import { createClient } from "@supabase/supabase-js";
import AsyncStorage from "@react-native-async-storage/async-storage";
import * as SecureStore from "expo-secure-store";
import * as aesjs from "aes-js";
import "react-native-get-random-values";
import { AppState } from "react-native";

// As Expo's SecureStore does not support values larger than 2048
// bytes, an AES-256 key is generated and stored in SecureStore, while
// it is used to encrypt/decrypt values stored in AsyncStorage.
class LargeSecureStore {
    private async _encrypt(key: string, value: string) {
    const encryptionKey = crypto.getRandomValues(new Uint8Array(256 / 8));

    const cipher = new aesjs.ModeOfOperation.ctr(encryptionKey,new aesjs.Counter(1));
    const encryptedBytes = cipher.encrypt(aesjs.utils.utf8.toBytes(value));

    await SecureStore.setItemAsync(key,aesjs.utils.hex.fromBytes(encryptionKey));

    return aesjs.utils.hex.fromBytes(encryptedBytes);
    }

    private async _decrypt(key: string, value: string) {
        const encryptionKeyHex = await SecureStore.getItemAsync(key);
        if (!encryptionKeyHex) {
            return encryptionKeyHex;
        }

        const cipher = new aesjs.ModeOfOperation.ctr(
            aesjs.utils.hex.toBytes(encryptionKeyHex),
            new aesjs.Counter(1)
        );
        const decryptedBytes = cipher.decrypt(aesjs.utils.hex.toBytes(value));

        return aesjs.utils.utf8.fromBytes(decryptedBytes);
    }

    async getItem(key: string) {
        const encrypted = await AsyncStorage.getItem(key);
        if (!encrypted) {
            return encrypted;
        }

        return await this._decrypt(key, encrypted);
    }

    async removeItem(key: string) {
        await AsyncStorage.removeItem(key);
        await SecureStore.deleteItemAsync(key);
    }

    async setItem(key: string, value: string) {
        const encrypted = await this._encrypt(key, value);

        await AsyncStorage.setItem(key, encrypted);
    }
}

//Supabase client component
export const supabase = createClient(
    process.env.EXPO_PUBLIC_SUPABASE_URL || "",
    process.env.EXPO_PUBLIC_SUPABASE_ANON_KEY || "",
    {
        auth: {
        storage: new LargeSecureStore(),
        persistSession: true,
        autoRefreshToken: true,
        detectSessionInUrl: false,
        flowType: "implicit",
        },
    }
);

AppState.addEventListener("change", (nextAppState) => {
    if (nextAppState === "active") {
        supabase.auth.startAutoRefresh();
    } else {
        supabase.auth.stopAutoRefresh();
    }
});