import { Link, router } from "expo-router";
import { useState } from "react";
import {
  KeyboardAvoidingView,
  Platform,
  Pressable,
  ScrollView,
  StyleSheet,
  Text,
  View,
} from "react-native";
import { AuthBackground } from "@/components/AppBackground";
import { AuthServerPicker } from "@/components/AuthServerPicker";
import { HeadingText, Logo } from "@/components/Logo";
import { FullScreen } from "@/components/Screen";
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 { finalizeAuthenticatedAccount } from "@/lib/auth-storage";
import { isRequiredString, isValidEmail, useFieldVisibility } from "@/lib/form-validation";

export default function SignInScreen() {
  const authClient = useAuthClient();
  const { apiUrl, activeAccountId, registerAccount } = useAccounts();
  const { colors } = useAppTheme();
  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 emailValidationError = !email.trim()
    ? "Email is required"
    : isValidEmail(email)
      ? undefined
      : "Enter a valid email";
  const passwordValidationError = password.trim() ? undefined : "Password is required";
  const canSignIn = isValidEmail(email) && isRequiredString(password) && serverReady;

  async function handleSignIn() {
    markSubmitted();
    if (!canSignIn) return;
    setError(null);
    setLoading(true);

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

      if (signInError) {
        const message = signInError.message ?? "";
        if (message.toLowerCase().includes("internal") || message.includes("500")) {
          setError("Server error — is the API running with Postgres? Check beenvoice dev + docker.");
        } else {
          setError(message || "Invalid email or password");
        }
        return;
      }

      const session = await authClient.getSession();
      const user = session.data?.user;
      if (user) {
        await finalizeAuthenticatedAccount({
          apiUrl,
          userId: user.id,
          email: user.email,
          name: user.name,
          activeAccountId,
          registerAccount,
        });
      }
    } 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"
          >
            <AuthServerPicker onReadyChange={setServerReady} />
            <Card style={styles.card}>
              <View style={styles.header}>
                <Logo size="lg" />
                <HeadingText style={styles.title}>Welcome back</HeadingText>
                <Text style={[styles.subtitle, { color: colors.mutedForeground }]}>
                  Sign in to manage invoices on the go
                </Text>
              </View>

              <View style={styles.form}>
                <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="password"
                  value={password}
                  onChangeText={setPassword}
                  onBlur={() => touch("password")}
                  placeholder="••••••••"
                  required
                  error={visible("password") ? passwordValidationError : undefined}
                />

                <Pressable onPress={() => router.push("/(auth)/forgot-password")}>
                  <Text style={[styles.forgot, { color: colors.mutedForeground }]}>
                    Forgot password?
                  </Text>
                </Pressable>

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

                <Button
                  title="Sign In"
                  loading={loading}
                  disabled={!canSignIn}
                  onPress={handleSignIn}
                />
              </View>

              <Text style={[styles.footer, { color: colors.mutedForeground }]}>
                Don&apos;t have an account?{" "}
                <Link href="/(auth)/register" style={[styles.link, { color: colors.foreground }]}>
                  Create one
                </Link>
              </Text>
            </Card>
          </ScrollView>
        </KeyboardAvoidingView>
      </FullScreen>
    </AuthBackground>
  );
}

const styles = StyleSheet.create({
  safe: {
    flex: 1,
  },
  flex: {
    flex: 1,
  },
  container: {
    flexGrow: 1,
    justifyContent: "center",
    padding: spacing.lg,
    paddingBottom: spacing.md,
  },
  card: {
    gap: spacing.lg,
  },
  header: {
    gap: spacing.sm,
  },
  title: {
    fontSize: 24,
    marginTop: spacing.sm,
  },
  subtitle: {
    fontSize: 14,
    fontFamily: fonts.body,
  },
  form: {
    gap: spacing.md,
  },
  forgot: {
    alignSelf: "flex-end",
    fontFamily: fonts.bodyMedium,
    fontSize: 12,
  },
  error: {
    fontSize: 14,
    fontFamily: fonts.body,
  },
  footer: {
    textAlign: "center",
    fontSize: 14,
    fontFamily: fonts.body,
  },
  link: {
    fontFamily: fonts.bodySemiBold,
  },
});