const { query } = require('../database/db');

class AuditLog {
    /**
     * Create a new audit log entry
     * @param {string} tableName - Name of the table that was modified
     * @param {string} recordId - ID of the record that was modified
     * @param {string} action - Type of action: CREATE, UPDATE, DELETE
     * @param {Object} oldValues - Previous values (null for CREATE)
     * @param {Object} newValues - New values (null for DELETE)
     * @param {string[]} changedFields - Array of field names that changed
     * @returns {Promise<Object>} Created audit log entry
     */
    static async create(tableName, recordId, action, oldValues, newValues, changedFields) {
        const result = await query(
            `INSERT INTO audit_logs (table_name, record_id, action, old_values, new_values, changed_fields)
             VALUES ($1, $2, $3, $4, $5, $6)
             RETURNING *`,
            [
                tableName,
                recordId.toString(),
                action,
                oldValues ? JSON.stringify(oldValues) : null,
                newValues ? JSON.stringify(newValues) : null,
                changedFields || []
            ]
        );
        return result.rows[0];
    }

    /**
     * Get audit logs for a specific table
     * @param {string} tableName - Name of the table
     * @param {number} limit - Maximum number of logs to return (default: 50)
     * @param {number} offset - Number of logs to skip (for pagination)
     * @returns {Promise<Array>} Array of audit log entries
     */
    static async getByTable(tableName, limit = 50, offset = 0) {
        const result = await query(
            `SELECT * FROM audit_logs
             WHERE table_name = $1
             ORDER BY created_at DESC
             LIMIT $2 OFFSET $3`,
            [tableName, limit, offset]
        );
        return result.rows;
    }

    /**
     * Get audit logs for a specific record
     * @param {string} tableName - Name of the table
     * @param {string} recordId - ID of the record
     * @returns {Promise<Array>} Array of audit log entries for this record
     */
    static async getByRecord(tableName, recordId) {
        const result = await query(
            `SELECT * FROM audit_logs
             WHERE table_name = $1 AND record_id = $2
             ORDER BY created_at DESC`,
            [tableName, recordId.toString()]
        );
        return result.rows;
    }

    /**
     * Get recent audit logs across all tables
     * @param {number} limit - Maximum number of logs to return
     * @returns {Promise<Array>} Array of recent audit log entries
     */
    static async getRecent(limit = 50) {
        const result = await query(
            `SELECT * FROM audit_logs
             ORDER BY created_at DESC
             LIMIT $1`,
            [limit]
        );
        return result.rows;
    }

    /**
     * Get audit logs by date range
     * @param {string} tableName - Name of the table (optional)
     * @param {string} startDate - Start date (YYYY-MM-DD)
     * @param {string} endDate - End date (YYYY-MM-DD)
     * @param {number} limit - Maximum number of logs to return
     * @returns {Promise<Array>} Array of audit log entries
     */
    static async getByDateRange(tableName, startDate, endDate, limit = 50) {
        let queryStr;
        let params;

        if (tableName) {
            queryStr = `SELECT * FROM audit_logs
                        WHERE table_name = $1
                        AND created_at >= $2
                        AND created_at <= $3
                        ORDER BY created_at DESC
                        LIMIT $4`;
            params = [tableName, startDate, endDate, limit];
        } else {
            queryStr = `SELECT * FROM audit_logs
                        WHERE created_at >= $1
                        AND created_at <= $2
                        ORDER BY created_at DESC
                        LIMIT $3`;
            params = [startDate, endDate, limit];
        }

        const result = await query(queryStr, params);
        return result.rows;
    }

    /**
     * Get count of audit logs for a table
     * @param {string} tableName - Name of the table
     * @returns {Promise<number>} Count of audit logs
     */
    static async getCount(tableName) {
        const result = await query(
            `SELECT COUNT(*) as count FROM audit_logs WHERE table_name = $1`,
            [tableName]
        );
        return parseInt(result.rows[0].count, 10);
    }
}

module.exports = AuditLog;