config_parser.h

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/*
  Copyright (c) 2015, 2024, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
  This program is designed to work with certain software (including
  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
  separately licensed software that they have either included with
  the program or referenced in the documentation.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef MYSQL_HARNESS_CONFIG_PARSER_INCLUDED
#define MYSQL_HARNESS_CONFIG_PARSER_INCLUDED
 
#include <functional>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <stdexcept>
#include <string>
#include <vector>
 
#include "harness_export.h"
 
namespace mysql_harness {
 
class ConfigSection;
class Path;
 
/**
 * Convenience class for handling iterator range.
 *
 * This is a template class that accept a pair of iterators and
 * implement the necessary methods to be able to be used as a sequence
 * container.
 */
template <class Iter>
class Range {
 public:
  using value_type = typename Iter::value_type;
  using reference = typename Iter::reference;
  using iterator = Iter;
  using const_iterator = iterator;
  using difference_type = typename std::iterator_traits<Iter>::difference_type;
  using size_type = difference_type;
 
  Range(Iter start, Iter finish) : begin_(start), end_(finish) {}
 
  /** Get iterator to beginning of range. */
  Iter begin() const { return begin_; }
 
  /** Get iterator to end of range. */
  Iter end() const { return end_; }
 
  /** Check if range is empty. */
  bool empty() const { return begin_ == end_; }
 
  /**
   * Get size of the range, that is, number of elements in the range.
   *
   * @note This call `std::distance` internally.
   *
   * @returns The number of elements in the range.
   */
  size_type size() const { return std::distance(begin_, end_); }
 
 private:
  Iter begin_;
  Iter end_;
};
 
/**
 * Exception thrown for syntax errors.
 *
 * @ingroup ConfigParser
 * Exception thrown for errors during parsing configuration file.
 */
 
class syntax_error : public std::logic_error {
 public:
  explicit syntax_error(const std::string &msg) : std::logic_error(msg) {}
};
 
/**
 * Exception thrown for section problems.
 *
 * @ingroup ConfigParser
 */
 
class bad_section : public std::runtime_error {
 public:
  explicit bad_section(const std::string &msg) : std::runtime_error(msg) {}
};
 
/**
 * Exception thrown for option problems.
 *
 * @ingroup ConfigParser
 */
 
class bad_option : public std::runtime_error {
 public:
  explicit bad_option(const std::string &msg) : std::runtime_error(msg) {}
};
 
/**
 * Exception thrown for option value problems.
 *
 * @ingroup ConfigParser
 */
 
class bad_option_value : public std::runtime_error {
 public:
  explicit bad_option_value(const std::string &msg) : std::runtime_error(msg) {}
};
 
/**
 * Configuration section.
 *
 * @ingroup ConfigParser
 *
 * A named configuration file section with a zero or more
 * configuration file options.
 */
 
class HARNESS_EXPORT ConfigSection {
 public:
  using OptionMap = std::map<std::string, std::string>;
  using OptionRange = Range<OptionMap::const_iterator>;
 
  ConfigSection(const std::string &name_arg, const std::string &key_arg,
                const std::shared_ptr<const ConfigSection> &defaults);
 
  ConfigSection(const ConfigSection &,
                const std::shared_ptr<const ConfigSection> &defaults);
  ConfigSection &operator=(const ConfigSection &) = delete;
  ConfigSection(const ConfigSection &) = default;
 
  /**
   * Clear the options in the section.
   *
   * This will remove options from the configuration section.
   */
  void clear();
 
  /**
   * Update section with contents of another section.
   *
   * The configuration section will be updated with the contents of
   * the other section. For any options that exist in the section, the
   * value will be overwritten by the values in the `other`
   * section. If the option do not exist, a new option will be created
   * and the value set to the value of the option in the `other`
   * section.
   *
   * @note The section name and key have to match for the update to be
   * done.
   *
   * @exception bad_section Thrown if the section name or section key
   * do not match.
   *
   * @param other Section to copy options and values from.
   */
  void update(const ConfigSection &other);  // throws bad_section
 
  std::string get(std::string_view option) const;
  void set(std::string_view option,
           const std::string &value);  // throws bad_option
  void add(const std::string &option, const std::string &value);
  bool has(std::string_view option) const;
 
  /**
   * Range for options in section.
   *
   * Typical usage is:
   *
   * @code
   * for (auto elem: section.get_options())
   *   std::cout << "Option " << elem.first
   *             << " has value " << elem.second
   *             << std::endl;
   * @endcode
   *
   * @returns a range of options each consisting of a pair
   * option-value.
   */
  OptionRange get_options() const {
    return OptionRange(options_.begin(), options_.end());
  }
 
  /*
   * Returns name of the section in which option is specified. The returned
   * name may be the name of the section or the name of the default section.
   *
   * @option option The name of the option
   * @return The name of the ConfigSection which option is specified.
   */
  std::string get_section_name(std::string_view option) const;
 
  /*
   * Returns name of the section.
   */
  std::string get_section_name() const;
 
#ifndef NDEBUG
  bool assert_default(const ConfigSection *def) const {
    return def == defaults_.get();
  }
#endif
 
 public:
  const std::string name;
  const std::string key;
 
 private:
  std::string do_replace(const std::string &value, int depth = 0) const;
 
  const int kMaxInterpolationDepth = 10;
 
  std::pair<OptionMap::const_iterator, bool> do_locate(
      std::string_view option) const noexcept;
 
  const std::shared_ptr<const ConfigSection> defaults_;
  OptionMap options_;
};
 
/**
 * Configuration.
 *
 * @ingroup ConfigParser
 *
 * A configuration consisting of named configuration sections.
 *
 * There are three different constructors that are available with
 * different kind of parameters.
 */
 
class HARNESS_EXPORT Config {
 public:
  using SectionKey = std::pair<std::string, std::string>;
  using OptionMap = ConfigSection::OptionMap;
  using SectionList = std::list<ConfigSection *>;
  using ConstSectionList = std::list<const ConfigSection *>;
  using ConfigOverwrites = std::map<std::pair<std::string, std::string>,
                                    std::map<std::string, std::string>>;
 
  /**@{*/
  /** Flags for construction of configurations. */
 
  static constexpr unsigned int allow_keys = 1U;
 
  /**@}*/
 
  /**
   * Default pattern to used to identify configuration files.
   */
  static constexpr const char *DEFAULT_PATTERN = "*.cfg";
 
  /**
   * Construct a configuration.
   *
   * @param flags flags.
   * @param config_overwrites overwrites for selected configuration options.
   */
  explicit Config(unsigned int flags = 0U,
                  const ConfigOverwrites &config_overwrites = {});
 
  /**
   * Construct a configuration.
   *
   * @tparam AssocT Associate container type
   * @arg @c parameters Associative container with parameters.
   * @arg @c flags flags.
   * @arg @c config_overwrites overwrites for selected configuration options.
   * @throws bad_option on bad options
   */
  template <class AssocT>
  explicit Config(const AssocT &parameters, unsigned int flags = 0U,
                  const ConfigOverwrites &config_overwrites = {})
      : Config(flags, config_overwrites) {
    for (auto item : parameters)
      defaults_->set(item.first, item.second);  // throws bad_option
    apply_overwrites();
  }
 
  /**
   * Construct a configuration.
   *
   * Construct a configuration instance by reading a configuration file
   * and overriding the values read from a list of supplied
   * parameters.
   *
   * @tparam AssocT Associate container type
   * @tparam SeqT  Sequence container type
   * @arg @c parameters Associative container with parameters.
   * @arg @c reserved Sequence container of reserved words.
   * @arg @c flags flags.
   * @arg @c config_overwrites overwrites for selected configuration options.
   * @throws bad_option on bad options
   */
  template <class AssocT, class SeqT>
  explicit Config(const AssocT &parameters, const SeqT &reserved,
                  unsigned int flags = 0U,
                  const ConfigOverwrites &config_overwrites = {})
      : Config(parameters, flags, config_overwrites) /* throws bad_option */ {
    for (auto word : reserved) reserved_.push_back(word);
  }
 
  Config(const Config &) = default;
  Config &operator=(const Config &) = default;
  virtual ~Config() = default;
 
  template <class SeqT>
  void set_reserved(const SeqT &reserved) {
    reserved_.assign(reserved.begin(), reserved.end());
  }
 
  /**
   * Read configuration file from file, directory, or input stream.
   *
   * If there are conflicting sections (several instance sections with
   * identical name and key) or conflicting options (several instances
   * of an option in the same section) in the input, an exception will
   * be thrown.
   *
   * If the input is a stream, the contents of the stream will be
   * added to the configuration, but if the input is either a file or
   * a directory, the exisisting contents of the configuration will be
   * removed.
   *
   * If a `pattern` is given, the path is assumed to be a directory
   * and all files matching the pattern will be read into the the
   * configuration object. The files together will be treated as if it
   * is a single file, that is, no conflicting option values or
   * sections are allowed and will raise an exception.
   *
   * @param input Input stream to read from.
   *
   * @exception syntax_error Raised if there is a syntax error in the
   * configuration file and the configuration file have to be corrected.
   *
   * @exception bad_section Raised if there is a duplicate section
   * (section with the same name and key) in the input stream.
   *
   * @exception bad_option Raised if there is a duplicate definition
   * of an option (same option is given twice in a section).
   */
  void read(std::istream &input);
 
  /** @overload */
  void read(const Path &path);
 
  /*
   * @param path Path to directory or file to read from.
   * @param pattern Glob pattern for configuration files in the directory.
   */
  /** @overload */
  void read(const Path &path, const std::string &pattern);
 
  /**
   * Check if the configuration is empty.
   *
   * @return `true` if there are any sections in the configuration
   * (not counting the default section), `false` otherwise.
   */
  bool empty() const;
 
  /**
   * Clear the configuration.
   *
   * This will remove all configuration information from the
   * configuration, including the default section, but not the
   * reserved words nor the flags set.
   */
  void clear();
 
  /**
   * Remove section from configuration
   *
   * @param section_key section+key to remove.
   *
   * @return true if section was removed, false if section did not exist
   */
  bool remove(const SectionKey &section_key) noexcept;
 
  /*
   * @param section Name of section to remove.
   * @param key Optional key of section to remove.
   */
  /** @overload */
  bool remove(const std::string &section,
              const std::string &key = std::string()) noexcept;
 
  /**
   * Update configuration using another configuration.
   *
   * This will incorporate all the sections and options from the
   * `other` configuration by adding sections that are missing and
   * overwriting option values for sections that exist in the current
   * configuration.
   *
   * @param other Configuration to read section, options, and values
   * from.
   */
  void update(const Config &other);
 
  /**
   * Get a list of sections having a name.
   *
   * There can be several sections under the same name, but they will
   * have different keys.
   *
   * @note The empty string is used to denote the keyless section.
   *
   * @param section Section name of sections to fetch.
   */
  ConstSectionList get(const std::string &section) const;
 
  /** @overload */
  SectionList get(const std::string &section);
 
  ConfigSection &get_default_section() const;
 
  /**
   * Get a section by name and key.
   *
   * Get a section given a name and a key. Since there can be several
   * sections with the same name (but different keys) this will always
   * return a unique section.
   *
   * @note The empty string is used to denote the keyless section.
   *
   * @param section Name of section to fetch.
   * @param key Key for section to fetch.
   *
   * @return Reference to section instance.
   *
   * @exception bad_section Thrown if the section do not exist or if a
   * key were used but is not allowed.
   */
  ConfigSection &get(const std::string &section, const std::string &key);
 
  /** @overload */
  const ConfigSection &get(const std::string &section,
                           const std::string &key) const;
 
  /**
   * Add a new section to the configuration.
   *
   * @param section Name of section to add.
   * @param key Optional key of section to add.
   *
   * @return Reference to newly constructed configuration section
   * instance.
   */
  ConfigSection &add(const std::string &section,
                     const std::string &key = std::string());
 
  bool has(const std::string &section,
           const std::string &key = std::string()) const;
 
  /**
   * @return True if a section exists, no matter what the key is.
   */
  bool has_any(std::string_view section) const;
 
  // all 3 below throw bad_option (std::runtime_error) on illegal option name
  // (one that contains illegal characters) */
  std::string get_default(std::string_view option) const;
  bool has_default(std::string_view option) const;
  void set_default(std::string_view option, const std::string &value);
 
  bool is_reserved(const std::string &word) const;
 
  std::list<Config::SectionKey> section_names() const {
    decltype(section_names()) result;
    for (auto &section : sections_) result.push_back(section.first);
    return result;
  }
 
  /**
   * Get a list of all sections in the configuration.
   */
  ConstSectionList sections() const;
 
  bool error_on_unsupported_option{false};
 
 protected:
  using SectionMap = std::map<SectionKey, ConfigSection>;
  using ReservedList = std::vector<std::string>;
 
  /**
   * Copy the guts of another configuration.
   *
   * This member function is used to copy configuration state (the
   * "guts") but not the sections and options, including not copying
   * the default section.
   */
  void copy_guts(const Config &source) noexcept;
 
  /**
   * Function to read single file.
   *
   * @throws std::runtime_error, syntax_error
   */
  virtual void do_read_file(const Path &path);
 
  /**
   * Function to read the configuration from a stream.
   *
   * @throws syntax_error, maybe bad_section (not sure if it can happen)
   *
   * @note This function is guaranteeed to be called for reading all
   * configurations so it can be overridden to handle post- or
   * pre-parsing actions.
   */
  virtual void do_read_stream(std::istream &input);
 
  void apply_overwrites();
 
  SectionMap sections_;
  ReservedList reserved_;
  std::shared_ptr<ConfigSection> defaults_;
  unsigned int flags_;
  ConfigOverwrites config_overwrites_;
};
 
/**
 * Returns true if a character given as a parameter is valid for config
 * identifier (section, section key or option name)
 */
bool HARNESS_EXPORT is_valid_conf_ident_char(const char ch);
 
}  // namespace mysql_harness
 
#endif /* MYSQL_HARNESS_CONFIG_PARSER_INCLUDED */