import re
from urllib.parse import urlsplit, urlunsplit

from tasks.models import TaskExternalLink


HTTP_LINK_PATTERN = re.compile(r"https?://[^\s<>\"']+", re.IGNORECASE)
TRAILING_LINK_PUNCTUATION = ".,;:!?)]}"


def normalize_http_link(value):
    candidate = str(value or "").strip().rstrip(TRAILING_LINK_PUNCTUATION)
    if not candidate or len(candidate) > 2048:
        return None
    try:
        parsed = urlsplit(candidate)
    except ValueError:
        return None
    if parsed.scheme.lower() not in {"http", "https"} or not parsed.hostname:
        return None
    return urlunsplit(
        (
            parsed.scheme.lower(),
            parsed.netloc.lower(),
            parsed.path,
            parsed.query,
            parsed.fragment,
        )
    )


def http_link_identity(value):
    normalized = normalize_http_link(value)
    if normalized is None:
        return None
    parsed = urlsplit(normalized)
    path = "" if parsed.path == "/" else parsed.path
    return urlunsplit((parsed.scheme, parsed.netloc, path, parsed.query, parsed.fragment))


def extract_http_links(text):
    links = []
    identities = set()
    for match in HTTP_LINK_PATTERN.finditer(text or ""):
        link = normalize_http_link(match.group(0))
        identity = http_link_identity(link)
        if link is None or identity is None or identity in identities:
            continue
        identities.add(identity)
        links.append(link)
    return links


def add_comment_links_to_task(*, task, text, created_by):
    existing_identities = {
        identity
        for url in task.external_links.values_list("url", flat=True)
        if (identity := http_link_identity(url)) is not None
    }
    created = []
    for url in extract_http_links(text):
        identity = http_link_identity(url)
        if identity in existing_identities:
            continue
        link, was_created = TaskExternalLink.objects.get_or_create(
            task=task,
            url=url,
            defaults={"created_by": created_by},
        )
        existing_identities.add(identity)
        if was_created:
            created.append(link)
    return created