: { totalCount: 0, totalAmount: 0, incomeTotal: 0, expenseTotal: 0 },
  categoryBreakdown: [],
  categoryOverTime: { categories: [], data: [], colors: {}, categoryIds: {}, types: {}, tree: [] },
  budgetVsActual: [],
  period: "year",
  budgetYear: now.getMonth() === 0 ? now.getFullYear() - 1 : now.getFullYear(),
  budgetMonth: now.getMonth() === 0 ? 12 : now.getMonth(),
  customDateFrom: yearStartStr,
  customDateTo: todayStr,
  isLoading: false,
  error: null,
};

function reducer(state: DashboardState, action: DashboardAction): DashboardState {
  switch (action.type) {
    case "SET_LOADING":
      return { ...state, isLoading: action.payload };
    case "SET_ERROR":
      return { ...state, error: action.payload, isLoading: false };
    case "SET_DATA":
      return {
        ...state,
        summary: action.payload.summary,
        categoryBreakdown: action.payload.categoryBreakdown,
        categoryOverTime: action.payload.categoryOverTime,
        budgetVsActual: action.payload.budgetVsActual,
        isLoading: false,
      };
    case "SET_PERIOD":
      return { ...state, period: action.payload };
    case "SET_BUDGET_MONTH":
      return { ...state, budgetYear: action.payload.year, budgetMonth: action.payload.month };
    case "SET_CUSTOM_DATES":
      return { ...state, period: "custom" as DashboardPeriod, customDateFrom: action.payload.dateFrom, customDateTo: action.payload.dateTo };
    default:
      return state;
  }
}

export function useDashboard() {
  const [state, dispatch] = useReducer(reducer, initialState);
  const fetchIdRef = useRef(0);

  const fetchData = useCallback(async (
    period: DashboardPeriod,
    customFrom: string | undefined,
    customTo: string | undefined,
    bYear: number,
    bMonth: number,
  ) => {
    const fetchId = ++fetchIdRef.current;
    dispatch({ type: "SET_LOADING", payload: true });
    dispatch({ type: "SET_ERROR", payload: null });

    try {
      const { dateFrom, dateTo } = computeDateRange(period, customFrom, customTo);
      const [summary, categoryBreakdown, categoryOverTime, budgetVsActual] = await Promise.all([
        getDashboardSummary(dateFrom, dateTo),
        getExpensesByCategory(dateFrom, dateTo),
        getCategoryOverTime(dateFrom, dateTo),
        getBudgetVsActualData(bYear, bMonth),
      ]);

      if (fetchId !== fetchIdRef.current) return;
      dispatch({ type: "SET_DATA", payload: { summary, categoryBreakdown, categoryOverTime, budgetVsActual } });
    } catch (e) {
      if (fetchId !== fetchIdRef.current) return;
      dispatch({
        type: "SET_ERROR",
        payload: e instanceof Error ? e.message : String(e),
      });
    }
  }, []);

  useEffect(() => {
    fetchData(state.period, state.customDateFrom, state.customDateTo, state.budgetYear, state.budgetMonth);
  }, [state.period, state.customDateFrom, state.customDateTo, state.budgetYear, state.budgetMonth, fetchData]);

  const setPeriod = useCallback((period: DashboardPeriod) => {
    dispatch({ type: "SET_PERIOD", payload: period });
  }, []);

  const setCustomDates = useCallback((dateFrom: string, dateTo: string) => {
    dispatch({ type: "SET_CUSTOM_DATES", payload: { dateFrom, dateTo } });
  }, []);

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

  return { state, setPeriod, setCustomDates, setBudgetMonth };
}