/*
 * Copyright (c) 2014 ThoughtWorks, Inc.
 *
 * Pixelated is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Pixelated is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with Pixelated. If not, see <http://www.gnu.org/licenses/>.
 */

/* jshint curly: false */
define([], function () {
  'use strict';
  var exports = {};

  // Licence: PUBLIC DOMAIN <http://unlicense.org/>
  // Author: Austin Wright <http://github.com/Acubed>

  function MediaType(s, p){
	this.type = '';
	this.params = {};
    var c, i, n;
	if(typeof s==='string'){
	  c = splitQuotedString(s);
	  this.type = c.shift();
	  for(i=0; i<c.length; i++){
		this.parseParameter(c[i]);
	  }
	}else if(s instanceof MediaType){
	  this.type = s.type;
	  this.q = s.q;
	  for(n in s.params) this.params[n]=s.params[n];
	}
	if(typeof p==='string'){
	  c = splitQuotedString(p);
	  for(i=0; i<c.length; i++){
		this.parseParameter(c[i]);
	  }
	}else if(typeof p==='object'){
	  for(n in p) this.params[n]=p[n];
	}
  }
  MediaType.prototype.parseParameter = function parseParameter(s){
	var param = s.split('=',1);
	var name = param[0].trim();
	var value = s.substr(param[0].length+1).trim();
	if(!value || !name) return;
	if(name==='q' && this.q===undefined){
	  this.q=parseFloat(value);
	}else{
	  if(value[0]==='"' && value[value.length-1]==='"'){
		value = value.substr(1, value.length-2);
		value = value.replace(/\\(.)/g, function(a,b){return b;});
	  }
	  this.params[name]=value;
	}
  };
  MediaType.prototype.toString = function toString(){
	var str = this.type + ';q='+this.q;
	for(var n in this.params){
	  str += ';'+n+'=';
	  if(this.params[n].match(/["=;<>\[\]\(\) ,\-]/)){
		str += '"' + this.params[n].replace(/["\\]/g, function(a){return '\\'+a;}) + '"';
	  }else{
		str += this.params[n];
	  }
	}
	return str;
  };
  exports.MediaType = MediaType;

  // Split a string by character, but ignore quoted parts and backslash-escaped characters
  function splitQuotedString(str, delim, quote){
	delim = delim || ';';
	quote = quote || '"';
	var res = [];
	var start = 0;
	var offset = 0;
	function findNextChar(v, c, i, a){
	  var p = str.indexOf(c, offset+1);
	  return (p<0)?v:Math.min(p,v);
	}
	while(offset>=0){
	  offset = [delim,quote].reduce(findNextChar, 1/0);
	  if(offset===1/0) break;
	  switch(str[offset]){
	  case quote:
		// Skip to end of quoted string
		while(1){
		  offset=str.indexOf(quote, offset+1);
		  if(offset<0) break;
		  if(str[offset-1]==='\\') continue;
		  break;
		}
		continue;
	  case delim:
		res.push(str.substr(start, offset-start).trim());
		start = ++offset;
		break;
	  }
	}
	res.push(str.substr(start).trim());
	return res;
  }
  exports.splitQuotedString = splitQuotedString;

  // Split a list of content types found in an Accept header
  // Maybe use it like: splitContentTypes(request.headers.accept).map(parseMedia)
  function splitContentTypes(str){
	return splitQuotedString(str, ',');
  }
  exports.splitContentTypes = splitContentTypes;

  function parseMedia(str){
	var o = new MediaType(str);
	if(o.q===undefined) o.q=1;
	return o;
  }
  exports.parseMedia = parseMedia;

  // Pick an ideal representation to send given a list of representations to choose from and the client-preferred list
  function select(reps, accept){
	var cr = {q:0};
	var ca = {q:0};
	var cq = 0;
	for(var i=0; i<reps.length; i++){
	  var r = reps[i];
	  var rq = r.q || 1;
	  for(var j=0; j<accept.length; j++){
		var a=accept[j];
		var aq = a.q || 1;
		var cmp = mediaCmp(a, r);
		if(cmp!==null && cmp>=0){
		  if(aq*rq>cq){
			ca = a;
			cr = r;
			cq = ca.q*cr.q;
			if(cq===1 && cr.type) return cr;
		  }
		}
	  }
	}
	return cr.type&&cr;
  }
  exports.select = select;

  // Determine if one media type is a subset of another
  // If a is a superset of b (b is smaller than a), return 1
  // If b is a superset of a, return -1
  // If they are the exact same, return 0
  // If they are disjoint, return null
  function mediaCmp(a, b){
	if(a.type==='*/*' && b.type!=='*/*') return 1;
	else if(a.type!=='*/*' && b.type==='*/*') return -1;
	var ac = (a.type||'').split('/');
	var bc = (b.type||'').split('/');
	if(ac[0]==='*' && bc[0]!=='*') return 1;
	if(ac[0]!=='*' && bc[0]==='*') return -1;
	if(a.type!==b.type) return null;
	var ap = a.params || {};
	var bp = b.params || {};
	var ak = Object.keys(ap);
	var bk = Object.keys(bp);
	if(ak.length < bk.length) return 1;
	if(ak.length > bk.length) return -1;
	var k = ak.concat(bk).sort();
	var dir = 0;
	for(var n in ap){
	  if(ap[n] && !bp[n]){ if(dir<0) return null; else dir=1; }
	  if(!ap[n] && bp[n]){ if(dir>0) return null; else dir=-1; }
	}
	return dir;
  }
  exports.mediaCmp = mediaCmp;

  return exports;
});