new revenue getters

internal/database/main.go

@@ -55,7 +55,8 @@ func InitDB(db *sql.DB) {
         FOREIGN KEY (company_id)  REFERENCES companies(id),
         FOREIGN KEY (currency_id) REFERENCES currencies(id),
         FOREIGN KEY (category_id) REFERENCES category(id),
-        FOREIGN KEY (period_id)   REFERENCES periods(id)
+        FOREIGN KEY (period_id)   REFERENCES periods(id),
+        UNIQUE(company_id, category_id, period_id)
     );`
 
 	if _, err := db.Exec(schema); err != nil {
@@ -63,3 +64,37 @@ func InitDB(db *sql.DB) {
 	}
 	fmt.Println("Tables ready")
 }
+
+func MigrateAddUniqueToRevenueEntries(db *sql.DB) error {
+	steps := []string{
+		// 1. copy existing data into a temp table with the new constraint
+		`CREATE TABLE IF NOT EXISTS revenue_entries_new (
+			id          INTEGER PRIMARY KEY AUTOINCREMENT,
+			company_id  INTEGER NOT NULL,
+			currency_id INTEGER NOT NULL,
+			category_id INTEGER NOT NULL,
+			period_id   INTEGER NOT NULL,
+			value       REAL    NOT NULL,
+			FOREIGN KEY (company_id)  REFERENCES companies(id),
+			FOREIGN KEY (currency_id) REFERENCES currencies(id),
+			FOREIGN KEY (category_id) REFERENCES category(id),
+			FOREIGN KEY (period_id)   REFERENCES periods(id),
+			UNIQUE(company_id, category_id, period_id)
+		)`,
+		// 2. copy data over
+		`INSERT OR IGNORE INTO revenue_entries_new
+			SELECT id, company_id, currency_id, category_id, period_id, value
+			FROM revenue_entries`,
+		// 3. drop old table
+		`DROP TABLE revenue_entries`,
+		// 4. rename new table
+		`ALTER TABLE revenue_entries_new RENAME TO revenue_entries`,
+	}
+
+	for _, step := range steps {
+		if _, err := db.Exec(step); err != nil {
+			return fmt.Errorf("migration failed: %w", err)
+		}
+	}
+	return nil
+}