z-bar-qt/Plugins/ZShell/Config/migration.hpp

#pragma once

#include <QJsonObject>
#include <QStringList>

namespace ZShell::config {

// A single migration rule: move the value stored at the dotted `from` path
// to the dotted `to` path, then delete the old key (and any parent objects
// left empty).
//
// Rules are applied to the raw JSON file on every load, before the schema
// loads it. They are idempotent: once the old key is gone the rule never
// fires again, so no version stamping is needed. Old rules can stay in the
// table forever.
//
// WARNING: the target path must exist in the schema (i.e. a ConfigObject
// property somewhere in the tree). If it does not, the migrated value is
// loaded as an unknown key and silently dropped on the next save.
struct ConfigMigrationRule {
	QString from;
	QString to;
};

// Helper for writing rules: migrate("general.color.foo", "display.bar.foo")
inline ConfigMigrationRule migrate(const QString& from, const QString& to) {
	return {from, to};
}

class ConfigMigrations {
	public:
	[[nodiscard]] static const QList<ConfigMigrationRule>& rules();

	// Applies all rules to `json`, returning the migrated object.
	[[nodiscard]] static QJsonObject apply(const QJsonObject& json);
};

} // namespace ZShell::config