# SPDX-FileCopyrightText: Freya Bruhin (The Compiler) <mail@qutebrowser.org>
#
# SPDX-License-Identifier: GPL-3.0-or-later

"""Utilities used for the documentation and built-in help."""

import re
import sys
import inspect
import os.path
import collections
import enum
from typing import Any, Optional, Union
from collections.abc import MutableMapping, Callable

import qutebrowser
from qutebrowser.utils import log, utils


def is_git_repo() -> bool:
    """Check if we're running from a git repository."""
    gitfolder = os.path.join(qutebrowser.basedir, os.path.pardir, '.git')
    return os.path.isdir(gitfolder)


def docs_up_to_date(path: str) -> bool:
    """Check if the generated html documentation is up to date.

    Args:
        path: The path of the document to check.

    Return:
        True if they are up to date or we couldn't check.
        False if they are outdated.
    """
    if hasattr(sys, 'frozen') or not is_git_repo():
        return True
    html_path = os.path.join(qutebrowser.basedir, 'html', 'doc', path)
    filename = os.path.splitext(path)[0]
    asciidoc_path = os.path.join(qutebrowser.basedir, os.path.pardir,
                                 'doc', 'help', filename + '.asciidoc')
    try:
        html_time = os.path.getmtime(html_path)
        asciidoc_time = os.path.getmtime(asciidoc_path)
    except FileNotFoundError:
        return True
    return asciidoc_time <= html_time


class DocstringParser:

    """Generate documentation based on a docstring of a command handler.

    The docstring needs to follow the format described in doc/contributing.

    Attributes:
        _state: The current state of the parser state machine.
        _cur_arg_name: The name of the argument we're currently handling.
        _short_desc_parts: The short description of the function as list.
        _long_desc_parts: The long description of the function as list.
        short_desc: The short description of the function.
        long_desc: The long description of the function.
        arg_descs: A dict of argument names to their descriptions
    """

    class State(enum.Enum):

        """The current state of the parser."""

        short = enum.auto()
        desc = enum.auto()
        desc_hidden = enum.auto()
        arg_start = enum.auto()
        arg_inside = enum.auto()
        misc = enum.auto()

    def __init__(self, func: Callable[..., Any]) -> None:
        """Constructor.

        Args:
            func: The function to parse the docstring for.
        """
        self._state = self.State.short
        self._cur_arg_name: Optional[str] = None
        self._short_desc_parts: list[str] = []
        self._long_desc_parts: list[str] = []
        self.arg_descs: MutableMapping[
            str, Union[str, list[str]]] = collections.OrderedDict()
        doc = inspect.getdoc(func)
        handlers = {
            self.State.short: self._parse_short,
            self.State.desc: self._parse_desc,
            self.State.desc_hidden: self._skip,
            self.State.arg_start: self._parse_arg_start,
            self.State.arg_inside: self._parse_arg_inside,
            self.State.misc: self._skip,
        }
        if doc is None:
            if sys.flags.optimize < 2:
                log.commands.warning(
                    "Function {}() from {} has no docstring".format(
                        utils.qualname(func),
                        inspect.getsourcefile(func)))
            self.long_desc = ""
            self.short_desc = ""
            return
        for line in doc.splitlines():
            handler = handlers[self._state]
            stop = handler(line)
            if stop:
                break
        for k, v in self.arg_descs.items():
            desc = ' '.join(v)
            desc = re.sub(r', or None($|\.)', r'\1', desc)
            desc = re.sub(r', or None', r', or not given', desc)
            self.arg_descs[k] = desc
        self.long_desc = ' '.join(self._long_desc_parts)
        self.short_desc = ' '.join(self._short_desc_parts)

    def _process_arg(self, line: str) -> None:
        """Helper method to process a line like 'fooarg: Blah blub'."""
        self._cur_arg_name, argdesc = line.split(':', maxsplit=1)
        self._cur_arg_name = self._cur_arg_name.strip().lstrip('*')
        self.arg_descs[self._cur_arg_name] = [argdesc.strip()]

    def _skip(self, line: str) -> None:
        """Handler to ignore everything until we get 'Args:'."""
        if line.startswith('Args:'):
            self._state = self.State.arg_start

    def _parse_short(self, line: str) -> None:
        """Parse the short description (first block) in the docstring."""
        if not line:
            self._state = self.State.desc
        else:
            self._short_desc_parts.append(line.strip())

    def _parse_desc(self, line: str) -> None:
        """Parse the long description in the docstring."""
        if line.startswith('Args:'):
            self._state = self.State.arg_start
        elif line.strip() == '//' or line.startswith('Attributes:'):
            self._state = self.State.desc_hidden
        elif line.strip():
            self._long_desc_parts.append(line.strip())

    def _parse_arg_start(self, line: str) -> None:
        """Parse first argument line."""
        self._process_arg(line)
        self._state = self.State.arg_inside

    def _parse_arg_inside(self, line: str) -> bool:
        """Parse subsequent argument lines."""
        argname = self._cur_arg_name
        assert argname is not None

        descs = self.arg_descs[argname]
        assert isinstance(descs, list)

        if re.fullmatch(r'[A-Z][a-z]+:', line):
            if not descs[-1].strip():
                del descs[-1]
                return True
        elif not line.strip():
            descs.append('\n\n')
        elif line[4:].startswith(' '):
            descs.append(line.strip() + '\n')
        else:
            self._process_arg(line)
        return False
