basic_connection.cpp

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// BSD 3-Clause License
// Copyright (c) 2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include <iostream>
#include <memory>
#include <string>
#include <variant>
 
#include "database/database_manager.h"
#include "database/core/database_context.h"
 
using namespace database;
 
int main()
{
    std::cout << "=== basic_connection example ===" << std::endl;
 
    // Step 1: Create a dependency injection context.
    // database_context manages shared components such as the performance
    // monitor and entity manager.
    auto context = std::make_shared<database_context>();
 
    // Step 2: Create the database manager using the context.
    auto db_manager = std::make_shared<database_manager>(context);
 
    // Step 3: Select the database backend.
    // Available types: database_types::postgres, database_types::sqlite, etc.
    if (!db_manager->set_mode(database_types::postgres))
    {
        std::cerr << "Failed to set database mode to PostgreSQL" << std::endl;
        return 1;
    }
    std::cout << "Database mode set to PostgreSQL" << std::endl;
 
    // Step 4: Connect to the database.
    // Adjust the connection string to match your environment.
    std::string connection_string
        = "host=localhost port=5432 dbname=example_db user=user password=password";
 
    std::cout << "Connecting to database..." << std::endl;
    auto connect_result = db_manager->connect_result(connection_string);
 
    if (!connect_result.is_ok())
    {
        std::cerr << "Connection failed. Make sure PostgreSQL is running and\n"
                  << "the connection string is correct.\n"
                  << "Connection string format:\n"
                  << "  host=<host> port=<port> dbname=<db> user=<user> password=<pass>"
                  << std::endl;
        return 1;
    }
    std::cout << "Connected successfully" << std::endl;
 
    // Step 5: Create a table (DDL query).
    std::string create_sql = R"(
        CREATE TABLE IF NOT EXISTS greetings (
            id    SERIAL PRIMARY KEY,
            message VARCHAR(200) NOT NULL
        )
    )";
 
    auto create_result = db_manager->create_query_result(create_sql);
    if (create_result.is_ok())
    {
        std::cout << "Table 'greetings' is ready" << std::endl;
    }
    else
    {
        std::cerr << "Failed to create table" << std::endl;
    }
 
    // Step 6: Insert a row (DML query).
    auto insert_result = db_manager->execute_query_result(
        "INSERT INTO greetings (message) VALUES ('Hello from database_system!')");
 
    if (insert_result.is_ok())
    {
        std::cout << "Row inserted" << std::endl;
    }
 
    // Step 7: Select rows and display results.
    auto select_result
        = db_manager->select_query_result("SELECT id, message FROM greetings ORDER BY id");
 
    if (select_result.is_ok())
    {
        const auto& rows = select_result.value();
        std::cout << "Query returned " << rows.size() << " row(s):" << std::endl;
 
        for (const auto& row : rows)
        {
            for (const auto& [column, value] : row)
            {
                std::cout << "  " << column << " = ";
                std::visit([](const auto& v) { std::cout << v; }, value);
                std::cout << std::endl;
            }
        }
    }
    else
    {
        std::cerr << "Select query failed: " << select_result.error().message << std::endl;
    }
 
    // Step 8: Disconnect.
    db_manager->disconnect_result();
    std::cout << "Disconnected" << std::endl;
 
    std::cout << "=== basic_connection example completed ===" << std::endl;
    return 0;
}