"use client";

import React, { useEffect, useState } from "react";
import {
    TextInput,
    PasswordInput,
    Button,
    Title,
    Paper,
    Group,
    Text
} from "@mantine/core";
import { notifications } from "@mantine/notifications";
import { IconLock, IconRefresh } from "@tabler/icons-react";
import { generateCaptcha } from "@/app/captcha";
import { useRouter } from "next/navigation";

export default function ChangePassword() {
    const [newPassword, setNewPassword] = useState("");
    const [confirmPassword, setConfirmPassword] = useState("");
    const [captcha, setCaptcha] = useState("");
    const [captchaInput, setCaptchaInput] = useState("");
    const [otp, setOtp] = useState("");
    const [otpValidated, setOtpValidated] = useState(false);
    const [countdown, setCountdown] = useState(180);
    const [timerActive, setTimerActive] = useState(false);
    const [step, setStep] = useState<"form" | "otp" | "final">("form");
    const [generatedOtp, setGeneratedOtp] = useState('');
    const router = useRouter();

    const icon = <IconLock size={18} stroke={1.5} />;

    const handleGenerateOtp = async () => {
        const value = "123456"; // Or generate a random OTP
        setGeneratedOtp(value);
        setCountdown(180);
        setTimerActive(true);
        return value;
    };

    const regenerateCaptcha = async () => {
        const newCaptcha = await generateCaptcha();
        setCaptcha(newCaptcha);
        setCaptchaInput("");
    };

    useEffect(() => {
        let interval: number | undefined;
        if (timerActive && countdown > 0) {
            interval = window.setInterval(() => {
                setCountdown((prev) => prev - 1);
            }, 1000);
        }
        if (countdown === 0) {
            if (interval) clearInterval(interval);
            setTimerActive(false);
        }
        return () => {
            if (interval) clearInterval(interval);
        };
    }, [timerActive, countdown]);

    useEffect(() => {
        regenerateCaptcha();
    }, []);

    const validatePasswordPolicy = (password: string) => {
        return /^(?=.*[a-zA-Z])(?=.*\d)(?=.*[!@#$%^&*])[A-Za-z\d!@#$%^&*]{8,}$/.test(
            password
        );
    };

    const handleSubmit = async () => {
        // Step 1 → validate form
        if (step === "form") {
            if (!newPassword || !confirmPassword || !captchaInput) {
                notifications.show({
                    title: "Missing Field",
                    message: "Please fill all mandatory fields.",
                    color: "red",
                });
                return;
            }

            if (!validatePasswordPolicy(newPassword)) {
                notifications.show({
                    title: "Invalid Password",
                    message:
                        "Password must be at least 8 characters and contain alphanumeric and special characters.",
                    color: "red",
                });
                return;
            }

            if (newPassword !== confirmPassword) {
                notifications.show({
                    title: "Password Mismatch",
                    message: "Confirm password does not match new password.",
                    color: "red",
                });
                return;
            }

            if (captchaInput !== captcha) {
                notifications.show({
                    title: "Invalid Captcha",
                    message: "Please enter correct Captcha",
                    color: "red",
                });
                regenerateCaptcha();
                return;
            }
            //  Passed → move to OTP step
            await handleGenerateOtp();
            setStep("otp");
            notifications.show({
                title: "OTP Sent",
                message: "An OTP has been sent to your registered mobile.",
                color: "blue",
            });
            return;
        }
        // Step 2 → validate OTP
        if (step === "otp") {
            if (otp !== generatedOtp) {
                notifications.show({
                    title: "Invalid OTP",
                    message: "Please enter the correct OTP.",
                    color: "red",
                });
                return;
            }

            setOtpValidated(true);
            setStep("final");
            notifications.show({
                title: "OTP Verified",
                message: "OTP has been successfully verified.",
                color: "green",
            });
            return;
        }
        // Step 3 → Final API call to set transaction password
        if (step === "final") {
            const token = localStorage.getItem("access_token");
            if (!token) {
                router.push("/login");
                return;
            }
            try {
                const response = await fetch("/api/auth/transaction_password", {
                    method: "POST",
                    headers: {
                        "Content-Type": "application/json",
                        Authorization: `Bearer ${token}`,
                    },
                    body: JSON.stringify({
                        transaction_password: newPassword,
                    }),
                });

                if (response.status === 401) {
                    localStorage.removeItem("access_token");
                    localStorage.clear();
                    sessionStorage.clear();
                    router.push("/login");
                    return;
                }

                const result = await response.json();

                if (!response.ok) {
                    throw new Error(result.message || "Failed to set transaction password");
                }

                notifications.show({
                    title: "Success",
                    message: "Transaction password set successfully.",
                    color: "green",
                });

                resetForm();
            } catch (err: any) {
                notifications.show({
                    title: "Error",
                    message: err.message || "Server error, please try again later",
                    color: "red",
                });
            }
        }
    };

    const resetForm = () => {
        setNewPassword("");
        setConfirmPassword("");
        setCaptchaInput("");
        setOtp("");
        setOtpValidated(false);
        setStep("form");
        regenerateCaptcha();
    };

    return (
        <Paper shadow="sm" radius="md" p="md" withBorder h={400} >
            <Title order={3} mb="sm">
                Set Transaction Password
            </Title>

            <div style={{ overflowY: "auto", maxHeight: "280px", paddingRight: 8 }}>
                <Group grow>
                    <PasswordInput
                        label="New Transaction Password"
                        placeholder="Enter new Transaction password"
                        value={newPassword}
                        onChange={(e) => setNewPassword(e.currentTarget.value)}
                        withAsterisk
                        mb="xs"
                    />

                    <PasswordInput
                        label="Confirm Transaction Password"
                        placeholder="Re-enter new Transaction password"
                        value={confirmPassword}
                        onChange={(e) => setConfirmPassword(e.currentTarget.value)}
                        withAsterisk
                        rightSection={icon}
                        mb="sm"
                        readOnly={step !== "form"}
                        onCopy={(e) => e.preventDefault()}
                        onPaste={(e) => e.preventDefault()}
                        onCut={(e) => e.preventDefault()}
                    />
                </Group>

                {/* CAPTCHA */}
                <div style={{ marginTop: 5 }}>
                    <label
                        style={{ display: "block", marginBottom: 4, fontSize: "14px" }}
                    >
                        Enter CAPTCHA <span style={{ color: "red" }}>*</span>
                    </label>
                    <div
                        style={{
                            display: "flex",
                            alignItems: "center",
                            gap: 10,
                            marginBottom: 5,
                        }}
                    >
                        <div
                            style={{
                                fontSize: "18px",
                                letterSpacing: "3px",
                                background: "#f3f4f6",
                                padding: "6px 12px",
                                borderRadius: "6px",
                                border: "1px solid #d1d5db",
                                userSelect: "none",
                                textDecoration: "line-through",
                                fontFamily: "cursive",
                            }}
                        >
                            {captcha}
                        </div>

                        <Button
                            size="xs"
                            variant="outline"
                            onClick={regenerateCaptcha}
                            style={{ height: 30, padding: "0 10px", lineHeight: "1" }}
                            disabled={step !== "form"}
                        >
                            Refresh
                        </Button>

                        <TextInput
                            placeholder="Enter above text"
                            value={captchaInput}
                            onChange={(e) => setCaptchaInput(e.currentTarget.value)}
                            withAsterisk
                            style={{ flexGrow: 1 }}
                            readOnly={step !== "form"}
                        />
                    </div>
                </div>

                <Group grow>
                    {step !== "form" && (
                        <>
                            <Group gap="xs" align="flex-end">
                                <PasswordInput
                                    label="OTP"
                                    placeholder="Enter OTP"
                                    type="otp"
                                    value={otp}
                                    maxLength={6}
                                    onChange={(e) => setOtp(e.currentTarget.value)}
                                    withAsterisk
                                    disabled={otpValidated}
                                    style={{ flex: 1 }}
                                />
                                {!otpValidated && (
                                    timerActive ? (
                                        <Text size="xs" c="dimmed" style={{ minWidth: "120px" }}>
                                            Resend OTP will be enabled in{" "}
                                            {String(Math.floor(countdown / 60)).padStart(2, "0")}:
                                            {String(countdown % 60).padStart(2, "0")}
                                        </Text>
                                    ) : (
                                        <IconRefresh
                                            size={22}
                                            style={{ cursor: "pointer", color: "blue", marginBottom: "6px" }}
                                            onClick={handleGenerateOtp}
                                        />
                                    )
                                )}

                            </Group>
                        </>
                    )}
                </Group>


            </div>

            <Group mt="md" gap="sm">
                <Button onClick={handleSubmit}>
                    {step === "form" && "Submit"}
                    {step === "otp" && "Validate OTP"}
                    {step === "final" && "Set Password"}
                </Button>
                <Button variant="outline" color="gray" onClick={resetForm}>
                    Reset
                </Button>
            </Group>

            <Text size="sm" style={{ marginTop: "40px" }}>
                <Text span c='red' fw={600}>Note : </Text>{""}
                <Text span >Your new Login password must be 8–15 characters long and contain at least one number and one special character.</Text>
            </Text>
        </Paper>
    );
}