feat: simulation state management (React Context) and sharing/export

src/contexts/SimulationContext.tsx

@@ -0,0 +1,192 @@
+'use client';
+
+import React, {
+  createContext,
+  useContext,
+  useReducer,
+  useMemo,
+  useEffect,
+  useCallback,
+  type ReactNode,
+} from 'react';
+import type { SimulationState, SimulationResults, LoanInput } from '@/lib/types';
+import { computeSimulation } from '@/lib/calculations';
+import { defaultStateNeuf, defaultStateAncien, createEmptyLoan, generateLoanId } from '@/lib/defaults';
+import { decodeState } from '@/lib/sharing';
+
+// ─── Actions ────────────────────────────────────────────────────────────────
+
+type Action =
+  | { type: 'SET_FIELD'; field: keyof SimulationState; value: unknown }
+  | { type: 'SET_PROPERTY_TYPE'; value: 'neuf' | 'ancien' }
+  | { type: 'ADD_LOAN'; loan: LoanInput }
+  | { type: 'REMOVE_LOAN'; id: string }
+  | { type: 'UPDATE_LOAN'; id: string; field: keyof LoanInput; value: unknown }
+  | { type: 'TOGGLE_LOAN'; id: string }
+  | { type: 'LOAD_STATE'; state: SimulationState }
+  | { type: 'RESET' };
+
+function reducer(state: SimulationState, action: Action): SimulationState {
+  switch (action.type) {
+    case 'SET_FIELD':
+      return { ...state, [action.field]: action.value };
+
+    case 'SET_PROPERTY_TYPE': {
+      if (action.value === state.propertyType) return state;
+      // Switch between neuf and ancien defaults
+      const base = action.value === 'neuf' ? defaultStateNeuf() : defaultStateAncien();
+      return {
+        ...state,
+        propertyType: action.value,
+        notaryFeesRate: base.notaryFeesRate,
+        loans: action.value === 'ancien'
+          ? state.loans.filter((l) => l.name !== 'Prêt Taux Zéro')
+          : state.loans,
+      };
+    }
+
+    case 'ADD_LOAN':
+      return { ...state, loans: [...state.loans, action.loan] };
+
+    case 'REMOVE_LOAN':
+      return { ...state, loans: state.loans.filter((l) => l.id !== action.id) };
+
+    case 'UPDATE_LOAN':
+      return {
+        ...state,
+        loans: state.loans.map((l) =>
+          l.id === action.id ? { ...l, [action.field]: action.value } : l
+        ),
+      };
+
+    case 'TOGGLE_LOAN':
+      return {
+        ...state,
+        loans: state.loans.map((l) =>
+          l.id === action.id ? { ...l, enabled: !l.enabled } : l
+        ),
+      };
+
+    case 'LOAD_STATE':
+      return action.state;
+
+    case 'RESET':
+      return defaultStateNeuf();
+
+    default:
+      return state;
+  }
+}
+
+// ─── Context ────────────────────────────────────────────────────────────────
+
+interface SimulationContextValue {
+  state: SimulationState;
+  results: SimulationResults;
+  setField: (field: keyof SimulationState, value: unknown) => void;
+  setPropertyType: (type: 'neuf' | 'ancien') => void;
+  addLoan: (loan: LoanInput) => void;
+  removeLoan: (id: string) => void;
+  updateLoan: (id: string, field: keyof LoanInput, value: unknown) => void;
+  toggleLoan: (id: string) => void;
+  loadState: (state: SimulationState) => void;
+  reset: () => void;
+}
+
+const SimulationContext = createContext<SimulationContextValue | null>(null);
+
+// ─── Provider ───────────────────────────────────────────────────────────────
+
+export function SimulationProvider({ children }: { children: ReactNode }) {
+  const [state, dispatch] = useReducer(reducer, defaultStateNeuf());
+
+  // Load state from URL hash on mount
+  useEffect(() => {
+    const hash = window.location.hash.slice(1);
+    if (hash) {
+      decodeState(hash).then((loaded) => {
+        if (loaded) {
+          // Re-generate loan IDs to avoid conflicts
+          const withIds = {
+            ...loaded,
+            loans: loaded.loans.map((l) => ({ ...l, id: generateLoanId() })),
+          };
+          dispatch({ type: 'LOAD_STATE', state: withIds });
+        }
+      });
+    }
+  }, []);
+
+  const results = useMemo(() => computeSimulation(state), [state]);
+
+  const setField = useCallback(
+    (field: keyof SimulationState, value: unknown) =>
+      dispatch({ type: 'SET_FIELD', field, value }),
+    []
+  );
+
+  const setPropertyType = useCallback(
+    (type: 'neuf' | 'ancien') => dispatch({ type: 'SET_PROPERTY_TYPE', value: type }),
+    []
+  );
+
+  const addLoan = useCallback(
+    (loan: LoanInput) => dispatch({ type: 'ADD_LOAN', loan }),
+    []
+  );
+
+  const removeLoan = useCallback(
+    (id: string) => dispatch({ type: 'REMOVE_LOAN', id }),
+    []
+  );
+
+  const updateLoan = useCallback(
+    (id: string, field: keyof LoanInput, value: unknown) =>
+      dispatch({ type: 'UPDATE_LOAN', id, field, value }),
+    []
+  );
+
+  const toggleLoan = useCallback(
+    (id: string) => dispatch({ type: 'TOGGLE_LOAN', id }),
+    []
+  );
+
+  const loadState = useCallback(
+    (s: SimulationState) => dispatch({ type: 'LOAD_STATE', state: s }),
+    []
+  );
+
+  const reset = useCallback(() => dispatch({ type: 'RESET' }), []);
+
+  const value = useMemo(
+    () => ({
+      state,
+      results,
+      setField,
+      setPropertyType,
+      addLoan,
+      removeLoan,
+      updateLoan,
+      toggleLoan,
+      loadState,
+      reset,
+    }),
+    [state, results, setField, setPropertyType, addLoan, removeLoan, updateLoan, toggleLoan, loadState, reset]
+  );
+
+  return (
+    <SimulationContext.Provider value={value}>
+      {children}
+    </SimulationContext.Provider>
+  );
+}
+
+// ─── Hook ───────────────────────────────────────────────────────────────────
+
+export function useSimulation(): SimulationContextValue {
+  const ctx = useContext(SimulationContext);
+  if (!ctx) {
+    throw new Error('useSimulation must be used within SimulationProvider');
+  }
+  return ctx;
+}

src/lib/sharing.ts

@@ -0,0 +1,57 @@
+import type { SimulationState } from './types';
+
+/**
+ * Encode simulation state into a shareable URL hash.
+ * Uses lz-string for compression.
+ */
+export async function encodeState(state: SimulationState): Promise<string> {
+  const { compressToEncodedURIComponent } = await import('lz-string');
+  const json = JSON.stringify(state);
+  return compressToEncodedURIComponent(json);
+}
+
+/**
+ * Decode simulation state from a URL hash.
+ */
+export async function decodeState(hash: string): Promise<SimulationState | null> {
+  try {
+    const { decompressFromEncodedURIComponent } = await import('lz-string');
+    const json = decompressFromEncodedURIComponent(hash);
+    if (!json) return null;
+    return JSON.parse(json) as SimulationState;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Export yearly data as CSV.
+ */
+export function exportCSV(headers: string[], rows: (string | number)[][]): void {
+  const bom = '\uFEFF'; // UTF-8 BOM for Excel
+  const sep = ';';
+  const lines = [
+    headers.join(sep),
+    ...rows.map((row) => row.map((v) => (typeof v === 'number' ? v.toFixed(2) : v)).join(sep)),
+  ];
+  const csv = bom + lines.join('\n');
+  const blob = new Blob([csv], { type: 'text/csv;charset=utf-8;' });
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement('a');
+  a.href = url;
+  a.download = `simulation-pret-immo-${new Date().toISOString().slice(0, 10)}.csv`;
+  a.click();
+  URL.revokeObjectURL(url);
+}
+
+/**
+ * Copy text to clipboard.
+ */
+export async function copyToClipboard(text: string): Promise<boolean> {
+  try {
+    await navigator.clipboard.writeText(text);
+    return true;
+  } catch {
+    return false;
+  }
+}