import { useState } from "react";
import { useTranslation } from "react-i18next";
import { Link } from "react-router-dom";
import { ArrowLeft } from "lucide-react";
import PeriodSelector from "../components/dashboard/PeriodSelector";
import CompareModeTabs from "../components/reports/CompareModeTabs";
import CompareSubModeToggle from "../components/reports/CompareSubModeToggle";
import CompareReferenceMonthPicker from "../components/reports/CompareReferenceMonthPicker";
import ComparePeriodTable from "../components/reports/ComparePeriodTable";
import ComparePeriodChart from "../components/reports/ComparePeriodChart";
import CompareBudgetView from "../components/reports/CompareBudgetView";
import ViewModeToggle, { readViewMode, type ViewMode } from "../components/reports/ViewModeToggle";
import { useCompare, comparisonMeta } from "../hooks/useCompare";
import { useReportsPeriod } from "../hooks/useReportsPeriod";

const STORAGE_KEY = "reports-viewmode-compare";

function formatMonthLabel(year: number, month: number, language: string): string {
  const date = new Date(year, month - 1, 1);
  return new Intl.DateTimeFormat(language === "fr" ? "fr-CA" : "en-CA", {
    month: "long",
    year: "numeric",
  }).format(date);
}

export default function ReportsComparePage() {
  const { t, i18n } = useTranslation();
  const { period, setPeriod, from, to, setCustomDates } = useReportsPeriod();
  const {
    mode,
    subMode,
    setMode,
    setSubMode,
    setReferencePeriod,
    year,
    month,
    rows,
    isLoading,
    error,
  } = useCompare();
  const [viewMode, setViewMode] = useState<ViewMode>(() => readViewMode(STORAGE_KEY));

  const preserveSearch = typeof window !== "undefined" ? window.location.search : "";

  const { previousYear, previousMonth: prevMonth } = comparisonMeta(subMode, year, month);
  // Monthly block labels: a specific month on both sides. For MoM the
  // previous = previous month of same year; for YoY the previous = same
  // month one year earlier (comparisonMeta already resolves both).
  const currentLabel = formatMonthLabel(year, month, i18n.language);
  const previousLabel = formatMonthLabel(previousYear, prevMonth, i18n.language);
  // Cumulative YTD block labels. For MoM both sides live in the same year
  // but the previous side only covers up to the end of the previous month,
  // so we surface the end-of-window month label on each side. For YoY we
  // compare Jan→refMonth across two different years; the year + month label
  // makes the window boundary unambiguous.
  const cumulativeCurrentLabel =
    subMode === "mom"
      ? `→ ${formatMonthLabel(year, month, i18n.language)}`
      : `${String(year)} → ${formatMonthLabel(year, month, i18n.language)}`;
  const cumulativePreviousLabel =
    subMode === "mom"
      ? `→ ${formatMonthLabel(previousYear, prevMonth, i18n.language)}`
      : `${String(previousYear)} → ${formatMonthLabel(previousYear, prevMonth, i18n.language)}`;

  const showActualControls = mode === "actual";

  return (
    <div className={isLoading ? "opacity-60" : ""}>
      <div className="flex items-center gap-3 mb-4">
        <Link
          to={`/reports${preserveSearch}`}
          className="text-[var(--muted-foreground)] hover:text-[var(--foreground)] p-1 rounded-md hover:bg-[var(--muted)]"
          aria-label={t("reports.hub.title")}
        >
          <ArrowLeft size={18} />
        </Link>
        <h1 className="text-2xl font-bold">{t("reports.hub.compare")}</h1>
      </div>

      <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4 mb-4 flex-wrap">
        <PeriodSelector
          value={period}
          onChange={setPeriod}
          customDateFrom={from}
          customDateTo={to}
          onCustomDateChange={setCustomDates}
        />
        <div className="flex gap-2 items-center flex-wrap">
          <CompareModeTabs value={mode} onChange={setMode} />
        </div>
      </div>

      <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-3 mb-6 flex-wrap">
        <div className="flex items-center gap-3 flex-wrap">
          <CompareReferenceMonthPicker
            year={year}
            month={month}
            onChange={setReferencePeriod}
          />
          {showActualControls && (
            <CompareSubModeToggle value={subMode} onChange={setSubMode} />
          )}
        </div>
        {showActualControls && (
          <ViewModeToggle value={viewMode} onChange={setViewMode} storageKey={STORAGE_KEY} />
        )}
      </div>

      {error && (
        <div className="bg-[var(--negative)]/10 text-[var(--negative)] rounded-xl p-4 mb-6">
          {error}
        </div>
      )}

      {mode === "budget" ? (
        <CompareBudgetView year={year} month={month} />
      ) : viewMode === "chart" ? (
        <ComparePeriodChart
          rows={rows}
          previousLabel={previousLabel}
          currentLabel={currentLabel}
        />
      ) : (
        <ComparePeriodTable
          rows={rows}
          previousLabel={previousLabel}
          currentLabel={currentLabel}
          cumulativePreviousLabel={cumulativePreviousLabel}
          cumulativeCurrentLabel={cumulativeCurrentLabel}
        />
      )}
    </div>
  );
}