import { createContext, useCallback, useContext, useEffect, useState } from "react";
import i18n from "./i18n";
import { api } from "./api";
import { useAuth } from "./auth";
import { applyTheme } from "./theme";
import { formatMoney as fmtMoney, formatDate as fmtDate } from "./format";

const DEFAULTS = {
  base_currency: "EUR",
  locale: "de",
  theme: "system",
  date_format: "de",
  budget_start_day: "1",
};

const SettingsContext = createContext({
  ...DEFAULTS,
  formatMoney: (cents, currency) => fmtMoney(cents, currency),
  formatDate: (iso) => fmtDate(iso, "de"),
  update: async () => {},
  reload: async () => {},
});

export function SettingsProvider({ children }) {
  const { user } = useAuth();
  const [values, setValues] = useState(DEFAULTS);

  // Sprache und Thema anwenden, sobald sich die Werte ändern.
  useEffect(() => {
    if (i18n.language !== values.locale) i18n.changeLanguage(values.locale);
  }, [values.locale]);

  useEffect(() => {
    applyTheme(values.theme);
  }, [values.theme]);

  const reload = useCallback(async () => {
    try {
      const rows = await api.listSettings();
      const map = { ...DEFAULTS };
      for (const r of rows) {
        if (r.value != null) map[r.key] = r.value;
      }
      setValues(map);
    } catch {
      /* Einstellungen sind optional – Standardwerte bleiben bestehen. */
    }
  }, []);

  useEffect(() => {
    if (user) reload();
    else setValues(DEFAULTS); // nach Logout auf Standard zurück
  }, [user, reload]);

  // Eine Einstellung setzen: erst lokal (sofort sichtbar), dann speichern.
  const update = useCallback(async (key, value) => {
    setValues((prev) => ({ ...prev, [key]: value }));
    await api.setSetting(key, value);
  }, []);

  const value = {
    ...values,
    baseCurrency: values.base_currency,
    formatMoney: (cents, currency) => fmtMoney(cents, currency ?? values.base_currency),
    formatDate: (iso) => fmtDate(iso, values.locale),
    update,
    reload,
  };

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

export function useSettings() {
  return useContext(SettingsContext);
}