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

#pragma once

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

#include <jvalidate/compat/expected.h>
#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:
  static expected<RelativePointer, std::string> parse(std::string_view path) {
    if (path == "0") {
      return RelativePointer();
    }

    RelativePointer rval;
    if (auto pos = path.find('/'); pos != path.npos) {
      expected ptr = Pointer::parse(path.substr(pos));
      JVALIDATE_PROPIGATE_UNEXPECTED(ptr);
      rval.pointer_ = *std::move(ptr);
      path.remove_suffix(path.size() - pos);
    } else if (path.back() == '#') {
      rval.requests_key_ = true;
      path.remove_suffix(1);
    }

    if (path.find_first_not_of("0123456789") != std::string_view::npos) {
      return unexpected("RelativePointer must end in a pointer, or a '#'");
    }

    size_t read = 0;
    expected parent_steps = parse_integer<size_t>(path, {.read = read});

    JVALIDATE_PROPIGATE_UNEXPECTED(parent_steps.transform_error(to_message));
    EXPECT_M(read == path.size(), "Extra chars in RelativePointer");

    rval.parent_steps_ = *parent_steps;
    return rval;
  }

  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_ = {};
};
}