Add history entry and fix bug when completing task (#54)

The reward wasn't properly being distributed to all users

Reviewed-on: #54

backend/db.go

@@ -341,10 +341,22 @@ func (db *Db) CompleteTask(taskId int) error {
 			return err
 		}
 
+		// Add the history entry
+		err = tx.Query("insert into history (user_id, timestamp, amount) values (?, ?, ?)").
+			Bind(userId, time.Now().Unix(), reward).
+			Exec()
+		if err != nil {
+			return err
+		}
+
+		// Calculate the sums of all weights
 		var sumOfWeights float64
 		err = tx.Query("select sum(weight) from allowances where user_id = ? and weight > 0").Bind(userId).ScanSingle(&sumOfWeights)
 		sumOfWeights += userWeight
 
+		remainingReward := reward
+
+		// Distribute the reward to the allowances
 		for allowanceRow := range tx.Query("select id, weight from allowances where user_id = ? and weight > 0").Bind(userId).Range(&err) {
 			var allowanceId int
 			var allowanceWeight float64
@@ -354,19 +366,19 @@ func (db *Db) CompleteTask(taskId int) error {
 			}
 
 			// Calculate the amount to add to the allowance
-			amount := int((allowanceWeight / sumOfWeights) * float64(reward))
+			amount := int((allowanceWeight / sumOfWeights) * float64(remainingReward))
 			sumOfWeights -= allowanceWeight
 			err = tx.Query("update allowances set balance = balance + ? where id = ? and user_id = ?").
 				Bind(amount, allowanceId, userId).Exec()
 			if err != nil {
 				return err
 			}
-			reward -= amount
+			remainingReward -= amount
 		}
 
 		// Add the remaining reward to the user
 		err = tx.Query("update users set balance = balance + ? where id = ?").
-			Bind(reward, userId).Exec()
+			Bind(remainingReward, userId).Exec()
 		if err != nil {
 			return err
 		}