Math/IFI/calc_IFI.py

# calc_IFI.py
import json
import sys
import logging
from pathlib import Path
from typing import Dict, Any

log = logging.getLogger(__name__)

def load_json(file_path: str) -> Dict[str, Any]:
    """Load JSON with helpful error messages."""
    try:
        with open(file_path, 'r', encoding='utf-8') as f:
            return json.load(f)
    except FileNotFoundError:
        log.error(f"IFI JSON not found: {file_path}")
        raise
    except json.JSONDecodeError as e:
        log.error(f"IFI JSON corrupt ({file_path}): {e}")
        raise


def calculate_ifi(
    gross_assets: float,
    debts: float = 0.0,
    primary_residence_value: float = 0.0,
    json_file: str | None = None,
) -> dict:
    """
    IFI 2025 – progressive brackets + 30 % primary-residence abatement.
    """

    # 1. Resolve JSON path

    if json_file is None:
        json_file = getattr(sys.modules[__name__], "_JSON_PATH", None)

    if json_file is None:
        # Defensive fallback – same folder as this script
        json_file = str(Path(__file__).parent / "ifi_taux.json")
        log.debug(f"IFI JSON fallback → {json_file}")

    log.info(f"IFI calc: gross={gross_assets:,.0f}€, debt={debts:,.0f}€, primary={primary_residence_value:,.0f}€")


    # 2. Load rates
    # ------------------------------------------------------------------
    data = load_json(json_file)
    if not data:
        return {
            "tax": 0.0,
            "net_taxable": 0.0,
            "abattement": 0.0,
            "abattement_applied": False,
            "note": "Impossible de charger les taux IFI."
        }


    # 3. Net assets + primary-residence abatement

    net_assets = gross_assets - debts
    abatement = 0.0
    abatement_applied = primary_residence_value > 0

    if abatement_applied:
        abatement = primary_residence_value * data["abattement_primary_residence"]
        net_assets -= abatement

    net_assets = max(0.0, net_assets)

    result = {
        "tax": 0.0,
        "net_taxable": round(net_assets, 2),
        "abattement": round(abatement, 2),
        "abattement_applied": abatement_applied,
        "note": ""
    }

    # ------------------------------------------------------------------
    # 4. Below threshold → no IFI
    # ------------------------------------------------------------------
    if net_assets <= data["threshold"]:
        result["note"] = (
            f"Patrimoine net {net_assets:,.0f} € < seuil {data['threshold']:,.0f} € → pas d'IFI. "
            f"{'Abattement 30 % appliqué.' if abatement_applied else 'Aucun abattement.'}"
        )
        return result

    # ------------------------------------------------------------------
    # 5. Progressive tax
    # ------------------------------------------------------------------
    tax = 0.0
    remaining = net_assets
    prev_max = 0.0

    for bracket in data["brackets"]:
        current_max = bracket["max"] if bracket["max"] is not None else float("inf")
        taxable = min(remaining, current_max - prev_max)
        if taxable > 0:
            tax += taxable * bracket["rate"]
        remaining -= taxable
        prev_max = current_max
        if remaining <= 0:
            break

    result["tax"] = round(tax, 2)
    result["note"] = (
        f"IFI calculé sur {net_assets:,.0f} € net. "
        f"{'Abattement 30 % appliqué.' if abatement_applied else 'Aucun abattement.'} "
        f"Taux progressifs 2025."
    )
    log.info(f"IFI result → tax={result['tax']:,}€")
    return result