path: root/third_party/nix/src/libutil/config.hh

#include <map>
#include <set>

#include "libutil/types.hh"

#pragma once

namespace nix {

class Args;
class AbstractSetting;
class JSONPlaceholder;
class JSONObject;

class AbstractConfig {
 protected:
  StringMap unknownSettings;

  explicit AbstractConfig(const StringMap& initials = {})
      : unknownSettings(initials) {}

 public:
  virtual bool set(const std::string& name, const std::string& value) = 0;

  struct SettingInfo {
    std::string value;
    std::string description;
  };

  virtual void getSettings(std::map<std::string, SettingInfo>& res,
                           bool overridenOnly = false) = 0;

  void applyConfigFile(const Path& path);

  virtual void resetOverriden() = 0;

  virtual void toJSON(JSONObject& out) = 0;

  virtual void convertToArgs(Args& args, const std::string& category) = 0;

  void warnUnknownSettings();

  void reapplyUnknownSettings();
};

/* A class to simplify providing configuration settings. The typical
   use is to inherit Config and add Setting<T> members:

   class MyClass : private Config
   {
     Setting<int> foo{this, 123, "foo", "the number of foos to use"};
     Setting<std::string> bar{this, "blabla", "bar", "the name of the bar"};

     MyClass() : Config(readConfigFile("/etc/my-app.conf"))
     {
       std::cout << foo << "\n"; // will print 123 unless overriden
     }
   };
*/

class Config : public AbstractConfig {
  friend class AbstractSetting;

 public:
  struct SettingData {
    bool isAlias;
    AbstractSetting* setting;
    SettingData(bool isAlias, AbstractSetting* setting)
        : isAlias(isAlias), setting(setting) {}
  };

  typedef std::map<std::string, SettingData> Settings;

 private:
  Settings _settings;

 public:
  explicit Config(const StringMap& initials = {}) : AbstractConfig(initials) {}

  bool set(const std::string& name, const std::string& value) override;

  void addSetting(AbstractSetting* setting);

  void getSettings(std::map<std::string, SettingInfo>& res,
                   bool overridenOnly = false) override;

  void resetOverriden() override;

  void toJSON(JSONObject& out) override;

  void convertToArgs(Args& args, const std::string& category) override;
};

class AbstractSetting {
  friend class Config;

 public:
  const std::string name;
  const std::string description;
  const std::set<std::string> aliases;

  int created = 123;

  bool overriden = false;

 protected:
  AbstractSetting(std::string name, std::string description,
                  std::set<std::string> aliases);

  virtual ~AbstractSetting() {
    // Check against a gcc miscompilation causing our constructor
    // not to run (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431).
    assert(created == 123);
  }

  virtual void set(const std::string& value) = 0;

  virtual std::string to_string() = 0;

  virtual void toJSON(JSONPlaceholder& out);

  virtual void convertToArg(Args& args, const std::string& category);

  bool isOverriden() { return overriden; }
};

/* A setting of type T. */
template <typename T>
class BaseSetting : public AbstractSetting {
 protected:
  T value;

 public:
  BaseSetting(const T& def, const std::string& name,
              const std::string& description,
              const std::set<std::string>& aliases = {})
      : AbstractSetting(name, description, aliases), value(def) {}

  operator const T&() const { return value; }
  operator T&() { return value; }
  const T& get() const { return value; }
  bool operator==(const T& v2) const { return value == v2; }
  bool operator!=(const T& v2) const { return value != v2; }
  void operator=(const T& v) { assign(v); }
  virtual void assign(const T& v) { value = v; }

  void set(const std::string& str) override;

  virtual void override(const T& v) {
    overriden = true;
    value = v;
  }

  std::string to_string() override;

  void convertToArg(Args& args, const std::string& category) override;

  void toJSON(JSONPlaceholder& out) override;
};

template <typename T>
std::ostream& operator<<(std::ostream& str, const BaseSetting<T>& opt) {
  str << (const T&)opt;
  return str;
}

template <typename T>
bool operator==(const T& v1, const BaseSetting<T>& v2) {
  return v1 == (const T&)v2;
}

template <typename T>
class Setting : public BaseSetting<T> {
 public:
  Setting(Config* options, const T& def, const std::string& name,
          const std::string& description,
          const std::set<std::string>& aliases = {})
      : BaseSetting<T>(def, name, description, aliases) {
    options->addSetting(this);
  }

  void operator=(const T& v) { this->assign(v); }
};

/* A special setting for Paths. These are automatically canonicalised
   (e.g. "/foo//bar/" becomes "/foo/bar"). */
class PathSetting : public BaseSetting<Path> {
  bool allowEmpty;

 public:
  PathSetting(Config* options, bool allowEmpty, const Path& def,
              const std::string& name, const std::string& description,
              const std::set<std::string>& aliases = {})
      : BaseSetting<Path>(def, name, description, aliases),
        allowEmpty(allowEmpty) {
    options->addSetting(this);
  }

  void set(const std::string& str) override;

  Path operator+(const char* p) const { return value + p; }

  void operator=(const Path& v) { this->assign(v); }
};

struct GlobalConfig : public AbstractConfig {
  using ConfigRegistrations = std::vector<Config*>;
  static ConfigRegistrations* configRegistrations;

  bool set(const std::string& name, const std::string& value) override;

  void getSettings(std::map<std::string, SettingInfo>& res,
                   bool overridenOnly = false) override;

  void resetOverriden() override;

  void toJSON(JSONObject& out) override;

  void convertToArgs(Args& args, const std::string& category) override;

  struct Register {
    explicit Register(Config* config);
  };
};

extern GlobalConfig globalConfig;

}  // namespace nix