"""E-mail parsing: own-mail detection, project splitting, canonical URLs."""
from __future__ import annotations

import re
from urllib.parse import urlsplit, urlunsplit

import requests
from bs4 import BeautifulSoup

OWN_PREFIXES = ("[Projekt-Match]", "[Projekt-Match-Fehler]")
PROJECT_URL_RE = re.compile(
    r"https?://(?:www\.)?freelancermap\.de/(?:nproj/|projekt/)[^\s\"'<>)\]]+")
BROWSER_UA = ("Mozilla/5.0 (X11; Linux x86_64; rv:128.0) "
              "Gecko/20100101 Firefox/128.0")


def is_own_mail(subject) -> bool:
    return bool(subject) and subject.strip().startswith(OWN_PREFIXES)


def bodies(msg):
    """Return (html, text) of the first text/html and text/plain parts."""
    html = text = ""
    for part in msg.walk():
        if part.get_content_maintype() == "multipart":
            continue
        try:
            payload = part.get_content()
        except Exception:
            continue
        ctype = part.get_content_type()
        if ctype == "text/html" and not html:
            html = payload
        elif ctype == "text/plain" and not text:
            text = payload
    return html, text


def _url_key(url: str) -> str:
    return urlsplit(url).path


def split_projects(html: str, text: str) -> list:
    """Extract project items {title, url} from a mail body. HTML preferred;
    per project (URL path) the LONGEST anchor text wins (skips 'Zum Projekt'
    buttons). Plain-text fallback: URL line + nearest preceding non-empty line."""
    best = {}          # key -> {"title", "url"}
    order = []
    if html:
        soup = BeautifulSoup(html, "html.parser")
        for a in soup.find_all("a", href=PROJECT_URL_RE):
            url = a["href"]
            key = _url_key(url)
            title = " ".join(a.get_text(" ", strip=True).split())
            if key not in best:
                best[key] = {"title": title, "url": url}
                order.append(key)
            elif len(title) > len(best[key]["title"]):
                best[key]["title"] = title
    if not best and text:
        last_line = ""
        for line in text.splitlines():
            match = PROJECT_URL_RE.search(line)
            stripped = line.strip()
            if match:
                key = _url_key(match.group(0))
                if key not in best:
                    best[key] = {"title": last_line or match.group(0),
                                 "url": match.group(0)}
                    order.append(key)
            elif stripped:
                last_line = stripped
    return [best[k] for k in order if best[k]["title"]]


def canonical_url(url: str, session=None, timeout=20) -> str:
    """Follow redirects, strip query string and fragment."""
    sess = session or requests.Session()
    resp = sess.get(url, timeout=timeout, allow_redirects=True,
                    headers={"User-Agent": BROWSER_UA})
    resp.raise_for_status()
    parts = urlsplit(resp.url)
    return urlunsplit((parts.scheme, parts.netloc, parts.path, "", ""))