import type { NextRequest } from 'next/server'
import { NextResponse } from 'next/server'

/// Resend request to backend.
/// Body is being sent as stream.
export async function redirectRequest(
    req: NextRequest,
    proxyUrl: string,
    backendBaseUrl: string
): Promise<NextResponse> {
    const reqUrl = req.url // full URL e.g. http://localhost:3000/api/proxy?id=123

    // Find position of proxyPath in reqUrl
    const proxyIndex = reqUrl.indexOf(proxyUrl)
    if (proxyIndex === -1) {
        return new NextResponse('Invalid proxy path', { status: 400 })
    }

    // Replace '/api/proxy/parserBackend' with backend URL, preserve everything after
    // e.g. '/api/proxy/extra/path?id=123' -> 'http://backend-server/extra/path?id=123'
    const backendUrl = backendBaseUrl + reqUrl.substring(proxyIndex + proxyUrl.length)
    // console.log('redirecting', req.url, 'to', backendUrl)

    const backendRes = await fetch(backendUrl, {
        method: req.method,
        headers: req.headers,
        body: req.body,
        // @ts-ignore
        duplex: 'half', // some property required by nodejs but not defined in @types/node
    })

    return new NextResponse(backendRes.body, {
        status: backendRes.status,
        headers: {
            'Access-Control-Allow-Origin': '*',
            'Content-Type': backendRes.headers.get('content-type') || 'application/octet-stream',
        },
    })
}

/// Browsers send OPTIONS request sometimes to check webserver allowed headers and methods.
/// My backend doesn't support such requests so use proxy to answer to it that all headers and methods are allowed
export async function responseToOPTIONS(req: NextRequest): Promise<NextResponse> {
    // console.log('proxy responding to CORS OPTIONS', req.url)

    return new NextResponse(null, {
        status: 200,
        headers: {
            'Access-Control-Allow-Origin': '*',
            'Access-Control-Allow-Methods': 'GET, POST, PUT, PATCH, DELETE, HEAD',
            'Access-Control-Allow-Headers':
                req.headers.get('access-control-request-headers') || 'Content-Type, Authorization',
        },
    })
}