import os
from urllib.parse import quote_plus
from sqlalchemy import create_engine, event
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from dotenv import load_dotenv
import datetime
from sqlalchemy import inspect as sa_inspect
from .utils import audit_log_path, get_current_user_ctx

load_dotenv()

# Prefer per-component DB config when provided; fallback to DATABASE_URL; finally to sqlite for dev
db_driver = os.getenv("DB_DRIVER")
db_user = os.getenv("DB_USER")
db_password = os.getenv("DB_PASSWORD")
db_host = os.getenv("DB_HOST")
db_port = os.getenv("DB_PORT")
db_name = os.getenv("DB_NAME")

database_url = None
if db_driver and db_user and db_host and db_port and db_name is not None:
    # URL-encode username and password. If password is empty or None, omit the ':' portion
    user_enc = quote_plus(db_user)
    if db_password:
        pwd_enc = quote_plus(db_password)
        auth = f"{user_enc}:{pwd_enc}"
    else:
        auth = f"{user_enc}"
    database_url = f"{db_driver}://{auth}@{db_host}:{db_port}/{db_name}"

if not database_url:
    database_url = os.getenv("DATABASE_URL")

if not database_url:
    # final fallback for local dev
    database_url = "sqlite:///./test.db"

# Engine pool configuration to avoid QueuePool timeouts under concurrency
default_pool_size = int(os.getenv("DB_POOL_SIZE", "20"))
default_max_overflow = int(os.getenv("DB_POOL_MAX_OVERFLOW", "40"))
default_pool_timeout = int(os.getenv("DB_POOL_TIMEOUT", "60"))
default_pool_recycle = int(os.getenv("DB_POOL_RECYCLE", "1800"))  # seconds

if database_url.startswith("sqlite"):
    engine = create_engine(
        database_url,
        pool_pre_ping=True,
        connect_args={"check_same_thread": False},
    )
else:
    engine = create_engine(
        database_url,
        pool_pre_ping=True,
        pool_size=default_pool_size,
        max_overflow=default_max_overflow,
        pool_timeout=default_pool_timeout,
        pool_recycle=default_pool_recycle,
    )
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

def _write_audit(line: str) -> None:
    try:
        with open(audit_log_path(), "a", encoding="utf-8") as f:
            f.write(line)
    except Exception:
        pass

@event.listens_for(SessionLocal, "after_flush")
def _audit_after_flush(session, context):
    user = get_current_user_ctx() or {}
    uid = str((user.get("sub") or user.get("id") or "-"))
    email = user.get("email") or "-"
    now = datetime.datetime.utcnow().isoformat()
    for obj in list(session.new):
        ins = sa_inspect(obj)
        mapper = ins.mapper
        table = mapper.local_table.name if getattr(mapper, "local_table", None) is not None else getattr(obj, "__tablename__", obj.__class__.__name__)
        pk = ins.identity
        line = f"{now} | {uid} | {email} | INSERT {table} | pk={pk}\n"
        _write_audit(line)
    for obj in list(session.dirty):
        if not session.is_modified(obj, include_collections=False):
            continue
        ins = sa_inspect(obj)
        mapper = ins.mapper
        table = mapper.local_table.name if getattr(mapper, "local_table", None) is not None else getattr(obj, "__tablename__", obj.__class__.__name__)
        changes = []
        for attr in ins.attrs:
            hist = attr.history
            if hist.has_changes():
                old = hist.deleted[0] if hist.deleted else None
                new = hist.added[0] if hist.added else getattr(obj, attr.key)
                changes.append(f"{attr.key}={old}->{new}")
        pk = ins.identity
        chs = ", ".join(changes) if changes else "-"
        line = f"{now} | {uid} | {email} | UPDATE {table} | pk={pk} | {chs}\n"
        _write_audit(line)
    for obj in list(session.deleted):
        ins = sa_inspect(obj)
        mapper = ins.mapper
        table = mapper.local_table.name if getattr(mapper, "local_table", None) is not None else getattr(obj, "__tablename__", obj.__class__.__name__)
        pk = ins.identity
        line = f"{now} | {uid} | {email} | DELETE {table} | pk={pk}\n"
        _write_audit(line)