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

export type Theme = "catppuccin-mocha" | "tokyo-night" | "catppuccin-latte";

export const THEME_META: Record<Theme, { label: string; dark: boolean; bg: string; primary: string }> = {
  "catppuccin-mocha": { label: "Catppuccin Mocha", dark: true, bg: "#1e1e2e", primary: "#89b4fa" },
  "tokyo-night":      { label: "Tokyo Night",       dark: true, bg: "#1a1b26", primary: "#7aa2f7" },
  "catppuccin-latte": { label: "Catppuccin Latte",  dark: false, bg: "#eff1f5", primary: "#1e66f5" },
};

const VALID_THEMES: Theme[] = ["catppuccin-mocha", "tokyo-night", "catppuccin-latte"];
const DEFAULT_THEME: Theme = "catppuccin-mocha";

interface ThemeContextValue {
  theme: Theme;
  setTheme: (theme: Theme) => void;
  toggleTheme: () => void;
}

const THEME_STORAGE_KEY = "paperclip.theme";
const ThemeContext = createContext<ThemeContextValue | undefined>(undefined);

function isValidTheme(value: string | null): value is Theme {
  return value !== null && VALID_THEMES.includes(value as Theme);
}

function readStoredTheme(): Theme {
  if (typeof document === "undefined") return DEFAULT_THEME;
  try {
    const stored = localStorage.getItem(THEME_STORAGE_KEY);
    return isValidTheme(stored) ? stored : DEFAULT_THEME;
  } catch {
    return DEFAULT_THEME;
  }
}

function applyTheme(theme: Theme) {
  if (typeof document === "undefined") return;
  const meta = THEME_META[theme];
  const root = document.documentElement;
  root.classList.toggle("dark", meta.dark);
  root.classList.toggle("theme-tokyo-night", theme === "tokyo-night");
  root.style.colorScheme = meta.dark ? "dark" : "light";
  const themeColorMeta = document.querySelector('meta[name="theme-color"]');
  if (themeColorMeta instanceof HTMLMetaElement) {
    themeColorMeta.setAttribute("content", meta.bg);
  }
}

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setThemeState] = useState<Theme>(() => readStoredTheme());

  const setTheme = useCallback((nextTheme: Theme) => {
    setThemeState(nextTheme);
  }, []);

  const toggleTheme = useCallback(() => {
    setThemeState((current) => {
      const idx = VALID_THEMES.indexOf(current);
      return VALID_THEMES[(idx + 1) % VALID_THEMES.length];
    });
  }, []);

  useEffect(() => {
    applyTheme(theme);
    try {
      localStorage.setItem(THEME_STORAGE_KEY, theme);
    } catch {
      // Ignore localStorage write failures in restricted environments.
    }
  }, [theme]);

  const value = useMemo(
    () => ({
      theme,
      setTheme,
      toggleTheme,
    }),
    [theme, setTheme, toggleTheme],
  );

  return (
    <ThemeContext.Provider value={value}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  const context = useContext(ThemeContext);
  if (!context) {
    throw new Error("useTheme must be used within ThemeProvider");
  }
  return context;
}