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/// \file utils/config/parser.hpp
/// Utilities to read a configuration file into memory.

#if !defined(UTILS_CONFIG_PARSER_HPP)
#define UTILS_CONFIG_PARSER_HPP

#include <memory>

#include "utils/fs/path.hpp"
#include "utils/noncopyable.hpp"

namespace utils {
namespace config {


class tree;


/// A configuration parser.
///
/// This parser is a class rather than a function because we need to support
/// callbacks to perform the initialization of the config file schema.  The
/// configuration files always start with a call to syntax(), which define the
/// particular version of the schema being used.  Depending on such version, the
/// layout of the internal tree representation needs to be different.
///
/// A parser implementation must provide a setup() method to set up the
/// configuration schema based on the particular combination of syntax format
/// and version specified on the file.
///
/// Parser objects are not supposed to be reused, and specific trees are not
/// supposed to be passed to multiple parsers (even if sequentially).  Doing so
/// will cause all kinds of inconsistencies in the managed tree itself or in the
/// Lua state.
class parser : noncopyable {
public:
    struct impl;

private:
    /// Pointer to the internal implementation.
    std::unique_ptr< impl > _pimpl;

    /// Hook to initialize the tree keys before reading the file.
    ///
    /// This hook gets called when the configuration file defines its specific
    /// format by calling the syntax() function.  We have to delay the tree
    /// initialization until this point because, before we know what version of
    /// a configuration file we are parsing, we cannot know what keys are valid.
    ///
    /// \param [in,out] config_tree The tree in which to define the key
    ///     structure.
    /// \param syntax_version The version of the file format as specified in the
    ///     configuration file.
    virtual void setup(tree& config_tree, const int syntax_version) = 0;

public:
    explicit parser(tree&);
    virtual ~parser(void);

    void parse(const fs::path&);
};


}  // namespace config
}  // namespace utils

#endif  // !defined(UTILS_CONFIG_PARSER_HPP)