from __future__ import annotations

import re

SLACK_MENTION_STRIP_PATTERN = re.compile(r"<@[^>\s]+>")
SLACK_CHANNEL_PATTERN = re.compile(r"<#([A-Z0-9]+)(?:\|([^>]+))?>")
SLACK_URL_PATTERN = re.compile(r"<(https?://[^|>]+)(?:\|([^>]+))?>")
SLACK_SUBTEAM_PATTERN = re.compile(r"<!subteam\^([A-Z0-9]+)(?:\|([^>]+))?>")
SLACK_SPECIAL_MENTION_PATTERN = re.compile(r"<!([^>]+)>")
SLACK_HTML_ENTITY_PATTERN = re.compile(r"&(amp|lt|gt|quot);")

_HTML_ENTITIES = {"amp": "&", "lt": "<", "gt": ">", "quot": '"'}


def strip_mentions(text: str) -> str:
    return SLACK_MENTION_STRIP_PATTERN.sub("", text).strip()


def extract_mentions(text: str) -> list[str]:
    return re.findall(r"<@([A-Z0-9]+)>", text)


def normalize_channel_refs(text: str) -> str:
    def repl(m: re.Match) -> str:
        name = m.group(2)
        return f"#{name}" if name else f"#{m.group(1)}"

    return SLACK_CHANNEL_PATTERN.sub(repl, text)


def normalize_urls(text: str) -> str:
    def repl(m: re.Match) -> str:
        url = m.group(1)
        label = m.group(2)
        if label and label != url:
            return f"{label} ({url})"
        return url

    return SLACK_URL_PATTERN.sub(repl, text)


def normalize_special_mentions(text: str) -> str:
    return SLACK_SPECIAL_MENTION_PATTERN.sub(r"@\1", text)


def unescape_html_entities(text: str) -> str:
    def repl(m: re.Match) -> str:
        return _HTML_ENTITIES.get(m.group(1), m.group(0))

    return SLACK_HTML_ENTITY_PATTERN.sub(repl, text)


def normalize_slack_text(text: str) -> str:
    text = normalize_channel_refs(text)
    text = normalize_urls(text)
    text = normalize_special_mentions(text)
    text = unescape_html_entities(text)
    return text.strip()