mdb/src/core/juge/marginCalculator.ts

import type { DealTrafficLight } from '../../domain/dealSignals';
import {
  DEFAULT_VAT_ON_MARGIN_RATE,
  DVF_DISCOUNT_FLASH_PCT,
  MIN_NET_MARGIN_PCT,
} from './thresholds';

export type { DealTrafficLight };

export interface JugeInputs {
  purchasePrice: number;
  resalePrice: number;
  surfaceM2: number;
  dvfReferencePriceM2?: number | null;
  worksTotal: number;
  notaryFeeRate: number;
  saleAgencyFeeRate: number;
  miscAcquisitionCost: number;
  miscSaleCost: number;
  carryingMonths: number;
  carryingAnnualRate: number;
  carryingPrincipal?: number | null;
  vatOnMarginRate?: number;
}

export interface JugeResult {
  totalInvested: number;
  netResaleProceeds: number;
  grossMarginBeforeVat: number;
  vatOnMargin: number;
  netMarginAfterVat: number;
  netMarginPct: number;
  breakEvenResalePrice: number;
  purchasePricePerM2: number;
  dvfDiscountPct: number | null;
  /** Sous-cotation vs DVF (prix / m² ≤ référence × (1 − 20 %)). */
  dvfUnderMarketFlash: boolean;
  trafficLight: DealTrafficLight;
  scoreDeal: number;
}

function carryingCostEUR(input: JugeInputs): number {
  const principal =
    input.carryingPrincipal != null && input.carryingPrincipal > 0
      ? input.carryingPrincipal
      : input.purchasePrice;
  return principal * input.carryingAnnualRate * (input.carryingMonths / 12);
}

export function evaluateDeal(input: JugeInputs): JugeResult {
  const vatRate = input.vatOnMarginRate ?? DEFAULT_VAT_ON_MARGIN_RATE;

  const notaryFees = input.purchasePrice * input.notaryFeeRate;
  const carrying = carryingCostEUR(input);
  const totalInvested =
    input.purchasePrice +
    notaryFees +
    input.worksTotal +
    input.miscAcquisitionCost +
    carrying;

  const agencyFees = input.resalePrice * input.saleAgencyFeeRate;
  const netResaleProceeds =
    input.resalePrice - agencyFees - input.miscSaleCost;

  const grossMarginBeforeVat = netResaleProceeds - totalInvested;
  const vatOnMargin = Math.max(0, grossMarginBeforeVat) * vatRate;
  const netMarginAfterVat = grossMarginBeforeVat - vatOnMargin;

  const netMarginPct =
    totalInvested > 0 ? netMarginAfterVat / totalInvested : 0;

  const purchasePricePerM2 =
    input.surfaceM2 > 0 ? input.purchasePrice / input.surfaceM2 : 0;

  let dvfDiscountPct: number | null = null;
  let dvfUnderMarketFlash = false;
  if (
    input.dvfReferencePriceM2 != null &&
    input.dvfReferencePriceM2 > 0 &&
    input.surfaceM2 > 0
  ) {
    dvfDiscountPct =
      (input.dvfReferencePriceM2 - purchasePricePerM2) /
      input.dvfReferencePriceM2;
    dvfUnderMarketFlash =
      purchasePricePerM2 <=
      input.dvfReferencePriceM2 * (1 - DVF_DISCOUNT_FLASH_PCT);
  }

  const trafficLight = resolveTrafficLight(
    netMarginPct,
    dvfUnderMarketFlash,
    dvfDiscountPct,
  );

  const scoreDeal = computeScoreDeal(netMarginPct, dvfDiscountPct);

  return {
    totalInvested,
    netResaleProceeds,
    grossMarginBeforeVat,
    vatOnMargin,
    netMarginAfterVat,
    netMarginPct,
    breakEvenResalePrice: computeBreakEvenResale(input),
    purchasePricePerM2,
    dvfDiscountPct,
    dvfUnderMarketFlash,
    trafficLight,
    scoreDeal,
  };
}

/** Marge : feu rouge sous 15 %. DVF : flash vert indépendant (signal d’achat). */
function resolveTrafficLight(
  netMarginPct: number,
  dvfUnderMarketFlash: boolean,
  dvfDiscountPct: number | null,
): DealTrafficLight {
  if (netMarginPct < MIN_NET_MARGIN_PCT) {
    return 'red';
  }
  if (dvfUnderMarketFlash) {
    return 'green_flash_dvf';
  }
  if (dvfDiscountPct != null && dvfDiscountPct > 0.1) {
    return 'green';
  }
  if (netMarginPct < 0.18) {
    return 'orange';
  }
  return 'green';
}

function computeScoreDeal(
  netMarginPct: number,
  dvfDiscountPct: number | null,
): number {
  const marginScore = Math.min(
    100,
    Math.max(0, (netMarginPct / MIN_NET_MARGIN_PCT) * 60),
  );
  const dvfBonus =
    dvfDiscountPct != null && dvfDiscountPct > 0
      ? Math.min(40, dvfDiscountPct * 100)
      : 0;
  return Math.round(Math.min(100, marginScore + dvfBonus));
}

function computeBreakEvenResale(input: JugeInputs): number {
  const notaryFees = input.purchasePrice * input.notaryFeeRate;
  const carrying = carryingCostEUR(input);
  const fixedCosts =
    input.purchasePrice +
    notaryFees +
    input.worksTotal +
    input.miscAcquisitionCost +
    carrying +
    input.miscSaleCost;

  const agencyRate = input.saleAgencyFeeRate;
  const coeff = 1 - agencyRate;
  if (coeff <= 0) {
    return Number.POSITIVE_INFINITY;
  }
  return fixedCosts / coeff;
}

/**
 * Prix d’achat max pour tenir une marge nette cible (ex. 15 % après TVA sur marge).
 * Recalcul instantané quand la checklist visite augmente les travaux.
 */
export function maxPurchaseForTargetNetMarginPct(
  input: Omit<JugeInputs, 'purchasePrice'>,
  targetNetMarginPct: number,
): number {
  const vatRate = input.vatOnMarginRate ?? DEFAULT_VAT_ON_MARGIN_RATE;
  let low = 0;
  let high = Math.max(input.resalePrice * 1.5, 1);
  for (let i = 0; i < 56; i++) {
    const mid = (low + high) / 2;
    const { netMarginPct } = evaluateDeal({
      ...input,
      purchasePrice: mid,
      carryingPrincipal: input.carryingPrincipal ?? mid,
      vatOnMarginRate: vatRate,
    });
    if (netMarginPct >= targetNetMarginPct) {
      low = mid;
    } else {
      high = mid;
    }
  }
  return Math.max(0, Math.round(low));
}