from __future__ import annotations

import re
from dataclasses import dataclass, asdict
from datetime import date
from typing import List, Optional

MONTHS = {
    "jan": 1, "january": 1, "янв": 1, "январ": 1,
    "feb": 2, "february": 2, "фев": 2, "феврал": 2,
    "mar": 3, "march": 3, "мар": 3, "март": 3,
    "apr": 4, "april": 4, "апр": 4, "апрел": 4,
    "may": 5, "май": 5,
    "jun": 6, "june": 6, "июн": 6, "июнь": 6,
    "jul": 7, "july": 7, "июл": 7, "июль": 7,
    "aug": 8, "august": 8, "авг": 8, "август": 8,
    "sep": 9, "september": 9, "сен": 9, "сент": 9,
    "oct": 10, "october": 10, "окт": 10, "октя": 10,
    "nov": 11, "november": 11, "ноя": 11, "ноябр": 11,
    "dec": 12, "december": 12, "дек": 12, "дека": 12,
}

PRESENT_RE = re.compile(r"\b(present|now|current|настоящее время|по н\.в\.|по настоящее)\b", re.I)
MMYYYY_RE = re.compile(r"\b(0?[1-9]|1[0-2])[./-](\d{4})\b")
YYYY_RE = re.compile(r"\b(19\d{2}|20\d{2})\b")
MON_YYYY_RE = re.compile(r"\b([A-Za-z]{3,9}|[А-Яа-я]{3,9})\.?\s*(\d{4})\b")
RANGE_RE = re.compile(r"(?P<a>.+?)\s*(?:—|–|-|to|по)\s*(?P<b>.+?)$", re.I)
YEAR_RANGE_ONLY_RE = re.compile(r"^\s*\d{4}\s*(?:—|–|-|to|по)\s*\d{4}\s*$", re.I)
EDU_CONTEXT_RE = re.compile(
    r"\b("
    r"education|university|institute|college|academy|school|bachelor|master|degree|faculty|"
    r"образование|университет|институт|академ|колледж|школа|бакалав|магистр|факультет"
    r")\b",
    re.I,
)


@dataclass
class Position:
    title: Optional[str]
    company: Optional[str]
    date_from: Optional[str]
    date_to: Optional[str]
    is_current: Optional[bool]
    description: Optional[str]


def _parse_mon(mon: str) -> Optional[int]:
    m = mon.strip().lower()
    m = re.sub(r"[^\wа-я]+", "", m, flags=re.I)
    for k, v in MONTHS.items():
        if m.startswith(k):
            return v
    return None


def _as_ymd(y: int, m: int) -> date:
    return date(y, m, 1)


def _parse_one_date(s: str) -> Optional[date]:
    s = s.strip()
    if PRESENT_RE.search(s):
        today = date.today()
        return date(today.year, today.month, 1)
    m1 = MMYYYY_RE.search(s)
    if m1:
        mm = int(m1.group(1))
        yy = int(m1.group(2))
        return _as_ymd(yy, mm)
    m2 = MON_YYYY_RE.search(s)
    if m2:
        mon = _parse_mon(m2.group(1))
        yy = int(m2.group(2))
        if mon:
            return _as_ymd(yy, mon)
    m3 = YYYY_RE.search(s)
    if m3:
        yy = int(m3.group(1))
        return _as_ymd(yy, 1)
    return None


def extract_positions(text: str, max_items: int = 40) -> List[Position]:
    lines = [ln.strip() for ln in (text or "").splitlines() if ln.strip()]
    positions: List[Position] = []
    i = 0
    while i < len(lines) and len(positions) < max_items:
        ln = lines[i]
        if not any(x in ln for x in ("—", "–", "-", " to ", " по ")):
            i += 1
            continue
        rr = RANGE_RE.match(ln)
        if not rr:
            i += 1
            continue
        ctx = " ".join(lines[max(0, i - 2): min(len(lines), i + 4)])
        if YEAR_RANGE_ONLY_RE.match(ln) and EDU_CONTEXT_RE.search(ctx):
            i += 1
            continue
        da = _parse_one_date(rr.group("a"))
        db = _parse_one_date(rr.group("b"))
        if not da or not db:
            i += 1
            continue
        if da.year < 1990:
            i += 1
            continue
        is_current = PRESENT_RE.search(rr.group("b")) is not None
        title = None
        company = None
        desc_lines: List[str] = []
        if i + 1 < len(lines):
            if EDU_CONTEXT_RE.search(lines[i + 1]):
                i += 1
                continue
            header = lines[i + 1]
            parts = [p.strip() for p in re.split(r"[,|/]", header) if p.strip()]
            if parts:
                title = parts[0]
                if len(parts) > 1:
                    company = parts[1]
        j = i + 2
        while j < len(lines):
            if any(x in lines[j] for x in ("—", "–", "-", " to ", " по ")) and RANGE_RE.match(lines[j]):
                break
            desc_lines.append(lines[j])
            j += 1
        positions.append(
            Position(
                title=title,
                company=company,
                date_from=da.isoformat(),
                date_to=db.isoformat(),
                is_current=is_current,
                description="\n".join(desc_lines).strip() if desc_lines else None,
            )
        )
        i = j
    return positions


def positions_to_dicts(items: List[Position]) -> List[dict]:
    return [asdict(p) for p in items]