kima2/src/core/database.cpp

#include "database.h"

#include <filesystem>
#include <iostream>
#include <stdexcept>

Database::Database(const std::string& dbname) : db_(nullptr)
{
    dbname_ = dbname;
    const int errCode = sqlite3_open(dbname_.c_str(), &db_);
    if (errCode) {
        throw std::runtime_error("Could not open database file.");
    }
    sqlite3_db_config(db_, SQLITE_DBCONFIG_ENABLE_FKEY);
}

Database::~Database() { sqlite3_close(db_); }

void Database::exec(const std::string& sql)
{
    char* errMsg;
    const int errCode = sqlite3_exec(db_, sql.c_str(), nullptr, nullptr, &errMsg);
    if (errCode) {
        std::string errMsgString(errMsg); // Make a C++ string of the errMsg, so that we can call
                                          // sqlite3_free() before throwing the exception
        sqlite3_free(errMsg);
        throw std::runtime_error("Error in SQL execution: " + errMsgString);
    }
}

void Database::createNew()
{
    std::string sqlCreateKima2{"CREATE TABLE IF NOT EXISTS kima2 ("
                               "version INTEGER NOT NULL);"
                               "INSERT INTO kima2 (version) VALUES (1);"};
    std::string sqlCreateSellers{"CREATE TABLE IF NOT EXISTS sellers ("
                                 "id TEXT PRIMARY KEY NOT NULL, "
                                 "seller_no INTEGER, "
                                 "first_name TEXT, "
                                 "last_name TEXT, "
                                 "offered_articles INTEGER, "
                                 "UNIQUE (seller_no)"
                                 ");"};

    std::string sqlCreateArticles{
        "CREATE TABLE IF NOT EXISTS articles ("
        "id TEXT PRIMARY KEY NOT NULL, "
        "seller_id TEXT NOT NULL, "
        "source_no INTEGER NOT NULL, "
        "article_no INTEGER NOT NULL, "
        "description TEXT, "
        "price INTEGER NOT NULL, "
        "UNIQUE (source_no, article_no), "
        "FOREIGN KEY (seller_id) REFERENCES sellers(id) ON DELETE CASCADE, "
        "CHECK (article_no BETWEEN 0 AND 99999)"
        ");"};

    beginTransaction();
    exec(sqlCreateKima2);
    exec(sqlCreateSellers);
    exec(sqlCreateArticles);
    endTransaction();
}

void Database::init()
{
    int version = getVersion();

    switch (version) {
    case 0:
        createNew();
        break;
        // perhaps handle upgrades for db schema here...
    default:
        // Do nothing because we are up-to-date.
        break;
    }
}

int Database::getVersion()
{
    int retCode{};
    sqlite3_stmt* stmt;

    // Check if there's already a kima2 table available.
    // If not, return version == 0.
    retCode = sqlite3_prepare_v2(
        db_, "SELECT count(*) FROM sqlite_master WHERE type='table' AND name='kima2';", -1, &stmt,
        nullptr);
    if (retCode != SQLITE_OK)
        throw std::string(sqlite3_errmsg(db_));
    retCode = sqlite3_step(stmt);
    if (retCode != SQLITE_ROW && retCode != SQLITE_DONE) {
        std::string errMsg(sqlite3_errmsg(db_));
        sqlite3_finalize(stmt);
        throw errMsg;
    } else if (retCode != SQLITE_DONE) {
        int count = sqlite3_column_int(stmt, 0);
        sqlite3_finalize(stmt);
        if (count == 0)
            return 0; // no kima2 table, so version is 0
    }

    // Now that we know that the kima2 table is present, read and return the schema version.
    retCode = sqlite3_prepare_v2(db_, "SELECT version FROM kima2", -1, &stmt, nullptr);
    if (retCode != SQLITE_OK)
        throw std::string(sqlite3_errmsg(db_));

    retCode = sqlite3_step(stmt);

    if (retCode != SQLITE_ROW && retCode != SQLITE_DONE) {
        std::string errMsg(sqlite3_errmsg(db_));
        sqlite3_finalize(stmt);
        throw errMsg;
    } else if (retCode == SQLITE_DONE) {
        sqlite3_finalize(stmt);
        return 0; // no version entry, so version is 0
    }

    int version = sqlite3_column_int(stmt, 0);
    sqlite3_finalize(stmt);

    return version;
}

void Database::beginTransaction() { exec("BEGIN TRANSACTION"); }

void Database::endTransaction() { exec("END TRANSACTION"); }