from __future__ import annotations

import hashlib
import json
import os
import re

from app.dedupe_store import DedupeStore
from app.models import ClassificationResult, ClassifyRequest, DedupeResult


def normalize_subject(subject: str) -> str:
    value = subject.strip().lower()
    value = re.sub(r"^(re|fw|fwd)\s*:\s*", "", value)
    value = re.sub(r"\s+", " ", value)
    return value


def build_subject_key(request: ClassifyRequest) -> str:
    subject = normalize_subject(request.email_data.subject)
    sender = (request.from_address or "").strip().lower()
    return hashlib.sha256(f"{sender}\n{subject}".encode()).hexdigest()


def build_fingerprint(request: ClassifyRequest) -> str:
    subject = normalize_subject(request.email_data.subject)
    body = " ".join(request.email_data.body.split()).strip().lower()
    seed = f"{request.from_address or ''}\n{subject}\n{body[:2000]}"
    return hashlib.sha256(seed.encode()).hexdigest()


def build_result_hash(result: ClassificationResult) -> str:
    payload = result.model_dump(exclude={"dedupe"}, exclude_none=True)
    return hashlib.sha256(json.dumps(payload, sort_keys=True).encode()).hexdigest()


def apply_dedupe(request: ClassifyRequest, result: ClassificationResult) -> DedupeResult:
    store = DedupeStore(os.getenv("EMAIL_CLASSIFIER_DB_PATH", ".data/email_classifier.db"))
    subject_key = build_subject_key(request)
    fingerprint = build_fingerprint(request)
    result_hash = build_result_hash(result)
    existing = store.find_existing(subject_key=subject_key, fingerprint=fingerprint)

    if not existing:
        store.insert_or_update(
            existing_id=None,
            subject_key=subject_key,
            fingerprint=fingerprint,
            result_hash=result_hash,
            request_payload=request.model_dump(exclude={"api_key"}, exclude_none=True),
            result_payload=result.model_dump(exclude={"dedupe"}, exclude_none=True),
            seen_count=1,
        )
        return DedupeResult(status="new", seen_count=1, matched_on="none", subject_key=subject_key, fingerprint=fingerprint)

    matched_on = "fingerprint" if existing.get("fingerprint") == fingerprint else "subject"
    previous_hash = existing.get("result_hash")
    seen_count = int(existing.get("seen_count", 1)) + 1
    status = "duplicate" if previous_hash == result_hash else "updated"
    store.insert_or_update(
        existing_id=existing["id"],
        subject_key=subject_key,
        fingerprint=fingerprint,
        result_hash=result_hash,
        request_payload=request.model_dump(exclude={"api_key"}, exclude_none=True),
        result_payload=result.model_dump(exclude={"dedupe"}, exclude_none=True),
        seen_count=seen_count,
    )
    return DedupeResult(
        status=status,
        seen_count=seen_count,
        matched_on=matched_on,
        subject_key=subject_key,
        fingerprint=fingerprint,
    )