//===--- Relation.h ----------------------------------------------*- C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_RELATION_H
#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_RELATION_H

#include "index/SymbolID.h"
#include "llvm/ADT/iterator_range.h"
#include <cstdint>
#include <utility>

namespace clang {
namespace clangd {

enum class RelationKind : uint8_t {
  BaseOf,
  OverriddenBy,
};

/// Represents a relation between two symbols.
/// For an example:
///   - "A is a base class of B" is represented as
///     { Subject = A, Predicate = BaseOf, Object = B }.
///   - "Derived::Foo overrides Base::Foo" is represented as
///     { Subject = Base::Foo, Predicate = OverriddenBy, Object = Derived::Foo
///     }.
struct Relation {
  SymbolID Subject;
  RelationKind Predicate;
  SymbolID Object;

  bool operator==(const Relation &Other) const {
    return std::tie(Subject, Predicate, Object) ==
           std::tie(Other.Subject, Other.Predicate, Other.Object);
  }
  // SPO order
  bool operator<(const Relation &Other) const {
    return std::tie(Subject, Predicate, Object) <
           std::tie(Other.Subject, Other.Predicate, Other.Object);
  }
};
llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const RelationKind R);
llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Relation &R);

class RelationSlab {
public:
  using value_type = Relation;
  using const_iterator = std::vector<value_type>::const_iterator;
  using iterator = const_iterator;

  RelationSlab() = default;
  RelationSlab(RelationSlab &&Slab) = default;
  RelationSlab &operator=(RelationSlab &&RHS) = default;

  const_iterator begin() const { return Relations.begin(); }
  const_iterator end() const { return Relations.end(); }
  size_t size() const { return Relations.size(); }
  bool empty() const { return Relations.empty(); }

  size_t bytes() const {
    return sizeof(*this) + sizeof(value_type) * Relations.capacity();
  }

  /// Lookup all relations matching the given subject and predicate.
  llvm::iterator_range<iterator> lookup(const SymbolID &Subject,
                                        RelationKind Predicate) const;

  /// RelationSlab::Builder is a mutable container that can 'freeze' to
  /// RelationSlab.
  class Builder {
  public:
    /// Adds a relation to the slab.
    void insert(const Relation &R) { Relations.push_back(R); }

    /// Consumes the builder to finalize the slab.
    RelationSlab build() &&;

  private:
    std::vector<Relation> Relations;
  };

private:
  RelationSlab(std::vector<Relation> Relations)
      : Relations(std::move(Relations)) {}

  std::vector<Relation> Relations;
};

} // namespace clangd
} // namespace clang

#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_RELATION_H
