ConfigDB.h

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/* Copyright (C) 2022 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
    CConfigDB - Load, access and store configuration variables

    TDD     :   http://www.wildfiregames.com/forum/index.php?showtopic=1125
    OVERVIEW:

    JavaScript: Check this documentation: http://trac.wildfiregames.com/wiki/Exposed_ConfigDB_Functions
*/

#ifndef INCLUDED_CONFIGDB
#define INCLUDED_CONFIGDB

#include "lib/file/vfs/vfs_path.h"
#include "ps/CStr.h"

#include <array>
#include <map>
#include <memory>
#include <mutex>
#include <vector>

/**
 * Namespace priorities:
 * - Command line args override everything
 * - User supersedes HWDetect (let the user try crashing his system).
 * - HWDetect supersedes mods & default -> mods can mod hwdetect itself.
 * - SYSTEM is used for local.cfg and is basically for setting custom defaults.
 */
enum EConfigNamespace
{
    CFG_DEFAULT,
    CFG_MOD,
    CFG_SYSTEM,
    CFG_HWDETECT,
    CFG_USER,
    CFG_COMMAND,
    CFG_LAST
};

using CConfigValueSet = std::vector<CStr>;

// Opaque data type so that callers that hook into ConfigDB can delete their hooks.
// Would be defined in CConfigDB but then it couldn't be forward-declared, which is rather annoying.
// Actually defined below - requires access to CConfigDB.
class CConfigDBHook;

#define g_ConfigDB (*CConfigDB::Instance())

class CConfigDB
{
    friend CConfigDBHook;
public:
    CConfigDB();
    ~CConfigDB();
    CConfigDB(const CConfigDB&) = delete;
    CConfigDB(CConfigDB&&) = delete;

    static void Initialise();
    static void Shutdown();
    static bool IsInitialised();
    static CConfigDB* Instance();

    /**
     * Attempt to retrieve the value of a config variable with the given name;
     * will search CFG_COMMAND first, and then all namespaces from the specified
     * namespace down.
     */
    void GetValue(EConfigNamespace ns, const CStr& name, bool& value);
    ///@copydoc CConfigDB::GetValue
    void GetValue(EConfigNamespace ns, const CStr& name, int& value);
    ///@copydoc CConfigDB::GetValue
    void GetValue(EConfigNamespace ns, const CStr& name, u32& value);
    ///@copydoc CConfigDB::GetValue
    void GetValue(EConfigNamespace ns, const CStr& name, float& value);
    ///@copydoc CConfigDB::GetValue
    void GetValue(EConfigNamespace ns, const CStr& name, double& value);
    ///@copydoc CConfigDB::GetValue
    void GetValue(EConfigNamespace ns, const CStr& name, std::string& value);

    /**
     * Returns true if changed with respect to last write on file
     */
    bool HasChanges(EConfigNamespace ns) const;

    void SetChanges(EConfigNamespace ns, bool value);

    /**
     * Attempt to retrieve a vector of values corresponding to the given setting;
     * will search CFG_COMMAND first, and then all namespaces from the specified
     * namespace down.
     */
    void GetValues(EConfigNamespace ns, const CStr& name, CConfigValueSet& values) const;

    /**
     * Returns the namespace that the value returned by GetValues was defined in,
     * or CFG_LAST if it wasn't defined at all.
     */
    EConfigNamespace GetValueNamespace(EConfigNamespace ns, const CStr& name) const;

    /**
     * Retrieve a map of values corresponding to settings whose names begin
     * with the given prefix;
     * will search all namespaces from default up to the specified namespace.
     */
    std::map<CStr, CConfigValueSet> GetValuesWithPrefix(EConfigNamespace ns, const CStr& prefix) const;

    /**
     * Save a config value in the specified namespace. If the config variable
     * existed the value is replaced.
     */
    void SetValueString(EConfigNamespace ns, const CStr& name, const CStr& value);

    void SetValueBool(EConfigNamespace ns, const CStr& name, const bool value);

    void SetValueList(EConfigNamespace ns, const CStr& name, std::vector<CStr> values);

    /**
     * Remove a config value in the specified namespace.
     */
    bool RemoveValue(EConfigNamespace ns, const CStr& name);

    /**
     * Set the path to the config file used to populate the specified namespace
     * Note that this function does not actually load the config file. Use
     * the Reload() method if you want to read the config file at the same time.
     *
     * 'path': The path to the config file.
     */
    void SetConfigFile(EConfigNamespace ns, const VfsPath& path);

    /**
     * Reload the config file associated with the specified config namespace
     * (the last config file path set with SetConfigFile)
     *
     * Returns:
     *  true:   if the reload succeeded,
     *  false:  if the reload failed
     */
    bool Reload(EConfigNamespace);

    /**
     * Write the current state of the specified config namespace to the file
     * specified by 'path'
     *
     * Returns:
     *  true:   if the config namespace was successfully written to the file
     *  false:  if an error occurred
     */
    bool WriteFile(EConfigNamespace ns, const VfsPath& path) const;

    /**
     * Write the current state of the specified config namespace to the file
     * it was originally loaded from.
     *
     * Returns:
     *  true:   if the config namespace was successfully written to the file
     *  false:  if an error occurred
     */
    bool WriteFile(EConfigNamespace ns) const;

    /**
     * Write a config value to the file specified by 'path'
     *
     * Returns:
     *  true:   if the config value was successfully saved and written to the file
     *  false:  if an error occurred
     */
    bool WriteValueToFile(EConfigNamespace ns, const CStr& name, const CStr& value, const VfsPath& path);

    bool WriteValueToFile(EConfigNamespace ns, const CStr& name, const CStr& value);

    /**
     * Register a simple lambda that will be called anytime the value changes in any namespace
     * This is simple on purpose, the hook is responsible for checking if it should do something.
     * When RegisterHookAndCall is called, the hook is immediately triggered.
     * NB: CConfigDBHook will auto-unregister the hook when destroyed,
     * so you can use it to tie the lifetime of the hook to your object.
     * The hook will be deleted alongside ConfigDB anyways.
     */
    [[nodiscard]] CConfigDBHook RegisterHookAndCall(const CStr& name, std::function<void()> hook);

    void UnregisterHook(CConfigDBHook&& hook);
    void UnregisterHook(std::unique_ptr<CConfigDBHook> hook);

private:
    std::array<std::map<CStr, CConfigValueSet>, CFG_LAST> m_Map;
    std::multimap<CStr, std::function<void()>> m_Hooks;
    std::array<VfsPath, CFG_LAST> m_ConfigFile;
    std::array<bool, CFG_LAST> m_HasChanges;

    mutable std::recursive_mutex m_Mutex;
};

class CConfigDBHook
{
    friend class CConfigDB;
public:
    CConfigDBHook() = delete;
    CConfigDBHook(const CConfigDBHook&) = delete;
    // Point the moved-from hook to end, which is checked for in UnregisterHook,
    // to avoid a double-erase error.
    CConfigDBHook(CConfigDBHook&& h) : m_ConfigDB(h.m_ConfigDB)
    {
        m_Ptr = std::move(h.m_Ptr);
        h.m_Ptr = m_ConfigDB.m_Hooks.end();
    }
    // Unregisters the hook. Must be called before the original ConfigDB gets deleted.
    ~CConfigDBHook()
    {
        m_ConfigDB.UnregisterHook(std::move(*this));
    }
private:
    CConfigDBHook(CConfigDB& cdb, std::multimap<CStr, std::function<void()>>::iterator p)
        : m_ConfigDB(cdb), m_Ptr(p)
    {};

    std::multimap<CStr, std::function<void()>>::iterator m_Ptr;
    CConfigDB& m_ConfigDB;
};


// stores the value of the given key into <destination>. this quasi-template
// convenience wrapper on top of GetValue simplifies user code
#define CFG_GET_VAL(name, destination)\
    g_ConfigDB.GetValue(CFG_USER, name, destination)

#endif // INCLUDED_CONFIGDB