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.

1 files changed, 51 insertions, 3 deletions

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);
+})();