# Copyright (C) 2009 Canonical Ltd
#
# This program 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 2 of the License, or
# (at your option) any later version.
#
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Python implementation of _read_stanza_*."""

import re
from collections.abc import Iterator
from typing import Optional

from .rio import Stanza

_tag_re = re.compile(r"^[-a-zA-Z0-9_]+$")


def _valid_tag(tag: str) -> bool:
    if not isinstance(tag, str):
        raise TypeError(tag)
    return bool(_tag_re.match(tag))


def _read_stanza_utf8(line_iter: Iterator[bytes]) -> Optional[Stanza]:
    stanza = Stanza()
    tag = None
    accum_value = None

    # TODO: jam 20060922 This code should raise real errors rather than
    #       using 'assert' to process user input, or raising ValueError
    #       rather than a more specific error.

    for bline in line_iter:
        if not isinstance(bline, bytes):
            raise TypeError(bline)
        line = bline.decode("utf-8", "surrogateescape")
        if line is None or line == "":
            break  # end of file
        if line == "\n":
            break  # end of stanza
        real_l = line
        if line[0] == "\t":  # continues previous value
            if tag is None:
                raise ValueError("invalid continuation line {!r}".format(real_l))
            if accum_value is None:
                raise ValueError(
                    "missing initial line for continuation {!r}".format(real_l)
                )
            accum_value.append("\n" + line[1:-1])
        else:  # new tag:value line
            if tag is not None:
                if accum_value is None:
                    raise ValueError("missing value for tag {!r}".format(tag))
                stanza.add(tag, "".join(accum_value))
            try:
                colon_index = line.index(": ")
            except ValueError as e:
                raise ValueError(
                    "tag/value separator not found in line {!r}".format(real_l)
                ) from e
            tag = str(line[:colon_index])
            if not _valid_tag(tag):
                raise ValueError("invalid rio tag {!r}".format(tag))
            accum_value = [line[colon_index + 2 : -1]]

    if tag is not None:  # add last tag-value
        if accum_value is None:
            raise ValueError("missing value for tag {!r}".format(tag))
        stanza.add(tag, "".join(accum_value))  # type: ignore
        return stanza
    else:  # didn't see any content
        return None