import { NextRequest } from 'next/server';
import { cookies } from 'next/headers';
import prisma from '@/lib/prisma';

export const USER_SESSION_COOKIE_NAME = 'afro_session';
export const DEFAULT_USER_SESSION_DURATION = 7 * 24 * 60 * 60; // 7 days in seconds

export interface UserSessionPayload {
    userId: string;
    email: string;
    role: string;
    exp: number;
    iat: number;
}

export const USER_SAFE_SELECT = {
    id: true,
    name: true,
    email: true,
    role: true,
    avatar: true,
    bio: true,
    location: true,
    phone: true,
    countryId: true,
    isSuspended: true,
    suspensionReason: true,
    createdAt: true,
    updatedAt: true,
    emailVerified: true,
};

function getJwtSecret(): string {
    const secret = process.env.JWT_SECRET || process.env.NEXTAUTH_SECRET || process.env.ADMIN_JWT_SECRET;
    if (!secret) {
        if (process.env.NODE_ENV === 'production') {
            throw new Error('CRITICAL: JWT_SECRET or NEXTAUTH_SECRET environment variable must be set in production.');
        }
        return 'dev_only_afrohub_user_jwt_secret_key_change_in_prod';
    }
    return secret;
}

function base64UrlEncode(str: string): string {
    return Buffer.from(str, 'utf-8').toString('base64url');
}

function base64UrlDecode(str: string): string {
    return Buffer.from(str, 'base64url').toString('utf-8');
}

async function getCryptoKey(): Promise<CryptoKey> {
    const enc = new TextEncoder();
    return await crypto.subtle.importKey(
        'raw',
        enc.encode(getJwtSecret()),
        { name: 'HMAC', hash: 'SHA-256' },
        false,
        ['sign', 'verify']
    );
}

export async function signUserToken(
    payload: Omit<UserSessionPayload, 'exp' | 'iat'>,
    expiresInSeconds: number = DEFAULT_USER_SESSION_DURATION
): Promise<string> {
    const now = Math.floor(Date.now() / 1000);
    const fullPayload: UserSessionPayload = {
        ...payload,
        iat: now,
        exp: now + expiresInSeconds,
    };

    const header = { alg: 'HS256', typ: 'JWT' };
    const headerB64 = base64UrlEncode(JSON.stringify(header));
    const payloadB64 = base64UrlEncode(JSON.stringify(fullPayload));
    const dataToSign = `${headerB64}.${payloadB64}`;

    const key = await getCryptoKey();
    const signatureBuffer = await crypto.subtle.sign(
        'HMAC',
        key,
        new TextEncoder().encode(dataToSign)
    );

    const signatureB64 = Buffer.from(signatureBuffer).toString('base64url');
    return `${dataToSign}.${signatureB64}`;
}

export async function verifyUserToken(token?: string | null): Promise<UserSessionPayload | null> {
    if (!token || typeof token !== 'string') return null;
    const parts = token.split('.');
    if (parts.length !== 3) return null;

    const [headerB64, payloadB64, signatureB64] = parts;
    const dataToSign = `${headerB64}.${payloadB64}`;

    try {
        const key = await getCryptoKey();
        const signatureBytes = Buffer.from(signatureB64, 'base64url');

        const isValid = await crypto.subtle.verify(
            'HMAC',
            key,
            signatureBytes,
            new TextEncoder().encode(dataToSign)
        );

        if (!isValid) return null;

        const payloadJson = base64UrlDecode(payloadB64);
        const payload = JSON.parse(payloadJson) as UserSessionPayload;

        const now = Math.floor(Date.now() / 1000);
        if (!payload.exp || payload.exp < now || !payload.userId) {
            return null;
        }

        return payload;
    } catch {
        return null;
    }
}

export async function setUserSessionCookie(
    token: string,
    maxAgeSeconds: number = DEFAULT_USER_SESSION_DURATION
): Promise<void> {
    const cookieStore = await cookies();
    cookieStore.set(USER_SESSION_COOKIE_NAME, token, {
        httpOnly: true,
        secure: process.env.NODE_ENV === 'production',
        sameSite: 'lax',
        path: '/',
        maxAge: maxAgeSeconds,
    });
}

export async function clearUserSessionCookie(): Promise<void> {
    const cookieStore = await cookies();
    cookieStore.set(USER_SESSION_COOKIE_NAME, '', {
        httpOnly: true,
        secure: process.env.NODE_ENV === 'production',
        sameSite: 'lax',
        path: '/',
        maxAge: 0,
    });
}

export async function getAuthUser(request?: NextRequest) {
    try {
        let token: string | undefined;

        if (request) {
            token = request.cookies.get(USER_SESSION_COOKIE_NAME)?.value;
        }
        if (!token) {
            const cookieStore = await cookies();
            token = cookieStore.get(USER_SESSION_COOKIE_NAME)?.value;
        }

        const payload = await verifyUserToken(token);
        if (!payload?.userId) return null;

        const user = await prisma.user.findUnique({
            where: { id: payload.userId },
            select: {
                id: true,
                email: true,
                name: true,
                role: true,
                emailVerified: true,
                isSuspended: true,
                deletedAt: true,
            }
        });

        if (!user || user.deletedAt) {
            return null;
        }

        return user;
    } catch (error) {
        console.error('Error fetching auth user:', error);
        return null;
    }
}

export async function isAdmin(request?: NextRequest) {
    const user = await getAuthUser(request);
    return user?.role === 'ADMIN' && !user.isSuspended;
}