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getNarrative.js
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getNarrative.js
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const fetch = require('node-fetch');
const assert = require('assert').strict;
const utils = require("./utils");
const helpers = require("./getDatasetHelpers");
const getNarrative = async (req, res) => {
const query = req.query;
const prefix = query.prefix;
try {
assert(prefix);
} catch {
return res.status(400).send("No prefix in getNarrative URL query");
}
try {
assert(query.type);
assert(["markdown", "md"].includes(query.type.toLowerCase()));
} catch {
return res.status(400).send("The nextstrain.org server only serves getNarrative requests in markdown format. Please specify `?type=md`");
}
/*
* "inrb-drc" was the first of the Nextstrain groups. Groups now live at
* `nextstrain.org/groups`, but we want to support old URLs for INRB DRC by
* redirecting requests from "/inrb-drc" to "/groups/inrb-drc".
*/
if (prefix.startsWith('/inrb-drc')) {
return res.redirect("getNarrative?type=md&prefix=/groups" + prefix);
}
const {source, prefixParts} = helpers.splitPrefixIntoParts(prefix);
// Authorization
if (!source.visibleToUser(req.user)) {
return helpers.unauthorized(req, res);
}
// Remove 'en' from nCoV narrative prefixParts
if (prefixParts[0] === 'ncov') {
const index = prefixParts.indexOf('en');
if (index >= 0) {
prefixParts.splice(index, 1);
}
}
// Generate the narrative's origin URL for fetching.
const narrative = source.narrative(prefixParts);
const fetchURL = narrative.url();
try {
utils.log(`Fetching narrative ${fetchURL} and streaming to client for parsing`);
const response = await fetch(fetchURL);
if (response.status === 404) {
return res.status(404).send("The requested URL does not exist.");
} else if (!(response.status === 200 || response.status === 304)) {
throw new Error(`Failed to fetch ${fetchURL}: ${response.status} ${response.statusText}`);
}
res.set("Content-Type", "text/markdown");
return response.body.pipe(res);
} catch (err) {
return helpers.handle500Error(res, `Narratives couldn't be served -- ${err.message}`);
}
};
module.exports = {
default: getNarrative
};