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// mimeparse.js
//
// This module provides basic functions for handling mime-types. It can
// handle matching mime-types against a list of media-ranges. See section
// 14.1 of the HTTP specification [RFC 2616] for a complete explanation.
//
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
//
// A port to JavaScript of Joe Gregorio's MIME-Type Parser:
//
// http://code.google.com/p/mimeparse/
//
// Ported by J. Chris Anderson <jchris@apache.org>, targeting the Spidermonkey runtime.
//
// To run the tests, open mimeparse-js-test.html in a browser.
// Ported from version 0.1.2
// Comments are mostly excerpted from the original.
var Mimeparse = (function() {
// private helpers
function strip(string) {
return string.replace(/^\s+/, '').replace(/\s+$/, '');
};
function parseRanges(ranges) {
var parsedRanges = [], rangeParts = ranges.split(",");
for (var i=0; i < rangeParts.length; i++) {
parsedRanges.push(publicMethods.parseMediaRange(rangeParts[i]));
};
return parsedRanges;
};
var publicMethods = {
// Carves up a mime-type and returns an Array of the
// [type, subtype, params] where "params" is a Hash of all
// the parameters for the media range.
//
// For example, the media range "application/xhtml;q=0.5" would
// get parsed into:
//
// ["application", "xhtml", { "q" : "0.5" }]
parseMimeType : function(mimeType) {
var fullType, typeParts, params = {}, parts = mimeType.split(';');
for (var i=0; i < parts.length; i++) {
var p = parts[i].split('=');
if (p.length == 2) {
params[strip(p[0])] = strip(p[1]);
}
};
fullType = parts[0].replace(/^\s+/, '').replace(/\s+$/, '');
if (fullType == '*') fullType = '*/*';
typeParts = fullType.split('/');
return [typeParts[0], typeParts[1], params];
},
// Carves up a media range and returns an Array of the
// [type, subtype, params] where "params" is a Object with
// all the parameters for the media range.
//
// For example, the media range "application/*;q=0.5" would
// get parsed into:
//
// ["application", "*", { "q" : "0.5" }]
//
// In addition this function also guarantees that there
// is a value for "q" in the params dictionary, filling it
// in with a proper default if necessary.
parseMediaRange : function(range) {
var q, parsedType = this.parseMimeType(range);
if (!parsedType[2]['q']) {
parsedType[2]['q'] = '1';
} else {
q = parseFloat(parsedType[2]['q']);
if (isNaN(q)) {
parsedType[2]['q'] = '1';
} else if (q > 1 || q < 0) {
parsedType[2]['q'] = '1';
}
}
return parsedType;
},
// Find the best match for a given mime-type against
// a list of media_ranges that have already been
// parsed by parseMediaRange(). Returns an array of
// the fitness value and the value of the 'q' quality
// parameter of the best match, or (-1, 0) if no match
// was found. Just as for qualityParsed(), 'parsed_ranges'
// must be a list of parsed media ranges.
fitnessAndQualityParsed : function(mimeType, parsedRanges) {
var bestFitness = -1, bestFitQ = 0, target = this.parseMediaRange(mimeType);
var targetType = target[0], targetSubtype = target[1], targetParams = target[2];
for (var i=0; i < parsedRanges.length; i++) {
var parsed = parsedRanges[i];
var type = parsed[0], subtype = parsed[1], params = parsed[2];
if ((type == targetType || type == "*" || targetType == "*") &&
(subtype == targetSubtype || subtype == "*" || targetSubtype == "*")) {
var matchCount = 0;
for (var param in targetParams) {
if (param != 'q' && params[param] && params[param] == targetParams[param]) {
matchCount += 1;
}
}
var fitness = (type == targetType) ? 100 : 0;
fitness += (subtype == targetSubtype) ? 10 : 0;
fitness += matchCount;
if (fitness > bestFitness) {
bestFitness = fitness;
bestFitQ = params["q"];
}
}
};
return [bestFitness, parseFloat(bestFitQ)];
},
// Find the best match for a given mime-type against
// a list of media_ranges that have already been
// parsed by parseMediaRange(). Returns the
// 'q' quality parameter of the best match, 0 if no
// match was found. This function bahaves the same as quality()
// except that 'parsedRanges' must be a list of
// parsed media ranges.
qualityParsed : function(mimeType, parsedRanges) {
return this.fitnessAndQualityParsed(mimeType, parsedRanges)[1];
},
// Returns the quality 'q' of a mime-type when compared
// against the media-ranges in ranges. For example:
//
// >>> Mimeparse.quality('text/html','text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5')
// 0.7
quality : function(mimeType, ranges) {
return this.qualityParsed(mimeType, parseRanges(ranges));
},
// Takes a list of supported mime-types and finds the best
// match for all the media-ranges listed in header. The value of
// header must be a string that conforms to the format of the
// HTTP Accept: header. The value of 'supported' is a list of
// mime-types.
//
// >>> bestMatch(['application/xbel+xml', 'text/xml'], 'text/*;q=0.5,*/*; q=0.1')
// 'text/xml'
bestMatch : function(supported, header) {
var parsedHeader = parseRanges(header);
var weighted = [];
for (var i=0; i < supported.length; i++) {
weighted.push([publicMethods.fitnessAndQualityParsed(supported[i], parsedHeader), i, supported[i]]);
};
weighted.sort();
return weighted[weighted.length-1][0][1] ? weighted[weighted.length-1][2] : '';
}
};
return publicMethods;
})();
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