fbmessenger: add all.py, merge messages from different sources

followup for https://github.com/karlicoss/HPI/pull/179

my/fbmessenger/all.py

@@ -0,0 +1,48 @@
+from typing import Iterator
+from my.core import Res
+from my.core.common import Stats
+from my.core.source import import_source
+
+from .common import Message, _merge_messages
+
+
+src_export  = import_source(module_name=f'my.fbmessenger.export')
+src_android = import_source(module_name=f'my.fbmessenger.android')
+
+
+@src_export
+def _messages_export() -> Iterator[Res[Message]]:
+    from . import export
+    # ok, this one is a little tricky
+    # export.Message type is actually external (coming from fbmessengerexport module)
+    # so it's unclear how to make mypy believe/check that common.Message is a structural subtype of export.Message
+    # we could use runtime_checkable, but then it might also crash in runtime
+    # which feels somewhat mean if someone is only using fmbessenger.export module and needs its attributes only
+    # so perhaps it makes sense that the typecheck belongs here?
+    for m in export.messages():
+        # NOTE: just 'yield m' works and seems to type check properly
+        if isinstance(m, Exception):
+            yield m
+        else:
+            # however, this way it results in a nicer error (shows the missing Protocol attributes)
+            # https://github.com/python/mypy/issues/8235#issuecomment-570712356
+            m2: Message = m
+            yield m2
+
+
+@src_android
+def _messages_android() -> Iterator[Res[Message]]:
+    from . import android
+    yield from android.messages()
+
+
+def messages() -> Iterator[Res[Message]]:
+    yield from _merge_messages(
+        _messages_export(),
+        _messages_android(),
+    )
+
+
+def stats() -> Stats:
+    from my.core import stat
+    return stat(messages)

my/fbmessenger/android.py

@@ -38,10 +38,8 @@ class Thread:
 # todo not sure about order of fields...
 @dataclass
 class _BaseMessage:
-    # todo nice, ids are same as in fbchat??
     id: str
     dt: datetime
-    # is_incoming: bool
     text: Optional[str]
 
 
@@ -52,6 +50,8 @@ class _Message(_BaseMessage):
     reply_to_id: Optional[str]
 
 
+# todo hmm, on the one hand would be kinda nice to inherit common.Message protocol here
+# on the other, because the properties there are read only we can't construct the object anymore??
 @dataclass(unsafe_hash=True)
 class Message(_BaseMessage):
     thread: Thread

my/fbmessenger/common.py

@@ -0,0 +1,46 @@
+from datetime import datetime
+from typing import Iterator, Optional, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    try:
+        from typing import Protocol
+    except ImportError:
+        # requirement of mypy
+        from typing_extensions import Protocol  # type: ignore[misc]
+else:
+    Protocol = object
+
+
+class Thread(Protocol):
+    @property
+    def id(self) -> str: ...
+
+    # todo hmm it doesn't like it because one from .export is just str, not Optional...
+    # name: Optional[str]
+
+
+class Message(Protocol):
+    @property
+    def id(self) -> str: ...
+
+    @property
+    def dt(self) -> datetime: ...
+
+    @property
+    def text(self) -> Optional[str]: ...
+
+    @property
+    def thread(self) -> Thread: ...
+
+
+from itertools import chain
+from more_itertools import unique_everseen
+from my.core import Res
+def _merge_messages(*sources: Iterator[Res[Message]]) -> Iterator[Res[Message]]:
+    # todo might be nice to dump some stats for debugging, e.g. how many were overlapping?
+    def key(r: Res[Message]):
+        if isinstance(r, Exception):
+            return str(r)
+        else:
+            return r.id
+    yield from unique_everseen(chain(*sources), key=key)

my/fbmessenger/export.py

@@ -45,8 +45,8 @@ def _dal() -> messenger.DAL:
     return messenger.DAL(config.export_db)
 
 
-# TODO Result type?
-def messages() -> Iterator[messenger.Message]:
+from ..core import Res
+def messages() -> Iterator[Res[messenger.Message]]:
     model = _dal()
     for t in model.iter_threads():
         yield from t.iter_messages()