import logging
from logging.config import dictConfig
import os
from logging.handlers import RotatingFileHandler, HTTPHandler


def setup_logging(app):
    """Configure logging: console, optional file and external HTTP handler.

    Controlled by env vars:
    - LOG_FILE: path to write rotating logs
    - LOG_MAX_BYTES: max bytes per file (default 10MB)
    - LOG_BACKUP_COUNT: number of backups (default 5)
    - EXTERNAL_LOG_URL: if set, an HTTPHandler will POST logs to this URL
    """
    level = logging.DEBUG if app.config.get("DEBUG") else logging.INFO

    handlers = {
        "console": {
            "class": "logging.StreamHandler",
            "formatter": "default",
            "level": level,
        }
    }

    root_handlers = ["console"]

    log_file = os.getenv("LOG_FILE")
    if log_file:
        # ensure parent dirs exist
        os.makedirs(os.path.dirname(log_file), exist_ok=True)
        handlers["file"] = {
            "class": "logging.handlers.RotatingFileHandler",
            "formatter": "default",
            "level": level,
            "filename": log_file,
            "maxBytes": int(os.getenv("LOG_MAX_BYTES", 10 * 1024 * 1024)),
            "backupCount": int(os.getenv("LOG_BACKUP_COUNT", 5)),
        }
        root_handlers.append("file")

    external = os.getenv("EXTERNAL_LOG_URL")
    if external:
        handlers["external"] = {
            "class": "logging.handlers.HTTPHandler",
            "formatter": "default",
            "level": level,
            "host": external,
            "url": "/",
            "method": "POST",
        }
        root_handlers.append("external")

    config = {
        "version": 1,
        "disable_existing_loggers": False,
        "formatters": {
            "default": {
                "format": "%(asctime)s %(levelname)s %(name)s: %(message)s",
            }
        },
        "handlers": handlers,
        "root": {
            "handlers": root_handlers,
            "level": level,
        },
    }

    dictConfig(config)