# Copyright The Lightning AI team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# 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.

import fnmatch
import os
from functools import partial
from pathlib import Path
from shutil import copy2, copystat, Error
from typing import Callable, List, Optional, Set, Tuple, Union

from lightning.app.core.constants import DOT_IGNORE_FILENAME
from lightning.app.utilities.app_helpers import Logger

logger = Logger(__name__)

_IGNORE_FUNCTION = Callable[[Path, List[Path]], List[Path]]


def _copytree(
    src: Union[Path, str],
    dst: Union[Path, str],
    ignore_functions: Optional[List[_IGNORE_FUNCTION]] = None,
    dirs_exist_ok=False,
    dry_run=False,
) -> List[str]:
    """Vendor in from `shutil.copytree` to support ignoring files recursively based on `.lightningignore`, like
    `git` does with `.gitignore`. Also removed a few checks from the original copytree related to symlink checks.
    Differences between original and this function are.

    1. It supports a list of ignore function instead of a single one in the
        original. We can use this for filtering out files based on nested
        .lightningignore files
    2. It supports a dry run. When enabled, this function will not copy anything but just recursively
        find the source files which are not-ignored and return them. It is useful while calculating
        the hash or checking the size of files
    3. This function returns a list of copied files unlike the original which was returning the
        destination directory

    Recursively copy a directory tree and return the destination directory.

    Parameters
    ----------
    src:
        Source directory path to copy from
    dst:
        Destination directory path to copy to
    ignore_functions:
        List of functions that will be used to filter out files
        and directories. This isn't required to be passed when calling from outside but will be
        autopopulated by the recursive calls in this function itself (Original copytree doesn't have this argument)
    dirs_exist_ok:
        If true, the destination directory will be created if it doesn't exist.
    dry_run:
        If true, this function will not copy anything (this is not present in the original copytree)


    If exception(s) occur, an Error is raised with a list of reasons.
    """
    files_copied = []

    if ignore_functions is None:
        ignore_functions = []

    _ignore_filename_spell_check(src)
    src = Path(src)
    dst = Path(dst)
    ignore_filepath = src / DOT_IGNORE_FILENAME
    if ignore_filepath.is_file():
        patterns = _read_lightningignore(ignore_filepath)
        ignore_fn = partial(_filter_ignored, src, patterns)
        # creating new list so we won't modify the original
        ignore_functions = [*ignore_functions, ignore_fn]

    if not dry_run:
        os.makedirs(dst, exist_ok=dirs_exist_ok)

    errors = []

    entries = list(src.iterdir())
    for fn in ignore_functions:
        # ignore function return only the entries that are not ignored
        entries = fn(src, entries)

    for srcentry in entries:
        dstpath = dst / srcentry.name
        try:
            if srcentry.is_dir():
                _files = _copytree(
                    src=srcentry,
                    dst=dstpath,
                    ignore_functions=ignore_functions,
                    dirs_exist_ok=dirs_exist_ok,
                    dry_run=dry_run,
                )
                files_copied.extend(_files)
            else:
                files_copied.append(str(srcentry))
                if not dry_run:
                    # Will raise a SpecialFileError for unsupported file types
                    copy2(srcentry, dstpath)
        # catch the Error from the recursive copytree so that we can
        # continue with other files
        except Error as err:
            errors.extend(err.args[0])
        except OSError as why:
            errors.append((srcentry, dstpath, str(why)))
    try:
        if not dry_run:
            copystat(src, dst)
    except OSError as why:
        # Copying file access times may fail on Windows
        if getattr(why, "winerror", None) is None:
            errors.append((src, dst, str(why)))
    if errors:
        raise Error(errors)
    return files_copied


def _filter_ignored(src: Path, patterns: Set[str], current_dir: Path, entries: List[Path]) -> List[Path]:
    relative_dir = current_dir.relative_to(src)
    names = [str(relative_dir / entry.name) for entry in entries]
    ignored_names = set()
    for pattern in patterns:
        ignored_names.update(fnmatch.filter(names, pattern))
    return [entry for entry in entries if str(relative_dir / entry.name) not in ignored_names]


def _parse_lightningignore(lines: Tuple[str]) -> Set[str]:
    """Creates a set that removes empty lines and comments."""
    lines = [ln.strip() for ln in lines]
    # removes first `/` character for posix and `\\` for windows
    lines = [ln.lstrip("/").lstrip("\\") for ln in lines if ln != "" and not ln.startswith("#")]
    # convert to path and converting back to string to sanitize the pattern
    return {str(Path(ln)) for ln in lines}


def _read_lightningignore(path: Path) -> Set[str]:
    """Reads ignore file and filter and empty lines. This will also remove patterns that start with a `/`. That's
    done to allow `glob` to simulate the behavior done by `git` where it interprets that as a root path.

    Parameters
    ----------
    path: Path
        Path to .lightningignore file or equivalent.

    Returns
    -------
    Set[str]
        Set of unique lines.
    """
    raw_lines = path.open().readlines()
    return _parse_lightningignore(raw_lines)


def _ignore_filename_spell_check(src: Path):
    possible_spelling_mistakes = [
        ".gridignore",
        ".lightingignore",
        ".lightinginore",
        ".lightninginore",
        ".lightninignore",
        ".lightinignore",
    ]
    possible_spelling_mistakes.extend([p.lstrip(".") for p in possible_spelling_mistakes])
    for path in src.iterdir():
        if path.is_file() and path.name in possible_spelling_mistakes:
            logger.warn(
                f"Lightning uses `{DOT_IGNORE_FILENAME}` as the ignore file but found {path.name} at "
                f"{path.parent} instead. If this was a mistake, please rename the file."
            )
