import os
import re
import fnmatch
import functools
import operator


special_parts = ('', '.', '..')
magic_check = re.compile('([*?[])')
magic_check_bytes = re.compile(b'([*?[])')
no_recurse_symlinks = object()


def translate(pat, *, recursive=False, include_hidden=False, seps=None):
    """Translate a pathname with shell wildcards to a regular expression.

    If `recursive` is true, the pattern segment '**' will match any number of
    path segments.

    If `include_hidden` is true, wildcards can match path segments beginning
    with a dot ('.').

    If a sequence of separator characters is given to `seps`, they will be
    used to split the pattern into segments and match path separators. If not
    given, os.path.sep and os.path.altsep (where available) are used.
    """
    if not seps:
        if os.path.altsep:
            seps = (os.path.sep, os.path.altsep)
        else:
            seps = os.path.sep
    escaped_seps = ''.join(map(re.escape, seps))
    any_sep = f'[{escaped_seps}]' if len(seps) > 1 else escaped_seps
    not_sep = f'[^{escaped_seps}]'
    if include_hidden:
        one_last_segment = f'{not_sep}+'
        one_segment = f'{one_last_segment}{any_sep}'
        any_segments = f'(?:.+{any_sep})?'
        any_last_segments = '.*'
    else:
        one_last_segment = f'[^{escaped_seps}.]{not_sep}*'
        one_segment = f'{one_last_segment}{any_sep}'
        any_segments = f'(?:{one_segment})*'
        any_last_segments = f'{any_segments}(?:{one_last_segment})?'

    results = []
    parts = re.split(any_sep, pat)
    last_part_idx = len(parts) - 1
    for idx, part in enumerate(parts):
        if part == '*':
            results.append(one_segment if idx < last_part_idx else one_last_segment)
        elif recursive and part == '**':
            if idx < last_part_idx:
                if parts[idx + 1] != '**':
                    results.append(any_segments)
            else:
                results.append(any_last_segments)
        else:
            if part:
                if not include_hidden and part[0] in '*?':
                    results.append(r'(?!\.)')
                results.extend(fnmatch._translate(part, f'{not_sep}*', not_sep))
            if idx < last_part_idx:
                results.append(any_sep)
    res = ''.join(results)
    return fr'(?s:{res})\Z'


@functools.lru_cache(maxsize=512)
def compile_pattern(pat, sep, case_sensitive, recursive=True):
    """Compile given glob pattern to a re.Pattern object (observing case
    sensitivity)."""
    flags = re.NOFLAG if case_sensitive else re.IGNORECASE
    regex = translate(pat, recursive=recursive, include_hidden=True, seps=sep)
    return re.compile(regex, flags=flags).match


class Globber:
    """Class providing shell-style pattern matching and globbing.
    """

    def __init__(self, sep, case_sensitive, case_pedantic=False, recursive=False):
        self.sep = sep
        self.case_sensitive = case_sensitive
        self.case_pedantic = case_pedantic
        self.recursive = recursive

    # Low-level methods

    lstat = operator.methodcaller('lstat')
    add_slash = operator.methodcaller('joinpath', '')

    @staticmethod
    def scandir(path):
        """Emulates os.scandir(), which returns an object that can be used as
        a context manager. This method is called by walk() and glob().
        """
        from contextlib import nullcontext
        return nullcontext(path.iterdir())

    @staticmethod
    def concat_path(path, text):
        """Appends text to the given path.
        """
        return path.with_segments(path._raw_path + text)

    @staticmethod
    def parse_entry(entry):
        """Returns the path of an entry yielded from scandir().
        """
        return entry

    # High-level methods

    def compile(self, pat):
        return compile_pattern(pat, self.sep, self.case_sensitive, self.recursive)

    def selector(self, parts):
        """Returns a function that selects from a given path, walking and
        filtering according to the glob-style pattern parts in *parts*.
        """
        if not parts:
            return self.select_exists
        part = parts.pop()
        if self.recursive and part == '**':
            selector = self.recursive_selector
        elif part in special_parts:
            selector = self.special_selector
        elif not self.case_pedantic and magic_check.search(part) is None:
            selector = self.literal_selector
        else:
            selector = self.wildcard_selector
        return selector(part, parts)

    def special_selector(self, part, parts):
        """Returns a function that selects special children of the given path.
        """
        select_next = self.selector(parts)

        def select_special(path, exists=False):
            path = self.concat_path(self.add_slash(path), part)
            return select_next(path, exists)
        return select_special

    def literal_selector(self, part, parts):
        """Returns a function that selects a literal descendant of a path.
        """

        # Optimization: consume and join any subsequent literal parts here,
        # rather than leaving them for the next selector. This reduces the
        # number of string concatenation operations and calls to add_slash().
        while parts and magic_check.search(parts[-1]) is None:
            part += self.sep + parts.pop()

        select_next = self.selector(parts)

        def select_literal(path, exists=False):
            path = self.concat_path(self.add_slash(path), part)
            return select_next(path, exists=False)
        return select_literal

    def wildcard_selector(self, part, parts):
        """Returns a function that selects direct children of a given path,
        filtering by pattern.
        """

        match = None if part == '*' else self.compile(part)
        dir_only = bool(parts)
        if dir_only:
            select_next = self.selector(parts)

        def select_wildcard(path, exists=False):
            try:
                # We must close the scandir() object before proceeding to
                # avoid exhausting file descriptors when globbing deep trees.
                with self.scandir(path) as scandir_it:
                    entries = list(scandir_it)
            except OSError:
                pass
            else:
                for entry in entries:
                    if match is None or match(entry.name):
                        if dir_only:
                            try:
                                if not entry.is_dir():
                                    continue
                            except OSError:
                                continue
                        entry_path = self.parse_entry(entry)
                        if dir_only:
                            yield from select_next(entry_path, exists=True)
                        else:
                            yield entry_path
        return select_wildcard

    def recursive_selector(self, part, parts):
        """Returns a function that selects a given path and all its children,
        recursively, filtering by pattern.
        """
        # Optimization: consume following '**' parts, which have no effect.
        while parts and parts[-1] == '**':
            parts.pop()

        # Optimization: consume and join any following non-special parts here,
        # rather than leaving them for the next selector. They're used to
        # build a regular expression, which we use to filter the results of
        # the recursive walk. As a result, non-special pattern segments
        # following a '**' wildcard don't require additional filesystem access
        # to expand.
        follow_symlinks = self.recursive is not no_recurse_symlinks
        if follow_symlinks:
            while parts and parts[-1] not in special_parts:
                part += self.sep + parts.pop()

        match = None if part == '**' else self.compile(part)
        dir_only = bool(parts)
        select_next = self.selector(parts)

        def select_recursive(path, exists=False):
            path = self.add_slash(path)
            match_pos = len(str(path))
            if match is None or match(str(path), match_pos):
                yield from select_next(path, exists)
            stack = [path]
            while stack:
                yield from select_recursive_step(stack, match_pos)

        def select_recursive_step(stack, match_pos):
            path = stack.pop()
            try:
                # We must close the scandir() object before proceeding to
                # avoid exhausting file descriptors when globbing deep trees.
                with self.scandir(path) as scandir_it:
                    entries = list(scandir_it)
            except OSError:
                pass
            else:
                for entry in entries:
                    is_dir = False
                    try:
                        if entry.is_dir(follow_symlinks=follow_symlinks):
                            is_dir = True
                    except OSError:
                        pass

                    if is_dir or not dir_only:
                        entry_path = self.parse_entry(entry)
                        if match is None or match(str(entry_path), match_pos):
                            if dir_only:
                                yield from select_next(entry_path, exists=True)
                            else:
                                # Optimization: directly yield the path if this is
                                # last pattern part.
                                yield entry_path
                        if is_dir:
                            stack.append(entry_path)

        return select_recursive

    def select_exists(self, path, exists=False):
        """Yields the given path, if it exists.
        """
        if exists:
            # Optimization: this path is already known to exist, e.g. because
            # it was returned from os.scandir(), so we skip calling lstat().
            yield path
        else:
            try:
                self.lstat(path)
                yield path
            except OSError:
                pass

    @classmethod
    def walk(cls, root, top_down, on_error, follow_symlinks):
        """Walk the directory tree from the given root, similar to os.walk().
        """
        paths = [root]
        while paths:
            path = paths.pop()
            if isinstance(path, tuple):
                yield path
                continue
            try:
                with cls.scandir(path) as scandir_it:
                    dirnames = []
                    filenames = []
                    if not top_down:
                        paths.append((path, dirnames, filenames))
                    for entry in scandir_it:
                        name = entry.name
                        try:
                            if entry.is_dir(follow_symlinks=follow_symlinks):
                                if not top_down:
                                    paths.append(cls.parse_entry(entry))
                                dirnames.append(name)
                            else:
                                filenames.append(name)
                        except OSError:
                            filenames.append(name)
            except OSError as error:
                if on_error is not None:
                    on_error(error)
            else:
                if top_down:
                    yield path, dirnames, filenames
                    if dirnames:
                        prefix = cls.add_slash(path)
                        paths += [cls.concat_path(prefix, d) for d in reversed(dirnames)]


class StringGlobber(Globber):
    lstat = staticmethod(os.lstat)
    scandir = staticmethod(os.scandir)
    parse_entry = operator.attrgetter('path')
    concat_path = operator.add

    if os.name == 'nt':
        @staticmethod
        def add_slash(pathname):
            tail = os.path.splitroot(pathname)[2]
            if not tail or tail[-1] in '\\/':
                return pathname
            return f'{pathname}\\'
    else:
        @staticmethod
        def add_slash(pathname):
            if not pathname or pathname[-1] == '/':
                return pathname
            return f'{pathname}/'