"use client";

import React, { createContext, useCallback, useContext, useEffect, useMemo, useState } from "react";

export type ConsentState = {
  analytics: boolean;
  chat: boolean;
};

const COOKIE_NAME = "dk0_consent_v1";

function readConsentFromCookie(): ConsentState | null {
  if (typeof document === "undefined") return null;
  const match = document.cookie
    .split(";")
    .map((c) => c.trim())
    .find((c) => c.startsWith(`${COOKIE_NAME}=`));
  if (!match) return null;
  const value = decodeURIComponent(match.split("=").slice(1).join("="));
  try {
    const parsed = JSON.parse(value) as Partial<ConsentState>;
    return {
      analytics: !!parsed.analytics,
      chat: !!parsed.chat,
    };
  } catch {
    return null;
  }
}

function writeConsentCookie(value: ConsentState) {
  const encoded = encodeURIComponent(JSON.stringify(value));
  // 180 days
  const maxAge = 60 * 60 * 24 * 180;
  document.cookie = `${COOKIE_NAME}=${encoded}; path=/; max-age=${maxAge}; samesite=lax`;
}

const ConsentContext = createContext<{
  consent: ConsentState | null;
  ready: boolean;
  setConsent: (next: ConsentState) => void;
  resetConsent: () => void;
}>({
  consent: null,
  ready: false,
  setConsent: () => {},
  resetConsent: () => {},
});

export function ConsentProvider({ children }: { children: React.ReactNode }) {
  // IMPORTANT:
  // Don't read `document.cookie` during SSR render (document is undefined), otherwise the
  // server will render the banner while the client immediately hides it -> hydration mismatch.
  // We resolve consent on the client after mount and only render the banner once `ready=true`.
  const [consent, setConsentState] = useState<ConsentState | null>(null);
  const [ready, setReady] = useState(false);

  useEffect(() => {
    setConsentState(readConsentFromCookie());
    setReady(true);
  }, []);

  const setConsent = useCallback((next: ConsentState) => {
    setConsentState(next);
    writeConsentCookie(next);
  }, []);

  const resetConsent = useCallback(() => {
    setConsentState(null);
    // expire cookie
    document.cookie = `${COOKIE_NAME}=; path=/; max-age=0; samesite=lax`;
  }, []);

  const value = useMemo(
    () => ({ consent, ready, setConsent, resetConsent }),
    [consent, ready, setConsent, resetConsent],
  );

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

export function useConsent() {
  return useContext(ConsentContext);
}

export const consentCookieName = COOKIE_NAME;