From 49894abaf4c7f8e1f91300dfe6e9d71cef132e60 Mon Sep 17 00:00:00 2001
From: William Jackson <matabele.bill@gmail.com>
Date: Sun, 18 Oct 2015 18:37:08 +0200
Subject: [PATCH] Create x-listops.js

These filters are designed to be used with the action-listops widget.
---
 core/modules/filters/x-listops.js | 170 ++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 core/modules/filters/x-listops.js

diff --git a/core/modules/filters/x-listops.js b/core/modules/filters/x-listops.js
new file mode 100644
index 000000000..9b61a8aef
--- /dev/null
+++ b/core/modules/filters/x-listops.js
@@ -0,0 +1,170 @@
+/*\
+title: $:/core/modules/filters/x-listops.js
+type: application/javascript
+module-type: filteroperator
+
+Extended filter operators to manipulate the current list.
+
+\*/
+(function () {
+
+  /*jslint node: true, browser: true */
+  /*global $tw: false */
+  "use strict";
+
+  var prepare_results = function (source) {
+    var results = [];
+    source(function (tiddler, title) {
+      results.push(title);
+    });
+    return results;
+  };
+
+  /*
+  Moves a number of items from the tail of the current list before the item named in the operand
+  */
+  exports.putbefore = function (source, operator, options) {
+    var results = prepare_results(source),
+        index = results.indexOf(operator.operand),
+        count = parseInt(operator.suffix) || 1;
+    if (index === -1) {
+      return results.slice(0, -1);
+    }
+    return results.slice(0, index).concat(results.slice(-count)).concat(results.slice(index, -count));
+  };
+
+  /*
+  Moves a number of items from the tail of the current list after the item named in the operand
+  */
+  exports.putafter = function (source, operator, options) {
+    var results = prepare_results(source),
+        index = results.indexOf(operator.operand),
+        count = parseInt(operator.suffix) || 1;
+    if (index === -1) {
+      return results.slice(0, -1);
+    }
+    return results.slice(0, index + 1).concat(results.slice(-count)).concat(results.slice(index + 1, -count));
+  };
+
+  /*
+  Replaces the item named in the operand with a number of items from the tail of the current list
+  */
+  exports.replace = function (source, operator, options) {
+    var results = prepare_results(source),
+        index = results.indexOf(operator.operand),
+        count = parseInt(operator.suffix) || 1;
+    if (index === -1) {
+      return results.slice(0, -count);
+    }
+    return results.slice(0, index).concat(results.slice(-count)).concat(results.slice(index + 1, -count));
+  };
+
+  /*
+  Moves a number of items from the tail of the current list to the head of the list
+  */
+  exports.putfirst = function (source, operator, options) {
+    var results = prepare_results(source),
+        count = parseInt(operator.suffix) || 1;
+    return results.slice(-count).concat(results.slice(0, -count));
+  };
+
+  /*
+  Moves a number of items from the head of the current list to the tail of the list
+  */
+  exports.putlast = function (source, operator, options) {
+    var results = prepare_results(source),
+        count = parseInt(operator.suffix) || 1;
+    return results.slice(count).concat(results.slice(0, count));
+  };
+
+  /*
+  Returns the items from the current list that are after the item named in the operand
+  */
+  exports.allafter = function (source, operator, options) {
+    var results = prepare_results(source),
+        index = results.indexOf(operator.operand);
+    if (index === -1 || index > (results.length - 2)) {
+      return [];
+    }
+    if (operator.suffix) {
+      return results.slice(index - 1);
+    }
+    return results.slice(index);
+  };
+
+  /*
+  Returns the items from the current list that are before the item named in the operand
+  */
+  exports.allbefore = function (source, operator, options) {
+    var results = prepare_results(source),
+        index = results.indexOf(operator.operand);
+    if (index <= 0) {
+      return [];
+    } 
+    if (operator.suffix) {
+      return results.slice(0, index + 1);
+    }
+    return results.slice(0, index);
+  };
+
+  /*
+  Appends the items listed in the operand array to the tail of the current list 
+  */
+  exports.append = function (source, operator, options) {
+    var results = prepare_results(source),
+        append = $tw.utils.parseStringArray(operator.operand);
+    if (append === "") {
+      return results;
+    }
+    return results.concat(append);
+  };
+
+  /*
+  Prepends the items listed in the operand array to the head of the current list 
+  */
+  exports.prepend = function (source, operator, options) {
+      var results = prepare_results(source),
+          prepend = $tw.utils.parseStringArray(operator.operand);
+    if (prepend === "") {
+      return results;
+    }
+    return prepend.concat(results);
+  };
+
+  /*
+  Returns all items from the current list except the items listed in the operand array
+  */
+  exports.remove = function (source, operator, options) {
+    var results = prepare_results(source),
+        count = parseInt(operator.suffix) || 1,
+        p, len, index, array = $tw.utils.parseStringArray(operator.operand);
+    len = array.length - 1;
+    for (p = 0; p < count; ++p) {
+      if (operator.prefix) {
+        index = results.indexOf(array[len - p]);
+      } else {
+        index = results.indexOf(array[p]);
+      }
+      if (index !== -1) {
+        results.splice(index, 1);
+      }
+    }
+    return results;
+  };
+
+  /*
+  Returns all items from the current list sorted in the order of the items in the operand array
+  */
+  exports.sortby = function (source, operator, options) {
+    var results = prepare_results(source);
+    if (!results || results.length < 2) {
+      return results;
+    }
+    var lookup = $tw.utils.parseStringArray(operator.operand);
+    results.sort(function (a, b) {
+      return lookup.indexOf(a) - lookup.indexOf(b);
+    });
+    return results;
+  };
+
+})();