message: introduced file suffix '.msg'

- '.msg' suffix is always used for writing
- 'Message.to_file()' will set the file suffix if the given file_path has none
- added 'mformat' argument to 'Message.to_file()' for choosing the file format
- '.txt' and '.yaml' suffixes are only supported for reading

chatmastermind/message.py

@@ -5,7 +5,8 @@ import pathlib
 import yaml
 import tempfile
 import shutil
-from typing import Type, TypeVar, ClassVar, Optional, Any, Union, Final, Literal, Iterable
+from typing import Type, TypeVar, ClassVar, Optional, Any, Union, Final, Literal, Iterable, Tuple
+from typing import get_args as typing_get_args
 from dataclasses import dataclass, asdict, field
 from .tags import Tag, TagLine, TagError, match_tags, rename_tags
 
@@ -15,6 +16,9 @@ MessageInst = TypeVar('MessageInst', bound='Message')
 AILineInst = TypeVar('AILineInst', bound='AILine')
 ModelLineInst = TypeVar('ModelLineInst', bound='ModelLine')
 YamlDict = dict[str, Union[QuestionInst, AnswerInst, set[Tag]]]
+MessageFormat = Literal['txt', 'yaml']
+message_valid_formats: Final[Tuple[MessageFormat, ...]] = typing_get_args(MessageFormat)
+message_default_format: Final[MessageFormat] = 'txt'
 
 
 class MessageError(Exception):
@@ -92,7 +96,7 @@ class MessageFilter:
 
 class AILine(str):
     """
-    A line that represents the AI name in a '.txt' file..
+    A line that represents the AI name in the 'txt' format.
     """
     prefix: Final[str] = 'AI:'
 
@@ -112,7 +116,7 @@ class AILine(str):
 
 class ModelLine(str):
     """
-    A line that represents the model name in a '.txt' file..
+    A line that represents the model name in the 'txt' format.
     """
     prefix: Final[str] = 'MODEL:'
 
@@ -216,7 +220,9 @@ class Message():
     model: Optional[str] = field(default=None, compare=False)
     file_path: Optional[pathlib.Path] = field(default=None, compare=False)
     # class variables
-    file_suffixes: ClassVar[list[str]] = ['.txt', '.yaml']
+    file_suffixes_read: ClassVar[list[str]] = ['.msg', '.txt', '.yaml']
+    file_suffix_write: ClassVar[str] = '.msg'
+    default_format: ClassVar[MessageFormat] = message_default_format
     tags_yaml_key: ClassVar[str] = 'tags'
     file_yaml_key: ClassVar[str] = 'file_path'
     ai_yaml_key: ClassVar[str] = 'ai'
@@ -276,16 +282,8 @@ class Message():
         tags: set[Tag] = set()
         if not file_path.exists():
             raise MessageError(f"Message file '{file_path}' does not exist")
-        if file_path.suffix not in cls.file_suffixes:
+        if file_path.suffix not in cls.file_suffixes_read:
             raise MessageError(f"File type '{file_path.suffix}' is not supported")
-        # for TXT, it's enough to read the TagLine
-        if file_path.suffix == '.txt':
-            with open(file_path, "r") as fd:
-                try:
-                    tags = TagLine(fd.readline()).tags(prefix, contain)
-                except TagError:
-                    pass  # message without tags
-        else:  # '.yaml'
         try:
             message = cls.from_file(file_path)
             if message:
@@ -328,15 +326,16 @@ class Message():
         """
         if not file_path.exists():
             raise MessageError(f"Message file '{file_path}' does not exist")
-        if file_path.suffix not in cls.file_suffixes:
+        if file_path.suffix not in cls.file_suffixes_read:
             raise MessageError(f"File type '{file_path.suffix}' is not supported")
-
+        # try TXT first
-        if file_path.suffix == '.txt':
+        try:
             message = cls.__from_file_txt(file_path,
                                           mfilter.tags_or if mfilter else None,
                                           mfilter.tags_and if mfilter else None,
                                           mfilter.tags_not if mfilter else None)
-        else:
+        # then YAML
+        except MessageError:
             message = cls.__from_file_yaml(file_path)
         if message and (mfilter is None or message.match(mfilter)):
             return message
@@ -442,21 +441,29 @@ class Message():
             output.append(self.answer)
         return '\n'.join(output)
 
-    def to_file(self, file_path: Optional[pathlib.Path]=None) -> None:  # noqa: 11
+    def to_file(self, file_path: Optional[pathlib.Path]=None, mformat: MessageFormat = message_default_format) -> None:  # noqa: 11
         """
-        Write a Message to the given file. Type is determined based on the suffix.
+        Write a Message to the given file. Supported message file formats are 'txt' and 'yaml'.
-        Currently supported suffixes: ['.txt', '.yaml']
+        Suffix is always '.msg'.
         """
         if file_path:
             self.file_path = file_path
         if not self.file_path:
             raise MessageError("Got no valid path to write message")
-        if self.file_path.suffix not in self.file_suffixes:
+        if mformat not in message_valid_formats:
-            raise MessageError(f"File type '{self.file_path.suffix}' is not supported")
+            raise MessageError(f"File format '{mformat}' is not supported")
+        # check for valid suffix
+        # -> add one if it's empty
+        # -> refuse old or otherwise unsupported suffixes
+        if not self.file_path.suffix:
+            self.file_path = self.file_path.with_suffix(self.file_suffix_write)
+        elif self.file_path.suffix != self.file_suffix_write:
+            raise MessageError(f"File suffix '{self.file_path.suffix}' is not supported")
         # TXT
-        if self.file_path.suffix == '.txt':
+        if mformat == 'txt':
             return self.__to_file_txt(self.file_path)
-        elif self.file_path.suffix == '.yaml':
+        # YAML
+        elif mformat == 'yaml':
             return self.__to_file_yaml(self.file_path)
 
     def __to_file_txt(self, file_path: pathlib.Path) -> None:
@@ -468,8 +475,8 @@ class Message():
             * Model [Optional]
             * Question.txt_header
             * Question
-            * Answer.txt_header
+            * Answer.txt_header [Optional]
-            * Answer
+            * Answer [Optional]
         """
         with tempfile.NamedTemporaryFile(dir=file_path.parent, prefix=file_path.name, mode="w", delete=False) as temp_fd:
             temp_file_path = pathlib.Path(temp_fd.name)