/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 * 
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

const STORAGE_KEY = "rustpad:theme";
const GUEST_STORAGE_KEY = "rustpad:guest-theme";
const AUTH_STATE_KEY = "rustpad:auth-state";
const THEMES = new Set(["dark", "light"]);
const systemThemeQuery = window.matchMedia("(prefers-color-scheme: light)");

function systemTheme() {
  return systemThemeQuery.matches ? "light" : "dark";
}

function normalizeTheme(value) {
  return THEMES.has(value) ? value : systemTheme();
}

function updateBrowserChrome(theme) {
  document.documentElement.dataset.theme = theme;
  document.documentElement.style.colorScheme = theme;
  document.querySelector('meta[name="color-scheme"]')?.setAttribute("content", theme);
}

export function getTheme() {
  return normalizeTheme(document.documentElement.dataset.theme);
}

function hasAccountSession() {
  try { return localStorage.getItem(AUTH_STATE_KEY) === "1"; } catch { return false; }
}

function persistTheme(theme, scope = "auto") {
  try {
    localStorage.setItem(STORAGE_KEY, theme);
    const guestScope = scope === "guest" || (scope === "auto" && !hasAccountSession());
    if (guestScope) localStorage.setItem(GUEST_STORAGE_KEY, theme);
  } catch { }
}

export function applyTheme(value, { persist = true, scope = "auto" } = {}) {
  const theme = normalizeTheme(value);
  const previousTheme = getTheme();
  updateBrowserChrome(theme);
  if (persist) persistTheme(theme, scope);
  if (theme !== previousTheme) {
    window.dispatchEvent(new CustomEvent("rustpad:theme-change", { detail: { theme } }));
  }
  return theme;
}

export function rememberGuestTheme(value = getTheme()) {
  try {
    if (THEMES.has(localStorage.getItem(GUEST_STORAGE_KEY))) return;
    localStorage.setItem(GUEST_STORAGE_KEY, normalizeTheme(value));
  } catch { }
}

export function restoreGuestTheme() {
  let saved = null;
  try { saved = localStorage.getItem(GUEST_STORAGE_KEY); } catch { }
  if (THEMES.has(saved)) {
    try { localStorage.setItem(STORAGE_KEY, saved); } catch { }
    return applyTheme(saved, { persist: false });
  }
  try { localStorage.removeItem(STORAGE_KEY); } catch { }
  return applyTheme(systemTheme(), { persist: false });
}

export function applySessionTheme(session) {
  if (session?.theme) applyTheme(session.theme, { scope: "account" });
}

window.addEventListener("storage", event => {
  if (event.key !== STORAGE_KEY && event.key !== GUEST_STORAGE_KEY && event.key !== AUTH_STATE_KEY) return;
  if (event.key === GUEST_STORAGE_KEY && hasAccountSession()) return;
  let saved = null;
  try {
    saved = hasAccountSession()
      ? localStorage.getItem(STORAGE_KEY)
      : (localStorage.getItem(GUEST_STORAGE_KEY) || localStorage.getItem(STORAGE_KEY));
  } catch { }
  applyTheme(THEMES.has(saved) ? saved : systemTheme(), { persist: false });
});

systemThemeQuery.addEventListener("change", () => {
  try {
    const saved = hasAccountSession()
      ? localStorage.getItem(STORAGE_KEY)
      : (localStorage.getItem(GUEST_STORAGE_KEY) || localStorage.getItem(STORAGE_KEY));
    if (THEMES.has(saved)) return;
  } catch { }
  applyTheme(systemTheme(), { persist: false });
});