feat: Add opening move sequence index

- Create buildOpeningIndex.js script to generate moveIndex.json
- Generate moveIndex.json with 12,377 unique move sequences
- Index maps move sequences to arrays of opening metadata
- Sorted by move length then alphabetically
- File size: 4.07 MB
- Enables fast lookup of multiple possible openings from move sequences

scripts/buildOpeningIndex.js

@@ -0,0 +1,122 @@
+#!/usr/bin/env node
+
+/**
+ * Build Opening Index Script
+ * 
+ * This script generates a move-sequence index from the ECO opening database files.
+ * It creates a JSON file that maps move sequences to arrays of opening metadata.
+ * 
+ * Usage: node scripts/buildOpeningIndex.js
+ * 
+ * Output: public/openings/moveIndex.json
+ */
+
+const fs = require('fs');
+const path = require('path');
+
+// Paths
+const ECO_DIR = path.join(__dirname, '../public/openings');
+const OUTPUT_FILE = path.join(ECO_DIR, 'moveIndex.json');
+
+// ECO files to process
+const ECO_FILES = ['ecoA.json', 'ecoB.json', 'ecoC.json', 'ecoD.json', 'ecoE.json'];
+
+console.log('🚀 Building opening move index...\n');
+
+// Load all ECO data
+const allOpenings = [];
+let totalOpenings = 0;
+
+for (const filename of ECO_FILES) {
+    const filepath = path.join(ECO_DIR, filename);
+    console.log(`📖 Reading ${filename}...`);
+    
+    try {
+        const data = JSON.parse(fs.readFileSync(filepath, 'utf8'));
+        const entries = Object.entries(data);
+        
+        for (const [fen, opening] of entries) {
+            allOpenings.push({
+                fen,
+                ...opening
+            });
+        }
+        
+        console.log(`   ✓ Loaded ${entries.length} openings`);
+        totalOpenings += entries.length;
+    } catch (error) {
+        console.error(`   ✗ Error reading ${filename}:`, error.message);
+        process.exit(1);
+    }
+}
+
+console.log(`\n📊 Total openings loaded: ${totalOpenings}\n`);
+
+// Build move sequence index
+console.log('🔨 Building move sequence index...');
+
+const moveIndex = {};
+let uniqueSequences = 0;
+
+for (const opening of allOpenings) {
+    const moveSequence = opening.moves.trim();
+    
+    if (!moveIndex[moveSequence]) {
+        moveIndex[moveSequence] = [];
+        uniqueSequences++;
+    }
+    
+    // Add opening to this move sequence
+    // Remove the 'fen' field to reduce file size (we don't need it in the index)
+    const { fen, ...openingData } = opening;
+    moveIndex[moveSequence].push(openingData);
+}
+
+console.log(`   ✓ Created ${uniqueSequences} unique move sequences\n`);
+
+// Sort each array of openings
+console.log('📋 Sorting openings...');
+
+for (const moveSequence in moveIndex) {
+    moveIndex[moveSequence].sort((a, b) => {
+        // Sort by move length (shorter first), then alphabetically by name
+        const aLength = a.moves.length;
+        const bLength = b.moves.length;
+        
+        if (aLength !== bLength) {
+            return aLength - bLength;
+        }
+        
+        return a.name.localeCompare(b.name);
+    });
+}
+
+console.log('   ✓ Sorted all opening arrays\n');
+
+// Write output file
+console.log(`💾 Writing to ${OUTPUT_FILE}...`);
+
+try {
+    fs.writeFileSync(OUTPUT_FILE, JSON.stringify(moveIndex, null, 2), 'utf8');
+    console.log('   ✓ File written successfully\n');
+} catch (error) {
+    console.error('   ✗ Error writing file:', error.message);
+    process.exit(1);
+}
+
+// Statistics
+const stats = {
+    totalOpenings,
+    uniqueSequences,
+    avgOpeningsPerSequence: (totalOpenings / uniqueSequences).toFixed(2),
+    fileSize: (fs.statSync(OUTPUT_FILE).size / 1024 / 1024).toFixed(2) + ' MB'
+};
+
+console.log('✅ Build complete!\n');
+console.log('📈 Statistics:');
+console.log(`   - Total openings: ${stats.totalOpenings}`);
+console.log(`   - Unique move sequences: ${stats.uniqueSequences}`);
+console.log(`   - Average openings per sequence: ${stats.avgOpeningsPerSequence}`);
+console.log(`   - Output file size: ${stats.fileSize}`);
+console.log('\n🎯 Next step: Run this file and commit public/openings/moveIndex.json to git\n');
+