json-validator/include/jvalidate/detail/relative_pointer.h

#pragma once

#include <ostream>
#include <string>
#include <string_view>

#include <jvalidate/detail/expect.h>
#include <jvalidate/detail/pointer.h>
#include <jvalidate/forward.h>

namespace jvalidate::detail {
class RelativePointer {
public:
  RelativePointer(std::string_view path) {
    if (path == "0") {
      return;
    }
    if (auto pos = path.find('/'); pos != path.npos) {
      pointer_ = Pointer(path.substr(pos));
      path.remove_suffix(path.size() - pos);
    } else {
      EXPECT_M(not path.empty() && path.back() == '#',
               "RelativePointer must end in a pointer, or a '#'");
      requests_key_ = true;
      path.remove_suffix(1);
    }
    parent_steps_ = std::stoull(std::string(path));
  }

  template <Adapter A>
  std::variant<std::string, A> inspect(Pointer const & where, A const & root) const {
    if (requests_key_) {
      return where.parent(parent_steps_).back();
    }
    auto rval = where.parent(parent_steps_).walk(root);
    return pointer_ ? pointer_->walk(rval) : rval;
  }

  friend std::ostream & operator<<(std::ostream & os, RelativePointer const & rel) {
    os << rel.parent_steps_;
    if (rel.requests_key_) {
      return os << '#';
    }
    if (rel.pointer_) {
      os << *rel.pointer_;
    }
    return os;
  }

private:
  size_t parent_steps_ = 0;
  bool requests_key_ = false;
  std::optional<Pointer> pointer_ = std::nullopt;
};
}