/*
 *  Copyright (c) 2014, Facebook, Inc.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 *
 */

#pragma once

#include <map>
#include <memory>
#include <vector>
#include <set>

#include <boost/lexical_cast.hpp>
#include <boost/property_tree/ptree.hpp>

#include <osquery/registry.h>
#include <osquery/core.h>
#include <osquery/database/results.h>
#include <osquery/status.h>

/// Allow Tables to use "tracked" depricated OS APIs.
#define OSQUERY_USE_DEPRECATED(expr)                                      \
  do {                                                                    \
    _Pragma("clang diagnostic push")                                      \
        _Pragma("clang diagnostic ignored \"-Wdeprecated-declarations\"") \
        expr;                                                             \
    _Pragma("clang diagnostic pop")                                       \
  } while (0)

namespace osquery {
namespace tables {

/**
 * @brief The SQLite type affinities are available as macros
 *
 * Type affinities: TEXT, INTEGER, BIGINT
 *
 * You can represent any data that can be lexically casted to a string.
 * Using the type affinity names helps table developers understand the data
 * types they are storing, and more importantly how they are treated at query
 * time.
 */
#define TEXT(x) boost::lexical_cast<std::string>(x)
/// See the affinity type documentation for TEXT.
#define INTEGER(x) boost::lexical_cast<std::string>(x)
/// See the affinity type documentation for TEXT.
#define BIGINT(x) boost::lexical_cast<std::string>(x)
/// See the affinity type documentation for TEXT.
#define UNSIGNED_BIGINT(x) boost::lexical_cast<std::string>(x)

/**
 * @brief The SQLite type affinities as represented as implementation literals.
 *
 * Type affinities: TEXT=std::string, INTEGER=int, BIGINT=long long int
 *
 * Just as the SQLite data is represented as lexically casted strings, as table
 * may make use of the implementation language literals.
 */
#define TEXT_LITERAL std::string
/// See the literal type documentation for TEXT_LITERAL.
#define INTEGER_LITERAL int
/// See the literal type documentation for TEXT_LITERAL.
#define BIGINT_LITERAL long long int
/// See the literal type documentation for TEXT_LITERAL.
#define UNSIGNED_BIGINT_LITERAL unsigned long long int
/// Cast an SQLite affinity type to the literal type.
#define AS_LITERAL(literal, value) boost::lexical_cast<literal>(value)

/// Helper alias for TablePlugin names.
typedef std::string TableName;
typedef std::vector<std::pair<std::string, std::string> > TableColumns;
typedef std::map<std::string, std::vector<std::string> > TableData;

/**
 * @brief A ConstraintOperator is applied in an query predicate.
 *
 * If the query contains a join or where clause with a constraint operator and
 * expression the table generator may limit the data appropriately.
 */
enum ConstraintOperator {
  EQUALS = 2,
  GREATER_THAN = 4,
  LESS_THAN_OR_EQUALS = 8,
  LESS_THAN = 16,
  GREATER_THAN_OR_EQUALS = 32
};

/**
 * @brief A Constraint is an operator and expression.
 *
 * The constraint is applied to columns which have literal and affinity types.
 */
struct Constraint {
  unsigned char op;
  std::string expr;

  /// Construct a Constraint with the most-basic information, the operator.
  Constraint(unsigned char _op) { op = _op; }

  // A constraint list in a context knows only the operator at creation.
  Constraint(unsigned char _op, const std::string& _expr) {
    op = _op;
    expr = _expr;
  }
};

/**
 * @brief A ConstraintList is a set of constraints for a column. This list
 * should be mapped to a left-hand-side column name.
 *
 * The table generator does not need to check each constraint in its decision
 * logic. The common constraint checking patterns (match) are abstracted using
 * simple logic operators on the literal SQLite affinity types.
 *
 * A constraint list supports all AS_LITERAL types, and all ConstraintOperators.
 */
struct ConstraintList {
  /// The SQLite affinity type.
  std::string affinity;

  /**
   * @brief Check if an expression matches the query constraints.
   *
   * Evaluate ALL constraints in this ConstraintList against the string
   * expression. The affinity of the constrait will be used as the affinite
   * and lexical type of the expression and set of constraint expressions.
   *
   * @param expr a SQL type expression of the column literal type to check.
   * @return If the expression matched all constraints.
   */
  bool matches(const std::string& expr) const;

  /**
   * @brief Check if an expression matches the query constraints.
   *
   * `matches` also supports the set of SQL affinite types.
   * The expression expr will be evaluated as a string and compared using
   * the affinity of the constraint.
   *
   * @param expr a SQL type expression of the column literal type to check.
   * @return If the expression matched all constraints.
   */
  template <typename T>
  bool matches(const T& expr) const {
    return matches(TEXT(expr));
  }

  /**
   * @brief Check and return if there are any constraints on this column.
   *
   * A ConstraintList is used in a ConstraintMap with a column name as the
   * map index. Tables that act on optional constraints should check if any
   * constraint was provided.
   *
   * @return true if any constraint exists.
   */
  bool exists() const { return (constraints_.size() > 0); }

  /**
   * @brief Check if a constrait exist AND matches the type expression.
   *
   * See ConstraintList::exists and ConstraintList::matches.
   *
   * @param expr The expression to match.
   * @return true if any constraint exists AND matches the type expression.
   */
  template <typename T>
  bool existsAndMatches(const T& expr) const {
    return (exists() && matches(expr));
  }

  /**
   * @brief Check if a constraint is missing or matches a type expression.
   *
   * A ConstraintList is used in a ConstraintMap with a column name as the
   * map index. Tables that act on required constraints can make decisions
   * on missing constraints or a constraint match.
   *
   * @param expr The expression to match.
   * @return true if constraint is missing or matches the type expression.
   */
  template <typename T>
  bool notExistsOrMatches(const T& expr) const {
    return (!exists() || matches(expr));
  }

  /**
   * @brief Helper templated function for ConstraintList::matches.
   */
  template <typename T>
  bool literal_matches(const T& base_expr) const;

  /**
   * @brief Get all expressions for a given ConstraintOperator.
   *
   * This is most useful if the table generation requires as column.
   * The generator may `getAll(EQUALS)` then iterate.
   *
   * @param op the ConstraintOperator.
   * @return A list of TEXT%-represented types matching the operator.
   */
  std::set<std::string> getAll(ConstraintOperator op) const;

  template<typename T>
  std::set<T> getAll(ConstraintOperator op) const {
    std::set<T> literal_matches;
    auto matches = getAll(op);
    for (const auto& match : matches) {
      literal_matches.insert(AS_LITERAL(T, match));
    }
    return literal_matches;
  }

  /**
   * @brief Add a new Constraint to the list of constraints.
   *
   * @param constraint a new operator/expression to constrain.
   */
  void add(const struct Constraint& constraint) {
    constraints_.push_back(constraint);
  }

  /**
   * @brief Serialize a ConstraintList into a property tree.
   *
   * The property tree will use the format:
   * {
   *   "affinity": affinity,
   *   "list": [
   *     {"op": op, "expr": expr}, ...
   *   ]
   * }
   */
  void serialize(boost::property_tree::ptree& tree) const;
  void unserialize(const boost::property_tree::ptree& tree);

  ConstraintList() { affinity = "TEXT"; }

 private:
  /// List of constraint operator/expressions.
  std::vector<struct Constraint> constraints_;

 private:
  FRIEND_TEST(TablesTests, test_constraint_list);
};

/// Pass a constraint map to the query request.
typedef std::map<std::string, struct ConstraintList> ConstraintMap;
/// Populate a containst list from a query's parsed predicate.
typedef std::vector<std::pair<std::string, struct Constraint> > ConstraintSet;

/**
 * @brief A QueryContext is provided to every table generator for optimization
 * on query components like predicate constraints and limits.
 */
struct QueryContext {
  ConstraintMap constraints;
  /// Support a limit to the number of results.
  int limit;

  QueryContext() : limit(0) {}
};

typedef struct QueryContext QueryContext;
typedef struct Constraint Constraint;

/**
 * @brief The TablePlugin defines the name, types, and column information.
 *
 * To attach a virtual table create a TablePlugin subclass and register the
 * virtual table name as the plugin ID. osquery will enumerate all registered
 * TablePlugins and attempt to attach them to SQLite at instanciation.
 *
 * Note: When updating this class, be sure to update the corresponding template
 * in osquery/tables/templates/default.cpp.in
 */
class TablePlugin : public Plugin {
 protected:
  /// Helper method to generate the virtual table CREATE statement.
  virtual std::string statement() const;
  virtual std::string columnDefinition() const;
  virtual TableColumns columns() const {
    TableColumns columns;
    return columns;
  }

  virtual QueryData generate(QueryContext& request) {
    QueryData data;
    return data;
  }

 public:
  /// Public API methods.
  Status call(const PluginRequest& request, PluginResponse& response);

 public:
  /// Helper data structure transformation methods
  static void setRequestFromContext(const QueryContext& context,
                                    PluginRequest& request);
  static void setResponseFromQueryData(const QueryData& data,
                                       PluginResponse& response);
  static void setContextFromRequest(const PluginRequest& request,
                                    QueryContext& context);

 private:
  FRIEND_TEST(VirtualTableTests, test_tableplugin_columndefinition);
  FRIEND_TEST(VirtualTableTests, test_tableplugin_statement);
};

CREATE_REGISTRY(TablePlugin, "table");
}
}