user_cache.h

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#pragma once
 
#include <cstdint>
#include <expected>
#include <filesystem>
#include <functional>
#include <nlohmann/json_fwd.hpp>
#include <set>
#include <span>
#include <string>
#include <string_view>
#include <vector>
 
namespace mm::core {
 
struct UserCacheFile {
  std::string path;
  uint64_t size = 0;       
  int64_t modifiedMs = 0;  
  bool deletable = true;
};
 
void to_json(nlohmann::json& j, const UserCacheFile& f);
 
class UserCache {
 public:
  explicit UserCache(std::filesystem::path root);
 
  const std::filesystem::path& root() const { return root_; }
 
  std::expected<std::filesystem::path, std::string> resolve(std::string_view relPath) const;
 
  std::expected<std::vector<UserCacheFile>, std::string> list() const;
 
  std::expected<std::vector<uint8_t>, std::string> read(std::string_view relPath) const;
 
  std::expected<void, std::string> write(std::string_view relPath, std::span<const uint8_t> data);
 
  std::expected<bool, std::string> remove(std::string_view relPath);
 
  void retain(std::string relPath);
 
  bool isRetained(std::string_view relPath) const;
 
 private:
  std::filesystem::path root_;
  std::set<std::string, std::less<>> retained_;
};
 
}  // namespace mm::core