Refactor application configuration; implement dynamic database URI setup based on environment variables for improved flexibility and maintainability

config.py

@@ -0,0 +1,60 @@
+import os
+import urllib.parse
+from dotenv import load_dotenv
+
+load_dotenv()
+
+def quote(value):
+    return urllib.parse.quote_plus(value)
+
+class Config:
+    SQLALCHEMY_TRACK_MODIFICATIONS = False
+    DEBUG = False
+    TESTING = False
+
+    DB_BACKEND = os.getenv('DB_BACKEND', 'sqlite').lower()
+    DB_WINDOWS_AUTH = os.getenv('DB_WINDOWS_AUTH', 'false').strip().lower() in ['true', '1', 'yes']
+
+    DB_USER = os.getenv('DB_USER', '')
+    DB_PASSWORD = os.getenv('DB_PASSWORD', '')
+    DB_HOST = os.getenv('DB_HOST', 'localhost')
+    DB_PORT = os.getenv('DB_PORT', '')
+    DB_NAME = os.getenv('DB_NAME', 'app.db')  # default file for sqlite
+
+    SQLALCHEMY_DATABASE_URI = None  # <-- initialize properly
+
+    if DB_BACKEND == 'mssql':
+        driver = os.getenv('DB_DRIVER', 'ODBC Driver 17 for SQL Server')
+        quoted_driver = quote(driver)
+
+        if DB_WINDOWS_AUTH:
+            SQLALCHEMY_DATABASE_URI = (
+                f"mssql+pyodbc://@{DB_HOST}/{DB_NAME}?driver={quoted_driver}&Trusted_Connection=yes"
+            )
+        else:
+            SQLALCHEMY_DATABASE_URI = (
+                f"mssql+pyodbc://{quote(DB_USER)}:{quote(DB_PASSWORD)}@{DB_HOST}:{DB_PORT}/{DB_NAME}"
+                f"?driver={quoted_driver}"
+            )
+
+    elif DB_BACKEND == 'postgres':
+        SQLALCHEMY_DATABASE_URI = (
+            f"postgresql://{quote(DB_USER)}:{quote(DB_PASSWORD)}@{DB_HOST}:{DB_PORT or '5432'}/{DB_NAME}"
+        )
+
+    elif DB_BACKEND in ['mariadb', 'mysql']:
+        SQLALCHEMY_DATABASE_URI = (
+            f"mysql+pymysql://{quote(DB_USER)}:{quote(DB_PASSWORD)}@{DB_HOST}:{DB_PORT or '3306'}/{DB_NAME}"
+        )
+
+    elif DB_BACKEND == 'sqlite':
+        if DB_NAME == ':memory:':
+            SQLALCHEMY_DATABASE_URI = 'sqlite:///:memory:'
+        else:
+            SQLALCHEMY_DATABASE_URI = f"sqlite:///{DB_NAME}"
+
+    else:
+        raise ValueError(
+            f"Unsupported DB_BACKEND: {DB_BACKEND}. "
+            "Supported backends: mssql, postgres, mariadb, mysql, sqlite."
+        )