import { router, useLocalSearchParams } from "expo-router";
import { useEffect, useState } from "react";
import {
  KeyboardAvoidingView,
  Platform,
  Pressable,
  ScrollView,
  StyleSheet,
  Text,
  View,
} from "react-native";
import { FullScreen } from "@/components/Screen";
import { AuthBackground } from "@/components/AppBackground";
import { AuthServerPicker } from "@/components/AuthServerPicker";
import { HeadingText } from "@/components/Logo";
import { Button } from "@/components/ui/Button";
import { Card } from "@/components/ui/Card";
import { Input } from "@/components/ui/Input";
import { fonts, radii, spacing } from "@/constants/theme";
import { useAppTheme } from "@/contexts/ThemeContext";
import { resetPassword } from "@/lib/auth-api";
import type { ThemeColors } from "@/lib/theme-palette";
import { useThemedStyles } from "@/lib/use-themed-styles";
import { isRequiredString, isValidPassword } from "@/lib/form-validation";

export default function ResetPasswordScreen() {
  const styles = useThemedStyles(createResetPasswordStyles);
  const { token: tokenParam } = useLocalSearchParams<{ token?: string }>();
  const [token, setToken] = useState("");
  const [password, setPassword] = useState("");
  const [confirmPassword, setConfirmPassword] = useState("");
  const [error, setError] = useState<string | null>(null);
  const [success, setSuccess] = useState(false);
  const [loading, setLoading] = useState(false);
  const [serverReady, setServerReady] = useState(true);

  useEffect(() => {
    if (typeof tokenParam === "string" && tokenParam.length > 0) {
      setToken(tokenParam);
    }
  }, [tokenParam]);

  const tokenError = isRequiredString(token) ? undefined : "Reset token is required";
  const passwordError = isValidPassword(password)
    ? undefined
    : password
      ? "Password must be at least 8 characters"
      : "Password is required";
  const confirmError =
    confirmPassword && password !== confirmPassword ? "Passwords do not match" : undefined;
  const canSubmit =
    serverReady &&
    isRequiredString(token) &&
    isValidPassword(password) &&
    password === confirmPassword &&
    confirmPassword.length > 0;

  async function handleSubmit() {
    if (!canSubmit) return;
    setError(null);

    setLoading(true);

    try {
      await resetPassword(token.trim(), password);
      setSuccess(true);
    } catch (err) {
      setError(err instanceof Error ? err.message : "Reset failed");
    } finally {
      setLoading(false);
    }
  }

  return (
    <AuthBackground>
      <FullScreen style={styles.safe}>
        <KeyboardAvoidingView
          behavior={Platform.OS === "ios" ? "padding" : undefined}
          style={styles.flex}
        >
          <ScrollView contentContainerStyle={styles.container}>
            <Pressable onPress={() => router.back()}>
              <Text style={styles.back}>← Back</Text>
            </Pressable>

            <AuthServerPicker onReadyChange={setServerReady} />

            <Card style={styles.card}>
              <View style={styles.header}>
                <HeadingText style={styles.title}>Set new password</HeadingText>
                <Text style={styles.subtitle}>
                  Paste the reset token from your email, or open the link on this device.
                </Text>
              </View>

              {success ? (
                <View style={styles.successBox}>
                  <Text style={styles.successTitle}>Password updated</Text>
                  <Text style={styles.successText}>
                    You can now sign in with your new password.
                  </Text>
                  <Button
                    title="Go to sign in"
                    onPress={() => router.replace("/(auth)/sign-in")}
                  />
                </View>
              ) : (
                <View style={styles.form}>
                  <Input
                    label="Reset token"
                    autoCapitalize="none"
                    value={token}
                    onChangeText={setToken}
                    placeholder="Paste token from email"
                    required
                    error={tokenError}
                  />
                  <Input
                    label="New password"
                    secureTextEntry
                    value={password}
                    onChangeText={setPassword}
                    placeholder="At least 8 characters"
                    required
                    error={passwordError}
                  />
                  <Input
                    label="Confirm password"
                    secureTextEntry
                    value={confirmPassword}
                    onChangeText={setConfirmPassword}
                    placeholder="Repeat password"
                    required
                    error={confirmError}
                  />

                  {error ? <Text style={styles.error}>{error}</Text> : null}

                  <Button
                    title="Update password"
                    loading={loading}
                    disabled={!canSubmit}
                    onPress={handleSubmit}
                  />
                </View>
              )}
            </Card>
          </ScrollView>
        </KeyboardAvoidingView>
      </FullScreen>
    </AuthBackground>
  );
}

const createResetPasswordStyles = (colors: ThemeColors, _isDark: boolean) =>
  StyleSheet.create({
    safe: { flex: 1 },
    flex: { flex: 1 },
    container: {
      flexGrow: 1,
      padding: spacing.lg,
      gap: spacing.md,
      justifyContent: "center",
    },
    back: {
      color: colors.mutedForeground,
      fontFamily: fonts.bodyMedium,
      fontSize: 16,
      marginBottom: spacing.sm,
    },
    card: { gap: spacing.lg },
    header: { gap: spacing.sm },
    title: { fontSize: 28 },
    subtitle: {
      fontSize: 14,
      fontFamily: fonts.body,
      color: colors.mutedForeground,
      lineHeight: 20,
    },
    form: { gap: spacing.md },
    error: {
      color: colors.destructive,
      fontSize: 14,
      fontFamily: fonts.body,
    },
    successBox: {
      gap: spacing.md,
      padding: spacing.lg,
      backgroundColor: colors.muted,
      borderRadius: radii.xl,
      borderWidth: 1,
      borderColor: colors.border,
    },
    successTitle: {
      fontSize: 20,
      fontFamily: fonts.heading,
      color: colors.foreground,
    },
    successText: {
      color: colors.mutedForeground,
      fontFamily: fonts.body,
      lineHeight: 20,
    },
  });