epub/epub.js

var ZipFile = require("zipfile").ZipFile,
    XML2JS = require("xml2js").Parser,
    utillib = require("util"),
    EventEmitter = require('events').EventEmitter;


//TODO: Cache parsed data to DB

// export
module.exports = EPub;

/**
 *  new EPub(fname[, imageroot][, linkroot])
 *  - fname (String): filename for the ebook
 *  - imageroot (String): URL prefix for images
 *  - linkroot (String): URL prefix for links
 *
 *  Creates an Event Emitter type object for parsing epub files
 *
 *      var epub = new EPub("book.epub");
 *      epub.on("end", function(){
 *           console.log(epub.spine);
 *      });
 *      epub.on("error", function(error){ ... });
 *      epub.parse();
 *
 *  Image and link URL format is:
 *
 *      imageroot + img_id + img_zip_path
 *
 *  So an image "logo.jpg" which resides in "OPT/" in the zip archive
 *  and is listed in the manifest with id "logo_img" will have the 
 *  following url (providing that imageroot is "/images/"):
 *
 *      /images/logo_img/OPT/logo.jpg
 **/
function EPub(fname, imageroot, linkroot){
    EventEmitter.call(this);
    this.filename = fname;

    this.imageroot = (imageroot || "/images/").trim();
    this.linkroot = (linkroot || "/links/").trim();

    if(this.imageroot.substr(-1)!="/")this.imageroot+="/";
    if(this.linkroot.substr(-1)!="/")this.linkroot+="/";
}
utillib.inherits(EPub, EventEmitter);

/**
 *  EPub#parse() -> undefined
 *  
 *  Starts the parser, needs to be called by the script
 **/
EPub.prototype.parse = function(){
    
    this.containerFile = false;
    this.mimeFile = false;
    this.rootFile = false;

    this.metadata = {};
    this.manifest = {};
    this.spine    = {toc: false, contents:[]};
    this.toc = [];

    this.open();
}

/**
 *  EPub#open() -> undefined
 *
 *  Opens the epub file with Zip unpacker, retrieves file listing
 *  and runs mime type check
 **/
EPub.prototype.open = function(){
    try{
        this.zip = new ZipFile(this.filename);
    }catch(E){
        this.emit("error", new Error("Invalid/missing file"));
        return;
    }
    
    if(!this.zip.names || !this.zip.names.length){
        this.emit("error", new Error("No files in archive"));
        return;
    }

    this.checkMimeType();
}

/**
 *  EPub#checkMimeType() -> undefined
 *
 *  Checks if there's a file called "mimetype" and that it's contents
 *  are "application/epub+zip". On success runs root file check.
 **/
EPub.prototype.checkMimeType = function(){
    for(var i=0, len = this.zip.names.length; i<len; i++){
        if(this.zip.names[i].toLowerCase() == "mimetype"){
            this.mimeFile = this.zip.names[i];
            break;
        }
    }
    if(!this.mimeFile){
        this.emit("error", new Error("No mimetype file in archive"));
        return;
    }
    this.zip.readFile(this.mimeFile, (function(err, data){
        if(err){
            this.emit("error", new Error("Reading archive failed"));
            return;
        }
        var txt = data.toString("utf-8").toLowerCase().trim();

        if(txt != "application/epub+zip"){
            this.emit("error", new Error("Unsupported mime type"));
            return;
        }

        this.getRootFiles();
    }).bind(this));
}

/**
 *  EPub#getRootFiles() -> undefined
 *
 *  Looks for a "meta-inf/container.xml" file and searches for a
 *  rootfile element with mime type "application/oebps-package+xml".
 *  On success calls the rootfile parser
 **/
EPub.prototype.getRootFiles = function(){
    for(var i=0, len = this.zip.names.length; i<len; i++){
        if(this.zip.names[i].toLowerCase() == "meta-inf/container.xml"){
            this.containerFile = this.zip.names[i];
            break;
        }
    }
    if(!this.containerFile){
        this.emit("error", new Error("No container file in archive"));
        return;
    }

    this.zip.readFile(this.containerFile, (function(err, data){
        if(err){
            this.emit("error", new Error("Reading archive failed"));
            return;
        }
        var xml = data.toString("utf-8").toLowerCase().trim(),
            xmlparser = new XML2JS();
        
        xmlparser.on("end", (function(result){

            if(!result.rootfiles || !result.rootfiles.rootfile){
                this.emit("error", new Error("No rootfiles found"));
                return;
            }

            var rootfile = result.rootfiles.rootfile,
                filename = false;

            if(Array.isArray(rootfile)){
                
                for(var i=0, len = rootfile.length; i<len; i++){
                    if(rootfile[i]["@"]["media-type"] && 
                        rootfile[i]["@"]["media-type"] == "application/oebps-package+xml" && 
                        rootfile[i]["@"]["full-path"]){
                            filename = rootfile[i]["@"]["full-path"].toLowerCase().trim();
                            break;
                        }
                }

            }else if(rootfile["@"]){
                if(rootfile["@"]["media-type"] != "application/oebps-package+xml" || !rootfile["@"]["full-path"]){
                    this.emit("error", new Error("Rootfile in unknown format"));
                    return;
                }
                filename = rootfile["@"]["full-path"].toLowerCase().trim();
            }

            if(!filename){
                this.emit("error", new Error("Empty rootfile"));
                return; 
            }


            for(var i=0, len = this.zip.names.length; i<len; i++){
                if(this.zip.names[i].toLowerCase() == filename){
                    this.rootFile = this.zip.names[i];
                    break;
                }
            }

            if(!this.rootFile){
                this.emit("error", new Error("Rootfile not found from archive"));
                return; 
            }
            
            this.handleRootFile();

        }).bind(this));

        xmlparser.on("error", (function(err){
            this.emit("error", new Error("Parsing container XML failed"));
            return;
        }).bind(this));

        xmlparser.parseString(xml);

        
    }).bind(this));
}

/**
 *  EPub#handleRootFile() -> undefined
 *
 *  Parser the rootfile XML and calls rootfile parser
 **/
EPub.prototype.handleRootFile = function(){

    this.zip.readFile(this.rootFile, (function(err, data){
        if(err){
            this.emit("error", new Error("Reading archive failed"));
            return;
        }
        var xml = data.toString("utf-8"),
            xmlparser = new XML2JS();

        xmlparser.on("end", this.parseRootFile.bind(this));

        xmlparser.on("error", (function(err){
            this.emit("error", new Error("Parsing container XML failed"));
            return;
        }).bind(this));

        xmlparser.parseString(xml);

    }).bind(this));
}

/**
 *  EPub#parseRootFile() -> undefined
 *
 *  Parses elements "metadata," "manifest," "spine" and TOC. 
 *  Emits "end" if no TOC
 **/
EPub.prototype.parseRootFile = function(rootfile){

    var keys, keyparts, key;

    keys = Object.keys(rootfile);
    for(var i=0, len = keys.length; i<len; i++){
        keyparts = keys[i].split(":");
        key = (keyparts.pop() || "").toLowerCase().trim();
        switch(key){
            case "metadata":
                this.parseMetadata(rootfile[keys[i]]);
                break;
            case "manifest":
                this.parseManifest(rootfile[keys[i]]);
                break;
            case "spine":
                this.parseSpine(rootfile[keys[i]]);
                break;
            case "guide":
                //this.parseGuide(rootfile[keys[i]]);
                break;
        }
    }

    if(this.spine.toc){
        this.parseTOC();
    }else
        this.emit("end");
}

/**
 *  EPub#parseMetadata() -> undefined
 *
 *  Parses "metadata" block (book metadata, title, author etc.)
 **/
EPub.prototype.parseMetadata = function(metadata){
    var keys, keyparts, key;

    keys = Object.keys(metadata);
    for(var i=0, len = keys.length; i<len; i++){
        keyparts = keys[i].split(":");
        key = (keyparts.pop() || "").toLowerCase().trim();
        switch(key){
            case "publisher":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.publisher = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                }else{
                    this.metadata.publisher = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                }                
                break;
            case "language":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.language = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").toLowerCase().trim();
                }else{
                    this.metadata.language = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").toLowerCase().trim();
                }
                break;
            case "title":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.title = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                }else{
                    this.metadata.title = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                }
                break;
            case "subject":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.subject = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                }else{
                    this.metadata.subject = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                }
                break;
            case "description":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.description = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                }else{
                    this.metadata.description = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                }
                break;
            case "creator":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.creator = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                    this.metadata.creatorFileAs = String(metadata[keys[i]][0] && metadata[keys[i]][0]['@'] && metadata[keys[i]][0]['@']["opf:file-as"] || this.metadata.creator).trim();
                }else{
                    this.metadata.creator = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                    this.metadata.creatorFileAs = String(metadata[keys[i]]['@'] && metadata[keys[i]]['@']["opf:file-as"] || this.metadata.creator).trim();
                }
                break;
            case "date":
                if(Array.isArray(metadata[keys[i]])){
                    this.metadata.date = String(metadata[keys[i]][0] && metadata[keys[i]][0]["#"] || metadata[keys[i]][0] || "").trim();
                }else{
                    this.metadata.date = String(metadata[keys[i]]["#"] || metadata[keys[i]] || "").trim();
                }
                break;
            case "identifier":
                if(metadata[keys[i]]["@"] && metadata[keys[i]]["@"]["opf:scheme"]=="ISBN"){
                    this.metadata.ISBN = String(metadata[keys[i]]["#"] || "").trim();
                }else if(metadata[keys[i]]["@"] && metadata[keys[i]]["@"]["id"] && metadata[keys[i]]["@"]["id"].match(/uuid/i)){
                    this.metadata.UUID = String(metadata[keys[i]]["#"] || "").replace('urn:uuid:','').toUpperCase().trim();
                }else if(Array.isArray(metadata[keys[i]])){
                    for(var j=0; j<metadata[keys[i]].length; j++){
                        if(metadata[keys[i]][j]["@"]){
                            if(metadata[keys[i]][j]["@"]["opf:scheme"]=="ISBN"){
                                this.metadata.ISBN = String(metadata[keys[i]][j]["#"] || "").trim();
                            }else if(metadata[keys[i]][j]["@"]["id"] && metadata[keys[i]][j]["@"]["id"].match(/uuid/i)){
                                this.metadata.UUID = String(metadata[keys[i]][j]["#"] || "").replace('urn:uuid:','').toUpperCase().trim();
                            }
                        }
                    }
                }
                break;
        }
    }
}

/**
 *  EPub#parseManifest() -> undefined
 *
 *  Parses "manifest" block (all items included, html files, images, styles)
 **/
EPub.prototype.parseManifest = function(manifest){
    var path = this.rootFile.split("/"), element, path_str;
    path.pop();
    path_str = path.join("/");

    if(manifest.item){
        for(var i=0, len = manifest.item.length; i<len; i++){
            if(manifest.item[i]['@']){
                element = manifest.item[i]['@'];

                if(element.href && element.href.substr(0, path_str.length) != path_str){
                    element.href = path.concat([element.href]).join("/");
                }

                this.manifest[manifest.item[i]['@'].id] = element;

            }
        }
    }
}

/**
 *  EPub#parseSpine() -> undefined
 *
 *  Parses "spine" block (all html elements that are shown to the reader)
 **/
EPub.prototype.parseSpine = function(spine){
    var path = this.rootFile.split("/"), element, path_s
    path.pop();

    if(spine['@'] && spine['@'].toc){
        this.spine.toc = this.manifest[spine['@'].toc] || false;
    }

    if(spine.itemref){
        for(var i=0, len = spine.itemref.length; i<len; i++){
            if(spine.itemref[i]['@']){
                if(element = this.manifest[spine.itemref[i]['@'].idref]){
                    this.spine.contents.push(element);
                }
            }
        }
    }
}

/**
 *  EPub#parseTOC() -> undefined
 *
 *  Parses ncx file for table of contents (title, html file)
 **/
EPub.prototype.parseTOC = function(){
    var path = this.spine.toc.href.split("/"), id_list = {}, keys;
    path.pop();

    keys = Object.keys(this.manifest);
    for(var i=0, len = keys.length; i<len; i++){
        id_list[this.manifest[keys[i]].href] = keys[i];
    }

    this.zip.readFile(this.spine.toc.href, (function(err, data){
        if(err){
            this.emit("error", new Error("Reading archive failed"));
            return;
        }
        var xml = data.toString("utf-8"),
            xmlparser = new XML2JS();

        xmlparser.on("end", (function(result){
            if(result.navMap && result.navMap.navPoint){
                this.toc = this.walkNavMap(result.navMap.navPoint, path, id_list);
            }

            this.emit("end");
        }).bind(this));

        xmlparser.on("error", (function(err){
            this.emit("error", new Error("Parsing container XML failed"));
            return;
        }).bind(this));

        xmlparser.parseString(xml);

    }).bind(this));
}

/**
 *  EPub#walkNavMap(branch, path, id_list,[, level]) -> Array
 *  - branch (Array | Object): NCX NavPoint object
 *  - path (Array): Base path
 *  - id_list (Object): map of file paths and id values
 *  - level (Number): deepness
 *
 *  Walks the NavMap object through all levels and finds elements
 *  for TOC
 **/
EPub.prototype.walkNavMap = function(branch, path, id_list, level){
    level = level || 0;
    
    // don't go too far
    if(level>7)return [];

    var output = [], element, id, title, order, href;

    if(!Array.isArray(branch)){
        branch = [branch];
    }

    for(var i=0, len = branch.length; i<len; i++){
        if(branch[i]["navLabel"]){
            
            title = (branch[i]["navLabel"] && branch[i]["navLabel"].text || branch[i]["navLabel"] || "").trim();
            order = Number(branch[i]["@"] && branch[i]["@"].playOrder || 0);
            href = (branch[i]["content"] && branch[i]["content"]["@"] && branch[i]["content"]["@"].src || "").trim();
            
            element = {
                level: level,
                order: order,
                title: title
            }

            if(href){
                href = path.concat([href]).join("/")
                element.href = href;
                
                if(id_list[element.href]){
                    // link existing object
                    element = this.manifest[id_list[element.href]];
                    element.title = title;
                    element.order = order;
                    element.level = level;
                }else{
                    // use new one
                    element.href = href;
                    element.id =  (branch[i]["@"] && branch[i]["@"].id || "").trim();
                }
                   
                output.push(element);
            }
        }
        if(branch[i]["navPoint"]){
            output = output.concat(this.walkNavMap(branch[i]["navPoint"], path, id_list, level + 1));
        }
    }
    return output;
}

/**
 *  EPub#getChapter(id, callback) -> undefined
 *  - id (String): Manifest id value for a chapter
 *  - callback (Function): callback function
 *
 *  Finds a chapter text for an id. Replaces image and link URL's, removes
 *  <head> etc. elements
 **/
EPub.prototype.getChapter = function(id, callback){
    var path = this.rootFile.split("/"), keys = Object.keys(this.manifest);
    path.pop();

    if(this.manifest[id]){
        this.zip.readFile(this.manifest[id].href, (function(err, data){
            if(err){
                callback(new Error("Reading archive failed"));
                return;
            }

            var str = data.toString("utf-8");

            // remove linebreaks (no multi line matches in JS regex!)
            str = str.replace(/\r?\n/g,"\u0000");

            // keep only <body> contents
            str.replace(/<body[^>]*?>(.*)<\/body[^>]*?>/i, function(o,d){
                str = d.trim();
            });

            // remove <script> blocks if any
            str = str.replace(/<script[^>]*?>(.*?)<\/script[^>]*?>/ig, function(o, s){
                return "";
            });

            // remove <style> blocks if any
            str = str.replace(/<style[^>]*?>(.*?)<\/style[^>]*?>/ig, function(o, s){
                return "";
            });

            // remove onEvent handlers
            str = str.replace(/(\s)(on\w+)(\s*=\s*["']?[^"'\s>]*?["'\s>])/g, function(o, a,b,c){
                return a + "skip-" + b + c;
            });

            // replace images
            str = str.replace(/(\ssrc\s*=\s*["']?)([^"'\s>]*?)(["'\s>])/g, (function(o, a,b,c){
                var img = path.concat([b]).join("/").trim(),
                    element;

                for(var i=0, len=keys.length; i<len; i++){
                    if(this.manifest[keys[i]].href == img){
                        element = this.manifest[keys[i]];
                        break;
                    }
                }

                // include only images from manifest
                if(element){
                    return a + this.imageroot + element.id+ "/" + img + c;
                }else{
                    return "";
                }
                
            }).bind(this));

            // replace links
            str = str.replace(/(\shref\s*=\s*["']?)([^"'\s>]*?)(["'\s>])/g, (function(o, a, b, c){
                var linkparts = b && b.split("#"),
                    link = path.concat([(linkparts.shift() || "")]).join("/").trim(),
                    element;

                for(var i=0, len=keys.length; i<len; i++){
                    if(this.manifest[keys[i]].href.split("#")[0] == link){
                        element = this.manifest[keys[i]];
                        break;
                    }
                }

                if(linkparts.length){
                    link += "#" + linkparts.join("#");
                }

                // include only images from manifest
                if(element){
                    return a + this.linkroot + element.id+ "/" + link + c;
                }else{
                    return a + b + c;
                }
                
            }).bind(this));

            // bring back linebreaks
            str = str.replace(/\u0000/g,"\n").trim();

            callback(null, str);

        }).bind(this));
    }
}


/**
 *  EPub#getImage(id, callback) -> undefined
 *  - id (String): Manifest id value for an image
 *  - callback (Function): callback function
 *
 *  Finds an image an id. Returns the image as Buffer. Callback gets
 *  an error object, image buffer and image content-type
 **/
EPub.prototype.getImage = function(id, callback){
    if(this.manifest[id]){
        this.zip.readFile(this.manifest[id].href, (function(err, data){
            if(err){
                callback(new Error("Reading archive failed"));
                return;
            }

            callback(null, data, this.manifest[id]['media-type']);
        }).bind(this));
    }
}