import logging
import re
from typing import Optional

from gliner import GLiNER

logger = logging.getLogger("uvicorn")


LABELS = [
    "email",
    "date_of_birth",
    "last_name",
    "street_address",
]
LABELS_PLACEHOLDERS = {
    "email": "an email",
    "phone_number": "a phone number",
    "date_of_birth": "a date of birth",
    "last_name": "a last name",
    "street_address": "a location",
    "ssn": "a ssn",
}

RE_SSN = r"\b\d{3}[- ]?\d{3}[- ]?\d{3}\b"
RE_ZIP = (
    r"\b[ABCEGHJKLMNPRSTVXY]\d[ABCEGHJKLMNPRSTVWXYZ][ ]?\d[ABCEGHJKLMNPRSTVWXYZ]\d\b"
)
RE_PHONE = r"(?:\+?\d{1,3}[-\s.]?)?\(?\d{3}\)?[-\s.]?\d{3}[-\s.]?\d{4}"


def clean_backslashes(txt: str) -> str:
    """Cleans backslashes from a string.

    For example, passing the string "It\'s not for everyone" will return "It's not for everyone".

    Backslashes next to names or locations confuse the PII filter.

    Args:
        txt (str): String to clean

    Returns:
        str: Cleaned string
    """
    return txt.replace("\\'", "'")


def chunk_text(text: str, max_chars: int = 1000) -> list[tuple[str, int]]:
    """
    The text is sometimes too large for the model. We chunk it here so we can pass
    each chunk to the model one by one.
    """
    chunks = []
    start = 0
    text_len = len(text)

    while start < text_len:
        # On prend un bloc (environ 1000 caractères ~ 250-300 tokens)
        end = start + max_chars

        # Pour éviter de couper un mot au milieu, on recule jusqu'au dernier espace
        if end < text_len:
            end = text.rfind(" ", start, end)
            if end <= start:  # Si aucun espace n'est trouvé
                end = start + max_chars

        chunks.append((text[start:end], start))
        # On avance le curseur (on peut ajouter un overlap ici si nécessaire)
        start = end

    return chunks


class PIIFilter:
    _instance: Optional["PIIFilter"] = None
    model: None

    def __new__(cls):
        if cls._instance is None:
            logger.info("Loading the PII filter into memory...")
            cls._instance = super(PIIFilter, cls).__new__(cls)

            # TODO: manual SSN detection
            cls._instance.model = GLiNER.from_pretrained("nvidia/gliner-PII")

        return cls._instance

    def sanitize(self, text: str) -> str:
        if not text:
            return text

        text = clean_backslashes(text)
        all_entities = []

        # 1. Chunking pour GLiNER (max_chars=1000 pour rester sous les 384 tokens)
        chunks = chunk_text(text, max_chars=1000)
        for chunk, offset in chunks:
            chunk_entities = self.model.predict_entities(chunk, LABELS, threshold=0.6)
            for ent in chunk_entities:
                all_entities.append(
                    {
                        "start": ent["start"] + offset,
                        "end": ent["end"] + offset,
                        "label": ent["label"],
                    }
                )

        # 2. Ajout des détections par Regex
        regex_rules = [
            (RE_SSN, "ssn"),
            (RE_ZIP, "street_address"),
            (RE_PHONE, "phone_number"),
        ]

        for pattern, label in regex_rules:
            for match in re.finditer(pattern, text):
                all_entities.append(
                    {"start": match.start(), "end": match.end(), "label": label}
                )

        # 3. Gestion des chevauchements (Overlaps)
        # Si deux entités se chevauchent, on garde la plus large.
        all_entities.sort(key=lambda x: x["start"])
        merged_entities = []
        if all_entities:
            current = all_entities[0]
            for next_ent in all_entities[1:]:
                if next_ent["start"] < current["end"]:
                    # Chevauchement trouvé, on prend l'enveloppe maximale
                    current["end"] = max(current["end"], next_ent["end"])
                    # On peut aussi décider ici quel label prioriser
                else:
                    merged_entities.append(current)
                    current = next_ent
            merged_entities.append(current)

        # 4. Remplacement (en partant de la fin pour garder les index valides)
        redacted_text = text
        for entity in sorted(merged_entities, key=lambda x: x["start"], reverse=True):
            placeholder = LABELS_PLACEHOLDERS[entity["label"]]
            redacted_text = (
                redacted_text[: entity["start"]]
                + placeholder
                + redacted_text[entity["end"] :]
            )

        return redacted_text