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'use strict';
var as = require('../../lib/as.js');
var debug = require('debug')('express-http-proxy');
var zlib = require('zlib');
function isResGzipped(res) {
return res.headers['content-encoding'] === 'gzip';
}
function zipOrUnzip(method) {
return function (rspData, res) {
return new Promise(function (resolve, reject) {
if (isResGzipped(res) && rspData.length) {
zlib[method](rspData, function (err, buffer) {
if (err) {
reject(err);
} else {
resolve(buffer);
}
});
} else {
resolve(rspData);
}
});
};
}
var maybeUnzipPromise = zipOrUnzip('gunzip');
var maybeZipPromise = zipOrUnzip('gzip');
function verifyBuffer(rspd, reject) {
if (!Buffer.isBuffer(rspd)) {
return reject(new Error('userResDecorator should return string or buffer as data'));
}
}
function updateHeaders(res, rspdBefore, rspdAfter, reject) {
if (!res.headersSent) {
res.set('content-length', rspdAfter.length);
} else if (rspdAfter.length !== rspdBefore.length) {
var error = '"Content-Length" is already sent,' +
'the length of response data can not be changed';
return reject(new Error(error));
}
}
function decorateProxyResBody(container) {
var resolverFn = container.options.userResDecorator;
if (!resolverFn) {
return Promise.resolve(container);
}
var proxyResDataPromise = maybeUnzipPromise(container.proxy.resData, container.proxy.res);
var proxyRes = container.proxy.res;
var req = container.user.req;
var res = container.user.res;
var originalResData;
if (res.statusCode === 304) {
debug('Skipping userResDecorator on response 304');
return Promise.resolve(container);
}
return proxyResDataPromise
.then(function (proxyResData) {
originalResData = proxyResData;
return resolverFn(proxyRes, proxyResData, req, res);
})
.then(function (modifiedResData) {
return new Promise(function (resolve, reject) {
var rspd = as.buffer(modifiedResData, container.options);
verifyBuffer(rspd, reject);
updateHeaders(res, originalResData, rspd, reject);
maybeZipPromise(rspd, container.proxy.res).then(function (buffer) {
container.proxy.resData = buffer;
resolve(container);
}).catch(function (error) {
reject(error);
});
});
});
}
module.exports = decorateProxyResBody;