cpp/src/graphar/expression.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

#pragma once

#include <memory>
#include <string>

#include "arrow/compute/api.h"

#include "graphar/graph_info.h"

namespace graphar {

using ArrowExpression = arrow::compute::Expression;

/**
 * This class wraps an arrow::compute::Expression and provides a way to
 * construct it
 */
class Expression {
 public:
  Expression() = default;
  Expression(const Expression& other) = default;
  virtual ~Expression() = default;

  /**
   * @brief Evaluate Expression as arrow::compute::Expression e.g. new
   * ExpressionEqual(new ExpressionProperty("a"), new
   * ExpressionLiteral(1)) will be parsed as
   * arrow::compute::equal(arrow::compute::field_ref("a"),
   * arrow::compute::literal(1))
   *
   * @return The arrow::compute::Expression instance
   */
  virtual Result<ArrowExpression> Evaluate() = 0;
};

/**
 * This class wraps the Property and provides a way to construct property
 * expression
 */
class ExpressionProperty : public Expression {
 public:
  explicit ExpressionProperty(const Property& property) : property_(property) {}
  explicit ExpressionProperty(const std::string& name)
      : property_(Property(name)) {}
  ExpressionProperty(const ExpressionProperty& other) = default;
  ~ExpressionProperty() = default;

  Result<ArrowExpression> Evaluate() override;

 private:
  Property property_;
};

/**
 * This class wraps the literal. Only bool, int32, int64, float, double and
 * string are allowed.
 */
template <typename T,
          bool IsScalar =
              std::is_same_v<T, bool> || std::is_same_v<T, int32_t> ||
              std::is_same_v<T, int64_t> || std::is_same_v<T, float> ||
              std::is_same_v<T, double> || std::is_same_v<T, std::string> ||
              std::is_same_v<T, const char*> ||
              std::is_same_v<T, const char* const>,
          typename = std::enable_if_t<IsScalar>>
class ExpressionLiteral : public Expression {
 public:
  explicit ExpressionLiteral(T value) : value_(value) {}
  ExpressionLiteral(const ExpressionLiteral& other) = default;
  ~ExpressionLiteral() = default;

  Result<ArrowExpression> Evaluate() { return arrow::compute::literal(value_); }

 private:
  T value_;
};

/**
 * This class constructs a unary operator expression that accepts only one
 * expression
 */
class ExpressionUnaryOp : public Expression {
 public:
  ExpressionUnaryOp() = default;
  explicit ExpressionUnaryOp(std::shared_ptr<Expression> expr) : expr_(expr) {}
  ExpressionUnaryOp(const ExpressionUnaryOp& other) = default;
  virtual ~ExpressionUnaryOp() {}

 protected:
  std::shared_ptr<Expression> expr_;
};

/**
 * This class constructs a NOT operator expression. e.g. new ExpressionNot(new
 * ExpressionLiteral(true)) => NOT TRUE
 */
class ExpressionNot : public ExpressionUnaryOp {
 public:
  ExpressionNot() = default;
  explicit ExpressionNot(std::shared_ptr<Expression> expr)
      : ExpressionUnaryOp(expr) {}
  ExpressionNot(const ExpressionNot& other) = default;
  ~ExpressionNot() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a binary operator expression that accepts two
 * expressions e.g. a = 1, a > 1, a AND b, a OR b
 */
class ExpressionBinaryOp : public Expression {
 public:
  ExpressionBinaryOp() = default;
  ExpressionBinaryOp(std::shared_ptr<Expression> lhs,
                     std::shared_ptr<Expression> rhs)
      : lhs_(lhs), rhs_(rhs) {}
  ExpressionBinaryOp(const ExpressionBinaryOp& other) = default;
  ~ExpressionBinaryOp() = default;

 protected:
  inline Status CheckNullArgs(std::shared_ptr<Expression> lhs,
                              std::shared_ptr<Expression> rhs) noexcept {
    if (lhs == nullptr || rhs == nullptr) {
      return Status::Invalid("Invalid expression: lhs or rhs is null");
    }
    return Status::OK();
  }

 protected:
  std::shared_ptr<Expression> lhs_;
  std::shared_ptr<Expression> rhs_;
};

/**
 * This class constructs a EQUAL operator expression.
 * e.g. new ExpressionEqual(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a = 1
 */
class ExpressionEqual : public ExpressionBinaryOp {
 public:
  ExpressionEqual() = default;
  ExpressionEqual(std::shared_ptr<Expression> lhs,
                  std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionEqual(const ExpressionEqual& other) = default;
  ~ExpressionEqual() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a NOT EQUAL operator expression.
 * e.g. new ExpressionNotEqual(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a != 1
 */
class ExpressionNotEqual : public ExpressionBinaryOp {
 public:
  ExpressionNotEqual() = default;
  ExpressionNotEqual(std::shared_ptr<Expression> lhs,
                     std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionNotEqual(const ExpressionNotEqual& other) = default;
  ~ExpressionNotEqual() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a GREATER THAN operator expression.
 * e.g. new ExpressionGreaterThan(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a > 1
 */
class ExpressionGreaterThan : public ExpressionBinaryOp {
 public:
  ExpressionGreaterThan() = default;
  ExpressionGreaterThan(std::shared_ptr<Expression> lhs,
                        std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionGreaterThan(const ExpressionGreaterThan& other) = default;
  ~ExpressionGreaterThan() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a GREATER EQUAL operator expression.
 * e.g. new ExpressionGreaterEqual(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a >= 1
 */
class ExpressionGreaterEqual : public ExpressionBinaryOp {
 public:
  ExpressionGreaterEqual() = default;
  ExpressionGreaterEqual(std::shared_ptr<Expression> lhs,
                         std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionGreaterEqual(const ExpressionGreaterEqual& other) = default;
  ~ExpressionGreaterEqual() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a LESS THAN operator expression.
 * e.g. new ExpressionLessThan(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a < 1
 */
class ExpressionLessThan : public ExpressionBinaryOp {
 public:
  ExpressionLessThan() = default;
  ExpressionLessThan(std::shared_ptr<Expression> lhs,
                     std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionLessThan(const ExpressionLessThan& other) = default;
  ~ExpressionLessThan() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a LESS EQUAL operator expression.
 * e.g. new ExpressionLessEqual(new ExpressionProperty("a"), new
 * ExpressionLiteral(1)) => a <= 1
 */
class ExpressionLessEqual : public ExpressionBinaryOp {
 public:
  ExpressionLessEqual() = default;
  ExpressionLessEqual(std::shared_ptr<Expression> lhs,
                      std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionLessEqual(const ExpressionLessEqual& other) = default;
  ~ExpressionLessEqual() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a AND operator expression.
 * e.g. new ExpressionAnd(new ExpressionLiteral(true), new
 * ExpressionLiteral(1)) => TRUE AND 1
 */
class ExpressionAnd : public ExpressionBinaryOp {
 public:
  ExpressionAnd() = default;
  ExpressionAnd(std::shared_ptr<Expression> lhs,
                std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionAnd(const ExpressionAnd& other) = default;
  ~ExpressionAnd() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * This class constructs a OR operator expression.
 * e.g. new ExpressionOr(new ExpressionLiteral(0), new
 * ExpressionLiteral(true)) => 0 OR TRUE
 */
class ExpressionOr : public ExpressionBinaryOp {
 public:
  ExpressionOr() = default;
  ExpressionOr(std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs)
      : ExpressionBinaryOp(lhs, rhs) {}
  ExpressionOr(const ExpressionOr& other) = default;
  ~ExpressionOr() = default;

  Result<ArrowExpression> Evaluate() override;
};

/**
 * Helper functions to construct a Expression.
 */
[[nodiscard]] static inline std::shared_ptr<Expression> _Property(
    const Property& property) {
  return std::make_shared<ExpressionProperty>(property);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _Property(
    const std::string& name) {
  return std::make_shared<ExpressionProperty>(name);
}

template <typename T,
          bool IsScalar =
              std::is_same_v<T, bool> || std::is_same_v<T, int32_t> ||
              std::is_same_v<T, int64_t> || std::is_same_v<T, float> ||
              std::is_same_v<T, double> || std::is_same_v<T, std::string> ||
              std::is_same_v<T, const char*> ||
              std::is_same_v<T, const char* const>,
          typename = std::enable_if_t<IsScalar>>
[[nodiscard]] static inline std::shared_ptr<Expression> _Literal(T value) {
  return std::make_shared<ExpressionLiteral<T>>(value);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _Not(
    std::shared_ptr<Expression> expr) {
  return std::make_shared<ExpressionNot>(expr);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _Equal(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionEqual>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _NotEqual(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionNotEqual>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _GreaterThan(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionGreaterThan>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _GreaterEqual(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionGreaterEqual>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _LessThan(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionLessThan>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _LessEqual(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionLessEqual>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _And(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionAnd>(lhs, rhs);
}

[[nodiscard]] static inline std::shared_ptr<Expression> _Or(
    std::shared_ptr<Expression> lhs, std::shared_ptr<Expression> rhs) {
  return std::make_shared<ExpressionOr>(lhs, rhs);
}
}  // namespace graphar