"""
This module provides utility methods for dealing with path-specs.
"""

import os
import os.path
import pathlib
import posixpath
import stat
import sys
import warnings
from collections.abc import (
	Collection as CollectionType,
	Iterable as IterableType)
from os import (
	PathLike)
from typing import (
	Any,
	AnyStr,
	Callable,
	Collection,
	Dict,
	Iterable,
	Iterator,
	List,
	Optional,
	Sequence,
	Set,
	Union)

from .pattern import (
	Pattern)

if sys.version_info >= (3, 9):
	StrPath = Union[str, PathLike[str]]
else:
	StrPath = Union[str, PathLike]

NORMALIZE_PATH_SEPS = [
	__sep
	for __sep in [os.sep, os.altsep]
	if __sep and __sep != posixpath.sep
]
"""
*NORMALIZE_PATH_SEPS* (:class:`list` of :class:`str`) contains the path
separators that need to be normalized to the POSIX separator for the
current operating system. The separators are determined by examining
:data:`os.sep` and :data:`os.altsep`.
"""

_registered_patterns = {}
"""
*_registered_patterns* (:class:`dict`) maps a name (:class:`str`) to the
registered pattern factory (:class:`~collections.abc.Callable`).
"""


def append_dir_sep(path: pathlib.Path) -> str:
	"""
	Appends the path separator to the path if the path is a directory.
	This can be used to aid in distinguishing between directories and
	files on the file-system by relying on the presence of a trailing path
	separator.

	*path* (:class:`pathlib.path`) is the path to use.

	Returns the path (:class:`str`).
	"""
	str_path = str(path)
	if path.is_dir():
		str_path += os.sep

	return str_path


def detailed_match_files(
	patterns: Iterable[Pattern],
	files: Iterable[str],
	all_matches: Optional[bool] = None,
) -> Dict[str, 'MatchDetail']:
	"""
	Matches the files to the patterns, and returns which patterns matched
	the files.

	*patterns* (:class:`~collections.abc.Iterable` of :class:`~pathspec.pattern.Pattern`)
	contains the patterns to use.

	*files* (:class:`~collections.abc.Iterable` of :class:`str`) contains
	the normalized file paths to be matched against *patterns*.

	*all_matches* (:class:`boot` or :data:`None`) is whether to return all
	matches patterns (:data:`True`), or only the last matched pattern
	(:data:`False`). Default is :data:`None` for :data:`False`.

	Returns the matched files (:class:`dict`) which maps each matched file
	(:class:`str`) to the patterns that matched in order (:class:`.MatchDetail`).
	"""
	all_files = files if isinstance(files, CollectionType) else list(files)
	return_files = {}
	for pattern in patterns:
		if pattern.include is not None:
			result_files = pattern.match(all_files)  # TODO: Replace with `.match_file()`.
			if pattern.include:
				# Add files and record pattern.
				for result_file in result_files:
					if result_file in return_files:
						if all_matches:
							return_files[result_file].patterns.append(pattern)
						else:
							return_files[result_file].patterns[0] = pattern
					else:
						return_files[result_file] = MatchDetail([pattern])

			else:
				# Remove files.
				for file in result_files:
					del return_files[file]

	return return_files


def _filter_patterns(patterns: Iterable[Pattern]) -> List[Pattern]:
	"""
	Filters out null-patterns.

	*patterns* (:class:`Iterable` of :class:`.Pattern`) contains the
	patterns.

	Returns the patterns (:class:`list` of :class:`.Pattern`).
	"""
	return [
		__pat
		for __pat in patterns
		if __pat.include is not None
	]


def _is_iterable(value: Any) -> bool:
	"""
	Check whether the value is an iterable (excludes strings).

	*value* is the value to check,

	Returns whether *value* is a iterable (:class:`bool`).
	"""
	return isinstance(value, IterableType) and not isinstance(value, (str, bytes))


def iter_tree_entries(
	root: StrPath,
	on_error: Optional[Callable] = None,
	follow_links: Optional[bool] = None,
) -> Iterator['TreeEntry']:
	"""
	Walks the specified directory for all files and directories.

	*root* (:class:`str` or :class:`os.PathLike[str]`) is the root directory to
	search.

	*on_error* (:class:`~collections.abc.Callable` or :data:`None`)
	optionally is the error handler for file-system exceptions. It will be
	called with the exception (:exc:`OSError`). Reraise the exception to
	abort the walk. Default is :data:`None` to ignore file-system
	exceptions.

	*follow_links* (:class:`bool` or :data:`None`) optionally is whether
	to walk symbolic links that resolve to directories. Default is
	:data:`None` for :data:`True`.

	Raises :exc:`RecursionError` if recursion is detected.

	Returns an :class:`~collections.abc.Iterator` yielding each file or
	directory entry (:class:`.TreeEntry`) relative to *root*.
	"""
	if on_error is not None and not callable(on_error):
		raise TypeError(f"on_error:{on_error!r} is not callable.")

	if follow_links is None:
		follow_links = True

	yield from _iter_tree_entries_next(os.path.abspath(root), '', {}, on_error, follow_links)


def _iter_tree_entries_next(
	root_full: str,
	dir_rel: str,
	memo: Dict[str, str],
	on_error: Callable,
	follow_links: bool,
) -> Iterator['TreeEntry']:
	"""
	Scan the directory for all descendant files.

	*root_full* (:class:`str`) the absolute path to the root directory.

	*dir_rel* (:class:`str`) the path to the directory to scan relative to
	*root_full*.

	*memo* (:class:`dict`) keeps track of ancestor directories
	encountered. Maps each ancestor real path (:class:`str`) to relative
	path (:class:`str`).

	*on_error* (:class:`~collections.abc.Callable` or :data:`None`)
	optionally is the error handler for file-system exceptions.

	*follow_links* (:class:`bool`) is whether to walk symbolic links that
	resolve to directories.

	Yields each entry (:class:`.TreeEntry`).
	"""
	dir_full = os.path.join(root_full, dir_rel)
	dir_real = os.path.realpath(dir_full)

	# Remember each encountered ancestor directory and its canonical
	# (real) path. If a canonical path is encountered more than once,
	# recursion has occurred.
	if dir_real not in memo:
		memo[dir_real] = dir_rel
	else:
		raise RecursionError(real_path=dir_real, first_path=memo[dir_real], second_path=dir_rel)

	with os.scandir(dir_full) as scan_iter:
		node_ent: os.DirEntry
		for node_ent in scan_iter:
			node_rel = os.path.join(dir_rel, node_ent.name)

			# Inspect child node.
			try:
				node_lstat = node_ent.stat(follow_symlinks=False)
			except OSError as e:
				if on_error is not None:
					on_error(e)
				continue

			if node_ent.is_symlink():
				# Child node is a link, inspect the target node.
				try:
					node_stat = node_ent.stat()
				except OSError as e:
					if on_error is not None:
						on_error(e)
					continue
			else:
				node_stat = node_lstat

			if node_ent.is_dir(follow_symlinks=follow_links):
				# Child node is a directory, recurse into it and yield its
				# descendant files.
				yield TreeEntry(node_ent.name, node_rel, node_lstat, node_stat)

				yield from _iter_tree_entries_next(root_full, node_rel, memo, on_error, follow_links)

			elif node_ent.is_file() or node_ent.is_symlink():
				# Child node is either a file or an unfollowed link, yield it.
				yield TreeEntry(node_ent.name, node_rel, node_lstat, node_stat)

	# NOTE: Make sure to remove the canonical (real) path of the directory
	# from the ancestors memo once we are done with it. This allows the
	# same directory to appear multiple times. If this is not done, the
	# second occurrence of the directory will be incorrectly interpreted
	# as a recursion. See <https://github.com/cpburnz/python-path-specification/pull/7>.
	del memo[dir_real]


def iter_tree_files(
	root: StrPath,
	on_error: Optional[Callable] = None,
	follow_links: Optional[bool] = None,
) -> Iterator[str]:
	"""
	Walks the specified directory for all files.

	*root* (:class:`str` or :class:`os.PathLike[str]`) is the root directory to
	search for files.

	*on_error* (:class:`~collections.abc.Callable` or :data:`None`)
	optionally is the error handler for file-system exceptions. It will be
	called with the exception (:exc:`OSError`). Reraise the exception to
	abort the walk. Default is :data:`None` to ignore file-system
	exceptions.

	*follow_links* (:class:`bool` or :data:`None`) optionally is whether
	to walk symbolic links that resolve to directories. Default is
	:data:`None` for :data:`True`.

	Raises :exc:`RecursionError` if recursion is detected.

	Returns an :class:`~collections.abc.Iterator` yielding the path to
	each file (:class:`str`) relative to *root*.
	"""
	for entry in iter_tree_entries(root, on_error=on_error, follow_links=follow_links):
		if not entry.is_dir(follow_links):
			yield entry.path


def iter_tree(root, on_error=None, follow_links=None):
	"""
	DEPRECATED: The :func:`.iter_tree` function is an alias for the
	:func:`.iter_tree_files` function.
	"""
	warnings.warn((
		"util.iter_tree() is deprecated. Use util.iter_tree_files() instead."
	), DeprecationWarning, stacklevel=2)
	return iter_tree_files(root, on_error=on_error, follow_links=follow_links)


def lookup_pattern(name: str) -> Callable[[AnyStr], Pattern]:
	"""
	Lookups a registered pattern factory by name.

	*name* (:class:`str`) is the name of the pattern factory.

	Returns the registered pattern factory (:class:`~collections.abc.Callable`).
	If no pattern factory is registered, raises :exc:`KeyError`.
	"""
	return _registered_patterns[name]


def match_file(patterns: Iterable[Pattern], file: str) -> bool:
	"""
	Matches the file to the patterns.

	*patterns* (:class:`~collections.abc.Iterable` of :class:`~pathspec.pattern.Pattern`)
	contains the patterns to use.

	*file* (:class:`str`) is the normalized file path to be matched
	against *patterns*.

	Returns :data:`True` if *file* matched; otherwise, :data:`False`.
	"""
	matched = False
	for pattern in patterns:
		if pattern.include is not None:
			if pattern.match_file(file) is not None:
				matched = pattern.include

	return matched


def match_files(
	patterns: Iterable[Pattern],
	files: Iterable[str],
) -> Set[str]:
	"""
	DEPRECATED: This is an old function no longer used. Use the :func:`.match_file`
	function with a loop for better results.

	Matches the files to the patterns.

	*patterns* (:class:`~collections.abc.Iterable` of :class:`~pathspec.pattern.Pattern`)
	contains the patterns to use.

	*files* (:class:`~collections.abc.Iterable` of :class:`str`) contains
	the normalized file paths to be matched against *patterns*.

	Returns the matched files (:class:`set` of :class:`str`).
	"""
	warnings.warn((
		"util.match_files() is deprecated. Use util.match_file() with a "
		"loop for better results."
	), DeprecationWarning, stacklevel=2)

	use_patterns = _filter_patterns(patterns)

	return_files = set()
	for file in files:
		if match_file(use_patterns, file):
			return_files.add(file)

	return return_files


def normalize_file(
	file: StrPath,
	separators: Optional[Collection[str]] = None,
) -> str:
	"""
	Normalizes the file path to use the POSIX path separator (i.e.,
	:data:`'/'`), and make the paths relative (remove leading :data:`'/'`).

	*file* (:class:`str` or :class:`os.PathLike[str]`) is the file path.

	*separators* (:class:`~collections.abc.Collection` of :class:`str`; or
	:data:`None`) optionally contains the path separators to normalize.
	This does not need to include the POSIX path separator (:data:`'/'`),
	but including it will not affect the results. Default is :data:`None`
	for :data:`NORMALIZE_PATH_SEPS`. To prevent normalization, pass an
	empty container (e.g., an empty tuple :data:`()`).

	Returns the normalized file path (:class:`str`).
	"""
	# Normalize path separators.
	if separators is None:
		separators = NORMALIZE_PATH_SEPS

	# Convert path object to string.
	norm_file: str = os.fspath(file)

	for sep in separators:
		norm_file = norm_file.replace(sep, posixpath.sep)

	if norm_file.startswith('/'):
		# Make path relative.
		norm_file = norm_file[1:]

	elif norm_file.startswith('./'):
		# Remove current directory prefix.
		norm_file = norm_file[2:]

	return norm_file


def normalize_files(
	files: Iterable[StrPath],
	separators: Optional[Collection[str]] = None,
) -> Dict[str, List[StrPath]]:
	"""
	DEPRECATED: This function is no longer used. Use the :func:`.normalize_file`
	function with a loop for better results.

	Normalizes the file paths to use the POSIX path separator.

	*files* (:class:`~collections.abc.Iterable` of :class:`str` or
	:class:`os.PathLike[str]`) contains the file paths to be normalized.

	*separators* (:class:`~collections.abc.Collection` of :class:`str`; or
	:data:`None`) optionally contains the path separators to normalize.
	See :func:`normalize_file` for more information.

	Returns a :class:`dict` mapping each normalized file path (:class:`str`)
	to the original file paths (:class:`list` of :class:`str` or
	:class:`os.PathLike[str]`).
	"""
	warnings.warn((
		"util.normalize_files() is deprecated. Use util.normalize_file() "
		"with a loop for better results."
	), DeprecationWarning, stacklevel=2)

	norm_files = {}
	for path in files:
		norm_file = normalize_file(path, separators=separators)
		if norm_file in norm_files:
			norm_files[norm_file].append(path)
		else:
			norm_files[norm_file] = [path]

	return norm_files


def register_pattern(
	name: str,
	pattern_factory: Callable[[AnyStr], Pattern],
	override: Optional[bool] = None,
) -> None:
	"""
	Registers the specified pattern factory.

	*name* (:class:`str`) is the name to register the pattern factory
	under.

	*pattern_factory* (:class:`~collections.abc.Callable`) is used to
	compile patterns. It must accept an uncompiled pattern (:class:`str`)
	and return the compiled pattern (:class:`.Pattern`).

	*override* (:class:`bool` or :data:`None`) optionally is whether to
	allow overriding an already registered pattern under the same name
	(:data:`True`), instead of raising an :exc:`AlreadyRegisteredError`
	(:data:`False`). Default is :data:`None` for :data:`False`.
	"""
	if not isinstance(name, str):
		raise TypeError(f"name:{name!r} is not a string.")

	if not callable(pattern_factory):
		raise TypeError(f"pattern_factory:{pattern_factory!r} is not callable.")

	if name in _registered_patterns and not override:
		raise AlreadyRegisteredError(name, _registered_patterns[name])

	_registered_patterns[name] = pattern_factory


class AlreadyRegisteredError(Exception):
	"""
	The :exc:`AlreadyRegisteredError` exception is raised when a pattern
	factory is registered under a name already in use.
	"""

	def __init__(
		self,
		name: str,
		pattern_factory: Callable[[AnyStr], Pattern],
	) -> None:
		"""
		Initializes the :exc:`AlreadyRegisteredError` instance.

		*name* (:class:`str`) is the name of the registered pattern.

		*pattern_factory* (:class:`~collections.abc.Callable`) is the
		registered pattern factory.
		"""
		super(AlreadyRegisteredError, self).__init__(name, pattern_factory)

	@property
	def message(self) -> str:
		"""
		*message* (:class:`str`) is the error message.
		"""
		return "{name!r} is already registered for pattern factory:{pattern_factory!r}.".format(
			name=self.name,
			pattern_factory=self.pattern_factory,
		)

	@property
	def name(self) -> str:
		"""
		*name* (:class:`str`) is the name of the registered pattern.
		"""
		return self.args[0]

	@property
	def pattern_factory(self) -> Callable[[AnyStr], Pattern]:
		"""
		*pattern_factory* (:class:`~collections.abc.Callable`) is the
		registered pattern factory.
		"""
		return self.args[1]


class RecursionError(Exception):
	"""
	The :exc:`RecursionError` exception is raised when recursion is
	detected.
	"""

	def __init__(
		self,
		real_path: str,
		first_path: str,
		second_path: str,
	) -> None:
		"""
		Initializes the :exc:`RecursionError` instance.

		*real_path* (:class:`str`) is the real path that recursion was
		encountered on.

		*first_path* (:class:`str`) is the first path encountered for
		*real_path*.

		*second_path* (:class:`str`) is the second path encountered for
		*real_path*.
		"""
		super(RecursionError, self).__init__(real_path, first_path, second_path)

	@property
	def first_path(self) -> str:
		"""
		*first_path* (:class:`str`) is the first path encountered for
		:attr:`self.real_path <RecursionError.real_path>`.
		"""
		return self.args[1]

	@property
	def message(self) -> str:
		"""
		*message* (:class:`str`) is the error message.
		"""
		return "Real path {real!r} was encountered at {first!r} and then {second!r}.".format(
			real=self.real_path,
			first=self.first_path,
			second=self.second_path,
		)

	@property
	def real_path(self) -> str:
		"""
		*real_path* (:class:`str`) is the real path that recursion was
		encountered on.
		"""
		return self.args[0]

	@property
	def second_path(self) -> str:
		"""
		*second_path* (:class:`str`) is the second path encountered for
		:attr:`self.real_path <RecursionError.real_path>`.
		"""
		return self.args[2]


class MatchDetail(object):
	"""
	The :class:`.MatchDetail` class contains information about
	"""

	# Make the class dict-less.
	__slots__ = ('patterns',)

	def __init__(self, patterns: Sequence[Pattern]) -> None:
		"""
		Initialize the :class:`.MatchDetail` instance.

		*patterns* (:class:`~collections.abc.Sequence` of :class:`~pathspec.pattern.Pattern`)
		contains the patterns that matched the file in the order they were
		encountered.
		"""

		self.patterns = patterns
		"""
		*patterns* (:class:`~collections.abc.Sequence` of :class:`~pathspec.pattern.Pattern`)
		contains the patterns that matched the file in the order they were
		encountered.
		"""


class TreeEntry(object):
	"""
	The :class:`.TreeEntry` class contains information about a file-system
	entry.
	"""

	# Make the class dict-less.
	__slots__ = ('_lstat', 'name', 'path', '_stat')

	def __init__(
		self,
		name: str,
		path: str,
		lstat: os.stat_result,
		stat: os.stat_result,
	) -> None:
		"""
		Initialize the :class:`.TreeEntry` instance.

		*name* (:class:`str`) is the base name of the entry.

		*path* (:class:`str`) is the relative path of the entry.

		*lstat* (:class:`os.stat_result`) is the stat result of the direct
		entry.

		*stat* (:class:`os.stat_result`) is the stat result of the entry,
		potentially linked.
		"""

		self._lstat: os.stat_result = lstat
		"""
		*_lstat* (:class:`os.stat_result`) is the stat result of the direct
		entry.
		"""

		self.name: str = name
		"""
		*name* (:class:`str`) is the base name of the entry.
		"""

		self.path: str = path
		"""
		*path* (:class:`str`) is the path of the entry.
		"""

		self._stat: os.stat_result = stat
		"""
		*_stat* (:class:`os.stat_result`) is the stat result of the linked
		entry.
		"""

	def is_dir(self, follow_links: Optional[bool] = None) -> bool:
		"""
		Get whether the entry is a directory.

		*follow_links* (:class:`bool` or :data:`None`) is whether to follow
		symbolic links. If this is :data:`True`, a symlink to a directory
		will result in :data:`True`. Default is :data:`None` for :data:`True`.

		Returns whether the entry is a directory (:class:`bool`).
		"""
		if follow_links is None:
			follow_links = True

		node_stat = self._stat if follow_links else self._lstat
		return stat.S_ISDIR(node_stat.st_mode)

	def is_file(self, follow_links: Optional[bool] = None) -> bool:
		"""
		Get whether the entry is a regular file.

		*follow_links* (:class:`bool` or :data:`None`) is whether to follow
		symbolic links. If this is :data:`True`, a symlink to a regular file
		will result in :data:`True`. Default is :data:`None` for :data:`True`.

		Returns whether the entry is a regular file (:class:`bool`).
		"""
		if follow_links is None:
			follow_links = True

		node_stat = self._stat if follow_links else self._lstat
		return stat.S_ISREG(node_stat.st_mode)

	def is_symlink(self) -> bool:
		"""
		Returns whether the entry is a symbolic link (:class:`bool`).
		"""
		return stat.S_ISLNK(self._lstat.st_mode)

	def stat(self, follow_links: Optional[bool] = None) -> os.stat_result:
		"""
		Get the cached stat result for the entry.

		*follow_links* (:class:`bool` or :data:`None`) is whether to follow
		symbolic links. If this is :data:`True`, the stat result of the
		linked file will be returned. Default is :data:`None` for :data:`True`.

		Returns that stat result (:class:`os.stat_result`).
		"""
		if follow_links is None:
			follow_links = True

		return self._stat if follow_links else self._lstat
