#!/usr/bin/env node

/**
 * Script zur Analyse und Empfehlung von Indizes
 * 
 * Analysiert:
 * - Tabellen mit vielen Sequential Scans
 * - Fehlende Composite Indizes für häufige JOINs
 * - Ungenutzte Indizes
 */

import './config/loadEnv.js';
import { sequelize } from './utils/sequelize.js';

async function main() {
    try {
        console.log('🔍 Index-Analyse und Empfehlungen\n');
        console.log('='.repeat(60) + '\n');

        // 1. Tabellen mit vielen Sequential Scans
        await analyzeSequentialScans();

        // 2. Prüfe häufige JOIN-Patterns
        await analyzeJoinPatterns();

        // 3. Ungenutzte Indizes
        await analyzeUnusedIndexes();

        console.log('='.repeat(60));
        console.log('✅ Analyse abgeschlossen\n');

        await sequelize.close();
        process.exit(0);

    } catch (error) {
        console.error('❌ Fehler:', error.message);
        console.error(error.stack);
        process.exit(1);
    }
}

async function analyzeSequentialScans() {
    console.log('📊 1. Tabellen mit vielen Sequential Scans\n');

    const [tables] = await sequelize.query(`
        SELECT 
            schemaname || '.' || relname as table_name,
            seq_scan,
            seq_tup_read,
            idx_scan,
            seq_tup_read / NULLIF(seq_scan, 0) as avg_rows_per_scan,
            CASE 
                WHEN seq_scan + idx_scan > 0 
                THEN round((seq_scan::numeric / (seq_scan + idx_scan)) * 100, 2)
                ELSE 0
            END as seq_scan_percent
        FROM pg_stat_user_tables
        WHERE schemaname IN ('falukant_data', 'falukant_type', 'community', 'logs')
        AND seq_scan > 1000
        ORDER BY seq_tup_read DESC
        LIMIT 10;
    `);

    if (tables.length > 0) {
        console.log('   ⚠️  Tabellen mit vielen Sequential Scans:');
        tables.forEach(t => {
            console.log(`\n   ${t.table_name}:`);
            console.log(`      Sequential Scans: ${parseInt(t.seq_scan).toLocaleString()}`);
            console.log(`      Zeilen gelesen: ${parseInt(t.seq_tup_read).toLocaleString()}`);
            console.log(`      Index Scans: ${parseInt(t.idx_scan).toLocaleString()}`);
            console.log(`      Seq Scan Anteil: ${t.seq_scan_percent}%`);
            console.log(`      Ø Zeilen pro Scan: ${parseInt(t.avg_rows_per_scan).toLocaleString()}`);
            
            if (t.seq_scan_percent > 50) {
                console.log(`      ⚠️  KRITISCH: Mehr als 50% Sequential Scans!`);
            }
        });
        console.log('');
    }
}

async function analyzeJoinPatterns() {
    console.log('🔗 2. Analyse häufiger JOIN-Patterns\n');

    // Prüfe welche Indizes auf knowledge existieren
    const [knowledgeIndexes] = await sequelize.query(`
        SELECT 
            indexname,
            indexdef
        FROM pg_indexes
        WHERE schemaname = 'falukant_data'
        AND tablename = 'knowledge'
        ORDER BY indexname;
    `);

    console.log('   Indizes auf falukant_data.knowledge:');
    if (knowledgeIndexes.length > 0) {
        knowledgeIndexes.forEach(idx => {
            console.log(`      - ${idx.indexname}: ${idx.indexdef}`);
        });
    } else {
        console.log('      Keine Indizes gefunden');
    }
    console.log('');

    // Empfehlung: Composite Index auf (character_id, product_id)
    const [knowledgeUsage] = await sequelize.query(`
        SELECT 
            idx_scan,
            idx_tup_read,
            idx_tup_fetch
        FROM pg_stat_user_indexes
        WHERE schemaname = 'falukant_data'
        AND relname = 'knowledge'
        AND indexrelname = 'idx_knowledge_character_id';
    `);

    if (knowledgeUsage.length > 0) {
        const usage = knowledgeUsage[0];
        console.log('   Aktuelle Nutzung von idx_knowledge_character_id:');
        console.log(`      Scans: ${parseInt(usage.idx_scan).toLocaleString()}`);
        console.log(`      Zeilen gelesen: ${parseInt(usage.idx_tup_read).toLocaleString()}`);
        console.log('');
        
        console.log('   💡 Empfehlung:');
        console.log('      CREATE INDEX IF NOT EXISTS idx_knowledge_character_product');
        console.log('      ON falukant_data.knowledge(character_id, product_id);');
        console.log('      → Wird häufig für JOINs mit character_id UND product_id verwendet\n');
    }

    // Prüfe character Indizes
    const [characterIndexes] = await sequelize.query(`
        SELECT 
            indexname,
            indexdef
        FROM pg_indexes
        WHERE schemaname = 'falukant_data'
        AND tablename = 'character'
        ORDER BY indexname;
    `);

    console.log('   Indizes auf falukant_data.character:');
    if (characterIndexes.length > 0) {
        characterIndexes.forEach(idx => {
            console.log(`      - ${idx.indexname}: ${idx.indexdef}`);
        });
    }
    console.log('');
}

async function analyzeUnusedIndexes() {
    console.log('🗑️  3. Ungenutzte Indizes\n');

    const [unused] = await sequelize.query(`
        SELECT 
            schemaname || '.' || indexrelname as index_name,
            schemaname || '.' || relname as table_name,
            pg_size_pretty(pg_relation_size(indexrelid)) as index_size,
            idx_scan as scans,
            pg_relation_size(indexrelid) as size_bytes
        FROM pg_stat_user_indexes
        WHERE schemaname IN ('falukant_data', 'falukant_type', 'community', 'logs')
        AND idx_scan = 0
        AND pg_relation_size(indexrelid) > 1024 * 1024  -- Größer als 1MB
        ORDER BY pg_relation_size(indexrelid) DESC
        LIMIT 10;
    `);

    if (unused.length > 0) {
        console.log('   ⚠️  Ungenutzte Indizes (> 1MB):');
        unused.forEach(idx => {
            console.log(`      ${idx.index_name} auf ${idx.table_name}`);
            console.log(`         Größe: ${idx.index_size}, Scans: ${idx.scans}`);
        });
        console.log('');
        console.log('   💡 Überlege, ob diese Indizes gelöscht werden können:');
        console.log('      DROP INDEX IF EXISTS <index_name>;');
        console.log('');
    } else {
        console.log('   ✅ Keine großen ungenutzten Indizes gefunden\n');
    }
}

main();