# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:

# Copyright 2021 Ryan Roden-Corrent (rcorre) <ryan@rcorre.net>
#
# This file is part of qutebrowser.
#
# qutebrowser is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# qutebrowser is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""Module for parsing commands entered into the browser."""

import dataclasses
from typing import Optional, List, Mapping, Iterator, Union

from qutebrowser.commands import cmdexc, command
from qutebrowser.misc import split, objects
from qutebrowser.config import config


@dataclasses.dataclass
class ParseResult:

    """The result of parsing a commandline."""

    cmd: command.Command
    args: List[str]
    cmdline: List[str]


class CommandParser:

    """Parse qutebrowser commandline commands.

    Attributes:
        _partial_match: Whether to allow partial command matches.
    """

    def __init__(self, partial_match: bool = False) -> None:
        self._partial_match = partial_match

    def _get_alias(self, text: str, *, default: str) -> str:
        """Get an alias from the config.

        Args:
            text: The text to parse.
            aliases: A map of aliases to commands.
            default : Default value to return when alias was not found.

        Return:
            The new command string if an alias was found. Default value
            otherwise.
        """
        parts = text.strip().split(maxsplit=1)
        aliases = config.cache['aliases']
        if parts[0] not in aliases:
            return default
        alias = aliases[parts[0]]

        try:
            new_cmd = '{} {}'.format(alias, parts[1])
        except IndexError:
            new_cmd = alias
        if text.endswith(' '):
            new_cmd += ' '
        return new_cmd

    def _parse_all_gen(
            self,
            text: str,
            aliases: bool = True,
            **kwargs: bool,
    ) -> Iterator[ParseResult]:
        """Split a command on ;; and parse all parts.

        If the first command in the commandline is a non-split one, it only
        returns that.

        Args:
            text: Text to parse.
            aliases: Whether to handle aliases.
            **kwargs: Passed to parse().

        Yields:
            ParseResult tuples.
        """
        text = text.strip().lstrip(':').strip()
        if not text:
            raise cmdexc.NoSuchCommandError("No command given")

        if aliases:
            text = self._get_alias(text, default=text)

        if ';;' in text:
            # Get the first command and check if it doesn't want to have ;;
            # split.
            first = text.split(';;')[0]
            result = self.parse(first, **kwargs)
            if result.cmd.no_cmd_split:
                sub_texts = [text]
            else:
                sub_texts = [e.strip() for e in text.split(';;')]
        else:
            sub_texts = [text]
        for sub in sub_texts:
            yield self.parse(sub, **kwargs)

    def parse_all(self, text: str, **kwargs: bool) -> List[ParseResult]:
        """Wrapper over _parse_all_gen."""
        return list(self._parse_all_gen(text, **kwargs))

    def parse(self, text: str, *, keep: bool = False) -> ParseResult:
        """Split the commandline text into command and arguments.

        Args:
            text: Text to parse.
            keep: Whether to keep special chars and whitespace.
        """
        cmdstr, sep, argstr = text.partition(' ')

        if not cmdstr:
            raise cmdexc.NoSuchCommandError("No command given")

        if self._partial_match:
            cmdstr = self._completion_match(cmdstr)

        try:
            cmd = objects.commands[cmdstr]
        except KeyError:
            raise cmdexc.NoSuchCommandError(f'{cmdstr}: no such command')

        args = self._split_args(cmd, argstr, keep)
        if keep and args:
            cmdline = [cmdstr, sep + args[0]] + args[1:]
        elif keep:
            cmdline = [cmdstr, sep]
        else:
            cmdline = [cmdstr] + args[:]

        return ParseResult(cmd=cmd, args=args, cmdline=cmdline)

    def _completion_match(self, cmdstr: str) -> str:
        """Replace cmdstr with a matching completion if there's only one match.

        Args:
            cmdstr: The string representing the entered command so far.

        Return:
            cmdstr modified to the matching completion or unmodified
        """
        matches = [cmd for cmd in sorted(objects.commands, key=len)
                   if cmdstr in cmd]
        if len(matches) == 1:
            cmdstr = matches[0]
        elif len(matches) > 1 and config.val.completion.use_best_match:
            cmdstr = matches[0]
        return cmdstr

    def _split_args(self, cmd: command.Command, argstr: str, keep: bool) -> List[str]:
        """Split the arguments from an arg string.

        Args:
            cmd: The command we're currently handling.
            argstr: An argument string.
            keep: Whether to keep special chars and whitespace

        Return:
            A list containing the split strings.
        """
        if not argstr:
            return []
        elif cmd.maxsplit is None:
            return split.split(argstr, keep=keep)
        else:
            # If split=False, we still want to split the flags, but not
            # everything after that.
            # We first split the arg string and check the index of the first
            # non-flag args, then we re-split again properly.
            # example:
            #
            # input: "--foo -v bar baz"
            # first split: ['--foo', '-v', 'bar', 'baz']
            #                0        1     2      3
            # second split: ['--foo', '-v', 'bar baz']
            # (maxsplit=2)
            split_args = split.simple_split(argstr, keep=keep)
            flag_arg_count = 0
            for i, arg in enumerate(split_args):
                arg = arg.strip()
                if arg.startswith('-'):
                    if arg in cmd.flags_with_args:
                        flag_arg_count += 1
                else:
                    maxsplit = i + cmd.maxsplit + flag_arg_count
                    return split.simple_split(argstr, keep=keep,
                                              maxsplit=maxsplit)

            # If there are only flags, we got it right on the first try
            # already.
            return split_args