// Copyright (C) 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef ICING_SCORING_ADVANCED_SCORING_SCORING_VISITOR_H_
#define ICING_SCORING_ADVANCED_SCORING_SCORING_VISITOR_H_

#include "icing/text_classifier/lib3/utils/base/status.h"
#include "icing/text_classifier/lib3/utils/base/statusor.h"
#include "icing/legacy/core/icing-string-util.h"
#include "icing/proto/scoring.pb.h"
#include "icing/query/advanced_query_parser/abstract-syntax-tree.h"
#include "icing/scoring/advanced_scoring/score-expression.h"

namespace icing {
namespace lib {

class ScoringVisitor : public AbstractSyntaxTreeVisitor {
 public:
  explicit ScoringVisitor(double default_score)
      : default_score_(default_score) {}

  void VisitFunctionName(const FunctionNameNode* node) override;
  void VisitString(const StringNode* node) override;
  void VisitText(const TextNode* node) override;
  void VisitMember(const MemberNode* node) override;
  void VisitFunction(const FunctionNode* node) override;
  void VisitUnaryOperator(const UnaryOperatorNode* node) override;
  void VisitNaryOperator(const NaryOperatorNode* node) override;

  // RETURNS:
  //   - An ScoreExpression instance able to evaluate the expression on success.
  //   - INVALID_ARGUMENT if the AST does not conform to supported expressions,
  //   such as type errors.
  //   - INTERNAL if there are inconsistencies.
  libtextclassifier3::StatusOr<std::unique_ptr<ScoreExpression>>
  Expression() && {
    if (has_pending_error()) {
      return pending_error_;
    }
    if (stack.size() != 1) {
      return absl_ports::InternalError(IcingStringUtil::StringPrintf(
          "Expect to get only one result from "
          "ScoringVisitor, but got %zu. There must be inconsistencies.",
          stack.size()));
    }
    return std::move(stack[0]);
  }

 private:
  bool has_pending_error() const { return !pending_error_.ok(); }

  std::unique_ptr<ScoreExpression> pop_stack() {
    std::unique_ptr<ScoreExpression> result = std::move(stack.back());
    stack.pop_back();
    return result;
  }

  double default_score_;
  libtextclassifier3::Status pending_error_;
  std::vector<std::unique_ptr<ScoreExpression>> stack;
};

}  // namespace lib
}  // namespace icing

#endif  // ICING_SCORING_ADVANCED_SCORING_SCORING_VISITOR_H_