Add DBManager class and schema migrations

db/README.md

+# Database migrations
+
+This directory contains the database schema migrations and a script to generate
+the `DbManager::migrateFrom` method.  It uses the excellent [Sequel][sequel]
+library for defining the schema and performing migrations.
+
+## Usage
+
+Create a new migration in the `./migrations` directory:
+
+```
+cat > ./migrations/`date +%Y%m%d%H%M%S`_my_migration.rb <<EOF
+Sequel.migration do
+  change do
+    # your schema changes go here
+  end
+end
+EOF
+```
+
+Run `./gen_migration_data.rb`.  This will run the schema migrations from the
+very beginning to the end using an in-memory SQLite database, collect all the
+DDL statements it produces, and finally create a C++ header which defines the
+`DbManager::migrateFrom` method.  That method then runs those statements in the
+main Qt application.
+
+## But... why?
+
+I am way too lazy to write my own SQL statements for schema definitions and
+changes.  Sorry not sorry ¯\\\_(ツ)\_/¯ 
+
+[sequel]: http://sequel.jeremyevans.net/

db/gems.locked

+GEM
+  remote: https://rubygems.org/
+  specs:
+    erubis (2.7.0)
+    sequel (5.8.0)
+    sqlite3 (1.3.13)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  erubis (~> 2.7)
+  sequel (~> 5.8)
+  sqlite3 (~> 1.3)
+
+BUNDLED WITH
+   1.16.1

db/gems.rb

+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'erubis', '~> 2.7'
+gem 'sequel', '~> 5.8'
+gem 'sqlite3', '~> 1.3'

db/gen_migration_data.rb

+#!/usr/bin/env ruby
+# generates db schema + migration code
+
+require 'bundler'
+Bundler.setup :default
+
+require 'sequel'
+require 'sequel/extensions/migration'
+require 'sequel/adapters/sqlite'
+require 'erubis'
+
+# generic collector.  collects things by adding them to a collection hash
+class Collector
+  attr_reader :collection
+  attr_accessor :current
+
+  def initialize
+    @collection = {}
+    reset_current
+  end
+
+  def collect(thing)
+    collection[current] ||= []
+    collection[current] << thing
+  end
+
+  def reset_current
+    self.current = 'unknown'
+  end
+end
+
+# module to collect sql statements (only ddl for now)
+class SQLCollector < Module
+  def initialize(collector)
+    define_method :collector do
+      collector
+    end
+
+    define_method :execute_ddl do |sql, *rest|
+      collector.collect(sql)
+      super(sql, *rest)
+    end
+  end
+end
+
+# custom migrator which sets the collector's +current+ to the file name of the
+# migration
+class CollectorMigrator < Sequel::TimestampMigrator
+  # https://github.com/jeremyevans/sequel/blob/2241ce3/lib/sequel/extensions/migration.rb#L678
+  def run # rubocop:disable Metrics/AbcSize
+    migration_tuples.each do |m, f, direction|
+      checked_transaction(m) do
+        db.collector.current = f
+        m.apply(db, direction)
+        fi = f.downcase
+        direction == :up ? ds.insert(column => fi) : ds.where(column => fi).delete # rubocop:disable Metrics/LineLength
+        db.collector.reset_current
+      end
+    end
+    nil
+  end
+end
+
+###############################################################################
+
+collector = Collector.new
+Sequel::SQLite::Database.prepend(SQLCollector.new(collector))
+
+Sequel.extension :migration, :core_extensions
+
+DB = Sequel.connect('sqlite:/')
+CollectorMigrator.apply(DB, './migrations')
+
+@migrations = collector
+              .collection
+              .reject { |(k, _v)| k == 'unknown' }
+              .map { |(k, v)| [k.split('_', 2).first, v] }
+              .to_h
+
+Dir['./templates/*.erb'].each do |template_file_path|
+  target_file_name = File.basename(template_file_path, '.erb')
+  target_file_path = File.join(__dir__, 'inc', target_file_name)
+
+  puts "generating `#{target_file_name}'"
+
+  File.open(target_file_path, 'w') do |f|
+    f.puts Erubis::Eruby.new(File.read(template_file_path)).result(binding)
+  end
+end

db/inc/dbmanager_migrate_from.h

+#ifndef DBMANAGER_MIGRATE_FROM
+#define DBMANAGER_MIGRATE_FROM
+
+// This file was generated by `/db/gen_migration_data.rb`.
+// Last changed at: 2018-05-05 13:41:22 +0200
+
+void DbManager::migrateFrom(qlonglong version)
+{
+    QSqlQuery query;
+
+    if (version < 20180505002706)
+    {
+        // qDebug() << "migrating to version 20180505002706";
+        query.exec("CREATE TABLE `accounts` (`id` integer NOT NULL PRIMARY KEY AUTOINCREMENT, `username` varchar(255) NOT NULL)");
+        query.exec("CREATE UNIQUE INDEX `accounts_unique_username` ON `accounts` (`username`)");
+        query.exec("CREATE TABLE `cookies` (`id` integer NOT NULL PRIMARY KEY AUTOINCREMENT, `account_id` integer NOT NULL REFERENCES `accounts`, `name` varchar(255) NOT NULL, `value` varchar(255) NOT NULL, `cookies_unique_account_name` add_index UNIQUE)");
+
+        query.exec("INSERT INTO `schema_migrations` (`version`) VALUES (20180505002706)");
+        version = 20180505002706;
+        // qDebug() << "====== done ========";
+    }
+}
+
+#endif // DBMANAGER_MIGRATE_FROM

db/migrations/20180505002706_create_initial_schema.rb

+Sequel.migration do
+  change do
+    create_table(:accounts) do
+      primary_key :id
+      String :username, null: false, index: { name: 'accounts_unique_username', unique: true }
+    end
+
+    create_table(:cookies) do
+      primary_key :id
+      foreign_key :account_id, :accounts, null: false
+      String  :name,  null: false
+      String  :value, null: false
+
+      add_index %i[account_id name], name: 'cookies_unique_account_name', unique: true
+    end
+  end
+end

db/templates/dbmanager_migrate_from.h.erb

+#ifndef DBMANAGER_MIGRATE_FROM
+#define DBMANAGER_MIGRATE_FROM
+
+// This file was generated by `/db/gen_migration_data.rb`.
+// Last changed at: <%= Time.now %>
+
+void DbManager::migrateFrom(qlonglong version)
+{
+    QSqlQuery query;
+
+<% @migrations.each do |version, statements| %>
+    if (version < <%= version %>)
+    {
+        // qDebug() << "migrating to version <%= version %>";
+    <% statements.each do |statement| %>
+        query.exec(<%= statement.inspect %>);
+    <% end %>
+
+        query.exec("INSERT INTO `schema_migrations` (`version`) VALUES (<%= version %>)");
+        version = <%= version %>;
+        // qDebug() << "====== done ========";
+    }
+<% end %>
+}
+
+#endif // DBMANAGER_MIGRATE_FROM

nFurAffinity.pro

@@ -4,7 +4,7 @@
 #
 #-------------------------------------------------
 
-QT       += core gui widgets
+QT       += core gui widgets sql
 
 TARGET = nFurAffinity
 TEMPLATE = app
@@ -20,17 +20,22 @@ DEFINES += QT_DEPRECATED_WARNINGS
 # You can also select to disable deprecated APIs only up to a certain version of Qt.
 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
 
-INCLUDEPATH += src/
+INCLUDEPATH += \
+    src/ \
+    db/inc/
 
 SOURCES += \
     src/main.cpp \
     src/mainwindow.cpp \
-    src/furaffinityclient.cpp
+    src/furaffinityclient.cpp \
+    src/dbmanager.cpp
 
 HEADERS += \
     src/mainwindow.h \
     src/furaffinityclient.h \
-    src/settings/nsettings.h
+    src/settings/nsettings.h \
+    src/dbmanager.h \
+    db/inc/dbmanager_migrate_from.h
 
 FORMS += \
      src/mainwindow.ui

src/dbmanager.cpp

+#include "dbmanager.h"
+#include <QDir>
+#include <QVariant>
+#include <QStandardPaths>
+#include <QSqlQuery>
+#include <QSqlError>
+#include <QSqlRecord>
+
+#include "dbmanager_migrate_from.h"
+
+DbManager::DbManager(QObject *parent) : QObject(parent)
+{
+    db = QSqlDatabase::addDatabase("QSQLITE");
+    db.setDatabaseName(dbPath());
+
+    db.open();
+}
+
+DbManager::~DbManager()
+{
+    db.close();
+}
+
+void DbManager::init()
+{
+    auto db = new DbManager;
+
+    db->runMigrations();
+
+    db->deleteLater();
+}
+
+//!
+//! \brief DbManager::runMigrations runs the database migrations by first
+//! fetching the last migration version from the database and then running
+//! `migrateFrom` for that last version.
+//!
+void DbManager::runMigrations()
+{
+    QSqlQuery query;
+    if (!query.exec("SELECT NULL AS 'nil' FROM `schema_migrations` LIMIT 1"))
+    {
+        // TODO: maybe check the error code.  we will just assume this table
+        // does not exist yet.
+
+        query.exec("CREATE TABLE `schema_migrations` "
+                   "(`version` INTEGER NOT NULL PRIMARY KEY)");
+    }
+
+    query.exec("SELECT `version` FROM `schema_migrations`"
+               "ORDER BY `version`");
+    qlonglong lastVersion = 0;
+    while (query.next())
+    {
+        lastVersion = query.value("version").toLongLong();
+    }
+    migrateFrom(lastVersion);
+}
+
+//!
+//! \brief DbManager::dbPath returns the full path to the DB.
+//! \return path to the DB
+//!
+QString DbManager::dbPath()
+{
+    auto basePath =
+            QStandardPaths::standardLocations(QStandardPaths::AppDataLocation)
+            .at(0);
+    auto dbPath = QDir(basePath).filePath("application.db");
+
+    return dbPath;
+}

src/dbmanager.h

+#ifndef DBMANAGER_H
+#define DBMANAGER_H
+
+#include <QObject>
+#include <QSqlDatabase>
+
+class DbManager : public QObject
+{
+    Q_OBJECT
+public:
+    explicit DbManager(QObject *parent = nullptr);
+    ~DbManager();
+
+    static void init();
+
+signals:
+
+public slots:
+
+private:
+    static QString dbPath();
+
+    void runMigrations();
+    //!
+    //! \brief migrateFrom migrates the database schema from `version` to the
+    //! most recent version of the schema.  It is generated by a Ruby script in
+    //! the `/db` directory.
+    //! \param version version to migrate the schema from
+    //!
+    void migrateFrom(qlonglong version);
+
+    QSqlDatabase db;
+};
+
+#endif // DBMANAGER_H

src/main.cpp

-#include "mainwindow.h"
 #include <QApplication>
+#include <QDir>
+#include <QStandardPaths>
+
+#include "dbmanager.h"
+#include "mainwindow.h"
 
 int main(int argc, char *argv[])
 {
+    QApplication a(argc, argv);
+
     QCoreApplication::setApplicationName("nFurAffinity");
     QCoreApplication::setOrganizationName("nilsding");
 
-    QApplication a(argc, argv);
+    // create app data dir if it does not exist yet
+    auto appDataPath =
+            QStandardPaths::standardLocations(QStandardPaths::AppDataLocation)
+            .at(0);
+    auto appDataDir = QDir(appDataPath);
+    if (!appDataDir.exists())
+    {
+        appDataDir.mkpath(appDataPath);
+    }
+
+    // initialise database and run migrations if needed
+    DbManager::init();
+
+    // finally, run the application
     MainWindow w;
     w.show();