import { createSignal, createContext, useContext, createEffect, type ParentComponent } from "solid-js";

type Theme = "dark" | "light" | "system";

interface ThemeProviderState {
    theme: () => Theme;
    setTheme: (theme: Theme) => void;
    resolvedTheme: () => "light" | "dark";
}

const ThemeProviderContext = createContext<ThemeProviderState>();

export const ThemeProvider: ParentComponent = (props) => {
    const [theme, setTheme] = createSignal<Theme>("system");
    const [resolvedTheme, setResolvedTheme] = createSignal<"light" | "dark">("light");

    // Load from local storage on mount
    const storedTheme = localStorage.getItem("tasgrid-theme") as Theme | null;
    if (storedTheme) {
        setTheme(storedTheme);
    }

    createEffect(() => {
        const root = window.document.documentElement;
        root.classList.remove("light", "dark");

        const currentTheme = theme();
        let resolved: "light" | "dark";

        if (currentTheme === "system") {
            resolved = window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
            root.classList.add(resolved);
        } else {
            resolved = currentTheme === "dark" ? "dark" : "light";
            root.classList.add(resolved);
        }

        setResolvedTheme(resolved);
        localStorage.setItem("tasgrid-theme", currentTheme);
    });

    return (
        <ThemeProviderContext.Provider value={{ theme, setTheme, resolvedTheme }}>
            {props.children}
        </ThemeProviderContext.Provider>
    );
};

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