import json
import logging
import sys
from datetime import datetime, timezone
from typing import Any, Dict, Optional


class StructuredJsonFormatter(logging.Formatter):
    """
    JSON log formatter emitting structured log records with standard telecom pipeline fields:
    - timestamp (ISO 8601 UTC)
    - level (INFO, WARN, ERROR, DEBUG)
    - service (service name)
    - raw_id (record identifier or None)
    - event (message string)
    """

    def __init__(self, service_name: str):
        super().__init__()
        self.service_name = service_name

    def format(self, record: logging.LogRecord) -> str:
        log_entry: Dict[str, Any] = {
            "timestamp": datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ"),
            "level": record.levelname,
            "service": getattr(record, "service", self.service_name),
            "raw_id": getattr(record, "raw_id", None),
            "event": getattr(record, "event", record.getMessage()),
            "message": record.getMessage(),
        }

        # Include exception info if present
        if record.exc_info:
            log_entry["exception"] = self.formatException(record.exc_info)

        # Include additional extra context fields if present
        for key, value in record.__dict__.items():
            if key not in {
                "name",
                "msg",
                "args",
                "levelname",
                "levelno",
                "pathname",
                "filename",
                "module",
                "exc_info",
                "exc_text",
                "stack_info",
                "lineno",
                "funcName",
                "created",
                "msecs",
                "relativeCreated",
                "thread",
                "threadName",
                "processName",
                "process",
                "raw_id",
                "service",
            }:
                log_entry[key] = value

        return json.dumps(log_entry, default=str)


def setup_logger(
    service_name: str, level: Optional[str] = None
) -> logging.Logger:
    """
    Configures and returns a logger configured with StructuredJsonFormatter on stdout.
    """
    if level is None:
        from app.common.config import config

        level = config.log_level

    logger = logging.getLogger(service_name)
    logger.setLevel(getattr(logging, level.upper(), logging.INFO))
    logger.propagate = False

    # Avoid duplicate handlers if setup is called multiple times
    if not logger.handlers:
        handler = logging.StreamHandler(sys.stdout)
        handler.setFormatter(StructuredJsonFormatter(service_name=service_name))
        logger.addHandler(handler)

    return logger