"""
Database configuration for thrillwiki project.

This module configures database connections, connection pooling, and
GeoDjango settings using python-decouple for consistent environment
variable management.

Why python-decouple?
- Already used in base.py for consistency
- Simpler API than django-environ
- Sufficient for our configuration needs
- Better separation of config from code

Database URL Format:
- PostgreSQL: postgres://user:password@host:port/dbname
- PostGIS: postgis://user:password@host:port/dbname
- SQLite: sqlite:///path/to/db.sqlite3
- SpatiaLite: spatialite:///path/to/db.sqlite3
"""

from decouple import config
import dj_database_url

# =============================================================================
# Database Configuration
# =============================================================================
# Parse DATABASE_URL environment variable into Django database settings

DATABASE_URL = config(
    "DATABASE_URL",
    default="postgis://thrillwiki_user:thrillwiki@localhost:5432/thrillwiki_test_db"
)

# Parse the database URL
db_config = dj_database_url.parse(DATABASE_URL)

# Force PostGIS backend for spatial data support
# This ensures GeoDjango features work correctly
if "postgis" in DATABASE_URL or "postgresql" in DATABASE_URL:
    db_config["ENGINE"] = "django.contrib.gis.db.backends.postgis"

DATABASES = {
    "default": db_config,
}

# =============================================================================
# Database Connection Pooling Configuration
# =============================================================================
# Connection pooling improves performance by reusing database connections

# CONN_MAX_AGE: How long to keep connections open (in seconds)
# 0 = Close after each request (default Django behavior)
# None = Unlimited reuse (not recommended)
# 600 = 10 minutes (good balance for most applications)
CONN_MAX_AGE = config("DATABASE_CONN_MAX_AGE", default=600, cast=int)

# Apply CONN_MAX_AGE to the default database
DATABASES["default"]["CONN_MAX_AGE"] = CONN_MAX_AGE

# =============================================================================
# Database Connection Options (PostgreSQL-specific)
# =============================================================================
# These settings are passed to psycopg2 when creating new connections

DATABASE_OPTIONS = {
    # Connection timeout in seconds
    "connect_timeout": config("DATABASE_CONNECT_TIMEOUT", default=10, cast=int),
    # Query timeout in milliseconds (30 seconds default)
    # This prevents runaway queries from blocking the database
    "options": f"-c statement_timeout={config('DATABASE_STATEMENT_TIMEOUT', default=30000, cast=int)}",
}

# Apply options to PostgreSQL databases
if "postgis" in DATABASE_URL or "postgresql" in DATABASE_URL:
    DATABASES["default"].setdefault("OPTIONS", {})
    DATABASES["default"]["OPTIONS"].update(DATABASE_OPTIONS)

# =============================================================================
# GeoDjango Settings
# =============================================================================
# Library paths for GDAL and GEOS (required for GeoDjango)
# These vary by operating system and installation method

# macOS with Homebrew (default)
# Linux: /usr/lib/x86_64-linux-gnu/libgdal.so
# Docker: Usually handled by the image
GDAL_LIBRARY_PATH = config(
    "GDAL_LIBRARY_PATH",
    default="/opt/homebrew/lib/libgdal.dylib"
)
GEOS_LIBRARY_PATH = config(
    "GEOS_LIBRARY_PATH",
    default="/opt/homebrew/lib/libgeos_c.dylib"
)

# =============================================================================
# Read Replica Configuration (Optional)
# =============================================================================
# Configure read replicas for read-heavy workloads
# Set DATABASE_READ_REPLICA_URL to enable

DATABASE_READ_REPLICA_URL = config("DATABASE_READ_REPLICA_URL", default="")

if DATABASE_READ_REPLICA_URL:
    replica_config = dj_database_url.parse(DATABASE_READ_REPLICA_URL)
    if "postgis" in DATABASE_READ_REPLICA_URL or "postgresql" in DATABASE_READ_REPLICA_URL:
        replica_config["ENGINE"] = "django.contrib.gis.db.backends.postgis"
    replica_config["CONN_MAX_AGE"] = CONN_MAX_AGE
    DATABASES["replica"] = replica_config