from __future__ import annotations

import re
from datetime import date

import dateparser
import spacy
from spacy.language import Language

from models import ParseResponse

# ── Language model registry ──────────────────────────────────────────────────

_MODEL_NAMES: dict[str, str] = {
    "de": "de_core_news_sm",
    "en": "en_core_web_sm",
    "es": "es_core_news_sm",
}

_nlp_cache: dict[str, Language] = {}


def get_nlp(lang: str) -> Language:
    if lang not in _MODEL_NAMES:
        raise ValueError(f"Unsupported language: {lang!r}. Valid: {list(_MODEL_NAMES)}")
    if lang not in _nlp_cache:
        _nlp_cache[lang] = spacy.load(_MODEL_NAMES[lang])
    return _nlp_cache[lang]


def load_all_models() -> None:
    for lang in _MODEL_NAMES:
        get_nlp(lang)


# ── Step 1: Person name extraction ──────────────────────────────────────────

def extract_person_names(doc) -> list[str]:
    """Return PER entity texts in left-to-right span order."""
    return [ent.text for ent in doc.ents if ent.label_ == "PER"]


# ── Step 2: Role detection ───────────────────────────────────────────────────

_SENDER_PREPS: dict[str, frozenset[str]] = {
    "de": frozenset({"von", "vom"}),
    "en": frozenset({"from", "by"}),
    "es": frozenset({"de", "por"}),
}

_RECEIVER_PREPS: dict[str, frozenset[str]] = {
    "de": frozenset({"an", "nach", "für"}),
    "en": frozenset({"to", "for"}),
    "es": frozenset({"para", "a"}),
}


def detect_person_role(doc, per_spans: list, lang: str) -> str:
    """Return 'sender', 'receiver', or 'any'.

    Only meaningful for single-PER queries — two-person queries always return
    'any' because Java derives direction from list position.
    """
    if len(per_spans) != 1:
        return "any"

    span = per_spans[0]
    root = span.root
    sender = _SENDER_PREPS[lang]
    receiver = _RECEIVER_PREPS[lang]

    # Primary: dependency-tree children of the PER root
    for child in root.children:
        if child.dep_ in ("case", "prep", "mo"):
            if child.lower_ in sender:
                return "sender"
            if child.lower_ in receiver:
                return "receiver"

    # Fallback: token immediately before the span start
    if span.start > 0:
        prev = doc[span.start - 1]
        if prev.lower_ in sender:
            return "sender"
        if prev.lower_ in receiver:
            return "receiver"

    return "any"


# ── Step 3: Date parsing ─────────────────────────────────────────────────────

_YEAR_RE = re.compile(r"^\d{4}$")

_DATE_BEFORE: dict[str, frozenset[str]] = {
    "de": frozenset({"vor"}),
    "en": frozenset({"before"}),
    "es": frozenset({"antes"}),
}

_DATE_AFTER: dict[str, frozenset[str]] = {
    "de": frozenset({"nach"}),
    "en": frozenset({"after"}),
    "es": frozenset({"después", "despues"}),
}

_DATE_BETWEEN: dict[str, frozenset[str]] = {
    "de": frozenset({"zwischen"}),
    "en": frozenset({"between"}),
    "es": frozenset({"entre"}),
}


def _parse_date_text(text: str, lang: str) -> date | None:
    text = text.strip()
    if _YEAR_RE.match(text):
        year = int(text)
        if 1000 < year < 3000:
            return date(year, 1, 1)
    parsed = dateparser.parse(
        text,
        languages=[lang],
        settings={"PREFER_DAY_OF_MONTH": "first", "RETURN_AS_TIMEZONE_AWARE": False},
    )
    return parsed.date() if parsed else None


def _year_end(d: date) -> date:
    """If d is Jan 1, return Dec 31 of the same year (year-only boundary)."""
    if d.month == 1 and d.day == 1:
        return date(d.year, 12, 31)
    return d


def extract_dates(doc, lang: str) -> tuple[str | None, str | None]:
    """Return (date_from, date_to) as ISO strings or None."""
    date_spans = [ent for ent in doc.ents if ent.label_ == "DATE"]
    if not date_spans:
        return None, None

    between_tokens = _DATE_BETWEEN[lang]
    before_tokens = _DATE_BEFORE[lang]
    after_tokens = _DATE_AFTER[lang]

    # "zwischen X und Y" / "between X and Y" — two DATE spans form a range
    has_between = any(tok.lower_ in between_tokens for tok in doc)
    if has_between and len(date_spans) >= 2:
        parsed = []
        for span in date_spans[:2]:
            d = _parse_date_text(span.text, lang)
            if d:
                parsed.append(d)
        if len(parsed) == 2:
            parsed.sort()
            return parsed[0].isoformat(), _year_end(parsed[1]).isoformat()

    # Single DATE span — use direction token
    span = date_spans[0]
    d = _parse_date_text(span.text, lang)
    if not d:
        return None, None

    prev_lower = doc[span.start - 1].lower_ if span.start > 0 else ""

    if prev_lower in before_tokens:
        return None, _year_end(d).isoformat()
    if prev_lower in after_tokens:
        return d.isoformat(), None
    # Bare year/date — closed year-range
    return d.isoformat(), _year_end(d).isoformat()