var li = require('li');

var path = require('path');

var S = require('string');

var Negotiator = require('negotiator');

var metadata = require('./metadata.js');

var ldp = require('./ldp.js');

var utils = require('./utils.js');

var ldpVocab = require('./vocab/ldp.js');

var HttpError = require('./http-error');

function addLink(res, value, rel) {

var oldLink = res.get('Link');

if (oldLink === undefined)

res.set('Link', '<' + value + '>; rel="' + rel + '"');

else

res.set('Link', oldLink + ', ' + '<' + value +

'>; rel="' + rel + '"');

}

function addLinks(res, fileMetadata) {

if (fileMetadata.isResource)

addLink(res, ldpVocab.Resource, 'type');

if (fileMetadata.isSourceResource)

addLink(res, ldpVocab.RDFSource, 'type');

if (fileMetadata.isContainer)

addLink(res, ldpVocab.Container, 'type');

if (fileMetadata.isBasicContainer)

addLink(res, ldpVocab.BasicContainer, 'type');

if (fileMetadata.isDirectContainer)

addLink(res, ldpVocab.DirectContainer, 'type');

}

function linksHandler(req, res, next) {

var uri = utils.uriBase(req);

var ldp = req.app.locals.ldp;

var filename = utils.uriToFilename(req.url, ldp.root);

filename = path.join(filename, req.path);

if (ldp.isMetadataFile(filename)) {

debug.metadata("Trying to access metadata file as regular file.");

return next(new HttpError({

message: "Trying to access metadata file as regular file",

status: 404

}));

}

var fileMetadata = new metadata.Metadata();

if (S(filename).endsWith('/')) {

fileMetadata.isContainer = true;

fileMetadata.isBasicContainer = true;

} else {

fileMetadata.isResource = true;

}

// Add ACL and Meta Link in header

addLink(res, utils.pathBasename(req.path) + ldp.suffixAcl, 'acl');

addLink(res, utils.pathBasename(req.path) + ldp.suffixMeta, 'describedBy');

// Add other Link headers

addLinks(res, fileMetadata);

next();

}

function parseMetadataFromHeader(linkHeader) {

var fileMetadata = new metadata.Metadata();

if (linkHeader === undefined)

return fileMetadata;

var links = linkHeader.split(',');

for (var linkIndex in links) {

var link = links[linkIndex];

var parsedLinks = li.parse(link);

for (var rel in parsedLinks) {

if (rel === 'type') {

if (parsedLinks[rel] === ldpVocab.Resource)

fileMetadata.isResource = true;

else if (parsedLinks[rel] === ldpVocab.RDFSource)

fileMetadata.isSourceResource = true;

else if (parsedLinks[rel] === ldpVocab.Container)

fileMetadata.isContainer = true;

else if (parsedLinks[rel] === ldpVocab.BasicContainer)

fileMetadata.isBasicContainer = true;

else if (parsedLinks[rel] === ldpVocab.DirectContainer)

fileMetadata.isDirectContainer = true;

}

}

}

return fileMetadata;

}

// Returns an array containing mime types from Accept header, ordered by priority

// If no Accept value, serve turtle by default

function negotiateContentType(req) {

var negotiator = new Negotiator(req);

return negotiator.mediaTypes();

}

function parseAcceptRDFHeader(req) {

var acceptFinalValue;

var acceptHeader = negotiateContentType(req);

if (!acceptHeader || acceptHeader.length === 0) {

acceptFinalValue = undefined;

} else {

for (var i in acceptHeader) {

switch (acceptHeader[i]) {

case 'text/turtle':

case 'application/x-turtle':

case 'text/n3':

case 'application/rdf+xml':

case 'application/n3':

case 'application/ld+json':

case 'application/nquads':

case 'application/n-quads':

acceptFinalValue = acceptHeader[i];

break;

default:

acceptFinalValue = undefined;

}

if (acceptFinalValue !== undefined) {

break;

}

}

}

return acceptFinalValue;

}

module.exports.addLink = addLink;

module.exports.addLinks = addLinks;

module.exports.parseMetadataFromHeader = parseMetadataFromHeader;

module.exports.parseAcceptRDFHeader = parseAcceptRDFHeader;

module.exports.linksHandler = linksHandler;

module.exports.negotiateContentType = negotiateContentType;