"use client";
import React, { useEffect, useState, useRef } from "react";
import {
    Text,
    Title,
    Box,
    Image,
    Button,
    Group,
    Container,
    ActionIcon,
    Divider,
    PinInput,
    Paper,
    Stack,
    Center,
    Loader,
} from "@mantine/core";
import { Providers } from "@/app/providers";
import { useRouter } from "next/navigation";
import NextImage from "next/image";
import logo from "@/app/image/logo1.jpg";
import { IconLogout, IconShieldCheck, IconRefresh } from "@tabler/icons-react";
import { useMediaQuery } from "@mantine/hooks";
import { sendOtp, verifyOtp } from "../otpUtils";
import { fetchUserDetails } from "../authUtils";

export default function VerifyOtpPage() {
    const router = useRouter();
    const [authorized, setAuthorized] = useState<boolean | null>(null);
    const [custname, setCustname] = useState<string | null>(null);
    const [otp, setOtp] = useState("");
    const [isVerifying, setIsVerifying] = useState(false);
    const [isResending, setIsResending] = useState(false);
    const [timer, setTimer] = useState(60);
    const [canResend, setCanResend] = useState(false);
    const isMobile = useMediaQuery("(max-width: 768px)");
    const timerRef = useRef<NodeJS.Timeout | null>(null);
    const otpSentRef = useRef(false);

    //On First Load: Check Token → Fetch User → Send OTP
    useEffect(() => {
        const token = localStorage.getItem("mandate_token");
        if (!token) {
            handleLogout();
            setAuthorized(false);
            return;
        }

        setAuthorized(true);

        // Get User Name + Mobile
        fetchUserDetails().then((res) => {
            if (res) {
                setCustname(res.name);
                if (!otpSentRef.current) {
                    sendOtp(res.mobile);
                    // sendOtp("7890544527");
                    otpSentRef.current = true; // Prevent second OTP
                }
            }
        });

        // Prevent back button
        const handlePopState = () => {
            handleLogout();
        };
        window.addEventListener("popstate", handlePopState);
        window.history.pushState(null, "", window.location.href);

        return () => {
            window.removeEventListener("popstate", handlePopState);
            if (timerRef.current) clearInterval(timerRef.current);
        };
    }, []);


    // Timer Countdown
    useEffect(() => {
        timerRef.current = setInterval(() => {
            setTimer((prev) => {
                if (prev === 1) {
                    setCanResend(true);
                    clearInterval(timerRef.current!);
                }
                return prev - 1;
            });
        }, 1000);

        return () => clearInterval(timerRef.current!);
    }, []);


    // Logout
    const handleLogout = () => {
        localStorage.clear();
        router.push("/eMandate/logout");
    };

    //Resend OTP 
    const handleResendOtp = async () => {
        setIsResending(true);

        const mobile = localStorage.getItem("userMobNo");
        // const mobile = "7890544527";
        if (!mobile) return;

        await sendOtp(mobile);
        setTimer(60);
        setCanResend(false);
        setOtp("");

        setIsResending(false);
    };


    // Verify OTP using verifyOtp() Utility

    // const handleVerifyOtp = async () => {
    //     const mobile = localStorage.getItem("userMobNo");
    //     // const mobile = "7890544527";
    //     if (!mobile || otp.length !== 6) return;

    //     setIsVerifying(true);

    //     const success = await verifyOtp(otp, mobile);

    //     // if (success) {
    //     //     // const encoded_data = localStorage.getItem("Validate_data");
    //     //     // const res = await fetch(
    //     //     //     `https://apiemandate.kccb.in:9035/EMandate/auth-cbs-resp?data=${encoded_data}`,
    //     //     //     {
    //     //     //         method: "POST",
    //     //     //         headers: {
    //     //     //             "Content-Type": "application/json",
    //     //     //         },
    //     //     //     }
    //     //     // );
    //     //     const formData = new FormData();
    //     //     const encoded_data = localStorage.getItem("Validate_data");
    //     //     formData.append("data", encoded_data);

    //     //     const res = await fetch(
    //     //         "https://apiemandate.kccb.in:9035/EMandate/auth-cbs-resp",
    //     //         {
    //     //             method: "POST",
    //     //             body: formData,
    //     //         }
    //     //     );

    //     //     const result = await res.json();
    //     //     console.log(result);
    //     //     if (!res.ok) {
    //     //         throw new Error("CBS response API failed");
    //     //     }
    //     //     if (res.ok) {
    //     //         // navigate only after successful API hit
    //     //         setTimeout(() => {
    //     //             router.push("/eMandate/mandate_page");
    //     //         }, 1500);
    //     //     }
    //     // }
    //     if (success) {
    //         try {
    //             const encoded_data = localStorage.getItem("Validate_data");
    //             if (!encoded_data) {
    //                 console.error("Validate_data not found in localStorage");
    //                 return;
    //             }
    //             const formData = new FormData();
    //             formData.append("data", encoded_data);

    //             const res = await fetch(
    //                 "https://apiemandate.kccb.in:9035/EMandate/auth-cbs-resp",
    //                 {
    //                     method: "POST",
    //                     body: formData,
    //                 }
    //             );

    //             if (!res.ok) {
    //                 throw new Error(`CBS response API failed: ${res.status}`);
    //             }
    //             const contentType = res.headers.get("content-type");
    //             const result =
    //                 contentType && contentType.includes("application/json")
    //                     ? await res.json()
    //                     : await res.text();

    //             console.log("CBS Response:", result);
    //             setTimeout(() => {
    //                 router.push("/eMandate/mandate_page");
    //             }, 1000);

    //         } catch (error) {
    //             console.error("CBS API Error:", error);
    //         }
    //     }
    //     else {
    //         setOtp("");
    //     }
    //     setIsVerifying(false);
    // };

    const handleVerifyOtp = async () => {
        const mobile = localStorage.getItem("userMobNo");

        if (!mobile || otp.length !== 6) return;

        setIsVerifying(true);
        const success = await verifyOtp(otp, mobile);
        if (success) {
            const encoded_data = localStorage.getItem("Validate_data");

            if (!encoded_data) {
                console.error("Validate_data not found in localStorage");
                setIsVerifying(false);
                return;
            }
            const url = "https://apiemandate.kccb.in:9035/EMandate/auth-cbs-resp";
            console.log("Redirecting (POST) to URL:", url);
            console.log("POST Body Data:", { data: encoded_data });

            // Create a form for POST redirect
            const form = document.createElement("form");
            form.method = "POST";
            form.action = url;
            // Add hidden field "data"
            const input = document.createElement("input");
            input.type = "hidden";
            input.name = "data";
            input.value = encoded_data;

            form.appendChild(input);
            document.body.appendChild(form);
            
            // Submit → browser navigates to URL using POST
            form.submit();
            return;
        }
        else {
            setOtp("");
        }
        setIsVerifying(false);
    };


    if (authorized === null) {
        return (
            <Center style={{ height: "100vh" }}>
                <Loader size="lg" color="green" />
            </Center>
        );
    }

    return (
        <Providers>
            <Box
                style={{
                    minHeight: "100vh",
                    display: "flex",
                    flexDirection: "column",
                    // background: "linear-gradient(135deg, #667eea 0%, #764ba2 100%)",
                    background: 'linear-gradient(179deg, #3faa56ff 49%, #3aa760ff 80%)'
                }}
            >
                {/* HEADER */}
                <Paper
                    radius={0}
                    shadow="md"
                    style={{
                        position: "sticky",
                        top: 0,
                        zIndex: 100,
                        background: "linear-gradient(15deg, rgba(10, 114, 40, 1) 55%, rgba(101, 101, 184, 1) 100%)",
                        // padding: isMobile ? "0.75rem 1rem" : "1rem 1.5rem",
                    }}
                >
                    <Container size="xl">
                        <Group justify="space-between">
                            <Group gap="md">
                                <Image
                                    src={logo}
                                    component={NextImage}
                                    fit="contain"
                                    alt="KCC Bank Logo"
                                    style={{
                                        width: isMobile ? "50px" : "70px",
                                        height: isMobile ? "50px" : "70px",
                                    }}
                                />
                                {!isMobile && (
                                    <Title
                                        order={2}
                                        c="white"
                                        style={{
                                            fontSize: "clamp(1rem, 2vw, 1.5rem)",
                                            fontFamily: "Roboto",
                                        }}
                                    >
                                        THE KANGRA CENTRAL CO-OPERATIVE BANK LTD.
                                    </Title>
                                )}
                            </Group>

                            {isMobile ? (
                                <ActionIcon
                                    variant="subtle"
                                    color="white"
                                    size="lg"
                                    onClick={handleLogout}
                                    title="Logout"
                                >
                                    <IconLogout size={24} />
                                </ActionIcon>
                            ) : (
                                <Button
                                    variant="white"
                                    color="gray"
                                    onClick={handleLogout}
                                    leftSection={<IconLogout size={20} />}
                                >
                                    Logout
                                </Button>
                            )}
                        </Group>
                    </Container>
                </Paper>

                {/* WELCOME BAR */}
                <Paper
                    radius={0}
                    p={isMobile ? "sm" : "md"}
                    bg="white"
                    shadow="sm"
                    style={{ borderBottom: "3px solid #0a7228" }}
                >
                    <Container size="xl">
                        <Stack gap="xs">
                            <Text
                                fw={600}
                                size={isMobile ? "lg" : "xl"}
                                style={{ fontFamily: "Inter" }}
                            >
                                Welcome, {custname ?? "User"}
                            </Text>
                            <Divider />
                        </Stack>
                    </Container>
                </Paper>

                {/* MAIN CONTENT */}
                <Box style={{ flex: 1, padding: "2rem 1rem" }}>
                    <Container size="sm">
                        <Center>
                            <Paper
                                shadow="xl"
                                radius="xl"
                                p={isMobile ? "xl" : "2rem"}
                                style={{
                                    maxWidth: "500px",
                                    width: "100%",
                                    background: "rgba(255, 255, 255, 0.95)",
                                    backdropFilter: "blur(10px)",
                                }}
                            >
                                <Stack gap="xl" align="center">
                                    {/* Icon */}
                                    <Box
                                        style={{
                                            width: "80px",
                                            height: "80px",
                                            borderRadius: "50%",
                                            background:
                                                "linear-gradient(135deg, #0a7228 0%, #2563eb 100%)",
                                            display: "flex",
                                            alignItems: "center",
                                            justifyContent: "center",
                                        }}
                                    >
                                        <IconShieldCheck size={48} color="white" />
                                    </Box>

                                    {/* Title */}
                                    <Stack gap="xs" align="center">
                                        <Title
                                            order={2}
                                            ta="center"
                                            style={{
                                                fontSize: isMobile ? "1.5rem" : "2rem",
                                            }}
                                        >
                                            OTP Verification
                                        </Title>
                                        <Text size="sm" c="dimmed" ta="center">
                                            Enter the 6-digit OTP sent to your registered mobile
                                            number
                                        </Text>
                                        <Text size="sm" fw={600} c="blue">
                                            {localStorage.getItem("userMobNo")?.replace(
                                                /(\d{2})(\d{4})(\d{4})/,
                                                "+91 $1****$3"
                                            )}
                                        </Text>
                                    </Stack>

                                    {/* OTP Input */}
                                    <Stack gap="md" align="center" w="100%">
                                        <PinInput
                                            size={isMobile ? "lg" : "xl"}
                                            length={6}
                                            value={otp}
                                            onChange={setOtp}
                                            placeholder="○"
                                            type="number"
                                            oneTimeCode
                                            styles={{
                                                input: {
                                                    fontSize: isMobile ? "1.5rem" : "2rem",
                                                    fontWeight: 600,
                                                    borderColor: "#0a7228",
                                                },
                                            }}
                                        />

                                        {/* Timer */}
                                        <Group gap="xs">
                                            <Text size="sm" c="dimmed">
                                                {canResend ? (
                                                    "Didn't receive OTP?"
                                                ) : (
                                                    <>
                                                        Resend OTP in{" "}
                                                        <Text component="span" fw={600} c="blue">
                                                            {timer}s
                                                        </Text>
                                                    </>
                                                )}
                                            </Text>
                                        </Group>

                                        {/* Verify Button */}
                                        <Button
                                            fullWidth
                                            size="lg"
                                            onClick={handleVerifyOtp}
                                            loading={isVerifying}
                                            disabled={otp.length !== 6 || isVerifying}
                                            gradient={{ from: "teal", to: "blue", deg: 60 }}
                                            variant="gradient"
                                            radius="md"
                                        >
                                            {isVerifying ? "Verifying..." : "Verify OTP"}
                                        </Button>

                                        {/* Resend Button */}
                                        <Button
                                            fullWidth
                                            variant="light"
                                            size="md"
                                            onClick={handleResendOtp}
                                            disabled={!canResend || isResending}
                                            loading={isResending}
                                            leftSection={<IconRefresh size={18} />}
                                        >
                                            {isResending ? "Sending..." : "Resend OTP"}
                                        </Button>
                                    </Stack>

                                    {/* Info */}
                                    <Paper p="md" radius="md" bg="blue.0" w="100%">
                                        <Text size="xs" c="blue.9" ta="center">
                                            <Text component="span" fw={600}>
                                                Note:{" "}
                                            </Text>
                                            Please do not share your OTP with anyone. KCC Bank
                                            will never ask for your OTP.
                                        </Text>
                                    </Paper>
                                </Stack>
                            </Paper>
                        </Center>
                    </Container>
                </Box>

                {/* FOOTER */}
                <Paper
                    radius={0}
                    p="md"
                    bg="gray.9"
                    style={{
                        borderTop: "1px solid #ddd",
                    }}
                >
                    <Container size="xl">
                        <Text size="xs" c="white" ta="center">
                            © 2025 The Kangra Central Co-Operative Bank Ltd. All rights
                            reserved.
                        </Text>
                    </Container>
                </Paper>
            </Box>
        </Providers>
    );
}