import re

from sqlalchemy.orm import Session

from app.models.department import Department


def _normalize_words(value: str | None) -> set[str]:
    stop_words = {
        "i", "me", "my", "we", "our", "you", "your",
        "a", "an", "the", "is", "are", "am", "was", "were",
        "be", "been", "have", "has", "had", "do", "does",
        "and", "or", "but", "to", "of", "for", "in",
        "on", "at", "with", "this", "that", "these", "those",
        "please", "dear", "sir", "thank", "thanks", "also",
        "want", "need", "can", "could", "would",
    }

    return {
        word
        for word in re.split(r"[^a-zA-Z0-9]+", (value or "").lower())
        if word and word not in stop_words
    }


def score_department(department: Department, message: str) -> int:
    query_value = message.lower().strip()
    if not _normalize_words(query_value):
        return 0

    score = 0
    searchable_fields = [
        department.name,
        department.code,
        department.description or "",
        department.keywords or "",
        department.query or "",
    ]

    for field in searchable_fields:
        field_value = field.lower()
        if query_value in field_value:
            score += 10

    message_words = _normalize_words(query_value)
    department_keywords = _normalize_words(department.keywords)
    department_prompt_words = _normalize_words(department.query)

    score += len(message_words & department_keywords) * 5
    score += len(message_words & department_prompt_words) * 3

    return score


def match_department(db: Session, message: str) -> tuple[Department | None, int]:
    departments = (
        db.query(Department)
        .filter(Department.is_active.is_(True))
        .all()
    )

    best_department = None
    best_score = 0

    for department in departments:
        score = score_department(department, message)
        if score > best_score:
            best_department = department
            best_score = score

    if best_department is not None:
        return best_department, best_score

    fallback_department = next(
        (department for department in departments if department.name.lower() == "admin"),
        None,
    )
    if fallback_department is not None:
        return fallback_department, 0

    return None, 0