import { useState, useEffect } from "react";
import { useSignIn, useAuth } from "@clerk/clerk-expo";
import { useRouter } from "expo-router";
import {
  View,
  Text,
  TouchableOpacity,
  StyleSheet,
  ActivityIndicator,
  KeyboardAvoidingView,
  Platform,
  ScrollView,
} from "react-native";
import { OAuthButtons } from "../../components/auth/OAuthButtons";
import { Input } from "../../components/Input";
import { MinimalButton } from "../../components/MinimalButton";
import { useTheme } from "../../contexts/ThemeContext";
import { getErrorMessage, getClerkErrorCode } from "../../utils/error-helpers";
import log from "../../utils/logger";

export default function SignInScreen() {
  const { signIn, setActive, isLoaded } = useSignIn();
  const { isSignedIn } = useAuth();
  const router = useRouter();

  const [emailAddress, setEmailAddress] = useState("");
  const [password, setPassword] = useState("");
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState("");
  const { colors, typography } = useTheme();

  // Redirect if already signed in
  useEffect(() => {
    if (isSignedIn) {
      router.replace("/(tabs)");
    }
  }, [isSignedIn]);

  const onSignInPress = async () => {
    if (!isLoaded) return;

    setLoading(true);
    setError("");

    try {
      const signInAttempt = await signIn.create({
        identifier: emailAddress,
        password,
      });

      if (signInAttempt.status === "complete") {
        await setActive({ session: signInAttempt.createdSessionId });
        router.replace("/(tabs)");
      } else {
        log.warn("Sign-in incomplete", { status: signInAttempt.status });
        setError("Sign-in incomplete. Please try again.");
      }
    } catch (err: unknown) {
      log.error("Sign-in failed", err);

      // Handle specific error codes
      if (getClerkErrorCode(err) === "session_exists") {
        // User is already signed in, just redirect
        router.replace("/(tabs)");
        return;
      }

      setError(
        getErrorMessage(
          err,
          "Failed to sign in. Please check your credentials.",
        ),
      );
    } finally {
      setLoading(false);
    }
  };

  // Don't render the form if already signed in
  if (isSignedIn) {
    return (
      <View style={[styles.container, styles.centerContent]}>
        <ActivityIndicator size="large" color={colors.primary} />
        <Text
          style={[
            typography.body,
            { color: colors.textSecondary, marginTop: 12 },
          ]}
        >
          Redirecting...
        </Text>
      </View>
    );
  }

  return (
    <KeyboardAvoidingView
      behavior={Platform.OS === "ios" ? "padding" : "height"}
      style={[styles.container, { backgroundColor: colors.background }]}
    >
      <ScrollView
        contentContainerStyle={styles.scrollContent}
        keyboardShouldPersistTaps="handled"
      >
        <View style={styles.content}>
          <Text
            style={[typography.h1, { color: colors.textPrimary }, styles.title]}
          >
            Welcome Back
          </Text>
          <Text
            style={[
              typography.body,
              { color: colors.textSecondary },
              styles.subtitle,
            ]}
          >
            Sign in to continue to FitAI
          </Text>

          {error ? (
            <View style={styles.errorContainer}>
              <Text style={[typography.caption, { color: colors.danger }]}>
                {error}
              </Text>
            </View>
          ) : null}

          <OAuthButtons />

          <View style={styles.dividerContainer}>
            <View style={styles.dividerLine} />
            <Text style={styles.dividerText}>OR</Text>
            <View style={styles.dividerLine} />
          </View>

          <View style={styles.form}>
            <View style={styles.inputContainer}>
              <Input
                label="Email"
                autoCapitalize="none"
                value={emailAddress}
                placeholder="Enter your email"
                onChangeText={setEmailAddress}
                keyboardType="email-address"
                autoComplete="email"
                editable={!loading}
              />
            </View>

            <View style={styles.inputContainer}>
              <Input
                label="Password"
                value={password}
                placeholder="Enter your password"
                secureTextEntry={true}
                onChangeText={setPassword}
                autoComplete="password"
                editable={!loading}
              />
            </View>

            <MinimalButton
              title="Sign In"
              onPress={onSignInPress}
              loading={loading}
              disabled={loading || !emailAddress || !password}
              fullWidth
              size="lg"
            />
          </View>

          <View style={styles.footer}>
            <Text style={[typography.caption, { color: colors.textSecondary }]}>
              Don't have an account?{" "}
            </Text>
            <TouchableOpacity
              onPress={() => router.push("/(auth)/sign-up")}
              disabled={loading}
            >
              <Text
                style={[typography.bodyEmphasis, { color: colors.primary }]}
              >
                Sign Up
              </Text>
            </TouchableOpacity>
          </View>
        </View>
      </ScrollView>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  centerContent: {
    justifyContent: "center",
    alignItems: "center",
  },
  scrollContent: {
    flexGrow: 1,
    justifyContent: "center",
  },
  content: {
    flex: 1,
    justifyContent: "center",
    paddingHorizontal: 24,
    paddingVertical: 40,
  },
  title: {
    marginBottom: 8,
  },
  subtitle: {
    marginBottom: 32,
  },
  errorContainer: {
    backgroundColor: "rgba(255, 59, 59, 0.08)",
    padding: 12,
    borderRadius: 12,
    marginBottom: 16,
    borderLeftWidth: 4,
    borderLeftColor: "#FF3B3B",
  },
  form: {
    marginBottom: 24,
  },
  inputContainer: {
    marginBottom: 20,
  },
  footer: {
    flexDirection: "row",
    justifyContent: "center",
    alignItems: "center",
  },
  dividerContainer: {
    flexDirection: "row",
    alignItems: "center",
    marginBottom: 24,
  },
  dividerLine: {
    flex: 1,
    height: 1,
    backgroundColor: "#E5E5EA",
  },
  dividerText: {
    marginHorizontal: 10,
    color: "#8E8E93",
    fontSize: 14,
  },
});