simo/src/lib/types.ts

// ─── Property Type ───────────────────────────────────────────────────────────

export type PropertyType = 'neuf' | 'ancien';

// ─── Loan Input ──────────────────────────────────────────────────────────────

export interface LoanInput {
  id: string;
  name: string;
  amount: number;
  rate: number;            // Annual rate as decimal (3.25% → 0.0325)
  duration: number;        // Years
  deferral: number;        // Deferred period in years
  insuranceRate: number;   // Annual rate on initial capital (0.3% → 0.003)
  isMainLoan: boolean;     // If true, amount = totalCredit - sum(others)
  enabled: boolean;
}

// ─── Simulation State (all inputs) ──────────────────────────────────────────

export interface SimulationState {
  // Project
  propertyType: PropertyType;
  propertyPrice: number;
  notaryFeesRate: number;
  guaranteeRate: number;
  bankFees: number;
  worksCost: number;
  downPayment: number;

  // Current costs (tenant)
  currentRent: number;
  rentEvolutionRate: number;   // Annual evolution (1.2% → 0.012)
  currentUtilities: number;    // EDF / fibre / eau
  currentCharges: number;
  currentHomeInsurance: number;

  // Projected costs (owner)
  projectedCharges: number;    // Copropriété
  propertyTax: number;         // Taxe foncière (monthly)
  projectedUtilities: number;  // EDF / fibre / eau
  projectedHomeInsurance: number;

  // Loans
  loans: LoanInput[];

  // Resale parameters
  firstYearDepreciation: number;  // e.g., -0.05 (5% loss first year)
  annualAppreciation: number;     // e.g., 0.01 (1% per year)
  saleFees: number;               // e.g., 0.07 (7% agency + notary)
}

// ─── Monthly Amortization (per loan) ────────────────────────────────────────

export interface MonthlyRow {
  month: number;        // 1-based global month
  monthInYear: number;  // 1-12
  year: number;         // 1-based year
  interest: number;
  principal: number;
  insurance: number;
  remaining: number;
  payment: number;      // interest + principal + insurance
}

// ─── Yearly Amortization (per loan) ─────────────────────────────────────────

export interface YearlyRow {
  year: number;
  interest: number;
  principal: number;
  insurance: number;
  remaining: number;
  payment: number;
}

// ─── Loan Computation Result ────────────────────────────────────────────────

export interface LoanResult {
  loan: LoanInput;
  effectiveAmount: number;     // Actual amount (auto-calculated for main)
  monthlyPayment: number;     // Monthly principal + interest (excl. insurance)
  monthlyInsurance: number;
  monthly: MonthlyRow[];
  yearly: YearlyRow[];
  totalInterest: number;
  totalInsurance: number;
  totalCost: number;           // amount + totalInterest + totalInsurance
}

// ─── Yearly Summary (aggregated across all loans) ───────────────────────────

export interface YearlySummary {
  year: number;

  // Credits aggregated
  totalInterest: number;
  totalPrincipal: number;
  totalInsurance: number;
  totalRemaining: number;
  totalPayment: number;

  // Projected monthly costs (as owner)
  monthlyInterest: number;
  monthlyPrincipal: number;
  monthlyCharges: number;     // charges + tax + utilities + home insurance
  monthlyLoanInsurance: number;
  monthlyTotal: number;
  capitalRatio: number;       // Part of payment building equity
  yearlyTotal: number;

  // Current monthly costs (as tenant)
  currentRent: number;
  currentCharges: number;     // utilities + charges + insurance
  currentMonthlyTotal: number;
  currentYearlyTotal: number;

  // Comparison
  difference: number;         // projected - current (negative = savings)

  // Resale projection
  resalePrice: number;
  netResale: number;          // After fees - remaining debt - down payment
}

// ─── Final Simulation Results ───────────────────────────────────────────────

export interface SimulationResults {
  // Financing
  notaryFees: number;
  guaranteeFees: number;
  totalFinancing: number;
  totalCredit: number;
  mainLoanAmount: number;

  // Per-loan results
  loanResults: LoanResult[];

  // Yearly summaries (up to 30 years)
  yearlySummaries: YearlySummary[];

  // Global totals
  totalCapital: number;
  totalInterest: number;
  totalInsurance: number;
  grandTotal: number;

  // Year 1 monthly snapshot
  monthlyPaymentYear1: number;
  projectedMonthlyCharges: number;
  projectedMonthlyTotal: number;
  currentMonthlyTotal: number;

  // Max duration across all loans
  maxDuration: number;
}