Feat: add CHM file loader (#15519)

fix https://github.com/langchain-ai/langchain/issues/15469

libs/community/langchain_community/document_loaders/chm.py

@@ -0,0 +1,102 @@
+from typing import TYPE_CHECKING, Dict, List, Union
+
+from langchain_community.document_loaders.unstructured import UnstructuredFileLoader
+
+if TYPE_CHECKING:
+    from chm import chm
+
+
+class UnstructuredCHMLoader(UnstructuredFileLoader):
+    """Load `CHM` files using `Unstructured`.
+
+    CHM mean Microsoft Compiled HTML Help.
+
+    Examples
+    --------
+    from langchain_community.document_loaders import UnstructuredCHMLoader
+
+    loader = UnstructuredCHMLoader("example.chm")
+    docs = loader.load()
+
+    References
+    ----------
+    https://github.com/dottedmag/pychm
+    http://www.jedrea.com/chmlib/
+    """
+
+    def _get_elements(self) -> List:
+        from unstructured.partition.html import partition_html
+
+        with CHMParser(self.file_path) as f:
+            return [
+                partition_html(text=item["content"], **self.unstructured_kwargs)
+                for item in f.load_all()
+            ]
+
+
+class CHMParser(object):
+    path: str
+    file: "chm.CHMFile"
+
+    def __init__(self, path: str):
+        from chm import chm
+
+        self.path = path
+        self.file = chm.CHMFile()
+        self.file.LoadCHM(path)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        if self.file:
+            self.file.CloseCHM()
+
+    @property
+    def encoding(self) -> str:
+        return self.file.GetEncoding().decode("utf-8")
+
+    def index(self) -> List[Dict[str, str]]:
+        from urllib.parse import urlparse
+
+        from bs4 import BeautifulSoup
+
+        res = []
+        index = self.file.GetTopicsTree().decode(self.encoding)
+        soup = BeautifulSoup(index)
+        # <OBJECT ..>
+        for obj in soup.find_all("object"):
+            # <param name="Name" value="<...>">
+            # <param name="Local" value="<...>">
+            name = ""
+            local = ""
+            for param in obj.find_all("param"):
+                if param["name"] == "Name":
+                    name = param["value"]
+                if param["name"] == "Local":
+                    local = param["value"]
+            if not name or not local:
+                continue
+
+            local = urlparse(local).path
+            if not local.startswith("/"):
+                local = "/" + local
+            res.append({"name": name, "local": local})
+
+        return res
+
+    def load(self, path: Union[str, bytes]) -> str:
+        if isinstance(path, str):
+            path = path.encode("utf-8")
+        obj = self.file.ResolveObject(path)[1]
+        return self.file.RetrieveObject(obj)[1].decode(self.encoding)
+
+    def load_all(self) -> List[Dict[str, str]]:
+        res = []
+        index = self.index()
+        for item in index:
+            content = self.load(item["local"])
+            res.append(
+                {"name": item["name"], "local": item["local"], "content": content}
+            )
+        return res