import { Link } from "expo-router";
import { useState } from "react";
import {
  KeyboardAvoidingView,
  Platform,
  ScrollView,
  StyleSheet,
  Text,
  View,
} from "react-native";
import { FullScreen } from "@/components/Screen";
import { AuthBackground } from "@/components/AppBackground";
import { AuthServerPicker } from "@/components/AuthServerPicker";
import { HeadingText, Logo } from "@/components/Logo";
import { Button } from "@/components/ui/Button";
import { Card } from "@/components/ui/Card";
import { Input } from "@/components/ui/Input";
import { fonts, spacing } from "@/constants/theme";
import { useAccounts } from "@/contexts/AccountsContext";
import { useAuthClient } from "@/contexts/AuthContext";
import { useAppTheme } from "@/contexts/ThemeContext";
import { registerAccount } from "@/lib/auth-api";
import { completeSignInAfterAuth } from "@/lib/complete-sign-in";
import { isRequiredString, isValidEmail, isValidPassword, useFieldVisibility } from "@/lib/form-validation";

export default function RegisterScreen() {
  const authClient = useAuthClient();
  const { apiUrl, activeAccountId, registerAccount: saveAccount } = useAccounts();
  const { colors } = useAppTheme();
  const [firstName, setFirstName] = useState("");
  const [lastName, setLastName] = useState("");
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");
  const [error, setError] = useState<string | null>(null);
  const [loading, setLoading] = useState(false);
  const [serverReady, setServerReady] = useState(true);
  const { touch, visible, markSubmitted } = useFieldVisibility();

  const firstNameError = isRequiredString(firstName) ? undefined : "First name is required";
  const lastNameError = isRequiredString(lastName) ? undefined : "Last name is required";
  const emailValidationError = isValidEmail(email)
    ? undefined
    : email.trim()
      ? "Enter a valid email"
      : "Email is required";
  const passwordValidationError = isValidPassword(password)
    ? undefined
    : password
      ? "Password must be at least 8 characters"
      : "Password is required";
  const canRegister =
    isRequiredString(firstName) &&
    isRequiredString(lastName) &&
    isValidEmail(email) &&
    isValidPassword(password) &&
    serverReady;

  async function handleRegister() {
    markSubmitted();
    if (!canRegister) return;
    setError(null);
    setLoading(true);

    try {
      await registerAccount({
        firstName: firstName.trim(),
        lastName: lastName.trim(),
        email: email.trim(),
        password,
      });

      const { error: signInError } = await authClient.signIn.email({
        email: email.trim(),
        password,
      });

      if (signInError) {
        setError(signInError.message || "Account created but sign-in failed. Try signing in.");
        return;
      }

      const session = await authClient.getSession();
      const user = session.data?.user;
      if (user) {
        await completeSignInAfterAuth(authClient, {
          apiUrl,
          activeAccountId,
          registerAccount: saveAccount,
        });
      }
    } catch (err) {
      setError(err instanceof Error ? err.message : "Registration failed");
    } finally {
      setLoading(false);
    }
  }

  return (
    <AuthBackground>
      <FullScreen style={styles.safe}>
        <KeyboardAvoidingView
          behavior={Platform.OS === "ios" ? "padding" : undefined}
          style={styles.flex}
        >
          <ScrollView
            contentContainerStyle={styles.container}
            keyboardShouldPersistTaps="handled"
          >
            <View style={styles.content}>
              <Card style={styles.card}>
                <View style={styles.header}>
                  <Logo size="lg" />
                  <HeadingText style={styles.title}>Create your account</HeadingText>
                  <Text style={[styles.subtitle, { color: colors.mutedForeground }]}>
                    Get started today
                  </Text>
                </View>

                <AuthServerPicker onReadyChange={setServerReady} embedded />

              <View style={styles.form}>
                <View style={styles.row}>
                  <View style={styles.half}>
                    <Input
                      label="First name"
                      value={firstName}
                      onChangeText={setFirstName}
                      onBlur={() => touch("firstName")}
                      autoComplete="given-name"
                      placeholder="Jane"
                      required
                      error={visible("firstName") ? firstNameError : undefined}
                    />
                  </View>
                  <View style={styles.half}>
                    <Input
                      label="Last name"
                      value={lastName}
                      onChangeText={setLastName}
                      onBlur={() => touch("lastName")}
                      autoComplete="family-name"
                      placeholder="Doe"
                      required
                      error={visible("lastName") ? lastNameError : undefined}
                    />
                  </View>
                </View>

                <Input
                  label="Email"
                  autoCapitalize="none"
                  autoComplete="email"
                  keyboardType="email-address"
                  value={email}
                  onChangeText={setEmail}
                  onBlur={() => touch("email")}
                  placeholder="you@example.com"
                  required
                  error={visible("email") ? emailValidationError : undefined}
                />
                <Input
                  label="Password"
                  secureTextEntry
                  autoComplete="new-password"
                  value={password}
                  onChangeText={setPassword}
                  onBlur={() => touch("password")}
                  placeholder="At least 8 characters"
                  required
                  error={visible("password") ? passwordValidationError : undefined}
                />

                {error ? (
                  <Text style={[styles.error, { color: colors.destructive }]}>{error}</Text>
                ) : null}

                <Button
                  title="Create Account"
                  loading={loading}
                  disabled={!canRegister}
                  onPress={handleRegister}
                />
              </View>

              <Text style={[styles.footer, { color: colors.mutedForeground }]}>
                Already have an account?{" "}
                <Link href="/(auth)/sign-in" style={[styles.link, { color: colors.foreground }]}>
                  Sign in
                </Link>
              </Text>
            </Card>
            </View>
          </ScrollView>
        </KeyboardAvoidingView>
      </FullScreen>
    </AuthBackground>
  );
}

const styles = StyleSheet.create({
  safe: { flex: 1 },
  flex: { flex: 1 },
  container: {
    flexGrow: 1,
    justifyContent: "center",
    alignItems: "center",
    padding: spacing.lg,
    paddingVertical: spacing.xl,
  },
  content: {
    width: "100%",
    maxWidth: 420,
  },
  card: {
    gap: spacing.lg,
  },
  header: {
    alignItems: "center",
    gap: spacing.sm,
  },
  title: {
    fontSize: 24,
    marginTop: spacing.sm,
    textAlign: "center",
  },
  subtitle: {
    fontSize: 14,
    fontFamily: fonts.body,
    textAlign: "center",
  },
  form: { gap: spacing.md },
  row: { flexDirection: "row", gap: spacing.md },
  half: { flex: 1 },
  error: {
    fontSize: 14,
    fontFamily: fonts.body,
  },
  footer: {
    textAlign: "center",
    fontSize: 14,
    fontFamily: fonts.body,
  },
  link: {
    fontFamily: fonts.bodySemiBold,
  },
});