feat(formatter): create base formatter

src/bunyan_formatter/__init__.py

@@ -1,2 +1,3 @@
-def hello() -> str:
-    return "Hello from bunyan-formatter!"
+from .logger import BunyanFormatter
+
+__all__ = ("BunyanFormatter",)

src/bunyan_formatter/logger.py

@@ -0,0 +1,47 @@
+import json
+import logging
+import socket
+from logging import Formatter, LogRecord
+from pathlib import Path
+
+
+class BunyanFormatter(Formatter):
+    LEVEL_MAP = {
+        logging.NOTSET: 10,
+        logging.DEBUG: 20,
+        logging.INFO: 30,
+        logging.WARNING: 40,
+        logging.ERROR: 50,
+        logging.CRITICAL: 60,
+    }
+
+    def __init__(self, project_name: str, project_root: Path) -> None:
+        super().__init__()
+        self.project_name = project_name
+        self.project_root = project_root
+        self.hostname = socket.gethostname()
+
+    def format(self, record: LogRecord) -> str:
+        hostname = socket.gethostname()
+
+        file_path = Path(record.pathname)
+        try:
+            relative_path = file_path.relative_to(self.project_root)
+        except ValueError:
+            relative_path = file_path
+
+        log_entry = {
+            "v": 0,
+            "name": self.project_name,
+            "msg": record.getMessage(),
+            "level": self.LEVEL_MAP.get(record.levelno, record.levelno),
+            "levelname": record.levelname,
+            "hostname": hostname,
+            "pid": record.process,
+            "time": self.formatTime(record, "%Y-%m-%dT%H:%M:%S.%fZ"),
+            "target": record.name,
+            "line": record.lineno,
+            "file": str(relative_path),
+        }
+
+        return json.dumps(log_entry)