from __future__ import annotations

import hashlib
import json
import re
from datetime import datetime
from pathlib import Path
from typing import Any
from urllib.parse import urljoin


WHITESPACE_RE = re.compile(r"[ \t]+")
NEWLINES_RE = re.compile(r"\n{3,}")

RUSSIAN_MONTHS = {
    "января": 1,
    "февраля": 2,
    "марта": 3,
    "апреля": 4,
    "мая": 5,
    "июня": 6,
    "июля": 7,
    "августа": 8,
    "сентября": 9,
    "октября": 10,
    "ноября": 11,
    "декабря": 12,
}


def ensure_dir(path: Path) -> Path:
    path.mkdir(parents=True, exist_ok=True)
    return path


def read_json(path: Path, default: Any = None) -> Any:
    if not path.exists():
        return default
    return json.loads(path.read_text(encoding="utf-8"))


def write_json(path: Path, payload: Any) -> None:
    ensure_dir(path.parent)
    path.write_text(
        json.dumps(payload, ensure_ascii=False, indent=2, sort_keys=False),
        encoding="utf-8",
    )


def sha256_text(value: str) -> str:
    return hashlib.sha256(value.encode("utf-8")).hexdigest()


def normalize_text(value: str) -> str:
    cleaned = value.replace("\xa0", " ")
    cleaned = WHITESPACE_RE.sub(" ", cleaned)
    cleaned = re.sub(r" *\n *", "\n", cleaned)
    cleaned = NEWLINES_RE.sub("\n\n", cleaned)
    return cleaned.strip()


def slugify(value: str) -> str:
    slug = re.sub(r"[^a-zA-Z0-9]+", "-", value.lower()).strip("-")
    return slug or "document"


def to_absolute_url(url: str, base_url: str) -> str:
    return urljoin(base_url, url)


def parse_russian_date(value: str) -> str | None:
    match = re.search(r"(\d{1,2})\s+([а-я]+)\s+(\d{4})", value.lower())
    if not match:
        return None

    day = int(match.group(1))
    month = RUSSIAN_MONTHS.get(match.group(2))
    year = int(match.group(3))
    if month is None:
        return None

    return datetime(year, month, day).date().isoformat()


def chunk_paragraphs(
    paragraphs: list[str], max_chars: int = 4500, overlap_paragraphs: int = 1
) -> list[str]:
    if not paragraphs:
        return []

    chunks: list[str] = []
    current: list[str] = []
    current_len = 0

    for paragraph in paragraphs:
        paragraph_len = len(paragraph)
        if current and current_len + paragraph_len + 2 > max_chars:
            chunks.append("\n\n".join(current).strip())
            current = current[-overlap_paragraphs:] if overlap_paragraphs else []
            current_len = sum(len(item) + 2 for item in current)

        current.append(paragraph)
        current_len += paragraph_len + 2

    if current:
        chunks.append("\n\n".join(current).strip())

    return [chunk for chunk in chunks if chunk]