const mysql = require('mysql2/promise');
const path = require('path');
const fs = require('fs');
require('dotenv').config({ path: path.resolve(__dirname, '../.env') });

const dbConfig = {
    host: process.env.DB_HOST,
    user: process.env.DB_USER,
    password: process.env.DB_PASSWORD,
    database: process.env.DB_NAME,
    multipleStatements: true
};

function outputProgress(data) {
    console.log(JSON.stringify(data));
}

// Explicitly define all metrics-related tables
const METRICS_TABLES = [
    'temp_sales_metrics',
    'temp_purchase_metrics',
    'product_metrics',
    'product_time_aggregates',
    'vendor_metrics',
    'category_sales_metrics'
];

// Config tables that must exist
const CONFIG_TABLES = [
    'stock_thresholds',
    'lead_time_thresholds',
    'sales_velocity_config',
    'abc_classification_config',
    'safety_stock_config',
    'turnover_config'
];

// Core tables that must exist
const REQUIRED_CORE_TABLES = [
    'products',
    'orders',
    'purchase_orders'
];

async function resetMetrics() {
    outputProgress({
        status: 'running',
        operation: 'Starting metrics reset',
        percentage: '0'
    });

    const connection = await mysql.createConnection(dbConfig);
    
    try {
        // First verify that core tables exist
        outputProgress({
            status: 'running',
            operation: 'Verifying core tables exist',
            percentage: '10'
        });

        // Use SHOW TABLES to verify core tables exist
        const [showTables] = await connection.query('SHOW TABLES');
        const existingTables = showTables.map(t => Object.values(t)[0]);

        outputProgress({
            operation: 'Core tables verification',
            message: {
                found: existingTables,
                required: REQUIRED_CORE_TABLES
            }
        });

        // Check if any core tables are missing
        const missingCoreTables = REQUIRED_CORE_TABLES.filter(
            t => !existingTables.includes(t)
        );

        if (missingCoreTables.length > 0) {
            throw new Error(
                `Core tables missing: ${missingCoreTables.join(', ')}. Please run reset-db.js first.`
            );
        }

        // Verify all core tables use InnoDB
        const [engineStatus] = await connection.query('SHOW TABLE STATUS WHERE Name IN (?)', [REQUIRED_CORE_TABLES]);
        const nonInnoDBTables = engineStatus.filter(t => t.Engine !== 'InnoDB');
        
        if (nonInnoDBTables.length > 0) {
            throw new Error(
                `Tables using non-InnoDB engine: ${nonInnoDBTables.map(t => t.Name).join(', ')}`
            );
        }

        // Disable foreign key checks first
        await connection.query('SET FOREIGN_KEY_CHECKS = 0');

        // Drop the metrics views first
        outputProgress({
            status: 'running',
            operation: 'Dropping metrics views',
            percentage: '15'
        });
        await connection.query('DROP VIEW IF EXISTS inventory_health, product_sales_trends');

        // Drop only the metrics tables if they exist
        const [existing] = await connection.query(`
            SELECT GROUP_CONCAT(table_name) as tables 
            FROM information_schema.tables 
            WHERE table_schema = DATABASE()
              AND table_name IN (${METRICS_TABLES.map(table => `'${table}'`).join(',')})
        `);

        if (existing[0].tables) {
            outputProgress({
                status: 'running',
                operation: 'Dropping existing metrics tables',
                percentage: '20'
            });
            const dropQuery = `
                DROP TABLE IF EXISTS 
                ${existing[0].tables
                    .split(',')
                    .map(table => '`' + table + '`')
                    .join(', ')}
            `;
            await connection.query(dropQuery);
        }

        // Read metrics schema in its entirety
        outputProgress({
            status: 'running',
            operation: 'Creating metrics tables',
            percentage: '40'
        });
        const schemaPath = path.join(__dirname, '../db/metrics-schema.sql');
        const schemaSQL = fs.readFileSync(schemaPath, 'utf8');

        // Run the entire metrics-schema so it creates
        // the metrics tables and indexes in one shot
        await connection.query(schemaSQL);

        // Read and execute config schema
        outputProgress({
            status: 'running',
            operation: 'Creating configuration tables',
            percentage: '60'
        });
        const configSchemaPath = path.join(__dirname, '../db/config-schema.sql');
        const configSchemaSQL = fs.readFileSync(configSchemaPath, 'utf8');

        // Run the config schema
        await connection.query(configSchemaSQL);

        // Verify all tables were actually created using SHOW TABLES
        const [verifyTables] = await connection.query('SHOW TABLES');
        const tablesAfterCreation = verifyTables.map(t => Object.values(t)[0]);

        // First verify metrics tables
        outputProgress({
            status: 'running',
            operation: 'Verifying metrics tables',
            message: {
                found: tablesAfterCreation,
                required: METRICS_TABLES
            }
        });

        const missingMetricsTables = METRICS_TABLES.filter(
            t => !tablesAfterCreation.includes(t)
        );

        if (missingMetricsTables.length > 0) {
            throw new Error(
                `Failed to create metrics tables: ${missingMetricsTables.join(', ')}`
            );
        }

        // Then verify config tables
        outputProgress({
            status: 'running',
            operation: 'Verifying config tables',
            message: {
                found: tablesAfterCreation,
                required: CONFIG_TABLES
            }
        });

        const missingConfigTables = CONFIG_TABLES.filter(
            t => !tablesAfterCreation.includes(t)
        );

        if (missingConfigTables.length > 0) {
            throw new Error(
                `Failed to create config tables: ${missingConfigTables.join(', ')}`
            );
        }

        // Re-enable foreign key checks
        await connection.query('SET FOREIGN_KEY_CHECKS = 1');

        outputProgress({
            status: 'complete',
            operation: 'Metrics and config tables have been reset',
            percentage: '100'
        });

        return { success: true };
    } catch (error) {
        console.error('Error resetting metrics:', error);
        outputProgress({
            status: 'error',
            operation: 'Failed to reset metrics',
            error: error.message
        });
        throw error;
    } finally {
        await connection.end();
    }
}

// Export if required as a module
if (typeof module !== 'undefined' && module.exports) {
    module.exports = resetMetrics;
}

// Run if called from command line
if (require.main === module) {
    resetMetrics().catch(error => {
        console.error('Error:', error);
        process.exit(1);
    });
}