import datetime as dt
import json
import logging

LOG_RECORD_BUILTIN_ATTRS = {
    "args",
    "asctime",
    "created",
    "exc_info",
    "exc_text",
    "filename",
    "funcName",
    "levelname",
    "levelno",
    "lineno",
    "module",
    "msecs",
    "message",
    "msg",
    "name",
    "pathname",
    "process",
    "processName",
    "relativeCreated",
    "stack_info",
    "thread",
    "threadName",
    "taskName",
}

"""
    This isn't being used since the app will be run on gcloud run but this can be used for future apps.
    If you want to test it:
     
    formatters:
    
    "json": {
      "()": "json_formatter.JSONFormatter",
      "fmt_keys": {
        "level": "levelname",
        "message": "message",
        "timestamp": "timestamp",
        "logger": "name",
        "module": "module",
        "function": "funcName",
        "line": "lineno",
        "thread_name": "threadName"
      }
    } 
    
    handlers:
    
    "file_json": {
      "class": "logging.handlers.RotatingFileHandler",
      "level": "DEBUG",
      "formatter": "json",
      "filename": "logs/log",
      "maxBytes": 1000000,
      "backupCount": 3
    }
    
    and add "cfg://handlers.file_json" to queue handler
"""

# From this video https://www.youtube.com/watch?v=9L77QExPmI0
# Src here: https://github.com/mCodingLLC/VideosSampleCode/blob/master/videos/135_modern_logging/mylogger.py
class JSONFormatter(logging.Formatter):
    def __init__(
        self,
        *,
        fmt_keys: dict[str, str] | None = None,
    ):
        super().__init__()
        self.fmt_keys = fmt_keys if fmt_keys is not None else {}

    def format(self, record: logging.LogRecord) -> str:
        message = self._prepare_log_dict(record)
        return json.dumps(message, default=str)

    def _prepare_log_dict(self, record: logging.LogRecord):
        always_fields = {
            "message": record.getMessage(),
            "timestamp": dt.datetime.fromtimestamp(
                record.created, tz=dt.timezone.utc
            ).isoformat(),
        }
        if record.exc_info is not None:
            always_fields["exc_info"] = self.formatException(record.exc_info)

        if record.stack_info is not None:
            always_fields["stack_info"] = self.formatStack(record.stack_info)

        message = {
            key: msg_val
            if (msg_val := always_fields.pop(val, None)) is not None
            else getattr(record, val)
            for key, val in self.fmt_keys.items()
        }
        message.update(always_fields)

        for key, val in record.__dict__.items():
            if key not in LOG_RECORD_BUILTIN_ATTRS:
                message[key] = val

        return message