feat(chess): add JSON export/import with validation (P3.13)

packages/chess/src/app/App.tsx

@@ -2,9 +2,10 @@ import { Routes, Route, useNavigate } from 'react-router-dom'
 import { GameView } from '../ui/GameView'
 import { RulesView } from '../ui/RulesView'
 import { SavePanel } from '../ui/SavePanel'
+import { ImportExport } from '../ui/ImportExport'
 import { useChessEngine } from '../hooks/useChessEngine'
 import { ChessEngine } from '../engine'
-import type { AttrKey, FactValue } from '@paratype/rete'
+import type { AttrKey, FactValue, EntityId } from '@paratype/rete'
 
 export function App() {
   const chessState = useChessEngine()
@@ -23,22 +24,33 @@ export function App() {
 
 function SaveWrapper({ chessState }: { chessState: ReturnType<typeof useChessEngine> }) {
   const navigate = useNavigate()
+  
+  const handleLoad = (loadedFacts: Array<{ id: number; attr: string; value: unknown }>) => {
+    const newEngine = new ChessEngine()
+    const oldFacts = newEngine.session.allFacts();
+    for (const f of oldFacts) {
+      newEngine.session.retract(f.id, f.attr as AttrKey);
+    }
+    for (const fact of loadedFacts) {
+      newEngine.session.insert(fact.id as EntityId, fact.attr as AttrKey, fact.value as FactValue)
+    }
+    chessState.loadEngine(newEngine)
+    navigate('/game')
+  }
+
   return (
-    <SavePanel 
-      currentFacts={chessState.facts} 
-      onLoad={(loadedFacts) => {
-        const newEngine = new ChessEngine()
-        const oldFacts = newEngine.session.allFacts();
-        for (const f of oldFacts) {
-          newEngine.session.retract(f.id, f.attr as AttrKey);
-        }
-        for (const fact of loadedFacts) {
-          newEngine.session.insert(fact.id, fact.attr as AttrKey, fact.value as FactValue)
-        }
-        chessState.loadEngine(newEngine)
-        navigate('/game')
-      }}
-    />
+    <div className="flex flex-col gap-8">
+      <SavePanel 
+        currentFacts={chessState.facts} 
+        onLoad={handleLoad}
+      />
+      <div className="w-full max-w-2xl mx-auto px-4">
+        <ImportExport
+          currentFacts={chessState.facts}
+          onLoad={handleLoad}
+        />
+      </div>
+    </div>
   )
 }
 

packages/chess/src/persist/io.ts

@@ -0,0 +1,63 @@
+export interface GameExport {
+  version: 1;
+  exportedAt: number;
+  facts: Array<{ id: number; attr: string; value: unknown }>;
+}
+
+export class ImportError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = 'ImportError';
+  }
+}
+
+export function exportGame(facts: Array<{ id: number; attr: string; value: unknown }>): string {
+  const payload: GameExport = {
+    version: 1,
+    exportedAt: Date.now(),
+    facts
+  };
+  return JSON.stringify(payload, null, 2);
+}
+
+export function importGame(json: string): Array<{ id: number; attr: string; value: unknown }> {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(json);
+  } catch {
+    throw new ImportError('Invalid JSON format');
+  }
+
+  if (!parsed || typeof parsed !== 'object') {
+    throw new ImportError('Invalid export format: not an object');
+  }
+
+  const exportData = parsed as Record<string, unknown>;
+
+  if (exportData.version !== 1) {
+    throw new ImportError(`Unsupported export version: ${exportData.version}`);
+  }
+
+  if (!Array.isArray(exportData.facts)) {
+    throw new ImportError('Invalid export format: missing facts array');
+  }
+
+  for (let i = 0; i < exportData.facts.length; i++) {
+    const fact = exportData.facts[i];
+    if (!fact || typeof fact !== 'object') {
+      throw new ImportError(`Invalid fact at index ${i}: not an object`);
+    }
+
+    const { id, attr } = fact as Record<string, unknown>;
+
+    if (typeof id !== 'number') {
+      throw new ImportError(`Invalid fact at index ${i}: id must be a number`);
+    }
+
+    if (typeof attr !== 'string') {
+      throw new ImportError(`Invalid fact at index ${i}: attr must be a string`);
+    }
+  }
+
+  return exportData.facts as Array<{ id: number; attr: string; value: unknown }>;
+}

packages/chess/src/ui/ImportExport.tsx

@@ -0,0 +1,100 @@
+import { useState, useRef } from 'react';
+import { exportGame, importGame } from '../persist/io';
+
+interface ImportExportProps {
+  currentFacts?: Array<{ id: number; attr: string; value: unknown }>;
+  onLoad: (facts: Array<{ id: number; attr: string; value: unknown }>) => void;
+}
+
+export function ImportExport({ currentFacts, onLoad }: ImportExportProps) {
+  const [error, setError] = useState<string | null>(null);
+  const fileInputRef = useRef<HTMLInputElement>(null);
+
+  const handleExport = () => {
+    if (!currentFacts) return;
+    
+    try {
+      const json = exportGame(currentFacts);
+      const blob = new Blob([json], { type: 'application/json' });
+      const url = URL.createObjectURL(blob);
+      const a = document.createElement('a');
+      a.href = url;
+      a.download = `chess-game-${Date.now()}.json`;
+      a.click();
+      URL.revokeObjectURL(url);
+    } catch (err) {
+      console.error('Export failed:', err);
+    }
+  };
+
+  const handleImportClick = () => {
+    setError(null);
+    fileInputRef.current?.click();
+  };
+
+  const handleFileChange = (e: React.ChangeEvent<HTMLInputElement>) => {
+    const file = e.target.files?.[0];
+    if (!file) return;
+
+    const reader = new FileReader();
+    reader.onload = (event) => {
+      try {
+        const text = event.target?.result as string;
+        const facts = importGame(text);
+        onLoad(facts);
+        // Reset file input so the same file can be selected again
+        if (fileInputRef.current) fileInputRef.current.value = '';
+      } catch (err) {
+        setError(err instanceof Error ? err.message : 'Unknown import error');
+      }
+    };
+    reader.onerror = () => {
+      setError('Failed to read file');
+    };
+    reader.readAsText(file);
+  };
+
+  return (
+    <div className="w-full">
+      <h2 className="text-xl font-bold tracking-tight text-neutral-800 mb-6">Export / Import</h2>
+      
+      <div className="bg-white rounded-lg border border-neutral-200 shadow-sm overflow-hidden mb-8 p-6">
+        {error && (
+          <div 
+            data-testid="import-error"
+            className="mb-6 p-4 bg-red-50 text-red-700 rounded-md border border-red-200"
+          >
+            {error}
+          </div>
+        )}
+        
+        <div className="flex flex-col sm:flex-row gap-4">
+          <button
+            data-action="export"
+            onClick={handleExport}
+            disabled={!currentFacts}
+            className="flex-1 px-6 py-3 bg-neutral-900 text-white font-medium rounded-md hover:bg-neutral-800 active:bg-neutral-950 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
+          >
+            Export to File
+          </button>
+          
+          <button
+            data-action="import"
+            onClick={handleImportClick}
+            className="flex-1 px-6 py-3 text-neutral-700 bg-white border border-neutral-300 font-medium rounded-md hover:bg-neutral-50 active:bg-neutral-100 transition-colors"
+          >
+            Import from File
+          </button>
+          
+          <input
+            type="file"
+            ref={fileInputRef}
+            onChange={handleFileChange}
+            accept=".json,application/json"
+            className="hidden"
+          />
+        </div>
+      </div>
+    </div>
+  );
+}