"""
Implementation of a custom transfer agent for the transfer type "multipart" for
git-lfs.

Inspired by:
github.com/cbartz/git-lfs-swift-transfer-agent/blob/master/git_lfs_swift_transfer.py

Spec is: github.com/git-lfs/git-lfs/blob/master/docs/custom-transfers.md


To launch debugger while developing:

``` [lfs "customtransfer.multipart"]
path = /path/to/huggingface_hub/.env/bin/python args = -m debugpy --listen 5678
--wait-for-client
/path/to/huggingface_hub/src/huggingface_hub/commands/huggingface_cli.py
lfs-multipart-upload ```"""

import json
import os
import subprocess
import sys
from typing import Annotated, Optional

import typer

from huggingface_hub.lfs import LFS_MULTIPART_UPLOAD_COMMAND

from ..utils import get_session, hf_raise_for_status, logging
from ..utils._lfs import SliceFileObj


logger = logging.get_logger(__name__)


def lfs_enable_largefiles(
    path: Annotated[
        str,
        typer.Argument(
            help="Local path to repository you want to configure.",
        ),
    ],
) -> None:
    """
    Configure a local git repository to use the multipart transfer agent for large files.

    This command sets up git-lfs to use the custom multipart transfer agent
    which enables efficient uploading of large files in chunks.
    """
    local_path = os.path.abspath(path)
    if not os.path.isdir(local_path):
        print("This does not look like a valid git repo.")
        raise typer.Exit(code=1)
    subprocess.run(
        "git config lfs.customtransfer.multipart.path hf".split(),
        check=True,
        cwd=local_path,
    )
    subprocess.run(
        f"git config lfs.customtransfer.multipart.args {LFS_MULTIPART_UPLOAD_COMMAND}".split(),
        check=True,
        cwd=local_path,
    )
    print("Local repo set up for largefiles")


def write_msg(msg: dict):
    """Write out the message in Line delimited JSON."""
    msg_str = json.dumps(msg) + "\n"
    sys.stdout.write(msg_str)
    sys.stdout.flush()


def read_msg() -> Optional[dict]:
    """Read Line delimited JSON from stdin."""
    msg = json.loads(sys.stdin.readline().strip())

    if "terminate" in (msg.get("type"), msg.get("event")):
        # terminate message received
        return None

    if msg.get("event") not in ("download", "upload"):
        logger.critical("Received unexpected message")
        sys.exit(1)

    return msg


def lfs_multipart_upload() -> None:
    """Internal git-lfs custom transfer agent for multipart uploads.

    This function implements the custom transfer protocol for git-lfs multipart uploads.
    Handles chunked uploads of large files to Hugging Face Hub.
    """
    # Immediately after invoking a custom transfer process, git-lfs
    # sends initiation data to the process over stdin.
    # This tells the process useful information about the configuration.
    init_msg = json.loads(sys.stdin.readline().strip())
    if not (init_msg.get("event") == "init" and init_msg.get("operation") == "upload"):
        write_msg({"error": {"code": 32, "message": "Wrong lfs init operation"}})
        sys.exit(1)

    # The transfer process should use the information it needs from the
    # initiation structure, and also perform any one-off setup tasks it
    # needs to do. It should then respond on stdout with a simple empty
    # confirmation structure, as follows:
    write_msg({})

    # After the initiation exchange, git-lfs will send any number of
    # transfer requests to the stdin of the transfer process, in a serial sequence.
    while True:
        msg = read_msg()
        if msg is None:
            # When all transfers have been processed, git-lfs will send
            # a terminate event to the stdin of the transfer process.
            # On receiving this message the transfer process should
            # clean up and terminate. No response is expected.
            sys.exit(0)

        oid = msg["oid"]
        filepath = msg["path"]
        completion_url = msg["action"]["href"]
        header = msg["action"]["header"]
        chunk_size = int(header.pop("chunk_size"))
        presigned_urls: list[str] = list(header.values())

        # Send a "started" progress event to allow other workers to start.
        # Otherwise they're delayed until first "progress" event is reported,
        # i.e. after the first 5GB by default (!)
        write_msg(
            {
                "event": "progress",
                "oid": oid,
                "bytesSoFar": 1,
                "bytesSinceLast": 0,
            }
        )

        parts = []
        with open(filepath, "rb") as file:
            for i, presigned_url in enumerate(presigned_urls):
                with SliceFileObj(
                    file,
                    seek_from=i * chunk_size,
                    read_limit=chunk_size,
                ) as data:
                    r = get_session().put(presigned_url, data=data)
                    hf_raise_for_status(r)
                    parts.append(
                        {
                            "etag": r.headers.get("etag"),
                            "partNumber": i + 1,
                        }
                    )
                    # In order to support progress reporting while data is uploading / downloading,
                    # the transfer process should post messages to stdout
                    write_msg(
                        {
                            "event": "progress",
                            "oid": oid,
                            "bytesSoFar": (i + 1) * chunk_size,
                            "bytesSinceLast": chunk_size,
                        }
                    )

        r = get_session().post(
            completion_url,
            json={
                "oid": oid,
                "parts": parts,
            },
        )
        hf_raise_for_status(r)

        write_msg({"event": "complete", "oid": oid})
