import dataclasses
import re
from typing import Any, Dict, List, Optional

from .junkdrawer import MultipleReplacer

# http://ircv3.net/specs/core/message-tags-3.2.html#escaping-values
TAG_ESCAPE = [
    ("\\", "\\\\"),  # \ -> \\
    (" ", r"\s"),
    (";", r"\:"),
    ("\r", r"\r"),
    ("\n", r"\n"),
]
unescape_tag_value = MultipleReplacer(dict(map(lambda x: (x[1], x[0]), TAG_ESCAPE)))

# TODO: validate host
tag_key_validator = re.compile(r"\+?(\S+/)?[a-zA-Z0-9-]+")


def parse_tags(s):
    tags = {}
    for tag in s.split(";"):
        if "=" not in tag:
            tags[tag] = None
        else:
            (key, value) = tag.split("=", 1)
            assert tag_key_validator.match(key), "Invalid tag key: {}".format(key)
            tags[key] = unescape_tag_value(value)
    return tags


@dataclasses.dataclass(frozen=True)
class HistoryMessage:
    time: Any
    msgid: Optional[str]
    target: str
    text: str


@dataclasses.dataclass(frozen=True)
class Message:
    tags: Dict[str, Optional[str]]
    prefix: Optional[str]
    command: str
    params: List[str]

    def to_history_message(self) -> HistoryMessage:
        return HistoryMessage(
            time=self.tags.get("time"),
            msgid=self.tags.get("msgid"),
            target=self.params[0],
            text=self.params[1],
        )


def parse_message(s):
    """Parse a message according to
    http://tools.ietf.org/html/rfc1459#section-2.3.1
    and
    http://ircv3.net/specs/core/message-tags-3.2.html"""
    s = s.rstrip("\r\n")
    if s.startswith("@"):
        (tags, s) = s.split(" ", 1)
        tags = parse_tags(tags[1:])
    else:
        tags = {}
    if " :" in s:
        (other_tokens, trailing_param) = s.split(" :", 1)
        tokens = list(filter(bool, other_tokens.split(" "))) + [trailing_param]
    else:
        tokens = list(filter(bool, s.split(" ")))
    if tokens[0].startswith(":"):
        prefix = tokens.pop(0)[1:]
    else:
        prefix = None
    command = tokens.pop(0)
    params = tokens
    return Message(tags=tags, prefix=prefix, command=command, params=params)