1 files changed, 72 insertions, 0 deletions
diff --git a/build-es/priorityQueue.js b/build-es/priorityQueue.js
new file mode 100644
index 0000000..b22e96f
--- /dev/null
+++ b/build-es/priorityQueue.js
@@ -0,0 +1,72 @@
+'use strict';
+
+import arrayEach from 'lodash-es/_arrayEach';
+import isArray from 'lodash-es/isArray';
+import noop from 'lodash-es/noop';
+
+import setImmediate from './setImmediate';
+
+import queue from './queue';
+
+export default function(worker, concurrency) {
+    function _compareTasks(a, b) {
+        return a.priority - b.priority;
+    }
+
+    function _binarySearch(sequence, item, compare) {
+        var beg = -1,
+            end = sequence.length - 1;
+        while (beg < end) {
+            var mid = beg + ((end - beg + 1) >>> 1);
+            if (compare(item, sequence[mid]) >= 0) {
+                beg = mid;
+            } else {
+                end = mid - 1;
+            }
+        }
+        return beg;
+    }
+
+    function _insert(q, data, priority, callback) {
+        if (callback != null && typeof callback !== 'function') {
+            throw new Error('task callback must be a function');
+        }
+        q.started = true;
+        if (!isArray(data)) {
+            data = [data];
+        }
+        if (data.length === 0) {
+            // call drain immediately if there are no tasks
+            return setImmediate(function() {
+                q.drain();
+            });
+        }
+        arrayEach(data, function(task) {
+            var item = {
+                data: task,
+                priority: priority,
+                callback: typeof callback === 'function' ? callback : noop
+            };
+
+            q.tasks.splice(_binarySearch(q.tasks, item, _compareTasks) + 1, 0, item);
+
+            if (q.tasks.length === q.concurrency) {
+                q.saturated();
+            }
+            setImmediate(q.process);
+        });
+    }
+
+    // Start with a normal queue
+    var q = queue(worker, concurrency);
+
+    // Override push to accept second parameter representing priority
+    q.push = function(data, priority, callback) {
+        _insert(q, data, priority, callback);
+    };
+
+    // Remove unshift function
+    delete q.unshift;
+
+    return q;
+}