import collections
import functools
import textwrap

from ..constants import *  # NOQA
from ..helpers.nanorst import rst_to_terminal


class HelpMixIn:
    helptext = collections.OrderedDict()
    helptext["patterns"] = textwrap.dedent(
        """
        When specifying one or more file paths in a Borg command that supports
        patterns for the respective option or argument, you can apply the
        patterns described here to include only desired files and/or exclude
        unwanted ones. Patterns can be used

        - for ``--exclude`` option,
        - in the file given with ``--exclude-from`` option,
        - for ``--pattern`` option,
        - in the file given with ``--patterns-from`` option and
        - for ``PATH`` arguments that explicitly support them.

        The path/filenames used as input for the pattern matching start with the
        currently active recursion root. You usually give the recursion root(s)
        when invoking borg and these can be either relative or absolute paths.

        Be careful, your patterns must match the archived paths:

        - Archived paths never start with a leading slash ('/'), nor with '.', nor with '..'.

          - When you back up absolute paths like ``/home/user``, the archived
            paths start with ``home/user``.
          - When you back up relative paths like ``./src``, the archived paths
            start with ``src``.
          - When you back up relative paths like ``../../src``, the archived paths
            start with ``src``.

        Borg supports different pattern styles. To define a non-default
        style for a specific pattern, prefix it with two characters followed
        by a colon ':' (i.e. ``fm:path/*``, ``sh:path/**``).

        The default pattern style for ``--exclude`` differs from ``--pattern``, see below.

        `Fnmatch <https://docs.python.org/3/library/fnmatch.html>`_, selector ``fm:``
            This is the default style for ``--exclude`` and ``--exclude-from``.
            These patterns use a variant of shell pattern syntax, with '\\*' matching
            any number of characters, '?' matching any single character, '[...]'
            matching any single character specified, including ranges, and '[!...]'
            matching any character not specified. For the purpose of these patterns,
            the path separator (backslash for Windows and '/' on other systems) is not
            treated specially. Wrap meta-characters in brackets for a literal
            match (i.e. ``[?]`` to match the literal character '?'). For a path
            to match a pattern, the full path must match, or it must match
            from the start of the full path to just before a path separator. Except
            for the root path, paths will never end in the path separator when
            matching is attempted.  Thus, if a given pattern ends in a path
            separator, a '\\*' is appended before matching is attempted. A leading
            path separator is always removed.

        Shell-style patterns, selector ``sh:``
            This is the default style for ``--pattern`` and ``--patterns-from``.
            Like fnmatch patterns these are similar to shell patterns. The difference
            is that the pattern may include ``**/`` for matching zero or more directory
            levels, ``*`` for matching zero or more arbitrary characters with the
            exception of any path separator, ``{}`` containing comma-separated
            alternative patterns. A leading path separator is always removed.

        `Regular expressions <https://docs.python.org/3/library/re.html>`_, selector ``re:``
            Unlike shell patterns, regular expressions are not required to match the full
            path and any substring match is sufficient. It is strongly recommended to
            anchor patterns to the start ('^'), to the end ('$') or both. Path
            separators (backslash for Windows and '/' on other systems) in paths are
            always normalized to a forward slash '/' before applying a pattern.

        Path prefix, selector ``pp:``
            This pattern style is useful to match whole subdirectories. The pattern
            ``pp:root/somedir`` matches ``root/somedir`` and everything therein.
            A leading path separator is always removed.

        Path full-match, selector ``pf:``
            This pattern style is (only) useful to match full paths.
            This is kind of a pseudo pattern as it cannot have any variable or
            unspecified parts - the full path must be given. ``pf:root/file.ext``
            matches ``root/file.ext`` only. A leading path separator is always
            removed.

            Implementation note: this is implemented via very time-efficient O(1)
            hashtable lookups (this means you can have huge amounts of such patterns
            without impacting performance much).
            Due to that, this kind of pattern does not respect any context or order.
            If you use such a pattern to include a file, it will always be included
            (if the directory recursion encounters it).
            Other include/exclude patterns that would normally match will be ignored.
            Same logic applies for exclude.

        .. note::

            ``re:``, ``sh:`` and ``fm:`` patterns are all implemented on top of
            the Python SRE engine. It is very easy to formulate patterns for each
            of these types which requires an inordinate amount of time to match
            paths. If untrusted users are able to supply patterns, ensure they
            cannot supply ``re:`` patterns. Further, ensure that ``sh:`` and
            ``fm:`` patterns only contain a handful of wildcards at most.

        Exclusions can be passed via the command line option ``--exclude``. When used
        from within a shell, the patterns should be quoted to protect them from
        expansion.

        Patterns matching special characters, e.g. whitespace, within a shell may
        require adjustments, such as putting quotation marks around the arguments.
        Example:
        Using bash, the following command line option would match and exclude "item name":
        ``--pattern='-path/item name'``
        Note that when patterns are used within a pattern file directly read by borg,
        e.g. when using ``--exclude-from`` or ``--patterns-from``, there is no shell
        involved and thus no quotation marks are required.

        The ``--exclude-from`` option permits loading exclusion patterns from a text
        file with one pattern per line. Lines empty or starting with the hash sign
        '#' after removing whitespace on both ends are ignored. The optional style
        selector prefix is also supported for patterns loaded from a file. Due to
        whitespace removal, paths with whitespace at the beginning or end can only be
        excluded using regular expressions.

        To test your exclusion patterns without performing an actual backup you can
        run ``borg create --list --dry-run ...``.

        Examples::

            # Exclude a directory anywhere in the tree named ``steamapps/common``
            # (and everything below it), regardless of where it appears:
            $ borg create -e 'sh:**/steamapps/common/**' archive /

            # Exclude the contents of ``/home/user/.cache``:
            $ borg create -e 'sh:home/user/.cache/**' archive /home/user
            $ borg create -e home/user/.cache/ archive /home/user

            # The file '/home/user/.cache/important' is *not* backed up:
            $ borg create -e home/user/.cache/ archive / /home/user/.cache/important

            # Exclude '/home/user/file.o' but not '/home/user/file.odt':
            $ borg create -e '*.o' archive /

            # Exclude '/home/user/junk' and '/home/user/subdir/junk' but
            # not '/home/user/importantjunk' or '/etc/junk':
            $ borg create -e 'home/*/junk' archive /


            # The contents of directories in '/home' are not backed up when their name
            # ends in '.tmp'
            $ borg create --exclude 're:^home/[^/]+\\.tmp/' archive /

            # Load exclusions from file
            $ cat >exclude.txt <<EOF
            # Comment line
            home/*/junk
            *.tmp
            fm:aa:something/*
            re:^home/[^/]+\\.tmp/
            sh:home/*/.thumbnails
            # Example with spaces, no need to escape as it is processed by borg
            some file with spaces.txt
            EOF
            $ borg create --exclude-from exclude.txt archive /

        A more general and easier to use way to define filename matching patterns
        exists with the ``--pattern`` and ``--patterns-from`` options. Using
        these, you may specify the backup roots, default pattern styles and
        patterns for inclusion and exclusion.

        Root path prefix ``R``
            A recursion root path starts with the prefix ``R``, followed by a path
            (a plain path, not a file pattern). Use this prefix to have the root
            paths in the patterns file rather than as command line arguments.

        Pattern style prefix ``P`` (only useful within patterns files)
            To change the default pattern style, use the ``P`` prefix, followed by
            the pattern style abbreviation (``fm``, ``pf``, ``pp``, ``re``, ``sh``).
            All patterns following this line in the same patterns file will use this
            style until another style is specified or the end of the file is reached.
            When the current patterns file is finished, the default pattern style will
            reset.

        Exclude pattern prefix ``-``
            Use the prefix ``-``, followed by a pattern, to define an exclusion.
            This has the same effect as the ``--exclude`` option.

        Exclude no-recurse pattern prefix ``!``
            Use the prefix ``!``, followed by a pattern, to define an exclusion
            that does not recurse into subdirectories. This saves time, but
            prevents include patterns to match any files in subdirectories.

        Include pattern prefix ``+``
            Use the prefix ``+``, followed by a pattern, to define inclusions.
            This is useful to include paths that are covered in an exclude
            pattern and would otherwise not be backed up.

        The first matching pattern is used, so if an include pattern matches
        before an exclude pattern, the file is backed up. Note that a no-recurse
        exclude stops examination of subdirectories so that potential includes
        will not match - use normal excludes for such use cases.

        Example::

            # Define the recursion root
            R /
            # Exclude all iso files in any directory
            - **/*.iso
            # Explicitly include all inside etc and root
            + etc/**
            + root/**
            # Exclude a specific directory under each user's home directories
            - home/*/.cache
            # Explicitly include everything in /home
            + home/**
            # Explicitly exclude some directories without recursing into them
            ! re:^(dev|proc|run|sys|tmp)
            # Exclude all other files and directories
            # that are not specifically included earlier.
            - **

        **Tip: You can easily test your patterns with --dry-run and  --list**::

            $ borg create --dry-run --list --patterns-from patterns.txt archive

        This will list the considered files one per line, prefixed with a
        character that indicates the action (e.g. 'x' for excluding, see
        **Item flags** in `borg create` usage docs).

        .. note::

            It is possible that a subdirectory or file is matched while its parent
            directories are not. In that case, parent directories are not backed
            up and thus their user, group, permission, etc. cannot be restored.

        Patterns (``--pattern``) and excludes (``--exclude``) from the command line are
        considered first (in the order of appearance). Then patterns from ``--patterns-from``
        are added. Exclusion patterns from ``--exclude-from`` files are appended last.

        Examples::

            # back up pics, but not the ones from 2018, except the good ones:
            # note: using = is essential to avoid cmdline argument parsing issues.
            borg create --pattern=+pics/2018/good --pattern=-pics/2018 archive pics

            # back up only JPG/JPEG files (case insensitive) in all home directories:
            borg create --pattern '+ re:\\.jpe?g(?i)$' archive /home

            # back up homes, but exclude big downloads (like .ISO files) or hidden files:
            borg create --exclude 're:\\.iso(?i)$' --exclude 'sh:home/**/.*' archive /home

            # use a file with patterns (recursion root '/' via command line):
            borg create --patterns-from patterns.lst archive /

        The patterns.lst file could look like that::

            # "sh:" pattern style is the default
            # exclude caches
            - home/*/.cache
            # include susans home
            + home/susan
            # also back up this exact file
            + pf:home/bobby/specialfile.txt
            # don't back up the other home directories
            - home/*
            # don't even look in /dev, /proc, /run, /sys, /tmp (note: would exclude files like /device, too)
            ! re:^(dev|proc|run|sys|tmp)

        You can specify recursion roots either on the command line or in a patternfile::

            # these two commands do the same thing
            borg create --exclude home/bobby/junk archive /home/bobby /home/susan
            borg create --patterns-from patternfile.lst archive

        patternfile.lst::

            # note that excludes use fm: by default and patternfiles use sh: by default.
            # therefore, we need to specify fm: to have the same exact behavior.
            P fm
            R /home/bobby
            R /home/susan
            - home/bobby/junk

        This allows you to share the same patterns between multiple repositories
        without needing to specify them on the command line.\n\n"""
    )
    helptext["match-archives"] = textwrap.dedent(
        """
        The ``--match-archives`` option matches a given pattern against the list of all archives
        in the repository. It can be given multiple times.

        The patterns can have a prefix of:

        - name: pattern match on the archive name (default)
        - aid: prefix match on the archive id (only one result allowed)
        - user: exact match on the username who created the archive
        - host: exact match on the hostname where the archive was created
        - tags: match on the archive tags

        In case of a name pattern match,
        it uses pattern styles similar to the ones described by ``borg help patterns``:

        Identical match pattern, selector ``id:`` (default)
            Simple string match, must fully match exactly as given.

        Shell-style patterns, selector ``sh:``
            Match like on the shell, wildcards like `*` and `?` work.

        `Regular expressions <https://docs.python.org/3/library/re.html>`_, selector ``re:``
            Full regular expression support.
            This is very powerful, but can also get rather complicated.

        Examples::

            # name match, id: style
            borg delete --match-archives 'id:archive-with-crap'
            borg delete -a 'id:archive-with-crap'  # same, using short option
            borg delete -a 'archive-with-crap'  # same, because 'id:' is the default

            # name match, sh: style
            borg delete -a 'sh:home-kenny-*'

            # name match, re: style
            borg delete -a 're:pc[123]-home-(user1|user2)-2022-09-.*'

            # archive id prefix match:
            borg delete -a 'aid:d34db33f'

            # host or user match
            borg delete -a 'user:kenny'
            borg delete -a 'host:kenny-pc'

            # tags match
            borg delete -a 'tags:TAG1' -a 'tags:TAG2'\n\n"""
    )
    helptext["placeholders"] = textwrap.dedent(
        """
        Repository URLs, ``--name``, ``-a`` / ``--match-archives``, ``--comment``
        and ``--remote-path`` values support these placeholders:

        {hostname}
            The (short) hostname of the machine.

        {fqdn}
            The full name of the machine.

        {reverse-fqdn}
            The full name of the machine in reverse domain name notation.

        {now}
            The current local date and time, by default in ISO-8601 format.
            You can also supply your own `format string <https://docs.python.org/3.10/library/datetime.html#strftime-and-strptime-behavior>`_, e.g. {now:%Y-%m-%d_%H:%M:%S}

        {utcnow}
            The current UTC date and time, by default in ISO-8601 format.
            You can also supply your own `format string <https://docs.python.org/3.10/library/datetime.html#strftime-and-strptime-behavior>`_, e.g. {utcnow:%Y-%m-%d_%H:%M:%S}

        {user}
            The user name (or UID, if no name is available) of the user running borg.

        {pid}
            The current process ID.

        {borgversion}
            The version of borg, e.g.: 1.0.8rc1

        {borgmajor}
            The version of borg, only the major version, e.g.: 1

        {borgminor}
            The version of borg, only major and minor version, e.g.: 1.0

        {borgpatch}
            The version of borg, only major, minor and patch version, e.g.: 1.0.8

        If literal curly braces need to be used, double them for escaping::

            borg create --repo /path/to/repo {{literal_text}}

        Examples::

            borg create --repo /path/to/repo {hostname}-{user}-{utcnow} ...
            borg create --repo /path/to/repo {hostname}-{now:%Y-%m-%d_%H:%M:%S%z} ...
            borg prune -a 'sh:{hostname}-*' ...

        .. note::
            systemd uses a difficult, non-standard syntax for command lines in unit files (refer to
            the `systemd.unit(5)` manual page).

            When invoking borg from unit files, pay particular attention to escaping,
            especially when using the now/utcnow placeholders, since systemd performs its own
            %-based variable replacement even in quoted text. To avoid interference from systemd,
            double all percent signs (``{hostname}-{now:%Y-%m-%d_%H:%M:%S}``
            becomes ``{hostname}-{now:%%Y-%%m-%%d_%%H:%%M:%%S}``).\n\n"""
    )
    helptext["compression"] = textwrap.dedent(
        """
        It is no problem to mix different compression methods in one repository,
        deduplication is done on the source data chunks (not on the compressed
        or encrypted data).

        If some specific chunk was once compressed and stored into the repository, creating
        another backup that also uses this chunk will not change the stored chunk.
        So if you use different compression specs for the backups, whichever stores a
        chunk first determines its compression. See also ``borg recreate``.

        Compression is lz4 by default. If you want something else, you have to specify what you want.

        Valid compression specifiers are:

        none
            Do not compress.

        lz4
            Use lz4 compression. Very high speed, very low compression. (default)

        zstd[,L]
            Use zstd ("zstandard") compression, a modern wide-range algorithm.
            If you do not explicitly give the compression level L (ranging from 1
            to 22), it will use level 3.

        zlib[,L]
            Use zlib ("gz") compression. Medium speed, medium compression.
            If you do not explicitly give the compression level L (ranging from 0
            to 9), it will use level 6.
            Giving level 0 (means "no compression", but still has zlib protocol
            overhead) is usually pointless, you better use "none" compression.

        lzma[,L]
            Use lzma ("xz") compression. Low speed, high compression.
            If you do not explicitly give the compression level L (ranging from 0
            to 9), it will use level 6.
            Giving levels above 6 is pointless and counterproductive because it does
            not compress better due to the buffer size used by borg - but it wastes
            lots of CPU cycles and RAM.

        auto,C[,L]
            Use a built-in heuristic to decide per chunk whether to compress or not.
            The heuristic tries with lz4 whether the data is compressible.
            For incompressible data, it will not use compression (uses "none").
            For compressible data, it uses the given C[,L] compression - with C[,L]
            being any valid compression specifier. This can be helpful for media files
            which often cannot be compressed much more.

        obfuscate,SPEC,C[,L]
            Use compressed-size obfuscation to make fingerprinting attacks based on
            the observable stored chunk size more difficult. Note:

            - You must combine this with encryption, or it won't make any sense.
            - Your repo size will be bigger, of course.
            - A chunk is limited by the constant ``MAX_DATA_SIZE`` (cur. ~20MiB).

            The SPEC value determines how the size obfuscation works:

            *Relative random reciprocal size variation* (multiplicative)

            Size will increase by a factor, relative to the compressed data size.
            Smaller factors are used often, larger factors rarely.

            Available factors::

              1:     0.01 ..        100
              2:     0.1  ..      1,000
              3:     1    ..     10,000
              4:    10    ..    100,000
              5:   100    ..  1,000,000
              6: 1,000    .. 10,000,000

            Example probabilities for SPEC ``1``::

              90   %  0.01 ..   0.1
               9   %  0.1  ..   1
               0.9 %  1    ..  10
               0.09% 10    .. 100

            *Randomly sized padding up to the given size* (additive)

            ::

              110: 1kiB (2 ^ (SPEC - 100))
              ...
              120: 1MiB
              ...
              123: 8MiB (max.)

            *Padmé padding* (deterministic)

            ::

              250: pads to sums of powers of 2, max 12% overhead

            Uses the Padmé algorithm to deterministically pad the compressed size to a sum of
            powers of 2, limiting overhead to 12%. See https://lbarman.ch/blog/padme/ for details.

        Examples::

            borg create --compression lz4 --repo REPO ARCHIVE data
            borg create --compression zstd --repo REPO ARCHIVE data
            borg create --compression zstd,10 --repo REPO ARCHIVE data
            borg create --compression zlib --repo REPO ARCHIVE data
            borg create --compression zlib,1 --repo REPO ARCHIVE data
            borg create --compression auto,lzma,6 --repo REPO ARCHIVE data
            borg create --compression auto,lzma ...
            borg create --compression obfuscate,110,none ...
            borg create --compression obfuscate,3,auto,zstd,10 ...
            borg create --compression obfuscate,2,zstd,6 ...
            borg create --compression obfuscate,250,zstd,3 ...\n\n"""
    )

    def do_help(self, parser, commands, args):
        if not args.topic:
            parser.print_help()
        elif args.topic in self.helptext:
            print(rst_to_terminal(self.helptext[args.topic]))
        elif args.topic in commands:
            if args.epilog_only:
                print(commands[args.topic].epilog)
            elif args.usage_only:
                commands[args.topic].epilog = None
                commands[args.topic].print_help()
            else:
                commands[args.topic].print_help()
        else:
            msg_lines = []
            msg_lines += ["No help available on %s." % args.topic]
            msg_lines += ["Try one of the following:"]
            msg_lines += ["    Commands: %s" % ", ".join(sorted(commands.keys()))]
            msg_lines += ["    Topics: %s" % ", ".join(sorted(self.helptext.keys()))]
            parser.error("\n".join(msg_lines))

    def do_subcommand_help(self, parser, args):
        """display infos about subcommand"""
        parser.print_help()

    do_maincommand_help = do_subcommand_help

    def build_parser_help(self, subparsers, common_parser, mid_common_parser, parser):
        subparser = subparsers.add_parser("help", parents=[common_parser], add_help=False, description="Extra help")
        subparser.add_argument("--epilog-only", dest="epilog_only", action="store_true")
        subparser.add_argument("--usage-only", dest="usage_only", action="store_true")
        subparser.set_defaults(func=functools.partial(self.do_help, parser, subparsers.choices))
        subparser.add_argument("topic", metavar="TOPIC", type=str, nargs="?", help="additional help on TOPIC")
