"""Relate saved discussions by note identity, independent of signed URLs."""
from __future__ import annotations

import re
from urllib.parse import urlsplit


def note_key(source: dict) -> str:
    identity = source.get("note_id")
    if isinstance(identity, str) and identity:
        return "note:" + identity
    url = source.get("source_url") or ""
    try:
        parts = urlsplit(url)
    except ValueError:
        return "url:" + url
    if parts.hostname in {"www.xiaohongshu.com", "xiaohongshu.com"}:
        match = re.fullmatch(r"/(?:explore|discovery/item)/([^/]+)/?", parts.path)
        if match:
            return "note:" + match.group(1)
    return "url:" + url


def related_context(batch: list[dict], sources: list[dict]) -> list[dict]:
    by_id = {row["source_id"]: row for row in sources}
    notes = {note_key(row): row for row in sources if row.get("source_type") == "note"}
    own_ids = {row["source_id"] for row in batch}
    related = {}
    for source in batch:
        note = notes.get(note_key(source))
        if note and note["source_id"] not in own_ids:
            related[note["source_id"]] = note
        for key in ("parent_source_id", "root_source_id"):
            parent = by_id.get(source.get(key))
            if parent and parent["source_id"] not in own_ids:
                related[parent["source_id"]] = parent
    return list(related.values())