"""Service for importing household data from CSV/XLSX files."""

import io
import secrets
import string

import pandas as pd
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select

from app.models import Household

# Characters without ambiguous ones (O/0/I/1/l)
SAFE_CHARS = string.ascii_uppercase.replace("O", "").replace("I", "") + string.digits.replace("0", "").replace("1", "")


def generate_auth_code(length: int = 8) -> str:
    return "".join(secrets.choice(SAFE_CHARS) for _ in range(length))


VALID_STATUSES = {"RS", "RP", "PRO"}
REQUIRED_COLUMNS = {"identifier", "status", "volume_m3", "price_eur"}


def parse_import_file(file_bytes: bytes, filename: str) -> tuple[pd.DataFrame | None, list[str]]:
    """
    Parse a CSV or XLSX file and validate its contents.

    Returns (dataframe, errors). If errors is non-empty, dataframe may be None.
    """
    errors = []

    try:
        if filename.endswith(".csv"):
            df = pd.read_csv(io.BytesIO(file_bytes))
        elif filename.endswith((".xlsx", ".xls")):
            df = pd.read_excel(io.BytesIO(file_bytes))
        else:
            return None, ["Format non supporté. Utilisez CSV ou XLSX."]
    except Exception as e:
        return None, [f"Erreur de lecture du fichier: {e}"]

    # Normalize column names
    df.columns = [c.strip().lower().replace(" ", "_") for c in df.columns]

    missing = REQUIRED_COLUMNS - set(df.columns)
    if missing:
        return None, [f"Colonnes manquantes: {', '.join(missing)}"]

    # Validate rows
    for idx, row in df.iterrows():
        line = idx + 2  # Excel line number (1-indexed + header)
        status = str(row["status"]).strip().upper()
        if status not in VALID_STATUSES:
            errors.append(f"Ligne {line}: statut '{row['status']}' invalide (attendu: RS, RP, PRO)")

        try:
            vol = float(row["volume_m3"])
            if vol < 0:
                errors.append(f"Ligne {line}: volume négatif ({vol})")
        except (ValueError, TypeError):
            errors.append(f"Ligne {line}: volume invalide '{row['volume_m3']}'")

        price = row.get("price_eur")
        if pd.notna(price):
            try:
                p = float(price)
                if p < 0:
                    errors.append(f"Ligne {line}: prix négatif ({p})")
            except (ValueError, TypeError):
                errors.append(f"Ligne {line}: prix invalide '{price}'")

    # Normalize
    df["status"] = df["status"].str.strip().str.upper()
    df["identifier"] = df["identifier"].astype(str).str.strip()

    return df, errors


async def import_households(
    db: AsyncSession,
    commune_id: int,
    df: pd.DataFrame,
) -> tuple[int, list[str]]:
    """
    Import validated households into the database.

    Returns (created_count, errors).
    """
    created = 0
    errors = []

    # Get existing auth codes to avoid collisions
    existing_codes = set()
    result = await db.execute(select(Household.auth_code))
    for row in result.scalars():
        existing_codes.add(row)

    for idx, row in df.iterrows():
        identifier = str(row["identifier"]).strip()
        status = str(row["status"]).strip().upper()
        volume = float(row["volume_m3"])
        price = float(row["price_eur"]) if pd.notna(row.get("price_eur")) else 0.0

        # Check for duplicate
        existing = await db.execute(
            select(Household).where(
                Household.commune_id == commune_id,
                Household.identifier == identifier,
            )
        )
        if existing.scalar_one_or_none():
            errors.append(f"Foyer '{identifier}' existe déjà, ignoré.")
            continue

        # Generate unique auth code
        code = generate_auth_code()
        while code in existing_codes:
            code = generate_auth_code()
        existing_codes.add(code)

        household = Household(
            commune_id=commune_id,
            identifier=identifier,
            status=status,
            volume_m3=volume,
            price_paid_eur=price,
            auth_code=code,
        )
        db.add(household)
        created += 1

    await db.commit()
    return created, errors


def generate_template_csv() -> bytes:
    """Generate a template CSV file for household import."""
    content = "identifier,status,volume_m3,price_eur\n"
    content += "DUPONT Jean,RS,85.5,189.50\n"
    content += "MARTIN Pierre,RP,120.0,245.00\n"
    content += "SARL Boulangerie,PRO,350.0,\n"
    return content.encode("utf-8")