const createError = require('http-errors');
const axios = require('axios');


async function getRemoteDocument(url){
    const response = await axios.get(parsedUrl.toString(), {
            responseType: 'arraybuffer',
            headers: {
                Accept: req.headers['accept'] || '*/*',
            },
    });
    return response
}


/**
 * ITI-68: Retrieve Document (MHD)
 *
 * GET /fhir/Binary?url=[URL_Directa]
 *
 * Flow (diagram iti67.mmd, step 21-24):
 *   1. HIS_A supplies the direct document URL obtained from a prior ITI-67 response.
 *   2. This gateway performs a P2P GET to that URL, bypassing the Bus.
 *   3. The raw document (PDF, XML, etc.) is forwarded back to HIS_A.
 */
async function download(req, res, next) {
    try {
        const url = req.query.url;
        if (!url) {
            throw createError(400, 'Missing required query parameter: url');
        }
        let parsedUrl;
        try {
            parsedUrl = new URL(url);
        } catch {
            throw createError(400, 'Invalid document URL');
        }
        const response = await getRemoteDocument(url);

        const contentType = response.headers['content-type'];
        if (contentType) res.setHeader('Content-Type', contentType);

        const contentDisposition = response.headers['content-disposition'];
        if (contentDisposition) res.setHeader('Content-Disposition', contentDisposition);

        res.status(200).send(response.data);
    } catch (err) {
        if (err.response) {
            return next(createError(err.response.status, `Document source returned ${err.response.status}`));
        }
        next(err);
    }
}

module.exports = { download };