From f8e05f410fb344f78b23ab50c8e4827a72063e5c Mon Sep 17 00:00:00 2001
From: fred gibbs <fwgibbs@gmail.com>
Date: Thu, 27 Jul 2017 12:49:31 -0600
Subject: [PATCH] maintain filter and sort state via URI

---
 _includes/lesson-index.html |  18 +++-
 css/style.css               |   9 +-
 js/URI.min.js               |  90 ++++++++++++++++
 js/lessonfilter.js          | 197 ++++++++++++++++++++++++++++--------
 4 files changed, 265 insertions(+), 49 deletions(-)
 create mode 100644 js/URI.min.js

diff --git a/_includes/lesson-index.html b/_includes/lesson-index.html
index 186099383d..db1f0196a1 100644
--- a/_includes/lesson-index.html
+++ b/_includes/lesson-index.html
@@ -21,15 +21,24 @@
 
 <div id="filter-none">{{site.data.snippets.reset-button[page.lang]}} ({{  alllessons | size  }})</div>
 
-<!-- this div ('lesson-list', referenced in lessonfilter.js) needs to contain the sort button/elements AND the actual list for the sort buttons to work -->
+<!--
+this div ('lesson-list', referenced in lessonfilter.js) needs to contain the sort button/elements AND the actual list for the sort buttons to work
+-->
 <div id="lesson-list">
 
+<!--
+List.js uses button classes of asc and desc to control sorting functionality. It also toggles those classes off and on with click events.
+To not interfere with that, we use my-asc and my-desc to control the arrows, since our desired behavior is different from what list.js does.
+More concretely: to sort asc, the button class needs to contain asc, but we use the arrow ON THE BUTTON to indicate what WILL happen,
+not what IS HAPPENING (the filter header displays the current sort state). In order to have a down arrow, we use a my-desc class.
+Yes, this is confusing. But using two differnt classes allows us to separate functionality and presentation.
+-->
   <ul class="sort-by">
-    <li id="sort-by-date" class="sort asc" data-sort="date">{{site.data.snippets.sort-by-date[page.lang]}}</li>
-    <li id="sort-by-difficulty" class="sort desc" data-sort="difficulty">{{site.data.snippets.sort-by-difficulty[page.lang]}}</li>
+    <li id="sort-by-date" class="sort" data-sort="date">{{site.data.snippets.sort-by-date[page.lang]}}</li>
+    <li id="sort-by-difficulty" class="sort" data-sort="difficulty">{{site.data.snippets.sort-by-difficulty[page.lang]}}</li>
   </ul>
 
-  <h2 class="results-title">Filtering Results: <span id="results-value">All lessons </span><span id="current-sort" class="sort-asc">{{site.data.snippets.date[page.lang]}}</span></h2>
+  <h2 class="results-title">Filtering Results: <span id="results-value">All lessons </span><span id="current-sort" class="sort-desc">{{site.data.snippets.date[page.lang]}}</span></h2>
 
   <ul class="list">
     {% for lesson in alllessons %}
@@ -43,6 +52,7 @@ <h2 class="results-title">Filtering Results: <span id="results-value">All lesson
 
 <script src='//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js'></script>
 <script src='//cdnjs.cloudflare.com/ajax/libs/list.js/1.5.0/list.min.js'></script>
+<script src="{{ site.baseurl }}/js/URI.min.js"></script>
 <script src="{{ site.baseurl }}/js/lessonfilter.js"></script>
 
 <script>
diff --git a/css/style.css b/css/style.css
index c409c0167f..a5fff60b17 100644
--- a/css/style.css
+++ b/css/style.css
@@ -299,7 +299,7 @@ Lessons Index
     font-size:75%;
   }
 
-  .sort.asc:after, .sort-asc:after {
+  .sort.my-desc:after, .sort-desc:after {
     width: 0;
     height: 0;
     border-left: .4rem solid transparent;
@@ -311,7 +311,7 @@ Lessons Index
     right:-.3rem;
   }
 
-  .sort.desc:after, .sort-desc:after {
+  .sort.my-asc:after, .sort-asc:after {
     width: 0;
     height: 0;
     border-left: .4rem solid transparent;
@@ -323,12 +323,11 @@ Lessons Index
     right:-.3rem;
   }
 
-
-  .sort-asc:after {
+  .sort-desc:after {
     top:1rem;
   }
 
-  .sort-desc:after {
+  .sort-asc:after {
     bottom:1rem;
   }
 
diff --git a/js/URI.min.js b/js/URI.min.js
new file mode 100644
index 0000000000..9c66b0f91a
--- /dev/null
+++ b/js/URI.min.js
@@ -0,0 +1,90 @@
+/*! URI.js v1.18.10 http://medialize.github.io/URI.js/ */
+/* build contains: IPv6.js, punycode.js, SecondLevelDomains.js, URI.js, URITemplate.js */
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+for(m=0;m<b;m++){for(var l=h[m].split(""),g=0;3>g;g++)if("0"===l[0]&&1<l.length)l.splice(0,1);else break;h[m]=l.join("")}var l=-1,k=g=0,f=-1,n=!1;for(m=0;m<b;m++)n?"0"===h[m]?k+=1:(n=!1,k>g&&(l=f,g=k)):"0"===h[m]&&(n=!0,f=m,k=1);k>g&&(l=f,g=k);1<g&&h.splice(l,g,"");l=h.length;b="";""===h[0]&&(b=":");for(m=0;m<l;m++){b+=h[m];if(m===l-1)break;b+=":"}""===h[l-1]&&(b+=":");return b},noConflict:function(){g.IPv6===this&&(g.IPv6=k);return this}}});
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+this.build(!c);return this};e.subdomain=function(a,c){if(this._parts.urn)return void 0===a?"":this;if(void 0===a){if(!this._parts.hostname||this.is("IP"))return"";var d=this._parts.hostname.length-this.domain().length-1;return this._parts.hostname.substring(0,d)||""}d=this._parts.hostname.length-this.domain().length;d=this._parts.hostname.substring(0,d);d=new RegExp("^"+m(d));a&&"."!==a.charAt(a.length-1)&&(a+=".");a&&b.ensureValidHostname(a);this._parts.hostname=this._parts.hostname.replace(d,a);
+this.build(!c);return this};e.domain=function(a,c){if(this._parts.urn)return void 0===a?"":this;"boolean"===typeof a&&(c=a,a=void 0);if(void 0===a){if(!this._parts.hostname||this.is("IP"))return"";var d=this._parts.hostname.match(/\./g);if(d&&2>d.length)return this._parts.hostname;d=this._parts.hostname.length-this.tld(c).length-1;d=this._parts.hostname.lastIndexOf(".",d-1)+1;return this._parts.hostname.substring(d)||""}if(!a)throw new TypeError("cannot set domain empty");b.ensureValidHostname(a);
+!this._parts.hostname||this.is("IP")?this._parts.hostname=a:(d=new RegExp(m(this.domain())+"$"),this._parts.hostname=this._parts.hostname.replace(d,a));this.build(!c);return this};e.tld=function(a,c){if(this._parts.urn)return void 0===a?"":this;"boolean"===typeof a&&(c=a,a=void 0);if(void 0===a){if(!this._parts.hostname||this.is("IP"))return"";var d=this._parts.hostname.lastIndexOf("."),d=this._parts.hostname.substring(d+1);return!0!==c&&h&&h.list[d.toLowerCase()]?h.get(this._parts.hostname)||d:d}if(a)if(a.match(/[^a-zA-Z0-9-]/))if(h&&
+h.is(a))d=new RegExp(m(this.tld())+"$"),this._parts.hostname=this._parts.hostname.replace(d,a);else throw new TypeError('TLD "'+a+'" contains characters other than [A-Z0-9]');else{if(!this._parts.hostname||this.is("IP"))throw new ReferenceError("cannot set TLD on non-domain host");d=new RegExp(m(this.tld())+"$");this._parts.hostname=this._parts.hostname.replace(d,a)}else throw new TypeError("cannot set TLD empty");this.build(!c);return this};e.directory=function(a,c){if(this._parts.urn)return void 0===
+a?"":this;if(void 0===a||!0===a){if(!this._parts.path&&!this._parts.hostname)return"";if("/"===this._parts.path)return"/";var d=this._parts.path.length-this.filename().length-1,d=this._parts.path.substring(0,d)||(this._parts.hostname?"/":"");return a?b.decodePath(d):d}d=this._parts.path.length-this.filename().length;d=this._parts.path.substring(0,d);d=new RegExp("^"+m(d));this.is("relative")||(a||(a="/"),"/"!==a.charAt(0)&&(a="/"+a));a&&"/"!==a.charAt(a.length-1)&&(a+="/");a=b.recodePath(a);this._parts.path=
+this._parts.path.replace(d,a);this.build(!c);return this};e.filename=function(a,c){if(this._parts.urn)return void 0===a?"":this;if("string"!==typeof a){if(!this._parts.path||"/"===this._parts.path)return"";var d=this._parts.path.lastIndexOf("/"),d=this._parts.path.substring(d+1);return a?b.decodePathSegment(d):d}d=!1;"/"===a.charAt(0)&&(a=a.substring(1));a.match(/\.?\//)&&(d=!0);var e=new RegExp(m(this.filename())+"$");a=b.recodePath(a);this._parts.path=this._parts.path.replace(e,a);d?this.normalizePath(c):
+this.build(!c);return this};e.suffix=function(a,c){if(this._parts.urn)return void 0===a?"":this;if(void 0===a||!0===a){if(!this._parts.path||"/"===this._parts.path)return"";var d=this.filename(),e=d.lastIndexOf(".");if(-1===e)return"";d=d.substring(e+1);d=/^[a-z0-9%]+$/i.test(d)?d:"";return a?b.decodePathSegment(d):d}"."===a.charAt(0)&&(a=a.substring(1));if(d=this.suffix())e=a?new RegExp(m(d)+"$"):new RegExp(m("."+d)+"$");else{if(!a)return this;this._parts.path+="."+b.recodePath(a)}e&&(a=b.recodePath(a),
+this._parts.path=this._parts.path.replace(e,a));this.build(!c);return this};e.segment=function(a,c,d){var b=this._parts.urn?":":"/",e=this.path(),f="/"===e.substring(0,1),e=e.split(b);void 0!==a&&"number"!==typeof a&&(d=c,c=a,a=void 0);if(void 0!==a&&"number"!==typeof a)throw Error('Bad segment "'+a+'", must be 0-based integer');f&&e.shift();0>a&&(a=Math.max(e.length+a,0));if(void 0===c)return void 0===a?e:e[a];if(null===a||void 0===e[a])if(u(c)){e=[];a=0;for(var g=c.length;a<g;a++)if(c[a].length||
+e.length&&e[e.length-1].length)e.length&&!e[e.length-1].length&&e.pop(),e.push(z(c[a]))}else{if(c||"string"===typeof c)c=z(c),""===e[e.length-1]?e[e.length-1]=c:e.push(c)}else c?e[a]=z(c):e.splice(a,1);f&&e.unshift("");return this.path(e.join(b),d)};e.segmentCoded=function(a,c,d){var e,f;"number"!==typeof a&&(d=c,c=a,a=void 0);if(void 0===c){a=this.segment(a,c,d);if(u(a))for(e=0,f=a.length;e<f;e++)a[e]=b.decode(a[e]);else a=void 0!==a?b.decode(a):void 0;return a}if(u(c))for(e=0,f=c.length;e<f;e++)c[e]=
+b.encode(c[e]);else c="string"===typeof c||c instanceof String?b.encode(c):c;return this.segment(a,c,d)};var J=e.query;e.query=function(a,c){if(!0===a)return b.parseQuery(this._parts.query,this._parts.escapeQuerySpace);if("function"===typeof a){var d=b.parseQuery(this._parts.query,this._parts.escapeQuerySpace),e=a.call(this,d);this._parts.query=b.buildQuery(e||d,this._parts.duplicateQueryParameters,this._parts.escapeQuerySpace);this.build(!c);return this}return void 0!==a&&"string"!==typeof a?(this._parts.query=
+b.buildQuery(a,this._parts.duplicateQueryParameters,this._parts.escapeQuerySpace),this.build(!c),this):J.call(this,a,c)};e.setQuery=function(a,c,d){var e=b.parseQuery(this._parts.query,this._parts.escapeQuerySpace);if("string"===typeof a||a instanceof String)e[a]=void 0!==c?c:null;else if("object"===typeof a)for(var f in a)q.call(a,f)&&(e[f]=a[f]);else throw new TypeError("URI.addQuery() accepts an object, string as the name parameter");this._parts.query=b.buildQuery(e,this._parts.duplicateQueryParameters,
+this._parts.escapeQuerySpace);"string"!==typeof a&&(d=c);this.build(!d);return this};e.addQuery=function(a,c,d){var e=b.parseQuery(this._parts.query,this._parts.escapeQuerySpace);b.addQuery(e,a,void 0===c?null:c);this._parts.query=b.buildQuery(e,this._parts.duplicateQueryParameters,this._parts.escapeQuerySpace);"string"!==typeof a&&(d=c);this.build(!d);return this};e.removeQuery=function(a,c,d){var e=b.parseQuery(this._parts.query,this._parts.escapeQuerySpace);b.removeQuery(e,a,c);this._parts.query=
+b.buildQuery(e,this._parts.duplicateQueryParameters,this._parts.escapeQuerySpace);"string"!==typeof a&&(d=c);this.build(!d);return this};e.hasQuery=function(a,c,d){var e=b.parseQuery(this._parts.query,this._parts.escapeQuerySpace);return b.hasQuery(e,a,c,d)};e.setSearch=e.setQuery;e.addSearch=e.addQuery;e.removeSearch=e.removeQuery;e.hasSearch=e.hasQuery;e.normalize=function(){return this._parts.urn?this.normalizeProtocol(!1).normalizePath(!1).normalizeQuery(!1).normalizeFragment(!1).build():this.normalizeProtocol(!1).normalizeHostname(!1).normalizePort(!1).normalizePath(!1).normalizeQuery(!1).normalizeFragment(!1).build()};
+e.normalizeProtocol=function(a){"string"===typeof this._parts.protocol&&(this._parts.protocol=this._parts.protocol.toLowerCase(),this.build(!a));return this};e.normalizeHostname=function(a){this._parts.hostname&&(this.is("IDN")&&g?this._parts.hostname=g.toASCII(this._parts.hostname):this.is("IPv6")&&k&&(this._parts.hostname=k.best(this._parts.hostname)),this._parts.hostname=this._parts.hostname.toLowerCase(),this.build(!a));return this};e.normalizePort=function(a){"string"===typeof this._parts.protocol&&
+this._parts.port===b.defaultPorts[this._parts.protocol]&&(this._parts.port=null,this.build(!a));return this};e.normalizePath=function(a){var c=this._parts.path;if(!c)return this;if(this._parts.urn)return this._parts.path=b.recodeUrnPath(this._parts.path),this.build(!a),this;if("/"===this._parts.path)return this;var c=b.recodePath(c),d,e="",f,g;"/"!==c.charAt(0)&&(d=!0,c="/"+c);if("/.."===c.slice(-3)||"/."===c.slice(-2))c+="/";c=c.replace(/(\/(\.\/)+)|(\/\.$)/g,"/").replace(/\/{2,}/g,"/");d&&(e=c.substring(1).match(/^(\.\.\/)+/)||
+"")&&(e=e[0]);for(;;){f=c.search(/\/\.\.(\/|$)/);if(-1===f)break;else if(0===f){c=c.substring(3);continue}g=c.substring(0,f).lastIndexOf("/");-1===g&&(g=f);c=c.substring(0,g)+c.substring(f+3)}d&&this.is("relative")&&(c=e+c.substring(1));this._parts.path=c;this.build(!a);return this};e.normalizePathname=e.normalizePath;e.normalizeQuery=function(a){"string"===typeof this._parts.query&&(this._parts.query.length?this.query(b.parseQuery(this._parts.query,this._parts.escapeQuerySpace)):this._parts.query=
+null,this.build(!a));return this};e.normalizeFragment=function(a){this._parts.fragment||(this._parts.fragment=null,this.build(!a));return this};e.normalizeSearch=e.normalizeQuery;e.normalizeHash=e.normalizeFragment;e.iso8859=function(){var a=b.encode,c=b.decode;b.encode=escape;b.decode=decodeURIComponent;try{this.normalize()}finally{b.encode=a,b.decode=c}return this};e.unicode=function(){var a=b.encode,c=b.decode;b.encode=y;b.decode=unescape;try{this.normalize()}finally{b.encode=a,b.decode=c}return this};
+e.readable=function(){var a=this.clone();a.username("").password("").normalize();var c="";a._parts.protocol&&(c+=a._parts.protocol+"://");a._parts.hostname&&(a.is("punycode")&&g?(c+=g.toUnicode(a._parts.hostname),a._parts.port&&(c+=":"+a._parts.port)):c+=a.host());a._parts.hostname&&a._parts.path&&"/"!==a._parts.path.charAt(0)&&(c+="/");c+=a.path(!0);if(a._parts.query){for(var d="",e=0,f=a._parts.query.split("&"),h=f.length;e<h;e++){var n=(f[e]||"").split("="),d=d+("&"+b.decodeQuery(n[0],this._parts.escapeQuerySpace).replace(/&/g,
+"%26"));void 0!==n[1]&&(d+="="+b.decodeQuery(n[1],this._parts.escapeQuerySpace).replace(/&/g,"%26"))}c+="?"+d.substring(1)}return c+=b.decodeQuery(a.hash(),!0)};e.absoluteTo=function(a){var c=this.clone(),d=["protocol","username","password","hostname","port"],e,f;if(this._parts.urn)throw Error("URNs do not have any generally defined hierarchical components");a instanceof b||(a=new b(a));if(c._parts.protocol)return c;c._parts.protocol=a._parts.protocol;if(this._parts.hostname)return c;for(e=0;f=d[e];e++)c._parts[f]=
+a._parts[f];c._parts.path?(".."===c._parts.path.substring(-2)&&(c._parts.path+="/"),"/"!==c.path().charAt(0)&&(d=(d=a.directory())?d:0===a.path().indexOf("/")?"/":"",c._parts.path=(d?d+"/":"")+c._parts.path,c.normalizePath())):(c._parts.path=a._parts.path,c._parts.query||(c._parts.query=a._parts.query));c.build();return c};e.relativeTo=function(a){var c=this.clone().normalize(),d,e,f;if(c._parts.urn)throw Error("URNs do not have any generally defined hierarchical components");a=(new b(a)).normalize();
+d=c._parts;e=a._parts;f=c.path();a=a.path();if("/"!==f.charAt(0))throw Error("URI is already relative");if("/"!==a.charAt(0))throw Error("Cannot calculate a URI relative to another relative URI");d.protocol===e.protocol&&(d.protocol=null);if(d.username===e.username&&d.password===e.password&&null===d.protocol&&null===d.username&&null===d.password&&d.hostname===e.hostname&&d.port===e.port)d.hostname=null,d.port=null;else return c.build();if(f===a)return d.path="",c.build();f=b.commonPath(f,a);if(!f)return c.build();
+e=e.path.substring(f.length).replace(/[^\/]*$/,"").replace(/.*?\//g,"../");d.path=e+d.path.substring(f.length)||"./";return c.build()};e.equals=function(a){var c=this.clone(),d=new b(a),e;a={};var f,g;c.normalize();d.normalize();if(c.toString()===d.toString())return!0;f=c.query();e=d.query();c.query("");d.query("");if(c.toString()!==d.toString()||f.length!==e.length)return!1;c=b.parseQuery(f,this._parts.escapeQuerySpace);e=b.parseQuery(e,this._parts.escapeQuerySpace);for(g in c)if(q.call(c,g)){if(!u(c[g])){if(c[g]!==
+e[g])return!1}else if(!B(c[g],e[g]))return!1;a[g]=!0}for(g in e)if(q.call(e,g)&&!a[g])return!1;return!0};e.duplicateQueryParameters=function(a){this._parts.duplicateQueryParameters=!!a;return this};e.escapeQuerySpace=function(a){this._parts.escapeQuerySpace=!!a;return this};return b});
+(function(g,k){"object"===typeof module&&module.exports?module.exports=k(require("./URI")):"function"===typeof define&&define.amd?define(["./URI"],k):g.URITemplate=k(g.URI,g)})(this,function(g,k){function h(b){if(h._cache[b])return h._cache[b];if(!(this instanceof h))return new h(b);this.expression=b;h._cache[b]=this;return this}function l(b){this.data=b;this.cache={}}var b=k&&k.URITemplate,m=Object.prototype.hasOwnProperty,A=h.prototype,u={"":{prefix:"",separator:",",named:!1,empty_name_separator:!1,
+encode:"encode"},"+":{prefix:"",separator:",",named:!1,empty_name_separator:!1,encode:"encodeReserved"},"#":{prefix:"#",separator:",",named:!1,empty_name_separator:!1,encode:"encodeReserved"},".":{prefix:".",separator:".",named:!1,empty_name_separator:!1,encode:"encode"},"/":{prefix:"/",separator:"/",named:!1,empty_name_separator:!1,encode:"encode"},";":{prefix:";",separator:";",named:!0,empty_name_separator:!1,encode:"encode"},"?":{prefix:"?",separator:"&",named:!0,empty_name_separator:!0,encode:"encode"},
+"&":{prefix:"&",separator:"&",named:!0,empty_name_separator:!0,encode:"encode"}};h._cache={};h.EXPRESSION_PATTERN=/\{([^a-zA-Z0-9%_]?)([^\}]+)(\}|$)/g;h.VARIABLE_PATTERN=/^([^*:.](?:\.?[^*:.])*)((\*)|:(\d+))?$/;h.VARIABLE_NAME_PATTERN=/[^a-zA-Z0-9%_.]/;h.LITERAL_PATTERN=/[<>{}"`^| \\]/;h.expand=function(b,g,l){var f=u[b.operator],n=f.named?"Named":"Unnamed";b=b.variables;var k=[],m,x,v;for(v=0;x=b[v];v++){m=g.get(x.name);if(0===m.type&&l&&l.strict)throw Error('Missing expansion value for variable "'+
+x.name+'"');if(m.val.length){if(1<m.type&&x.maxlength)throw Error('Invalid expression: Prefix modifier not applicable to variable "'+x.name+'"');k.push(h["expand"+n](m,f,x.explode,x.explode&&f.separator||",",x.maxlength,x.name))}else m.type&&k.push("")}return k.length?f.prefix+k.join(f.separator):""};h.expandNamed=function(b,h,k,l,m,y){var f="",n=h.encode;h=h.empty_name_separator;var z=!b[n].length,e=2===b.type?"":g[n](y),q,r,B;r=0;for(B=b.val.length;r<B;r++)m?(q=g[n](b.val[r][1].substring(0,m)),
+2===b.type&&(e=g[n](b.val[r][0].substring(0,m)))):z?(q=g[n](b.val[r][1]),2===b.type?(e=g[n](b.val[r][0]),b[n].push([e,q])):b[n].push([void 0,q])):(q=b[n][r][1],2===b.type&&(e=b[n][r][0])),f&&(f+=l),k?f+=e+(h||q?"=":"")+q:(r||(f+=g[n](y)+(h||q?"=":"")),2===b.type&&(f+=e+","),f+=q);return f};h.expandUnnamed=function(b,h,k,l,m){var f="",n=h.encode;h=h.empty_name_separator;var z=!b[n].length,B,e,q,r;q=0;for(r=b.val.length;q<r;q++)m?e=g[n](b.val[q][1].substring(0,m)):z?(e=g[n](b.val[q][1]),b[n].push([2===
+b.type?g[n](b.val[q][0]):void 0,e])):e=b[n][q][1],f&&(f+=l),2===b.type&&(B=m?g[n](b.val[q][0].substring(0,m)):b[n][q][0],f+=B,f=k?f+(h||e?"=":""):f+","),f+=e;return f};h.noConflict=function(){k.URITemplate===h&&(k.URITemplate=b);return h};A.expand=function(b,g){var f="";this.parts&&this.parts.length||this.parse();b instanceof l||(b=new l(b));for(var n=0,k=this.parts.length;n<k;n++)f+="string"===typeof this.parts[n]?this.parts[n]:h.expand(this.parts[n],b,g);return f};A.parse=function(){var b=this.expression,
+g=h.EXPRESSION_PATTERN,k=h.VARIABLE_PATTERN,l=h.VARIABLE_NAME_PATTERN,m=h.LITERAL_PATTERN,y=[],A=0,x,v,e,q=function(b){if(b.match(m))throw Error('Invalid Literal "'+b+'"');return b};for(g.lastIndex=0;;){v=g.exec(b);if(null===v){y.push(q(b.substring(A)));break}else y.push(q(b.substring(A,v.index))),A=v.index+v[0].length;if(!u[v[1]])throw Error('Unknown Operator "'+v[1]+'" in "'+v[0]+'"');if(!v[3])throw Error('Unclosed Expression "'+v[0]+'"');x=v[2].split(",");for(var r=0,C=x.length;r<C;r++){e=x[r].match(k);
+if(null===e)throw Error('Invalid Variable "'+x[r]+'" in "'+v[0]+'"');if(e[1].match(l))throw Error('Invalid Variable Name "'+e[1]+'" in "'+v[0]+'"');x[r]={name:e[1],explode:!!e[3],maxlength:e[4]&&parseInt(e[4],10)}}if(!x.length)throw Error('Expression Missing Variable(s) "'+v[0]+'"');y.push({expression:v[0],operator:v[1],variables:x})}y.length||y.push(q(b));this.parts=y;return this};l.prototype.get=function(b){var f=this.data,g={type:0,val:[],encode:[],encodeReserved:[]},h;if(void 0!==this.cache[b])return this.cache[b];
+this.cache[b]=g;f="[object Function]"===String(Object.prototype.toString.call(f))?f(b):"[object Function]"===String(Object.prototype.toString.call(f[b]))?f[b](b):f[b];if(void 0!==f&&null!==f)if("[object Array]"===String(Object.prototype.toString.call(f))){h=0;for(b=f.length;h<b;h++)void 0!==f[h]&&null!==f[h]&&g.val.push([void 0,String(f[h])]);g.val.length&&(g.type=3)}else if("[object Object]"===String(Object.prototype.toString.call(f))){for(h in f)m.call(f,h)&&void 0!==f[h]&&null!==f[h]&&g.val.push([h,
+String(f[h])]);g.val.length&&(g.type=2)}else g.type=1,g.val.push([void 0,String(f)]);return g};g.expand=function(b,k){var f=(new h(b)).expand(k);return new g(f)};return h});
diff --git a/js/lessonfilter.js b/js/lessonfilter.js
index d2e1cfbe26..31dceba1f6 100644
--- a/js/lessonfilter.js
+++ b/js/lessonfilter.js
@@ -1,7 +1,65 @@
 ---
 ---
 
-function wireButtons(featureList) {
+
+function resetSort() {
+  $('#current-sort').text(" {{site.data.snippets.date[page.lang]}} ");
+  $('#current-sort').removeClass().addClass("sort-desc");
+  $("#sort-by-date").removeClass().addClass("sort desc my-asc");
+  $("#sort-by-difficulty").removeClass().addClass("sort my-desc");
+}
+
+
+function applySortFromURI(uri,featureList) {
+
+  console.log("applying sort from URI");
+
+  var params = uri.search(true);
+  var sortOrder = params.sortOrder;
+  var sortType = params.sortType;
+  var nonSortOrder = (sortOrder == "desc" ? "asc" : "desc");
+
+  if (sortType) {
+    console.log("SortType: " + sortType);
+    console.log("sortOrder: " + sortOrder);
+    console.log("nonSortOrder: " + nonSortOrder);
+
+    // Update arrow of selected sort button
+    $("#sort-by-" + sortType).removeClass().addClass("sort " + sortOrder + " my-" + nonSortOrder);
+
+    // Update arrow of filter header
+    $('#current-sort').removeClass().addClass("sort-" + sortOrder);
+
+    // Update filter header and restore defaults to other button
+    if (sortType == "date") {
+      $('#current-sort').text(" {{site.data.snippets.date[page.lang]}} ");
+      $('#sort-by-difficulty').removeClass().addClass("sort my-asc");
+    }
+    else {
+      $('#current-sort').text(" {{site.data.snippets.difficulty[page.lang]}} ");
+      $('#sort-by-date').removeClass().addClass("sort my-desc");
+    }
+  }
+  else {
+    // If no sort params, perform default sort
+    console.log("default sorting");
+    sortType = "date";
+    sortOrder = "desc";
+
+    // Set button classes to defaults
+    resetSort();
+  }
+
+  // Performm new sort
+  featureList.sort(sortType, { order: sortOrder });
+}
+
+
+function wireButtons() {
+
+  // set URI object to current Window location
+  var uri = new URI(location);
+  console.log(uri.toString());
 
   var options = {
     valueNames: [ 'date', 'title', 'difficulty', 'activity', 'topics' ]
@@ -9,55 +67,90 @@ function wireButtons(featureList) {
 
   var featureList = new List('lesson-list', options);
 
-  // when a filter button is clicked, update the results header
+  // We need a stateObj for adjusting the URIs on button clicks, but the value is moot for now; could be useful for future functionality.
+  var stateObj = { foo: "bar" };
+
+  // When a filter button is clicked
   $('.filter').children().click(function() {
+      // Set clicked button as current
       $('.filter').children().removeClass("current");
       $(this).addClass("current");
+
+      // Update the results header
       $('#results-value').text($(this).text() + " ");
       $('#results-value').css('textTransform', 'uppercase');
+
+      applySortFromURI(uri,featureList);
   });
 
-  // when the reset button is clicked, undo filtering, blank out the results header, and sort alphabetically.
+
+  // When the reset button is clicked
   $('#filter-none').click(function() {
+      // Remove highlighting from filter buttons
       $('.filter').children().removeClass("current");
+
+      // Reset filter results header
       $('#results-value').text('All lessons');
-      $(this).addClass("current");
-      $('#current-sort').text("");
-      $('#current-sort').removeClass();
+
+      // Reset uri to remove query params
+      uri.search("");
+      history.pushState(stateObj, "", uri.toString());
+
+      // Reset filtering and perform default sort
       featureList.filter();
-      featureList.sort('title', { order: "asc" });
+      featureList.sort('date', { order: "desc" });
+
+      // Reset sort buttons to defaults
+      resetSort();
   });
 
-  // when a sort button is clicked, update the results header to show current sorting status
-  $('.sort').click(function() {
-      $('.sort').removeClass("current");
-      $(this).addClass("current");
-      $('#current-sort').removeClass();
 
-      // update filter results header to show current sorting (date or difficulty)
-      if ($(this).attr("data-sort") == "date") {
-        $('#current-sort').text(" {{site.data.snippets.date[page.lang]}} ");
-      }
-      else {
-        $('#current-sort').text(" {{site.data.snippets.difficulty[page.lang]}} ");
-      }
+  // When a sort button is clicked, update the results header to show current sorting status
+  $('.sort').click(function() {
 
-      // if the filter button has class of 'asc', that's what the next click will do. Therefore, the current sorting must be desc
-      if ( $(this).hasClass("asc") ) {
-        $('#current-sort').addClass("sort-desc")
-      }
-      else {
-        $('#current-sort').addClass("sort-asc");
-      }
+    // Get sort type from button (date or difficulty)
+    var sortType = $(this).attr("data-sort");
+
+    // Get sort order info from button
+    var curSortOrder = $(this).hasClass("my-asc") ? "desc" : "asc";
+    var newSortOrder = (curSortOrder == "asc" ? "desc" : "asc");
+
+    console.log("curSort:" + curSortOrder);
+    console.log("newSort:" + newSortOrder);
+
+    // update class for clicked button
+    $(this).removeClass("my-" + newSortOrder).addClass("my-" + curSortOrder);
+
+    // Update filter results header to show current sorting (date or difficulty)
+    // Reset the other (non-pressed) button to its default sort arrow.
+    if (sortType == "date") {
+      $('#current-sort').text(" {{site.data.snippets.date[page.lang]}} ");
+      $('#sort-by-difficulty').removeClass().addClass("sort my-asc");
+    }
+    else {
+      $('#current-sort').text(" {{site.data.snippets.difficulty[page.lang]}} ");
+      $('#sort-by-date').removeClass().addClass("sort my-desc");
+    }
+
+    // Set CSS class for results header (the arrow)
+    $('#current-sort').removeClass().addClass("sort-"+newSortOrder);
+
+    // Manually sort to override default behavior of list.js, which does not support multiple sort buttons very well.
+    // The problem is that when changing sort type, list.js automatically sorts asc on the first sort. This is not
+    // necessarily what we want to do.
+    featureList.sort(sortType, { order: newSortOrder });
+
+    // update url parameters
+    uri.setSearch("sortType", sortType);
+    uri.setSearch("sortOrder", newSortOrder);
+    history.pushState(stateObj, "", uri.toString());
+    console.log(uri.toString());
   });
 
-  /*
-  Wire up each of the activity filter buttons.
-  */
+  // Wire up each of the activity filter buttons.
   $('.filter.activities').children().click(function() {
 
     var type = $(this).attr("id").substr(7);
-    //console.log(type);
 
     featureList.filter(function(item) {
       if (item.values().activity == type) {
@@ -66,16 +159,21 @@ function wireButtons(featureList) {
         return false;
       }
     });
+
+    // reset url parameter
+    uri.removeSearch("topic");
+    uri.setSearch("activity", type); // returns the URI instance for chaining
+    history.pushState(stateObj, "", uri.toString());
+    console.log(uri.toString());
+
     return false;
   });
 
-  /*
-  Wire up each of the topic filter buttons.
-  */
+
+  // Wire up each of the topic filter buttons.
   $('.filter.topics').children().click(function() {
 
     var type = $(this).attr("id").substr(7);
-    //console.log(type);
 
     featureList.filter(function(item) {
       if (item.values().topics.includes(type)) {
@@ -84,13 +182,32 @@ function wireButtons(featureList) {
         return false;
       }
     });
-    return false;
-  });
 
+    // Reset url parameters
+    uri.removeSearch("activity");
+    uri.setSearch("topic", type); // returns the URI instance for chaining
+    history.pushState(stateObj, "", uri.toString());
+    console.log(uri.toString());
 
-  // perform initial, default sort
-  featureList.sort('date', { order: "desc" });
-  //$('#sort-by-date').trigger("click");
-  // restore arrow to next option
+    return false;
+  });
 
+  /***************************************
+    All below code runs on each page load
+  ****************************************/
+
+  // Look for URI query params
+  var params = uri.search(true);
+  var filter = params.activity ? params.activity : params.topic;
+
+  // If a filter is present in the URI, simulate a click to run filter
+  // Clicking a filter button checks for sort params in URI, so don't do it twice.
+  if (filter) {
+    console.log("FILTER:" + filter);
+    $("#filter-" + filter).click();
+  }
+  else {
+    // Apply sorting criteria from the URI if no filter
+    applySortFromURI(uri,featureList);
+  }
 };