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/number.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 if (path.ends_with('#')) {
      requests_key_ = true;
      path.remove_suffix(1);
    }

    EXPECT_M(path == "0" || not path.starts_with("0"), "Cannot zero-prefix a relative pointer");
    parent_steps_ = from_str<size_t>(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_.walk(rval);
  }

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

private:
  size_t parent_steps_ = 0;
  bool requests_key_ = false;
  Pointer pointer_ = {};
};
}