Download file with a REST request needing headers and giving the content

Question

I am using AngularJs with a REST API. I don't have the hand on the REST API. I can store digital object with the API by sending a REST request. I can get it also with a GET request. The requests needs to have some specific headers.

My goal is to give the user a "download and save as" link. For now on the click event i make the request :

    this.file = function (file) {
        var url = config.domain + 'file/' + file;

        var methods = resource(url, null, { 
            'get': {
                method:'GET', 
                headers:{   'Authorization' : user.auth, 
                            'secret-key' : user.secretkey}
            }
            transformResponse : function(data, headersGetter){
                                    return {content:data}; //transform octet stream into text, angular returns an array containing 1 character per element.
                                },
        });
        return methods;
    };

in the return body I have the file content (see below). I would like to download it. How is it possible ? Notice that I can't store the file as a URL.

Would it be possible to open a window wich make the rest call with the good headers and save the file ?

EDIT

I need the solution to be able to work well with a 50Mo File.

example of a PDF file content I have :

%PDF-1.7
£´ÅÖçø
2 0 obj
[/ICCBased 3 0 R]
endobj
3 0 obj
<<
/Filter /FlateDecode 
/Length 2596 
/N 3 
>>
stream
xwTSÙϽ7½PÐkhRH
½H.*1   JÀ"6DTpDQ¦2(à£C±"Q±ëDÔqpId­ß¼yïÍß÷~k½ÏÝgï}ÖºüÂLX    ¡XáçÅg`ðlàp³³BøF|Ølø½º         ùû*Ó?Áÿ¹Y"1PçòøÙ\É8=W%·Oɶ4MÎ0JÎ"Y2Vsò,[|öe9ó2<ËsÎâeðäÜ'ã9¾`çø¹2¾&ctI@Æoä±|N6(Ü.æsSdl-c(2-        ãyàHÉ_ðÒ/XÌÏËÅÎÌZ.$§&\SáÏÏMçÅÌ07#â1ØYárfÏüYym²";Ø8980m-m¾(Ô]ü÷v^îDøÃöW~
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[.....]

Answer 1

I think you could using blob, something like

var content=...the content of your request;
var mypdf = new Blob(content, {type : 'application/pdf'});

and check answer from "panzi" in this other question Using HTML5/Javascript to generate and save a file

(One character per element in the array seem pretty nice binary. Probably you don't need to transform it. https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data )