js: Extract pagination model.

* js/utils.js (guix.clamp): New function.
* js/controller/packages.js (guix.packages.controller): Remove 'pages',
  'currentPageIndex', and 'pageSize' properties.  Add 'pager' prop.
  Delete 'paginate', 'currentPage', 'isFirstPage', 'isLastPage', and
  'isCurrentPage' methods.
* js/model/packages.js (guix.packages.Pager): New function.
* js/view/packages.js (guix.packages.view): Use new Pager API.

4 files changed, 82 insertions, 49 deletions

diff --git a/js/controller/packages.js b/js/controller/packages.js
index db94d72..89f01e9 100644
--- a/js/controller/packages.js
+++ b/js/controller/packages.js
@@ -15,14 +15,19 @@
 // License along with this program.  If not, see
 // <http://www.gnu.org/licenses/>.
 
-(function(packages) {
+(function() {
+  var packages = guix.packages;
+
   packages.controller = (function() {
+    var PAGE_SIZE = 20;
+
+    function Pager(items) {
+      return new packages.Pager(items, PAGE_SIZE);
+    }
+
     function controller() {
       var self = this;
 
-      this.pages = m.prop([]);
-      this.currentPageIndex = 0;
-      this.pageSize = 20;
       this.searchTerm = m.prop("");
       this.columns = [
         { header: "Name", sortField: "name" },
@@ -43,40 +48,20 @@
         }
       ];
       this.sorter = m.prop(new packages.Sorter("name"));
+      this.pager = m.prop(Pager([]));
       this.phase = m.prop(packages.PHASE_NONE);
       this.selectedPackage = m.prop(null);
 
       this.packages = packages.Packages()
         .then(function(packages) {
           // All packages are visible initially
-          self.pages(self.paginate(packages, self.pageSize));
+          self.pager(Pager(packages));
         })
         .then(m.redraw);
     };
 
-
-    controller.prototype.paginate = function(array, pageSize) {
-      return guix.chunk(this.sorter().sort(array), pageSize);
-    };
-
-    controller.prototype.currentPage = function() {
-      return this.pages()[this.currentPageIndex] || [];
-    };
-
-    controller.prototype.isFirstPage = function() {
-      return this.currentPageIndex === 0;
-    };
-
-    controller.prototype.isLastPage = function() {
-      return this.currentPageIndex === this.pages().length - 1;
-    };
-
-    controller.prototype.isCurrentPage = function(i) {
-      return this.currentPageIndex === i;
-    };
-
     controller.prototype.packageCount = function() {
-      return this.pages().reduce(function(memo, page) {
+      return this.pager().pages.reduce(function(memo, page) {
         return memo + page.length;
       }, 0);
     };
@@ -84,12 +69,10 @@
     controller.prototype.doSearch = function() {
       var regexp = new RegExp(this.searchTerm(), "i");
 
-      this.pages(this.paginate(this.packages().filter(function(package) {
+      this.pager(Pager(this.packages().filter(function(package) {
         return regexp.test(package.name) ||
           regexp.test(package.synopsis);
-      }), this.pageSize));
-      // Reset pagination
-      this.currentPageIndex = 0;
+      })));
     };
 
     controller.prototype.sortBy = function(field) {
@@ -122,4 +105,4 @@
 
     return controller;
   })();
-})(guix.packages);
+})();
diff --git a/js/model/packages.js b/js/model/packages.js
index 652d11a..1c61d25 100644
--- a/js/model/packages.js
+++ b/js/model/packages.js
@@ -15,9 +15,11 @@
 // License along with this program.  If not, see
 // <http://www.gnu.org/licenses/>.
 
-guix.packages = {};
 
-(function(packages) {
+
+(function() {
+  var packages = guix.packages = {};
+
   packages.Packages = function() {
     return m.request({
       method: "GET",
@@ -45,9 +47,55 @@ guix.packages = {};
     return Sorter;
   })();
 
+  packages.Pager = (function() {
+    function Pager(items, pageSize) {
+      this.pageSize= pageSize;
+      this.pageIndex = 0;
+      this.pages = guix.chunk(items, pageSize);
+    }
+
+    Pager.prototype.currentPage = function() {
+      return this.pages[this.pageIndex];
+    };
+
+    Pager.prototype.pageCount = function() {
+      return this.pages.length;
+    };
+
+    Pager.prototype.isEmpty = function() {
+      return this.pageCount() === 0;
+    };
+
+    Pager.prototype.isFirstPage = function() {
+      return this.pageIndex === 0;
+    };
+
+    Pager.prototype.isLastPage = function() {
+      return this.pageIndex === this.pages.length - 1;
+    };
+
+    Pager.prototype.isCurrentPage = function(i) {
+      return this.pageIndex === i;
+    };
+
+    Pager.prototype.nextPage = function() {
+      this.pageIndex = Math.min(this.pageCount() - 1, this.pageIndex + 1);
+    };
+
+    Pager.prototype.previousPage = function() {
+      this.pageIndex = Math.max(0, this.pageIndex - 1);
+    };
+
+    Pager.prototype.gotoPage = function(page) {
+      this.pageIndex = guix.clamp(page, 0, this.pageCount() -1);
+    };
+
+    return Pager;
+  })();
+
   packages.PHASE_NONE = 0;
   packages.PHASE_PROMPT = 1;
   packages.PHASE_DERIVATION = 2;
   packages.PHASE_SUCCESS = 3;
   packages.PHASE_ERROR = 4;
-})(guix.packages);
+})();
diff --git a/js/utils.js b/js/utils.js
index b3e4768..c44ee23 100644
--- a/js/utils.js
+++ b/js/utils.js
@@ -17,6 +17,10 @@
 
 var guix = {};
 
+guix.clamp = function(n, min, max) {
+  return Math.max(Math.min(n, max), min);
+};
+
 guix.chunk = function(array, size) {
   return array.reduce(function(memo, value, i) {
     var currentSlice = _(memo).last();
diff --git a/js/view/packages.js b/js/view/packages.js
index e202471..7c55486 100644
--- a/js/view/packages.js
+++ b/js/view/packages.js
@@ -15,7 +15,8 @@
 // License along with this program.  If not, see
 // <http://www.gnu.org/licenses/>.
 
-(function(packages) {
+(function() {
+  var packages = guix.packages;
   var spinner = m(".spinner-container", m(".spinner"));
 
   packages.view = function(ctrl) {
@@ -75,7 +76,7 @@
           ])
         ]),
         m("tbody", [
-          ctrl.currentPage().map(function(package) {
+          ctrl.pager().currentPage().map(function(package) {
             return m("tr", [
               m("td", renderName(package)),
               m("td", package.version),
@@ -100,30 +101,27 @@
       return m("div", m("ul.pagination", [
         // Back page
         renderPage("«", {
-          class: ctrl.isFirstPage() ? "disabled" : "",
+          class: ctrl.pager().isFirstPage() ? "disabled" : "",
           onclick: function() {
-            ctrl.currentPageIndex--;
-
+            ctrl.pager().previousPage();
             return false;
           }
         })
-      ].concat(ctrl.pages().map(function(page, i) {
+      ].concat(ctrl.pager().pages.map(function(page, i) {
         // Jump to page
         return renderPage(i + 1, {
-          class: ctrl.isCurrentPage(i) ? "active" : "",
+          class: ctrl.pager().isCurrentPage(i) ? "active" : "",
           onclick: function() {
-            ctrl.currentPageIndex = i;
-
+            ctrl.pager().gotoPage(i);
             return false;
           }
         });
       })).concat([
         // Forward page
         renderPage("»", {
-          class: ctrl.isLastPage() ? "disabled" : "",
+          class: ctrl.pager().isLastPage() ? "disabled" : "",
           onclick: function() {
-            ctrl.currentPageIndex++;
-
+            ctrl.pager().nextPage();
             return false;
           }
         })
@@ -239,7 +237,7 @@
       return null;
     }
 
-    return guix.withLayout(_.isEmpty(ctrl.pages()) ? spinner : [
+    return guix.withLayout(ctrl.pager().isEmpty() ? spinner : [
       m("h2", [
         "Packages",
         m("span.badge", ctrl.packageCount())
@@ -250,4 +248,4 @@
       renderPagination()
     ]);
   };
-})(guix.packages);
+})();