Refactors backend

1 files changed, 141 insertions, 0 deletions

diff --git a/backend/src/utils/calculate_category_balance.rs b/backend/src/utils/calculate_category_balance.rs
new file mode 100644
index 0000000..3c1c62f
--- /dev/null
+++ b/backend/src/utils/calculate_category_balance.rs
@@ -0,0 +1,141 @@
+use crate::models::{budget_update::BudgetUpdate, category::Category};
+
+use super::{calculate_budgets_accrual, find_by_id_or};
+
+pub fn calculate_category_balance(
+    category: &Category,
+    transaction_sums: &[(i32, Option<i64>)],
+    category_transfer_from_sums: &[(i32, Option<i64>)],
+    category_transfer_to_sums: &[(i32, Option<i64>)],
+    budget_updates: &[BudgetUpdate],
+) -> i64 {
+    let transaction_sum = find_by_id_or(transaction_sums, category.id, 0);
+    let category_transfer_from_sum = find_by_id_or(category_transfer_from_sums, category.id, 0);
+    let category_transfer_to_sum = find_by_id_or(category_transfer_to_sums, category.id, 0);
+    let budget_accruals_sum = calculate_budgets_accrual(category, budget_updates);
+
+    transaction_sum + budget_accruals_sum + category_transfer_to_sum - category_transfer_from_sum
+}
+
+#[cfg(test)]
+mod test {
+    use chrono::{Days, Utc};
+
+    use crate::{
+        models::{budget_update::BudgetUpdate, category::Category, date_time_utc::DateTimeUtc},
+        utils::calculate_category_balance,
+    };
+
+    #[test]
+    fn when_no_data_then_returns_zero() {
+        let category = Category {
+            id: 0,
+            name: String::new(),
+        };
+
+        let result = calculate_category_balance(&category, &[], &[], &[], &[]);
+
+        assert_eq!(result, 0_i64);
+    }
+
+    #[test]
+    fn when_data_only_for_another_category_then_returns_zero() {
+        let category = Category {
+            id: 0,
+            name: String::new(),
+        };
+        let transaction_sums = [(1, Some(100))];
+        let category_transfer_from_sums = [(1, Some(91))];
+        let category_transfer_to_sums = [(2, Some(79))];
+        let budget_updates = [BudgetUpdate {
+            id: 0,
+            category_id: 1,
+            date: DateTimeUtc::new(Utc::now().checked_sub_days(Days::new(120)).unwrap()),
+            new_budget: 77,
+            new_period: 1,
+        }];
+
+        let result = calculate_category_balance(
+            &category,
+            &transaction_sums,
+            &category_transfer_from_sums,
+            &category_transfer_to_sums,
+            &budget_updates,
+        );
+
+        assert_eq!(result, 0_i64);
+    }
+
+    #[test]
+    fn when_transaction_sum_is_none_then_returns_zero() {
+        let category = Category {
+            id: 0,
+            name: String::new(),
+        };
+        let transaction_sums = [(0, None)];
+        let category_transfer_from_sums = [];
+        let category_transfer_to_sums = [];
+        let budget_updates = [];
+
+        let result = calculate_category_balance(
+            &category,
+            &transaction_sums,
+            &category_transfer_from_sums,
+            &category_transfer_to_sums,
+            &budget_updates,
+        );
+
+        assert_eq!(result, 0_i64);
+    }
+
+    #[test]
+    fn when_category_transfers_are_none_then_returns_zero() {
+        let category = Category {
+            id: 0,
+            name: String::new(),
+        };
+        let transaction_sums = [];
+        let category_transfer_from_sums = [(0, None)];
+        let category_transfer_to_sums = [(0, None)];
+        let budget_updates = [];
+
+        let result = calculate_category_balance(
+            &category,
+            &transaction_sums,
+            &category_transfer_from_sums,
+            &category_transfer_to_sums,
+            &budget_updates,
+        );
+
+        assert_eq!(result, 0_i64);
+    }
+
+    #[test]
+    fn when_some_data_then_calculates_as_expected() {
+        let category = Category {
+            id: 0,
+            name: String::new(),
+        };
+        let transaction_sums = [(0, Some(100))];
+        let category_transfer_from_sums = [(0, Some(91))];
+        let category_transfer_to_sums = [(0, Some(79))];
+        let budget_updates = [BudgetUpdate {
+            id: 0,
+            category_id: 0,
+            date: DateTimeUtc::new(Utc::now().checked_sub_days(Days::new(120)).unwrap()),
+            new_budget: 77,
+            new_period: 1,
+        }];
+
+        let result = calculate_category_balance(
+            &category,
+            &transaction_sums,
+            &category_transfer_from_sums,
+            &category_transfer_to_sums,
+            &budget_updates,
+        );
+
+        let expected_result = 100 + (-91) + 79 + 77 * 120;
+        assert_eq!(result, expected_result);
+    }
+}