// PhantomJS setup
var webPage = require('webpage');
var page = webPage.create();
var system = require('system');
var waitForMath;
var noLongerExecWaitForMathJax = false;

// Usage
if (system.args.length < 2) {
    console.log("Usage: phantomjs render-math-and-dump.js <filename>");
    console.log("Renders <filename> and dumps the DOM to the console.");
    phantom.exit();
};

// Open the page and on success set the window interval function
// Alternatives:
// page.open(encodeURI(system.args[1]), function(status) {
// page.open("file://" + encodeURI(system.args[1]), function(status) {
page.open(system.args[1], function(status) {
    if (status === "success") {
        // Execute the query every 20ms
        waitForMath = window.setInterval(
            waitForMathJax, 
            20
        );
    };
});

// This also works (to some extent) with web URLs.
// page.open(system.args[1], function(status){
//     if (status === "success") {
//         // In this setup a complete local MathJax installation
//         // is present in MathJax/
//         page.injectJs("MathJax/MathJax.js");
//         page.injectJs("ConfigMathJax.js");
//         // Execute the query every 20ms
//         waitForMath = window.setInterval(
//             waitForMathJax, 
//             20
//         );
//     };
// });


// Removes all MathJax <script> elements from the DOM.
// This avoids a second processing in PrinceXML, which
//  a) had nothing left to do (MathJax already).
//  b) probably would fail, since PrinceXML at the moment still lacks MathJax support
var removeMathJaxScripts = function() {
    // Does 'str' end with 'suffix'?
    var strEndsWith = function(str, suffix) {
        return str.indexOf(suffix, str.length - suffix.length) !== -1;
    };

    // Get and remove all MathJax related script elements
    var MathJaxScriptFound = true;
    var scripts = document.getElementsByTagName("script");
    // Repeating this loop until no more matching scripts are found seems 
    // to be necessary because removing children from the DOM did not always 
    // happen immediately, some of them were still written to the output when
    // dumping 'page.content'.
    while (MathJaxScriptFound) {
        MathJaxScriptFound = false;
        for (var i = scripts.length - 1; i >= 0; i--) {
            if (scripts[i].hasAttribute("id")) {
                var id = scripts[i].getAttribute("id");
                // Remove script if 'id' starts with 'MathJax-Element'
                if (id.indexOf("MathJax-Element") === 0) {
                    MathJaxScriptFound = true;
                    scripts[i].parentNode.removeChild(scripts[i]);
                };
            } else if (scripts[i].hasAttribute("src")) {
                var src = scripts[i].getAttribute("src");
                // Remove script if 'src' ends on 'ConfigMathJax.js', 
                // 'MathJax.js' or 'jax.js'
                if ((strEndsWith(src, "ConfigMathJax.js")) 
                    || (strEndsWith(src, "MathJax.js")) 
                    || (strEndsWith(src, "jax.js"))) {
                    MathJaxScriptFound = true;
                    scripts[i].parentNode.removeChild(scripts[i]);
                };
            };
        };
        scripts = document.getElementsByTagName("script");
    };

    // Remove div with ID 'MathJax_Font_Test'
    var fontTest = document.getElementById("MathJax_Font_Test");
    if (fontTest) {
        fontTest.parentNode.removeChild(fontTest);
    };

    // Avoid empty HTML-Syntax elements (<meta>, <link>, <br>, <hr>, ...),
    // this makes it possible to call PrinceXML in XML mode with the generated
    // output from PhantomJS. In mode 'auto' this code can be disabled 
    // completely. Please also note that for example the resulting <br></br> 
    // is not compliant with HTML, so you should keep an eye on the output
    // generated by PrinceXML. The same is probably true for <meta></meta>,
    // <link></link> and the like.
    elements = document.documentElement.getElementsByTagName("*");
    for (var i = elements.length - 1; i >= 0; i--) {
        if (elements[i].childNodes.length == 0) {
            elements[i].appendChild(document.createTextNode(""));
        };
    };
};


// The problem with processing SVG formulas generated by MathJax in PrinceXML
// is the location of the SVG glyphs which are used by MathJax to construct
// formulas. MathJax creates an SVG path for every symbol/letter in a hidden
// div at the beginning of the document. Every glyph (actually an SVG path)
// has an ID. In every formula the glyphs are only referenced by this ID and
// *not* recreated every time the glyph is needed. This keeps the amount of 
// markup added to the document small.
//
// Currently PrinceXML isn't able to use links to elements wich are defined
// in another SVG element (the so called SVG "islands" problem, mentioned for
// example here /forum/topic/1402/multiple-svg-regions-with-common-defs and
// here /forum/topic/2912/what-forms-does-prince-support-css-clip-path).
//
// This function collects all MathJax glyph definitions and copies them to any
// SVG formula element where they are used. The function does not copy *all*
// definitions to *all* formulas, only those needed for the current formula
// are copied.
//
// The function still has (at least) one "bug": By copying a glyph to more 
// than one formula you'll end up with elements that have the same ID in the 
// resulting document. For PrinceXML it doesn't seem to be a problem, but a
// validator will surely find it faulty.
var relocateMathJaxGlyphs = function () {
    // Container holding all MathJax glyphs, declared here for later removal.
    var mathJaxSVGGlyphContainer = null;

    // Get an array of all MathJax SVG paths which form a glyph.
    var getMathJaxGlyphs = function () {
        // These glyphs are located inside an SVG 'defs' element and
        // are later used/referenced to layout every formula.
        // This code currently only checks for the presence of one 
        // glyph container (the first).
        var glyphContainer = document.getElementById("MathJax_SVG_glyphs");
        if (!glyphContainer) {
            return [];
        };
        // Hold the container for later removal to avoid too many DOM queries.
        var gcpn = glyphContainer.parentNode;
        if (gcpn) {
            mathJaxSVGGlyphContainer = gcpn;
        };
        // This could be changed to use '*' instead of 'path', but so far
        // I haven't seen that MathJax uses something different than 'path'.
        var paths = glyphContainer.getElementsByTagName("path");
        var result = [];
        for (var i = paths.length - 1; i >= 0; i--) {
            var id = paths[i].getAttribute("id");
            if (id) {
                result.push({id:id, path:paths[i]});
            };
        };
        return result;
    };

    // Get an array of all MathJax SVG display areas (formulas).
    var getMathJaxSVGs = function () {
        // SVG formulas are located in a span with class name 'MathJax_SVG'.
        var svgContainers = document.getElementsByClassName("MathJax_SVG");
        if (svgContainers.length === 0) {
            return [];
        };
        var result = [];
        for (var i = svgContainers.length - 1; i >= 0; i--) {
            // Handle all embedded SVG containers (normally there should be
            // only one, but it doesn't hurt to visit all).
            var svgs = svgContainers[i].getElementsByTagName("svg");
            for (var a = svgs.length - 1; a >= 0; a--) {
                // At this stage we can already create the <defs> element (if
                // not present). The element is supposed holds copies of the
                // glyphs and later will be appended to *this* SVG element.
                var defs;
                var defsElements = svgs[a].getElementsByTagName("defs");
                if (defsElements.length === 0) {
                    defs = document.createElement("defs");
                } else {
                    defs = defsElements[0];
                };
                result.push({svg:svgs[a], defs:defs});
            };
        };
        return result;
    };

    // Find the matching glyph path by id in 'glyphs' and return a clone
    var getGlyphById = function (id, glyphs) {
        for (var i = glyphs.length - 1; i >= 0; i--) {
            // id and path are assumed to be always non-null
            if (id === glyphs[i].id) {
                return glyphs[i].path.cloneNode(true);
            };
        };
        return null;
    };

    // Copy every SVG glyph referenced in the SVG element into the <defs>
    // element (this was already created in getMathJaxSVGs, if not present).
    var copySVGGlyphsToSVGDefsElement = function (svgObject, glyphs) {
        // Get all nested <use> elements
        var useElements = svgObject.svg.getElementsByTagName("use");
        for (var i = useElements.length - 1; i >= 0; i--) {
            // First lookup the xlink:href attribute. If the attribute is 
            // present verbatim in this form we'll take this one.
            var id = useElements[i].getAttribute("xlink:href");
            if (!id) {
                // Next try the ordinary href attribute. Although PhantomJS 
                // later writes this as 'xlink:href' it seems that it only 
                // can be accessed using 'href'.
                id = useElements[i].getAttribute("href");
            };
            // No suitable id found...
            if ((!id) || (id.length < 2)) {
                continue;
            };
            // Get the matching glyph as a clone from the list of all glyps
            // and append it to the <defs> element.
            var glyph = getGlyphById(id.slice(1), glyphs);
            if (glyph) {
                svgObject.defs.appendChild(glyph);
            } else {
            };
        };
        // Finally append the <defs> element to its parent SVG element
        svgObject.svg.appendChild(svgObject.defs);
    };

    // This is the main loop which ...
    // ... gets all glyphs ...
    var mathJaxGlyphs = getMathJaxGlyphs();
    if (mathJaxGlyphs.length > 0) {
        // ... gets all formulas ...
        var mathJaxSVGs = getMathJaxSVGs();
        if (mathJaxSVGs.length > 0) {
            for (var i = mathJaxSVGs.length - 1; i >= 0; i--) {
                // ... and copies matching glyphs into every formula.
                copySVGGlyphsToSVGDefsElement(mathJaxSVGs[i], mathJaxGlyphs);
            };
        };
    };

    // Finally we can remove the glyph container from the DOM
    if (mathJaxSVGGlyphContainer) {
        mathJaxSVGGlyphContainer
          .parentNode
          .removeChild(mathJaxSVGGlyphContainer);
    };

};


// Query a variable named 'MathJaxFinished' in the document,
// see also ConfigMathJax.js.
var waitForMathJax = function () {
    if (noLongerExecWaitForMathJax) {
        return;
    };
    var mjFinished = page.evaluate(function () {
        return MathJaxFinished;
    });
    if (mjFinished) {
        // waitForMathJax was called at least twice (?), even after
        // window.clearInterval(). This flag prevents it (see above).
        noLongerExecWaitForMathJax = true;
        window.clearInterval(waitForMathJax);

        // Remove the scripts
        page.evaluate(removeMathJaxScripts);

        // Relocate/copy all SVG glyphs (paths)
        page.evaluate(relocateMathJaxGlyphs);

        // Dump the DOM to the console and exit.
        console.log(page.content);
        phantom.exit();
    };
}