# dumb.py -- Support for dumb HTTP(S) git repositories
# Copyright (C) 2025 Dulwich contributors
#
# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as published by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#

"""Support for dumb HTTP(S) git repositories."""

__all__ = [
    "DumbHTTPObjectStore",
    "DumbRemoteHTTPRepo",
]

import os
import tempfile
import zlib
from collections.abc import Callable, Iterator, Mapping, Sequence
from io import BytesIO
from typing import TYPE_CHECKING, Any
from urllib.parse import urljoin

if TYPE_CHECKING:
    from .object_format import ObjectFormat

from .errors import NotGitRepository, ObjectFormatException
from .object_store import BaseObjectStore
from .objects import (
    ZERO_SHA,
    Blob,
    Commit,
    ObjectID,
    RawObjectID,
    ShaFile,
    Tag,
    Tree,
    hex_to_sha,
    sha_to_hex,
)
from .pack import Pack, PackData, PackIndex, UnpackedObject, load_pack_index_file
from .protocol import split_peeled_refs
from .refs import Ref, read_info_refs


class DumbHTTPObjectStore(BaseObjectStore):
    """Object store implementation that fetches objects over dumb HTTP."""

    def __init__(
        self,
        base_url: str,
        http_request_func: Callable[
            [str, dict[str, str]], tuple[Any, Callable[..., bytes]]
        ],
        object_format: "ObjectFormat | None" = None,
    ) -> None:
        """Initialize a DumbHTTPObjectStore.

        Args:
          base_url: Base URL of the remote repository (e.g. "https://example.com/repo.git/")
          http_request_func: Function to make HTTP requests, should accept (url, headers)
                           and return (response, read_func).
          object_format: Object format to use (defaults to DEFAULT_OBJECT_FORMAT)
        """
        super().__init__(object_format=object_format)
        self.base_url = base_url.rstrip("/") + "/"
        self._http_request = http_request_func
        self._packs: list[tuple[str, PackIndex | None]] | None = None
        self._cached_objects: dict[bytes, tuple[int, bytes]] = {}
        self._temp_pack_dir: str | None = None

    def _ensure_temp_pack_dir(self) -> None:
        """Ensure we have a temporary directory for storing pack files."""
        if self._temp_pack_dir is None:
            self._temp_pack_dir = tempfile.mkdtemp(prefix="dulwich-dumb-")

    def _fetch_url(self, path: str) -> bytes:
        """Fetch content from a URL path relative to base_url.

        Args:
          path: Path relative to base URL
        Returns:
          Content as bytes
        Raises:
          IOError: If the URL cannot be fetched
        """
        url = urljoin(self.base_url, path)
        resp, read = self._http_request(url, {})
        try:
            if resp.status == 404:
                raise OSError(f"Not found: {url}")
            elif resp.status != 200:
                raise OSError(f"HTTP error {resp.status}: {url}")

            # Read all content
            chunks = []
            while True:
                chunk = read(4096)
                if not chunk:
                    break
                chunks.append(chunk)
            return b"".join(chunks)
        finally:
            resp.close()

    def _fetch_loose_object(self, sha: bytes) -> tuple[int, bytes]:
        """Fetch a loose object by SHA.

        Args:
          sha: SHA1 of the object (hex string as bytes)

        Returns:
          Tuple of (type_num, content)

        Raises:
          KeyError: If object not found
        """
        hex_sha = sha.decode("ascii")
        path = f"objects/{hex_sha[:2]}/{hex_sha[2:]}"

        try:
            compressed = self._fetch_url(path)
        except OSError:
            raise KeyError(sha)

        # Decompress and parse the object
        decompressed = zlib.decompress(compressed)

        # Parse header
        header_end = decompressed.find(b"\x00")
        if header_end == -1:
            raise ObjectFormatException("Invalid object header")

        header = decompressed[:header_end]
        content = decompressed[header_end + 1 :]

        parts = header.split(b" ", 1)
        if len(parts) != 2:
            raise ObjectFormatException("Invalid object header")

        obj_type = parts[0]
        obj_size = int(parts[1])

        if len(content) != obj_size:
            raise ObjectFormatException("Object size mismatch")

        # Convert type name to type number
        type_map = {
            b"blob": Blob.type_num,
            b"tree": Tree.type_num,
            b"commit": Commit.type_num,
            b"tag": Tag.type_num,
        }

        if obj_type not in type_map:
            raise ObjectFormatException(f"Unknown object type: {obj_type!r}")

        return type_map[obj_type], content

    def _load_packs(self) -> None:
        """Load the list of available packs from the remote."""
        if self._packs is not None:
            return

        self._packs = []
        try:
            packs_data = self._fetch_url("objects/info/packs")
        except OSError:
            # No packs file, repository might only have loose objects
            return

        for line in packs_data.strip().split(b"\n"):
            if line.startswith(b"P "):
                pack_name = line[2:].decode("utf-8")
                # Extract just the pack name without path
                if "/" in pack_name:
                    pack_name = pack_name.split("/")[-1]
                if pack_name.endswith(".pack"):
                    pack_name = pack_name[:-5]  # Remove .pack extension
                self._packs.append((pack_name, None))

    def _get_pack_index(self, pack_name: str) -> PackIndex:
        """Get or fetch a pack index.

        Args:
          pack_name: Name of the pack (without .idx extension)

        Returns:
          PackIndex object
        """
        # Find the pack in our list
        for i, (name, idx) in enumerate(self._packs or []):
            if name == pack_name:
                if idx is None:
                    # Fetch and cache the index
                    idx_data = self._fetch_url(f"objects/pack/{pack_name}.idx")

                    idx = load_pack_index_file("<http>", BytesIO(idx_data), self.object_format)
                    if self._packs is not None:
                        self._packs[i] = (name, idx)
                return idx
        raise KeyError(f"Pack not found: {pack_name}")

    def _fetch_from_pack(self, sha: RawObjectID | ObjectID) -> tuple[int, bytes]:
        """Try to fetch an object from pack files.

        Args:
          sha: SHA1 of the object (hex string as bytes)

        Returns:
          Tuple of (type_num, content)

        Raises:
          KeyError: If object not found in any pack
        """
        self._load_packs()
        # Convert hex to binary for pack operations
        if len(sha) == 20:
            binsha = RawObjectID(sha)  # Already binary
        else:
            binsha = hex_to_sha(ObjectID(sha))  # Convert hex to binary

        for pack_name, pack_idx in self._packs or []:
            if pack_idx is None:
                pack_idx = self._get_pack_index(pack_name)

            try:
                # Check if object is in this pack
                pack_idx.object_offset(binsha)
            except KeyError:
                continue

            # We found the object, now we need to fetch the pack data
            # For efficiency, we could fetch just the needed portion, but for
            # simplicity we'll fetch the whole pack and cache it
            self._ensure_temp_pack_dir()
            if self._temp_pack_dir is None:
                raise RuntimeError("Temp pack directory not initialized")
            pack_path = os.path.join(self._temp_pack_dir, f"{pack_name}.pack")

            if not os.path.exists(pack_path):
                # Download the pack file
                data = self._fetch_url(f"objects/pack/{pack_name}.pack")
                with open(pack_path, "wb") as f:
                    f.write(data)

            # Open the pack and get the object
            pack_data = PackData(pack_path, object_format=self.object_format)
            pack = Pack.from_objects(
                pack_data, pack_idx
            )
            try:
                return pack.get_raw(binsha)
            finally:
                pack.close()

        raise KeyError(sha)

    def get_raw(self, sha: RawObjectID | ObjectID) -> tuple[int, bytes]:
        """Obtain the raw text for an object.

        Args:
          sha: SHA1 of the object
        Returns:
          Tuple with numeric type and object contents
        """
        # Check cache first
        if sha in self._cached_objects:
            return self._cached_objects[sha]

        # Try packs first
        try:
            result = self._fetch_from_pack(sha)
            self._cached_objects[sha] = result
            return result
        except KeyError:
            pass

        # Try loose object
        result = self._fetch_loose_object(sha)
        self._cached_objects[sha] = result
        return result

    def contains_loose(self, sha: RawObjectID | ObjectID) -> bool:
        """Check if a particular object is present by SHA1 and is loose."""
        try:
            self._fetch_loose_object(sha)
            return True
        except KeyError:
            return False

    def __contains__(self, sha: RawObjectID | ObjectID) -> bool:
        """Check if a particular object is present by SHA1."""
        if sha in self._cached_objects:
            return True

        # Try packs
        try:
            self._fetch_from_pack(sha)
            return True
        except KeyError:
            pass

        # Try loose object
        try:
            self._fetch_loose_object(sha)
            return True
        except KeyError:
            return False

    def __iter__(self) -> Iterator[ObjectID]:
        """Iterate over all SHAs in the store.

        Note: This is inefficient for dumb HTTP as it requires
        downloading all pack indices.
        """
        seen = set()

        # We can't efficiently list loose objects over dumb HTTP
        # So we only iterate pack objects
        self._load_packs()

        for pack_name, idx in self._packs or []:
            if idx is None:
                idx = self._get_pack_index(pack_name)

            for sha in idx:
                if sha not in seen:
                    seen.add(sha)
                    yield sha_to_hex(RawObjectID(sha))

    @property
    def packs(self) -> list[Any]:
        """Iterable of pack objects.

        Note: Returns empty list as we don't have actual Pack objects.
        """
        return []

    def add_object(self, obj: ShaFile) -> None:
        """Add a single object to this object store."""
        raise NotImplementedError("Cannot add objects to dumb HTTP repository")

    def add_objects(
        self,
        objects: Sequence[tuple[ShaFile, str | None]],
        progress: Callable[[str], None] | None = None,
    ) -> "Pack | None":
        """Add a set of objects to this object store."""
        raise NotImplementedError("Cannot add objects to dumb HTTP repository")

    def __del__(self) -> None:
        """Clean up temporary directory on deletion."""
        if self._temp_pack_dir and os.path.exists(self._temp_pack_dir):
            import shutil

            shutil.rmtree(self._temp_pack_dir, ignore_errors=True)


class DumbRemoteHTTPRepo:
    """Repository implementation for dumb HTTP remotes."""

    def __init__(
        self,
        base_url: str,
        http_request_func: Callable[
            [str, dict[str, str]], tuple[Any, Callable[..., bytes]]
        ],
    ) -> None:
        """Initialize a DumbRemoteHTTPRepo.

        Args:
          base_url: Base URL of the remote repository
          http_request_func: Function to make HTTP requests.
        """
        self.base_url = base_url.rstrip("/") + "/"
        self._http_request = http_request_func
        self._refs: dict[Ref, ObjectID] | None = None
        self._peeled: dict[Ref, ObjectID] | None = None
        self.object_store = DumbHTTPObjectStore(base_url, http_request_func)

    def _fetch_url(self, path: str) -> bytes:
        """Fetch content from a URL path relative to base_url."""
        url = urljoin(self.base_url, path)
        resp, read = self._http_request(url, {})
        try:
            if resp.status == 404:
                raise OSError(f"Not found: {url}")
            elif resp.status != 200:
                raise OSError(f"HTTP error {resp.status}: {url}")

            chunks = []
            while True:
                chunk = read(4096)
                if not chunk:
                    break
                chunks.append(chunk)
            return b"".join(chunks)
        finally:
            resp.close()

    def get_refs(self) -> dict[Ref, ObjectID]:
        """Get dictionary with all refs."""
        if self._refs is None:
            # Fetch info/refs
            try:
                refs_data = self._fetch_url("info/refs")
            except OSError:
                raise NotGitRepository(f"Cannot read refs from {self.base_url}")

            refs_hex = read_info_refs(BytesIO(refs_data))
            # Keep SHAs as hex
            refs_raw, peeled_raw = split_peeled_refs(refs_hex)
            # Convert to typed dicts
            self._refs = {Ref(k): ObjectID(v) for k, v in refs_raw.items()}
            self._peeled = peeled_raw

        return dict(self._refs)

    def get_head(self) -> Ref:
        """Get the current HEAD reference.

        Returns:
          HEAD reference name or commit ID
        """
        head_resp_bytes = self._fetch_url("HEAD")
        head_split = head_resp_bytes.replace(b"\n", b"").split(b" ")
        head_target_bytes = head_split[1] if len(head_split) > 1 else head_split[0]
        # handle HEAD legacy format containing a commit id instead of a ref name
        for ref_name, ret_target in self.get_refs().items():
            if ret_target == head_target_bytes:
                return ref_name
        return Ref(head_target_bytes)

    def get_peeled(self, ref: Ref) -> ObjectID:
        """Get the peeled value of a ref."""
        # For dumb HTTP, we don't have peeled refs readily available
        # We would need to fetch and parse tag objects
        sha: ObjectID | None = self.get_refs().get(ref, None)
        return sha if sha is not None else ZERO_SHA

    def fetch_pack_data(
        self,
        determine_wants: Callable[[Mapping[Ref, ObjectID], int | None], list[ObjectID]],
        graph_walker: object,
        progress: Callable[[bytes], None] | None = None,
        *,
        get_tagged: bool | None = None,
        depth: int | None = None,
    ) -> Iterator[UnpackedObject]:
        """Fetch pack data from the remote.

        This is the main method for fetching objects from a dumb HTTP remote.
        Since dumb HTTP doesn't support negotiation, we need to download
        all objects reachable from the wanted refs.

        Args:
          determine_wants: Function that returns list of wanted SHAs
          graph_walker: GraphWalker instance (not used for dumb HTTP)
          progress: Optional progress callback
          get_tagged: Whether to get tagged objects
          depth: Depth for shallow clones (not supported for dumb HTTP)

        Returns:
          Iterator of UnpackedObject instances
        """
        refs = self.get_refs()
        wants = determine_wants(refs, depth)

        if not wants:
            return

        # For dumb HTTP, we traverse the object graph starting from wants
        to_fetch = set(wants)
        seen = set()

        while to_fetch:
            sha = to_fetch.pop()
            if sha in seen:
                continue
            seen.add(sha)

            # Fetch the object
            try:
                type_num, content = self.object_store.get_raw(sha)
            except KeyError:
                # Object not found, skip it
                continue

            unpacked = UnpackedObject(type_num, sha=sha, decomp_chunks=[content])
            yield unpacked

            # Parse the object to find references to other objects
            obj = ShaFile.from_raw_string(type_num, content)

            if isinstance(obj, Commit):  # Commit
                to_fetch.add(obj.tree)
                for parent in obj.parents:
                    to_fetch.add(parent)
            elif isinstance(obj, Tag):  # Tag
                to_fetch.add(obj.object[1])
            elif isinstance(obj, Tree):  # Tree
                for _, _, item_sha in obj.items():
                    assert item_sha is not None
                    to_fetch.add(item_sha)

            if progress:
                progress(f"Fetching objects: {len(seen)} done\n".encode())