#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2.

# pyre-strict

import binascii
import typing
from pathlib import Path
from typing import BinaryIO, Dict, Tuple

import eden.dirstate

from .config import EdenCheckout


_DEFAULT_EXTRA_HGRC_CONTENTS: str = """\
[extensions]
eden =
share =

[ui]
portablefilenames = ignore
"""


def setup_hg_dir(checkout: EdenCheckout, commit_id: str) -> None:
    checkout_hg_dir = checkout.path / ".hg"
    try:
        checkout_hg_dir.mkdir()
    except FileExistsError:
        raise Exception(f"{checkout_hg_dir} directory already exists")

    # hgrc
    hgrc_data = get_hgrc_data(checkout)
    (checkout_hg_dir / "hgrc").write_text(hgrc_data)

    # requires
    requires_data = get_requires_data(checkout)
    (checkout_hg_dir / "requires").write_text(requires_data)

    # Create the shared and sharedpath files, which tell mercurial where it should
    # really look for most of the mercurial state, and that bookmarks should also be
    # shared.
    #
    # Note that the sharedpath file intentionally does not include a trailing newline.
    # This matches how it is generated by mercurial.
    backing_hg_dir = get_backing_hg_dir(checkout)
    (checkout_hg_dir / "sharedpath").write_bytes(bytes(backing_hg_dir))
    (checkout_hg_dir / "shared").write_text("bookmarks\n")

    # Create an empty bookmarks file
    (checkout_hg_dir / "bookmarks").touch()

    # Create a branch file with the contents "default\n". Even though we do not
    # use branches, we have seen some users with a function in their .bashrc
    # that categorically reads the .hg/branch file to include in their prompt.
    (checkout_hg_dir / "branch").write_text("default\n")

    # Write the parents to the dirstate file.
    with typing.cast(BinaryIO, (checkout_hg_dir / "dirstate").open("wb")) as f:
        parents = (binascii.unhexlify(commit_id), b"\x00" * 20)
        tuples_dict: Dict[str, Tuple[str, int, int]] = {}
        copymap: Dict[str, str] = {}
        eden.dirstate.write(f, parents, tuples_dict, copymap)


def get_backing_hg_dir(checkout: EdenCheckout) -> Path:
    """Given an EdenCheckout object, return the path to the actual .hg/ directory that
    contains the mercurial data store.

    This is the path that .hg/sharedpath should point to.
    """
    return checkout.get_config().backing_repo / ".hg"


def get_hgrc_data(checkout: EdenCheckout) -> str:
    backing_hg_dir = get_backing_hg_dir(checkout)
    extra_hgrc = checkout.instance.get_config_value(
        "hg.extra_hgrc", default=_DEFAULT_EXTRA_HGRC_CONTENTS
    )

    if extra_hgrc and extra_hgrc[-1] != "\n":
        extra_hgrc += "\n"

    try:
        orig_hgrc = (backing_hg_dir / "hgrc").read_text()
    except FileNotFoundError:
        # Repositories aren't required to have an .hgrc file
        # Make sure the .hg directory itself exists though, to confirm
        # we weren't called with incorrect arguments.
        if not backing_hg_dir.is_dir():
            raise Exception(f"backing repository does not exist: {backing_hg_dir}")
        orig_hgrc = ""

    return orig_hgrc + "\n" + extra_hgrc


def get_requires_data(checkout: EdenCheckout) -> str:
    backing_hg_dir = get_backing_hg_dir(checkout)
    try:
        orig_requires_data = (backing_hg_dir / "requires").read_text()
        requires = set(orig_requires_data.splitlines())
    except FileNotFoundError:
        requires = set()

    # Add eden as a requirement
    requires.add("eden")

    # Drop other dirstate-related requirements that are specific to
    # the backing repository's dirstate.
    requires.discard("sqldirstate")
    requires.discard("treedirstate")

    return "\n".join(sorted(requires)) + "\n"