"""maild classification: rules + sentence-level negation, LLM optional.

Approval rule (audit round 2, point 2): a mail may only classify `approval`
when NO sentence contains a negation. Any negation token anywhere in the mail
(conservative: even outside the approval sentence) downgrades an approval to
`needs_review`. Rejections/questions/other are unaffected.

The LLM never decides alone: below-threshold confidence → `needs_review`.
With the `null` provider (default) only deterministic rules run.
"""

from __future__ import annotations

import json
import re

from cayceops.config import Config
from cayceops.models import MailClassification

_APPROVAL_WORDS = re.compile(r"\b(approv|accept|welcome)", re.I)

# any of these tokens anywhere in the mail vetoes an `approval` result.
# English and Spanish (merchants write in both; mixed mails are common).
_NEGATIONS = re.compile(
    r"\b(not|no|never|cannot|can'?t|won'?t|hasn'?t|isn'?t|"
    r"no\s+longer|unable|decline\w*|regret\w*|unfortunately|"
    # spanish: standalone negation words
    r"nunca|jam[aá]s|tampoco|ning[uú]n(?:a|o)?|nadie|nada|"
    # spanish: multi-word negations and rejection stems
    r"no\s+podemos|no\s+es\s+posible|no\s+acept(?:amos|ar[aá])|"
    r"rechaz\w*|lamentablemente|descartad\w*|"
    r"no\s+ha\s+sido\s+aprobad\w*|no\s+procede)\b",
    re.I,
)

_RULES: list[tuple[MailClassification, re.Pattern[str], float]] = [
    # (class, pattern, confidence when matched)
    (
        MailClassification.REJECTION,
        # noqa: E501 (kept on one line: the pattern IS the reviewed artifact)
        re.compile(r"\b(declin|reject|not able to|unable to|we regret|won.t be able)\w*", re.I),  # noqa: E501
        0.9,
    ),
    (
        MailClassification.REJECTION,
        # spanish rejections (strong stems, not just negation words)
        re.compile(r"\b(rechaz\w*|no\s+vamos\s+a\s+pod(?:er|emos)|su\s+solicitud\s+ha\s+sido\s+denegada|no\s+cumple\s+los\s+requisitos)\b", re.I),  # noqa: E501
        0.9,
    ),
    (
        MailClassification.APPROVAL,
        re.compile(r"\b(approv|accept|welcome to the|you.re (in|approved)|live|activated|glad to)\w*", re.I),  # noqa: E501
        0.85,
    ),
    (
        MailClassification.APPROVAL,
        # spanish approvals (standalone positive stems; the veto still
        # downgrades if ANY negation appears elsewhere in the mail)
        re.compile(r"\b(aprob\w*|aceptad\w*|bienvenid\w*|ha\s+sido\s+aceptada|encantados?\s+de\s+(trabajar|colaborar))\b", re.I),  # noqa: E501
        0.85,
    ),
    (
        MailClassification.QUESTION,
        re.compile(r"\b(could you|can you|please (provide|clarify|confirm)|what (is|are)|how (do|does|can)|need more (info|details))\b", re.I),  # noqa: E501
        0.7,
    ),
]

_LLM_PROMPT = """Classify this merchant email into exactly one of:
approval, rejection, question, other.
Reply with strict JSON: {{"classification": "...", "confidence": 0.0-1.0}}

Subject and body:
{body}"""


def _rules(text: str) -> tuple[MailClassification, float]:
    for kind, pattern, confidence in _RULES:
        if pattern.search(text):
            return kind, confidence
    return MailClassification.OTHER, 0.3


def _has_negation(text: str) -> bool:
    return bool(_NEGATIONS.search(text))


def _llm_classify(text: str, cfg: Config) -> tuple[MailClassification, float] | None:
    """Ask the configured LLM. Returns None on any failure (rules take over)."""
    from cayceops.llm import get_provider

    try:
        provider = get_provider(cfg)
        raw = provider.complete(
            _LLM_PROMPT.format(body=text[:4000]),
            system="You classify merchant emails. Reply with JSON only.",
        )
        data = json.loads(re.search(r"\{.*\}", raw, re.S).group(0))
        kind = MailClassification(data["classification"].lower())
        confidence = float(data["confidence"])
    except Exception:  # noqa: BLE001 — LLM is best-effort by design
        return None
    if kind not in MailClassification or kind is MailClassification.NEEDS_REVIEW:
        return None
    return kind, min(max(confidence, 0.0), 1.0)


def classify(text: str, cfg: Config) -> tuple[MailClassification, float]:
    """Classify merchant text. Degrades to rules when no LLM is configured."""
    if cfg.llm_provider != "null":
        llm_result = _llm_classify(text, cfg)
        if llm_result is not None:
            kind, confidence = llm_result
        else:  # LLM failed — fall through to rules
            kind, confidence = _rules(text)
    else:
        kind, confidence = _rules(text)

    # APPROVAL VETO (audit round 2): any negation anywhere in the mail
    # downgrades an approval to needs_review. Approval requires a mail with
    # zero negations — "cannot currently accept", "never accept",
    # "hasn't been approved", "no longer accepting" all land here.
    if kind is MailClassification.APPROVAL and _has_negation(text):
        return MailClassification.NEEDS_REVIEW, min(confidence, 0.6)

    if confidence < cfg.llm_review_threshold:
        return MailClassification.NEEDS_REVIEW, confidence
    return kind, confidence