var fs = require('fs'),
    url = require('url'),
    zlib = require('zlib'),
    querystring = require('querystring'),
    Promise = require('bluebird'),
    log4js = require('log4js'), // the logger
    express = require('express'),
    xmlCrypto = require('xml-crypto'),
    xmldom = require('xmldom'),
    xmlbuilder = require('xmlbuilder'),
    crypto = require('crypto'),
    bodyParser = require('body-parser'),
    http_app = express(),
    http_server = require('http').createServer(http_app);

http_app.use(bodyParser.urlencoded({extended: true}));
http_app.use(bodyParser.json());
http_server.listen(8085, 'localhost');

// ================================================================================
// The logger
// ================================================================================

log4js.loadAppender('file');
log4js.addAppender(log4js.appenders.file(process.env.CODEQ_SAML_LOG || 'codeq-saml.log'), 'log');
var logger = log4js.getLogger('log');

var logException = function (msg, error) {
    if ((error instanceof Error) && (typeof error.stack === 'string')) msg += '\n' + error.stack;
    logger.error(msg);
};

// prevent the node from exiting because of an unhandled exception
Promise.onPossiblyUnhandledRejection(function (error) {
    logException('Unhandled promise rejection: ' + error, error);
});

process.on('uncaughtException', function (error) {
    logException('Uncaught exception: ' + error, error);
});

// ================================================================================
// Misc
// ================================================================================

var assertionConsumerServiceURL = 'https://codeq.si/Shibboleth.sso/SAML2/POST',
    SPIssuer = 'https://codeq.si/sp/201509281041',
    privateCert = fs.readFileSync('/etc/shibboleth/sp-key.pem', 'utf8'),
    SamlStatusSuccess = 'urn:oasis:names:tc:SAML:2.0:status:Success';

// IdP: idp.aai.arnes.si
var SSOServiceURL = 'https://idp.aai.arnes.si/simplesaml/saml2/idp/SSOService.php',
    SLOServiceURL = 'https://idp.aai.arnes.si/simplesaml/saml2/idp/SingleLogoutService.php',
    IdPIssuer = 'https://idp.aai.arnes.si/idp/20090116',
    IdPKeyInfoProvider = new xmlCrypto.FileKeyInfo('/etc/shibboleth/idp.crt');

/*
// IdP: idp.uni-lj.si
var SSOServiceURL = 'https://idp.uni-lj.si/simplesaml/saml2/idp/SSOService.php',
    SLOServiceURL = 'https://idp.uni-lj.si/simplesaml/saml2/idp/SingleLogoutService.php',
    IdPIssuer = 'https://idp.uni-lj.si/idp/20100525',
    IdPKeyInfoProvider = new xmlCrypto.FileKeyInfo('/etc/shibboleth/idp.uni-lj.si.crt');
 */

var idChars = '0123456789abcdef',
    makeRequestId = function () {
        var idParts = [],
            i;
        for (i = 0; i < 20; i++) idParts.push(idChars[Math.floor(Math.random() * 15)]);
        return idParts.join('');
    };

var waitingLogins = {}, // maps sid to waiter
    waitingLogouts = {},
    parkedLoginRequests = {}, // maps SAML request ID to waiter
    parkedLogoutRequests = {};

var makeSamlRedirectUrl = function (serviceUrl, queryKey, queryObj, additionalData, callback) {
    var xml = xmlbuilder.create(queryObj).end();
    logger.debug('Redirecting with ' + queryKey + ' to ' + serviceUrl + ':\n' + xml);
    zlib.deflateRaw(xml, function (err, buffer) {
        var svcUrl, signer, query, keys, i, key;
        if (err) {
            callback(err, null);
            return;
        }
        query = {
            'SigAlg': 'http://www.w3.org/2000/09/xmldsig#rsa-sha1'
        };
        query[queryKey] = buffer.toString('base64');
        if (additionalData && (typeof additionalData === 'object')) {
            keys = Object.keys(additionalData);
            for (i = keys.length - 1; i >= 0; i--) {
                key = keys[i];
                query[key] = additionalData[key];
            }
        }
        signer = crypto.createSign('RSA-SHA1');
        signer.update(querystring.stringify(query));
        query.Signature = signer.sign(privateCert, 'base64');
        svcUrl = url.parse(serviceUrl);
        svcUrl.query = query;
        delete svcUrl.search;
        callback(null, url.format(svcUrl));
    });
};

var makeWaiter = function (sid) {
    var waiter = {
        'sid': sid,
        'created': Date.now(),
        'listeners': 0
    };
    waiter.promise = new Promise(function (resolve, reject) {
        waiter.resolve = resolve;
        waiter.reject = reject;
    });
    return waiter;
};

// ================================================================================
// XML DOM data extraction functions for SAML data
// ================================================================================

var validateXmlSignature = function (xml, signatureNode) {
    var sig = new xmlCrypto.SignedXml();
    sig.keyInfoProvider = IdPKeyInfoProvider;
    sig.loadSignature(signatureNode.toString());
    return sig.checkSignature(xml);
};

var xmlStatusOk = function (statusNode) {
    var node = statusNode.firstChild,
        attributes, i;
    while (node) {
        if (node.localName === 'StatusCode') {
            attributes = node.attributes;
            for (i = attributes.length - 1; i >= 0; i--) {
                if (attributes[i].localName === 'Value') return attributes[i].value == SamlStatusSuccess;
            }
        }
        node = node.nextSibling;
    }
    return null;
};

var parseAttributeValue = function (attributeNode) {
    var node = attributeNode.firstChild;
    while (node) {
        if (node.localName === 'AttributeValue') {
            return node.firstChild.data;
        }
        node = node.nextSibling;
    }
    return null;
};

var parseAttributes = function (attributeStatementNode) {
    var node = attributeStatementNode.firstChild,
        result = {},
        attributes, i, name;
    while (node) {
        if (node.localName === 'Attribute') {
            attributes = node.attributes;
            for (i = attributes.length - 1; i >= 0; i--) {
                if (attributes[i].localName === 'Name') {
                    name = attributes[i].value;
                    break;
                }
            }
            if (i < 0) {
                console.log('ERROR: an attribute without a name');
            }
            else {
                result[name] = parseAttributeValue(node);
            }
        }
        node = node.nextSibling;
    }
    return result;
};

// return the NameID in the format for use with xmlbuilder
var parseNameID = function (NameIDNode) {
    var result = {},
        i, attributes;
    result['#text'] = NameIDNode.firstChild.data;
    attributes = NameIDNode.attributes;
    for (i = attributes.length - 1; i >= 0; i--) {
        switch (attributes[i].localName) {
            case 'NameQualifier': // NameID namespace
                result['@NameQualifier'] = attributes[i].value;
                break;
            case 'SPNameQualifier': // 2nd level NameID namespace
                result['@SPNameQualifier'] = attributes[i].value;
                break;
            case 'Format':
                result['@Format'] = attributes[i].value;
                break;
            case 'SPProvidedID':
                result['@SPProvidedID'] = attributes[i].value;
                break;
        }
    }
    return result;
};

var parseSubject = function (subjectNode) {
    var node = subjectNode.firstChild,
        result = {};
    while (node) {
        if (node.localName === 'NameID') {
            result['NameID'] = parseNameID(node);
        }
        node = node.nextSibling;
    }
    return result;
};

var parseAssertion = function (xml, assertionNode) {
    var node = assertionNode.firstChild,
        result = {},
        attributes, i;
    while (node) {
        switch (node.localName) {
            case 'Signature':
                result.signatureOk = validateXmlSignature(xml, node);
                break;
            case 'Subject':
                // extract presenter identifier
                result.subject = parseSubject(node);
                break;
            case 'AuthnStatement':
                // extract the session index
                attributes = node.attributes;
                for (i = attributes.length - 1; i >= 0; i--) {
                    if (attributes[i].localName === 'SessionIndex') {
                        result.SessionIndex = attributes[i].value;
                        break;
                    }
                }
                break;
            case 'AttributeStatement':
                result.attributes = parseAttributes(node);
                break;
        }
        node = node.nextSibling;
    }
    return result;
};

// ================================================================================
// SAML logout handlers
// ================================================================================

// process response to our (global) logout request
var handleLogoutResponse = function (xml, form, res) {
    var errors = [],
        issuer = null,
        status = null,
        session = null,
        doc, rootNode, attributes, i, inResponseTo, node;
    doc = new xmldom.DOMParser().parseFromString(xml);
    rootNode = doc.documentElement;
    if (rootNode.localName != 'LogoutResponse') {
        errors.push('not a LogoutResponse: ' + rootNode.localName);
    }
    else {
        attributes = rootNode.attributes;
        for (i = attributes.length - 1; i >= 0; i--) {
            if (attributes[i].localName === 'InResponseTo') {
                inResponseTo = attributes[i].value;
                break;
            }
        }
        if (!inResponseTo) errors.push('request ID that this message is a response to is missing');
        else {
            session = waitingLogouts[inResponseTo];
            if (!session) errors.push('there is no session waiting on request ID ' + inResponseTo);
        }
        node = rootNode.firstChild;
        while (node) {
            switch (node.localName) {
                case 'Issuer':
                    issuer = node.firstChild.data;
                    break;
                case 'Status':
                    status = xmlStatusOk(node);
                    break;
                default:
//                    errors.push('Unknown/unsupported top XML node: ' + node.localName + ', prefix: ' + node.prefix);
                    break;
            }
            node = node.nextSibling;
        }
        if (issuer === null) errors.push('Issuer is not set');
        else if (issuer !== IdPIssuer) errors.push('Invalid IdP issuer: ' + issuer);
        if (status === null) errors.push('response status is not set');
        else if (!status) errors.push('response status is not OK');
    }
    res.set('Content-Type', 'text/plain');
    if (errors.length > 0) {
        if (errors.length > 1) res.send('Multiple errors:\n  ' + errors.join('\n  '));
        else res.send('Error: ' + errors[0]);
        session.samlLogout(errors.join('\n'));
    }
    else {
        res.send('OK');
        session.samlLogout(null);
    }
};

// a third party initiated the (global) logout, process the request and redirect with a response
var handleLogoutRequest = function (xml, form, res) {
    var errors = [],
        nameId = null,
        sessionIndex = null,
        doc, rootNode, attributes, i, requestId, node,
        responseObj, responseId;
    doc = new xmldom.DOMParser().parseFromString(xml);
    rootNode = doc.documentElement;
    if (rootNode.localName != 'LogoutRequest') {
        errors.push('not a LogoutRequest: ' + rootNode.localName);
    }
    else {
        attributes = rootNode.attributes;
        for (i = attributes.length - 1; i >= 0; i--) {
            if (attributes[i].localName === 'ID') {
                requestId = attributes[i].value;
                break;
            }
        }
        if (!requestId) errors.push('request ID is missing');
        node = rootNode.firstChild;
        while (node) {
            switch (node.localName) {
                case 'Issuer':
                    if (node.firstChild.data !== IdPIssuer) errors.push('ERROR: invalid IdP issuer: ' + node.firstChild.data);
                    break;
                case 'NameID':
                    nameId = parseNameID(node);
                    break;
                case 'SessionIndex':
                    sessionIndex = node.firstChild && node.firstChild.data;
                    break;
            }
            node = node.nextSibling;
        }
        if (!nameId) errors.push('NameID not present');
        else {
            if (!nameId['#text']) errors.push('NameID is empty');
        }
    }
    if (errors.length > 0) {
        res.set('Content-Type', 'text/plain');
        res.send(errors.join('\n'));
    }
    else {
        responseId = makeRequestId();
        responseObj = {
            'samlp:LogoutResponse': {
                '@xmlns:samlp': 'urn:oasis:names:tc:SAML:2.0:protocol',
                '@xmlns:saml': 'urn:oasis:names:tc:SAML:2.0:assertion',
                '@Version': '2.0',
                '@Destination': SLOServiceURL,
                '@ID': responseId,
                '@IssueInstant': new Date().toISOString(),
                '@InResponseTo': requestId,
                'saml:Issuer' : {
                    '#text': SPIssuer
                },
                'samlp:Status': {
                    'samlp:StatusCode': {
                        '@Value': 'urn:oasis:names:tc:SAML:2.0:status:Success'
                    }
                }
            }
        };
        makeSamlRedirectUrl(SLOServiceURL, 'SAMLRequest', responseObj, form.RelayState ? {RelayState: form.RelayState} : null, function (err, svcUrl) {
            if (err) {
                console.log('Error while assembling the Logout SAML response: ' + err);
                res.send('Failed: ' + err);
                return;
            }
            res.redirect(svcUrl); // redirect to the IdP
        });
    }
};

// ================================================================================
// SAML web request handlers
// ================================================================================

// redirect to login on Arnes AAI, https://codeq.si/Shibboleth.sso/Login
http_app.get('/Shibboleth.sso/Login', function (req, res) {
    var sid = req.query.sid,
        waiter, requestId, request;
    try {
        if (!sid) {
            res.send('SID not set');
            return;
        }
        waiter = waitingLogins[sid];
        if (!waiter) waitingLogins[sid] = waiter = makeWaiter(sid);

        requestId = makeRequestId();
        request = {
            'samlp:AuthnRequest': {
                '@xmlns:samlp': 'urn:oasis:names:tc:SAML:2.0:protocol',
                '@xmlns:saml': 'urn:oasis:names:tc:SAML:2.0:assertion',
                '@Version': '2.0',
                '@ProtocolBinding': 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST',
                '@AssertionConsumerServiceURL': assertionConsumerServiceURL,
                '@Destination': SSOServiceURL,
                '@ID': requestId,
                '@IssueInstant': new Date().toISOString(),
                'saml:Issuer': {
                    '#text': SPIssuer
                }
            }
        };
        makeSamlRedirectUrl(SSOServiceURL, 'SAMLRequest', request, null, function (err, svcUrl) {
            if (err) {
                logException('Error while assembling the Login SAML request: ' + err, err);
                res.send('Failed: ' + err);
                waiter.done = Date.now();
                waiter.reject(err instanceof Error ? err : new Error(err));
                return;
            }
            res.redirect(svcUrl); // redirect to the IdP
            parkedLoginRequests[requestId] = waiter;
            waiter.parked = Date.now();
            waiter.requestId = requestId;
        });
    }
    catch (e) {
        logException('Exception while processing login request: ' + e, e);
        res.send('Error: ' + e);
        if (waiter) {
            waiter.done = Date.now();
            waiter.reject(e);
        }
    }
});

// redirect to logout on Arnes AAI, https://codeq.si/Shibboleth.sso/Logout
http_app.get('/Shibboleth.sso/Logout', function (req, res) {
    var sid = req.query.sid,
        session, samlData, requestId, request;
    if (!sid) {
        res.send('SID not set');
        return;
    }
    session = sessions[sid];
    if (!session) {
        res.send('No such session: ' + sid);
        return;
    }
    samlData = session.saml;
    if (!samlData) {
        res.send('No SAML session associated with session ' + sid);
        return;
    }
    if (!samlData.NameID) {
        res.send('The SAML data for session ' + sid + ' does not contain the NameID');
        return;
    }

    requestId = makeRequestId();
    request = {
        'samlp:LogoutRequest': {
            '@xmlns:samlp': 'urn:oasis:names:tc:SAML:2.0:protocol',
            '@xmlns:saml': 'urn:oasis:names:tc:SAML:2.0:assertion',
            '@Version': '2.0',
            '@Destination': SLOServiceURL,
            '@ID': requestId,
            '@IssueInstant': new Date().toISOString(),
            'saml:Issuer' : {
                '#text': SPIssuer
            },
            'saml:NameID': samlData.NameID
        }
    };
    if (samlData.SessionIndex) requestObj['samlp:LogoutRequest']['samlp:SessionIndex'] = {'#text': samlData.SessionIndex};
    makeSamlRedirectUrl(SLOServiceURL, 'SAMLRequest', request, null, function (err, svcUrl) {
        if (err) {
            console.log('Error while assembling the Logout SAML request: ' + err);
            res.send('Failed: ' + err);
            return;
        }
        res.redirect(svcUrl); // redirect to the IdP
        parkedLogoutRequests[requestId] = session;
    });
});

// user logged in, read the credentials
http_app.post('/Shibboleth.sso/SAML2/POST', function (req, res) {
    var form = req.body,
        keys = [],
        errors = [],
        inResponseTo = null,
        issuer = null,
        signature = null,
        status = null,
        assertion = null,
        waiter = null,
        attributes, i, key, value, xml, doc, rootNode, node, NameID, Format, SPNameQualifier, SessionIndex, samlData, userData;
    value = form.SAMLResponse;
    if (!value) {
        errors.push('no SAMLResponse');
    }
    else {
        xml = new Buffer(value, 'base64').toString('utf8');
        doc = new xmldom.DOMParser().parseFromString(xml);
        rootNode = doc.documentElement;
        if (rootNode.localName != 'Response') {
            errors.push('the root XML node is not a Response: ' + rootNode.localName);
        }
        else {
            attributes = rootNode.attributes;
            for (i = attributes.length - 1; i >= 0; i--) {
                if (attributes[i].localName === 'InResponseTo') {
                    inResponseTo = attributes[i].value;
                    break;
                }
            }
            if (!inResponseTo) errors.push('request ID that this message is a response to is missing');
            else {
                waiter = parkedLoginRequests[inResponseTo];
                if (!waiter) errors.push('there is no session waiting on request ID ' + inResponseTo);
                else {
                    waiter.done = Date.now();
                    delete parkedLoginRequests[inResponseTo];
                }
                node = rootNode.firstChild;
                while (node) {
                    switch (node.localName) {
                        case 'Issuer':
                            issuer = node.firstChild.data;
                            break;
                        case 'Signature':
                            signature = validateXmlSignature(xml, node);
                            break;
                        case 'Status':
                            status = xmlStatusOk(node);
                            break;
                        case 'Assertion':
                            assertion = parseAssertion(xml, node);
                            break;
                        default:
//                                errors.push('Unknown/unsupported top XML node: ' + node.localName + ', prefix: ' + node.prefix + '<br>\n');
                            break;
                    }
                    node = node.nextSibling;
                }
                if (issuer === null) errors.push('Issuer is not set');
                else if (issuer !== IdPIssuer) errors.push('Invalid IdP issuer: ' + issuer);
                if (signature === null) errors.push('the response is not signed');
                else if (!signature) errors.push('IdP signature is invalid');
                if (status === null) errors.push('status is not set');
                else if (!status) errors.push('response status is not OK');
                if (!assertion) errors.push('no assertions supplied, no attributes present');
                else {
                    if ((typeof assertion.signatureOk !== 'undefined') && (!assertion.signatureOk)) errors.push('assertion signature is invalid');
                    samlData = {};
                    node = assertion.subject;
                    if (!node) errors.push('assertion subject is not set');
                    else {
                        node = node.NameID;
                        if (!node) errors.push('assertion subject\'s NameID is not set');
                        else {
                            if (!node['#text']) errors.push('assertion subject\'s NameID is empty');
                            samlData['NameID'] = node;
                        }
                    }
                    if (assertion.SessionIndex) samlData['SessionIndex'] = assertion.SessionIndex;
                    node = assertion.attributes;
                    if (!node) errors.push('no attributes supplied');
                    else {
                        userData = {};
                        samlData.userData = userData;
                        keys = Object.keys(node);
                        for (i = keys.length - 1; i >= 0; i--) {
                            key = keys[i];
                            userData[key] = node[key];
                        }
                    }
                }
            }
        }
    }
    res.set('Content-Type', 'text/plain');
    if (errors.length > 0) {
        if (errors.length > 1) res.send('Multiple errors:\n  ' + errors.join('\n  '));
        else res.send('Error: ' + errors[0]);
        if (waiter) waiter.reject(new Error(errors.join(', ')));
    }
    else {
        res.send('OK');
        if (waiter) waiter.resolve(samlData);
    }
});

// user logged out, the GET service
http_app.get('/Shibboleth.sso/SLO/Redirect', function (req, res) {
    var form = req.query,
        delegateToHandler = function (err, buffer, handler) {
            if (err) {
                console.log('Error while deflating request: ' + err);
                res.send('Failed: ' + err);
                return;
            }
            handler(buffer.toString('utf8'), form, res);
        };
    if (form.SAMLRequest) zlib.inflateRaw(new Buffer(form.SAMLRequest, 'base64'), function (err, buffer) {delegateToHandler(err, buffer, handleLogoutRequest);});
    else if (form.SAMLResponse) zlib.inflateRaw(new Buffer(form.SAMLResponse, 'base64'), function (err, buffer) {delegateToHandler(err, buffer, handleLogoutResponse);});
    else res.send('Invalid SAML logout request.');
});

// ================================================================================
// Web API handler
// ================================================================================

http_app.get('/Shibboleth.sso/WaitLogin', function (req, res) {
    var sid = req.query.sid,
        waiter;
    if (!sid) {
        res.set('Content-Type', 'text/plain');
        res.send('Provide sid as a query parameter');
        return;
    }
    waiter = waitingLogins[sid];
    if (!waiter) waitingLogins[sid] = waiter = makeWaiter(sid);
    waiter.listeners = waiter.listeners + 1;
    waiter.promise.then(function (jsonResponse) {
        res.json({'code': 0, 'message': 'OK', 'data': jsonResponse});
        delete waitingLogins[sid];
    }, function (err) {
        res.json({'code': 1, 'message': '' + err});
        delete waitingLogins[sid];
    }).done();
});