import { StatusBar } from "expo-status-bar";
import React, { useState, useEffect } from "react";
import { View, TextInput, Text, Button, Alert, StyleSheet } from "react-native";
import { db, firestore, auth } from "./FirebaseConfig";
import {
  createUserWithEmailAndPassword,
  signOut,
  signInWithEmailAndPassword,
  onAuthStateChanged,
} from "firebase/auth";
import { ref, set, onValue } from "firebase/database";
import { doc, setDoc, onSnapshot } from "firebase/firestore";

export default function App() {
  const [registrationEmail, setRegistrationEmail] = useState("");
  const [registrationPassword, setRegistrationPassword] = useState("");
  const [loginEmail, setLoginEmail] = useState("");
  const [loginPassword, setLoginPassword] = useState("");
  const [loggedIn, setLoggedIn] = useState(false);
  const [databaseData, setDatabaseData] = useState("");
  const [user, setUser] = useState(null);

  // Monitor authentication state
  useEffect(() => {
    const unsubscribe = onAuthStateChanged(auth, (currentUser) => {
      setUser(currentUser);
      setLoggedIn(!!currentUser);
    });
    return () => unsubscribe();
  }, []);

  const registerWithFirebase = () => {
    if (registrationEmail.length < 4) {
      Alert.alert("Please enter an email address.");
      return;
    }

    if (registrationPassword.length < 4) {
      Alert.alert("Please enter a password.");
      return;
    }

    createUserWithEmailAndPassword(
      auth,
      registrationEmail,
      registrationPassword
    )
      .then((userCredential) => {
        Alert.alert("User registered successfully!");
        setRegistrationEmail("");
        setRegistrationPassword("");
      })
      .catch((error) => {
        console.log("Registration error:", error);
        if (error.code === "auth/weak-password") {
          Alert.alert("The password is too weak.");
        } else if (error.code === "auth/email-already-in-use") {
          Alert.alert("This email is already registered.");
        } else {
          Alert.alert(error.message);
        }
      });
  };

  const loginWithFirebase = () => {
    if (loginEmail.length < 4) {
      Alert.alert("Please enter an email address.");
      return;
    }

    if (loginPassword.length < 4) {
      Alert.alert("Please enter a password.");
      return;
    }

    signInWithEmailAndPassword(auth, loginEmail, loginPassword)
      .then((userCredential) => {
        Alert.alert("User logged in successfully!");
        setLoginEmail("");
        setLoginPassword("");
      })
      .catch((error) => {
        console.log("Login error:", error);
        if (error.code === "auth/wrong-password") {
          Alert.alert("Wrong password.");
        } else if (error.code === "auth/user-not-found") {
          Alert.alert("User not found.");
        } else {
          Alert.alert(error.message);
        }
      });
  };

  const signoutWithFirebase = () => {
    signOut(auth)
      .then(() => {
        Alert.alert("User was logged out!");
        setDatabaseData("");
      })
      .catch((error) => {
        Alert.alert("Error signing out:", error.message);
      });
  };

  const saveDataWithFirebase = () => {
    if (!user) {
      Alert.alert("Please log in first.");
      return;
    }

    const userID = user.uid;

    // Save to Realtime DB
    set(ref(db, "users/" + userID), {
      text: databaseData,
      timestamp: Date.now(),
    })
      .then(() => {
        console.log("Data saved to Realtime DB");
      })
      .catch((error) => {
        console.log("Realtime DB error:", error);
      });

    // Save to Firestore
    setDoc(
      doc(firestore, "users", userID),
      {
        text: databaseData,
        timestamp: Date.now(),
      },
      { merge: true }
    )
      .then(() => {
        Alert.alert("Data saved successfully!");
      })
      .catch((error) => {
        Alert.alert("Error saving data");
        console.log("Firestore error:", error);
      });
  };

  const retrieveDataWithFirebase = () => {
    if (!user) {
      Alert.alert("Please log in first.");
      return;
    }

    const userID = user.uid;
    const dbRef = ref(db, "users/" + userID);

    // Using Realtime DB
    onValue(dbRef, (snapshot) => {
      if (snapshot.exists()) {
        const data = snapshot.val();
        setDatabaseData(data.text || "");
        Alert.alert("Data retrieved from Realtime DB");
      } else {
        Alert.alert("No data found");
      }
    });

    // Uncomment for Firestore
    /*
    const unsubscribe = onSnapshot(doc(firestore, "users", userID), (doc) => {
      if (doc.exists()) {
        const data = doc.data();
        setDatabaseData(data.text || "");
        Alert.alert("Data retrieved from Firestore");
      } else {
        Alert.alert("No data found in Firestore");
      }
    });
    */
  };

  return (
    <View style={styles.form}>
      <StatusBar style="auto" />

      {!loggedIn ? (
        <View>
          <View style={styles.section}>
            <Text style={styles.label}>Lab 5 - l_mclean215318</Text>
            <Text style={styles.label}>Register with Firebase</Text>
            <TextInput
              style={styles.textInput}
              onChangeText={setRegistrationEmail}
              value={registrationEmail}
              autoCapitalize="none"
              autoCorrect={false}
              autoCompleteType="email"
              keyboardType="email-address"
              placeholder="Email"
            />
            <TextInput
              style={styles.textInput}
              onChangeText={setRegistrationPassword}
              value={registrationPassword}
              autoCapitalize="none"
              autoCorrect={false}
              autoCompleteType="password"
              placeholder="Password"
              secureTextEntry={true}
            />
            <Button title="Register" onPress={registerWithFirebase} />
          </View>

          <View style={styles.section}>
            <Text style={styles.label}>Sign In with Firebase</Text>
            <TextInput
              style={styles.textInput}
              onChangeText={setLoginEmail}
              value={loginEmail}
              autoCapitalize="none"
              autoCorrect={false}
              autoCompleteType="email"
              keyboardType="email-address"
              placeholder="Email"
            />
            <TextInput
              style={styles.textInput}
              onChangeText={setLoginPassword}
              value={loginPassword}
              autoCapitalize="none"
              autoCorrect={false}
              autoCompleteType="password"
              placeholder="Password"
              secureTextEntry={true}
            />
            <Button title="Login" onPress={loginWithFirebase} />
          </View>
        </View>
      ) : (
        <View>
          <Text style={styles.welcome}>Welcome, {user?.email}</Text>
          <TextInput
            style={styles.textArea}
            multiline={true}
            numberOfLines={4}
            onChangeText={setDatabaseData}
            value={databaseData}
            placeholder="Enter your data here..."
          />
          <View style={styles.buttonContainer}>
            <Button title="Save Data" onPress={saveDataWithFirebase} />
            <Button title="Load Data" onPress={retrieveDataWithFirebase} />
          </View>
          <View style={styles.signOutButton}>
            <Button
              title="Sign Out"
              onPress={signoutWithFirebase}
              color="#ff4444"
            />
          </View>
        </View>
      )}
    </View>
  );
}

const styles = StyleSheet.create({
  form: {
    flex: 1,
    margin: 30,
    marginTop: 60,
  },
  section: {
    marginBottom: 30,
  },
  label: {
    fontSize: 18,
    marginBottom: 15,
    textAlign: "center",
    fontWeight: "bold",
  },
  welcome: {
    fontSize: 18,
    marginBottom: 20,
    textAlign: "center",
    fontWeight: "bold",
  },
  textInput: {
    borderColor: "#ccc",
    borderWidth: 1,
    marginBottom: 15,
    paddingVertical: 8,
    paddingHorizontal: 10,
    borderRadius: 5,
  },
  textArea: {
    borderColor: "#ccc",
    borderWidth: 1,
    marginBottom: 15,
    paddingVertical: 8,
    paddingHorizontal: 10,
    borderRadius: 5,
    height: 100,
    textAlignVertical: "top",
  },
  buttonContainer: {
    flexDirection: "row",
    justifyContent: "space-between",
    marginBottom: 20,
  },
  signOutButton: {
    marginTop: 20,
  },
});