Add tasks table and API

progress will be tracked with this table instead of being in-process
like progress.js

src/taskdb.js

@@ -0,0 +1,51 @@
+'use strict';
+
+exports = module.exports = {
+    setProgress: setProgress,
+    getProgress: getProgress
+};
+
+let assert = require('assert'),
+    database = require('./database.js'),
+    DatabaseError = require('./databaseerror'),
+    _ = require('underscore');
+
+const TASKS_FIELDS = [ 'id', 'percent', 'message', 'detail', 'creationTime', 'result', 'ts' ];
+
+function setProgress(id, progress, callback) {
+    assert.strictEqual(typeof id, 'string');
+    assert.strictEqual(typeof progress, 'object');
+    assert.strictEqual(typeof callback, 'function');
+
+    let data = _.extend({ id: id }, progress);
+
+    let keys = [ ],
+        questionMarks = Array(Object.keys(data).length).fill('?').join(','),
+        fields = [ ], values = [ ];
+
+    for (var f in data) {
+        keys.push(f);
+        fields.push(`${f} = ?`);
+        values.push(data[f]); // for the INSERT fields
+    }
+
+    values = values.concat(values); // for the UPDATE fields
+
+    database.query(`INSERT INTO tasks (${keys.join(', ')}) VALUES (${questionMarks}) ON DUPLICATE KEY UPDATE ${fields}`, values, function (error) {
+        if (error) return callback(new DatabaseError(DatabaseError.INTERNAL_ERROR, error));
+
+        callback(null);
+    });
+}
+
+function getProgress(id, callback) {
+    assert.strictEqual(typeof id, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    database.query('SELECT ' + TASKS_FIELDS + ' FROM tasks WHERE id = ?', [ id ], function (error, result) {
+        if (error) return callback(new DatabaseError(DatabaseError.INTERNAL_ERROR, error));
+        if (result.length === 0) return callback(new DatabaseError(DatabaseError.NOT_FOUND));
+
+        callback(null, result[0]);
+    });
+}