lokinet/llarp/config/definition.hpp
Thomas Winget 7caa87862e standardize include format and pragma once
All #ifndef guards on headers have been removed, I think,
in favor of #pragma once

Headers are now included as `#include "filename"` if the included file
resides in the same directory as the file including it, or any
subdirectory therein.  Otherwise they are included as
`#include <project/top/dir/relative/path/filename>`

The above does not include system/os headers.
2021-03-09 19:01:41 -05:00

580 lines
21 KiB
C++

#pragma once
#include <initializer_list>
#include <type_traits>
#include <llarp/util/str.hpp>
#include <llarp/util/fs.hpp>
#include <iostream>
#include <memory>
#include <set>
#include <sstream>
#include <stdexcept>
#include <unordered_map>
#include <vector>
#include <functional>
#include <optional>
#include <cassert>
namespace llarp
{
namespace config
{
// Base class for the following option flag types
struct option_flag
{};
struct Required_t : option_flag
{};
struct Hidden_t : option_flag
{};
struct MultiValue_t : option_flag
{};
struct RelayOnly_t : option_flag
{};
struct ClientOnly_t : option_flag
{};
struct Deprecated_t : option_flag
{};
/// Value to pass for an OptionDefinition to indicate that the option is required
inline constexpr Required_t Required{};
/// Value to pass for an OptionDefinition to indicate that the option should be hidden from the
/// generate config file if it is unset (and has no comment). Typically for deprecated, renamed
/// options that still do something, and for internal dev options that aren't usefully exposed.
/// (For do-nothing deprecated options use Deprecated instead).
inline constexpr Hidden_t Hidden{};
/// Value to pass for an OptionDefinition to indicate that the option takes multiple values
inline constexpr MultiValue_t MultiValue{};
/// Value to pass for an option that should only be set for relay configs. If found in a client
/// config it be ignored (but will produce a warning).
inline constexpr RelayOnly_t RelayOnly{};
/// Value to pass for an option that should only be set for client configs. If found in a relay
/// config it will be ignored (but will produce a warning).
inline constexpr ClientOnly_t ClientOnly{};
/// Value to pass for an option that is deprecated and does nothing and should be ignored (with
/// a deprecation warning) if specified. Note that Deprecated implies Hidden, and that
/// {client,relay}-only options in a {relay,client} config are also considered Deprecated.
inline constexpr Deprecated_t Deprecated{};
/// Wrapper to specify a default value to an OptionDefinition
template <typename T>
struct Default
{
T val;
constexpr explicit Default(T val) : val{std::move(val)}
{}
};
/// Adds one or more comment lines to the option definition.
struct Comment
{
std::vector<std::string> comments;
explicit Comment(std::initializer_list<std::string> comments) : comments{std::move(comments)}
{}
};
/// A convenience function that returns an acceptor which assigns to a reference.
///
/// Note that this holds on to the reference; it must only be used when this is safe to do. In
/// particular, a reference to a local variable may be problematic.
template <typename T>
auto
AssignmentAcceptor(T& ref)
{
return [&ref](T arg) { ref = std::move(arg); };
}
// C++20 backport:
template <typename T>
using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;
template <typename T>
constexpr bool is_default = false;
template <typename T>
constexpr bool is_default<Default<T>> = true;
template <typename U>
constexpr bool is_default<U&> = is_default<remove_cvref_t<U>>;
template <typename T, typename Option>
constexpr bool is_option =
std::is_base_of_v<
option_flag,
remove_cvref_t<
Option>> or std::is_same_v<Comment, Option> or is_default<Option> or std::is_invocable_v<remove_cvref_t<Option>, T>;
} // namespace config
/// A base class for specifying config options and their constraints. The basic to/from string
/// type functions are provided pure-virtual. The type-aware implementations which implement these
/// functions are templated classes. One reason for providing a non-templated base class is so
/// that they can all be mixed into the same containers (albiet as pointers).
struct OptionDefinitionBase
{
template <typename... T>
OptionDefinitionBase(std::string section_, std::string name_, const T&...)
: section(std::move(section_))
, name(std::move(name_))
, required{(std::is_same_v<T, config::Required_t> || ...)}
, multiValued{(std::is_same_v<T, config::MultiValue_t> || ...)}
, deprecated{(std::is_same_v<T, config::Deprecated_t> || ...)}
, hidden{deprecated || (std::is_same_v<T, config::Hidden_t> || ...)}
, relayOnly{(std::is_same_v<T, config::RelayOnly_t> || ...)}
, clientOnly{(std::is_same_v<T, config::ClientOnly_t> || ...)}
{}
virtual ~OptionDefinitionBase() = default;
/// Subclasses should provide their default value as a string
///
/// @return the option's default value represented as a string
virtual std::string
defaultValueAsString() = 0;
/// Subclasses should parse and store the provided input
///
/// @param input is the string input to interpret
virtual void
parseValue(const std::string& input) = 0;
/// Subclasses should provide the number of values found.
///
/// @return number of values found
virtual size_t
getNumberFound() const = 0;
/// Subclasess should write their parsed value as a string, optionally falling back to any
/// specified default if `useDefault` is true.
///
/// @param useDefault should specify whether to fallback to default when possible
/// @return the option's value as a string
virtual std::string
valueAsString(bool useDefault) = 0;
/// Subclassess should call their acceptor, if present. See OptionDefinition for more details.
///
/// @throws if the acceptor throws or the option is required but missing
virtual void
tryAccept() const = 0;
std::string section;
std::string name;
bool required = false;
bool multiValued = false;
bool deprecated = false;
bool hidden = false;
bool relayOnly = false;
bool clientOnly = false;
// Temporarily holds comments given during construction until the option is actually added to
// the owning ConfigDefinition.
std::vector<std::string> comments;
};
/// The primary type-aware implementation of OptionDefinitionBase, this templated class allows
/// for implementations which can use the std::ostringstream and std::istringstream for to/from
/// string functionality.
///
/// Note that types (T) used as template parameters here must be used verbatim when calling
/// ConfigDefinition::getConfigValue(). Similar types such as uint32_t and int32_t cannot be
/// mixed.
template <typename T>
struct OptionDefinition : public OptionDefinitionBase
{
/// Constructor. Arguments are passed directly to OptionDefinitionBase.
///
/// @param defaultValue_ is used in the following situations:
/// 1) as the return value for getValue() if there is no parsed value and required==false
/// 2) as the output in defaultValueAsString(), used to generate config files
/// 3) as the output in valueAsString(), used to generate config files
///
/// @param opts - 0 or more of config::Required, config::Hidden, config::Default{...}, etc.
/// tagged options or an invocable acceptor validate and internalize input (e.g. copy it for
/// runtime use). The acceptor should throw an exception with a useful message if it is not
/// acceptable. Parameters may be passed in any order.
template <
typename... Options,
std::enable_if_t<(config::is_option<T, Options> && ...), int> = 0>
OptionDefinition(std::string section_, std::string name_, Options&&... opts)
: OptionDefinitionBase(section_, name_, opts...)
{
(extractDefault(std::forward<Options>(opts)), ...);
(extractAcceptor(std::forward<Options>(opts)), ...);
(extractComments(std::forward<Options>(opts)), ...);
}
/// Extracts a default value from an config::Default<U>; ignores anything that isn't an
/// config::Default<U>.
template <typename U>
void
extractDefault(U&& defaultValue_)
{
if constexpr (config::is_default<U>)
{
static_assert(
std::is_convertible_v<decltype(std::forward<U>(defaultValue_).val), T>,
"Cannot convert given llarp::config::Default to the required value type");
defaultValue = std::forward<U>(defaultValue_).val;
}
}
/// Extracts an acceptor (i.e. something callable with a `T`) from options; ignores anything
/// that isn't callable.
template <typename U>
void
extractAcceptor(U&& acceptor_)
{
if constexpr (std::is_invocable_v<U, T>)
acceptor = std::forward<U>(acceptor_);
}
/// Extracts option Comments and forwards them addOptionComments.
template <typename U>
void
extractComments(U&& comment)
{
if constexpr (std::is_same_v<config::remove_cvref_t<U>, config::Comment>)
comments = std::forward<U>(comment).comments;
}
/// Returns the first parsed value, if available. Otherwise, provides the default value if the
/// option is not required. Otherwise, returns an empty optional.
///
/// @return an optional with the parsed value, the default value, or no value.
std::optional<T>
getValue() const
{
if (parsedValues.size())
return parsedValues[0];
else if (not required and not multiValued)
return defaultValue;
else
return std::nullopt;
}
/// Returns the value at the given index.
///
/// @param index
/// @return the value at the given index, if it exists
/// @throws range_error exception if index >= size
T
getValueAt(size_t index) const
{
if (index >= parsedValues.size())
throw std::range_error(
stringify("no value at index ", index, ", size: ", parsedValues.size()));
return parsedValues[index];
}
/// Returns the number of values found.
///
/// @return number of values found
size_t
getNumberFound() const override
{
return parsedValues.size();
}
std::string
defaultValueAsString() override
{
if (!defaultValue)
return "";
if constexpr (std::is_same_v<fs::path, T>)
return defaultValue->string();
std::ostringstream oss;
oss << *defaultValue;
return oss.str();
}
void
parseValue(const std::string& input) override
{
if (not multiValued and parsedValues.size() > 0)
{
throw std::invalid_argument(
stringify("duplicate value for ", name, ", previous value: ", parsedValues[0]));
}
parsedValues.emplace_back(fromString(input));
}
T
fromString(const std::string& input)
{
if constexpr (std::is_same_v<T, std::string>)
{
return input;
}
else
{
std::istringstream iss(input);
T t;
iss >> t;
if (iss.fail())
throw std::invalid_argument(stringify(input, " is not a valid ", typeid(T).name()));
else
return t;
}
}
std::string
valueAsString(bool useDefault) override
{
std::ostringstream oss;
if (parsedValues.size() > 0)
oss << parsedValues[0];
else if (useDefault and defaultValue)
oss << *defaultValue;
return oss.str();
}
/// Attempts to call the acceptor function, if present. This function may throw if the value is
/// not acceptable. Additionally, tryAccept should not be called if the option is required and
/// no value has been provided.
///
/// @throws if required and no value present or if the acceptor throws
void
tryAccept() const override
{
if (required and parsedValues.size() == 0)
{
throw std::runtime_error(stringify(
"cannot call tryAccept() on [",
section,
"]:",
name,
" when required but no value available"));
}
// don't use default value if we are multi-valued and have no value
if (multiValued and parsedValues.size() == 0)
return;
if (acceptor)
{
if (multiValued)
{
for (auto value : parsedValues)
{
acceptor(value);
}
}
else
{
auto maybe = getValue();
if (maybe)
{
acceptor(*maybe);
}
else
{
assert(not defaultValue); // maybe should have a value if defaultValue does
}
}
}
}
std::optional<T> defaultValue;
std::vector<T> parsedValues;
std::function<void(T)> acceptor;
};
/// Specialization for bool types. We don't want to use stringstream parsing in this
/// case because we want to accept "truthy" and "falsy" string values (e.g. "off" == false)
template <>
bool
OptionDefinition<bool>::fromString(const std::string& input);
using UndeclaredValueHandler =
std::function<void(std::string_view section, std::string_view name, std::string_view value)>;
using OptionDefinition_ptr = std::unique_ptr<OptionDefinitionBase>;
// map of k:v pairs
using DefinitionMap = std::unordered_map<std::string, OptionDefinition_ptr>;
// map of section-name to map-of-definitions
using SectionMap = std::unordered_map<std::string, DefinitionMap>;
/// A ConfigDefinition holds an ordered set of OptionDefinitions defining the allowable values and
/// their constraints (specified through calls to defineOption()).
///
/// The layout and grouping of the config options are modelled after the INI file format; each
/// option has a name and is grouped under a section. Duplicate option names are allowed only if
/// they exist in a different section. The ConfigDefinition can be serialized in the INI file
/// format using the generateINIConfig() function.
///
/// Configured values (e.g. those encountered when parsing a file) can be provided through calls
/// to addConfigValue(). These take a std::string as a value, which is automatically parsed.
///
/// The ConfigDefinition can be used to print out a full config string (or file), including fields
/// with defaults and optionally fields which have a specified value (values provided through
/// calls to addConfigValue()).
struct ConfigDefinition
{
explicit ConfigDefinition(bool relay) : relay{relay}
{}
/// Specify the parameters and type of a configuration option. The parameters are members of
/// OptionDefinitionBase; the type is inferred from OptionDefinition's template parameter T.
///
/// This function should be called for every option that this Configuration supports, and should
/// be done before any other interactions involving that option.
///
/// @param def should be a unique_ptr to a valid subclass of OptionDefinitionBase
/// @return `*this` for chaining calls
/// @throws std::invalid_argument if the option already exists
ConfigDefinition&
defineOption(OptionDefinition_ptr def);
/// Convenience function which calls defineOption with a OptionDefinition of the specified type
/// and with parameters passed through to OptionDefinition's constructor.
template <typename T, typename... Params>
ConfigDefinition&
defineOption(Params&&... args)
{
return defineOption(std::make_unique<OptionDefinition<T>>(std::forward<Params>(args)...));
}
/// Specify a config value for the given section and name. The value should be a valid string
/// representing the type used by the option (e.g. the type provided when defineOption() was
/// called).
///
/// If the specified option doesn't exist, an exception will be thrown. Otherwise, the option's
/// parseValue() will be invoked, and should throw an exception if the string can't be parsed.
///
/// @param section is the section this value resides in
/// @param name is the name of the value
/// @return `*this` for chaining calls
/// @throws if the option doesn't exist or the provided string isn't parseable
ConfigDefinition&
addConfigValue(std::string_view section, std::string_view name, std::string_view value);
/// Get a config value. If the value hasn't been provided but a default has, the default will
/// be returned. If no value and no default is provided, an empty optional will be returned.
///
/// The type T should exactly match that provided by the definition; it is not sufficient for
/// one type to be a valid substitution for the other.
///
/// @param section is the section this value resides in
/// @param name is the name of the value
/// @return an optional providing the configured value, the default, or empty
/// @throws std::invalid_argument if there is no such config option or the wrong type T was
// provided
template <typename T>
std::optional<T>
getConfigValue(std::string_view section, std::string_view name)
{
OptionDefinition_ptr& definition = lookupDefinitionOrThrow(section, name);
auto derived = dynamic_cast<const OptionDefinition<T>*>(definition.get());
if (not derived)
throw std::invalid_argument(
stringify("", typeid(T).name(), " is the incorrect type for [", section, "]:", name));
return derived->getValue();
}
/// Add an "undeclared" handler for the given section. This is a handler that will be called
/// whenever a k:v pair is found that doesn't match a provided definition.
///
/// Any exception thrown by the handler will progagate back through the call to
/// addConfigValue().
///
/// @param section is the section for which any undeclared values will invoke the provided
/// handler
/// @param handler
/// @throws if there is already a handler for this section
void
addUndeclaredHandler(const std::string& section, UndeclaredValueHandler handler);
/// Removes an "undeclared" handler for the given section.
///
/// @param section is the section which we want to remove the handler for
void
removeUndeclaredHandler(const std::string& section);
/// Validate that all required fields are present.
///
/// @throws std::invalid_argument if configuration constraints are not met
void
validateRequiredFields();
/// Accept all options. This will call the acceptor (if present) on each option. Note that this
/// should only be called if all required fields are present (that is, validateRequiredFields()
/// has been or could be called without throwing).
///
/// @throws if any option's acceptor throws
void
acceptAllOptions();
/// Add comments for a given section. Comments are replayed in-order during config file
/// generation. A proper comment prefix will automatically be applied, and the entire comment
/// will otherwise be used verbatim (no automatic line separation, etc.).
///
/// @param section
/// @param comment
void
addSectionComments(const std::string& section, std::vector<std::string> comments);
/// Add comments for a given option. Similar to addSectionComment, but applies to a specific
/// [section]:name pair.
///
/// @param section
/// @param name
/// @param comment
void
addOptionComments(
const std::string& section, const std::string& name, std::vector<std::string> comments);
/// Generate a config string from the current config definition, optionally using overridden
/// values. The generated config will preserve insertion order of both sections and their
/// definitions.
///
/// Definitions which are required or have an overriden value (and useValues == true) will be
/// written normally. Otherwise, they will be written commented-out in order to provide a
/// complete documentation of the configuration file.
///
/// @param useValues specifies whether we use specified values (e.g. those from calls to
/// addConfigValue()) or only definitions
/// @return a string containing the config in INI format
std::string
generateINIConfig(bool useValues = false);
private:
// If true skip client-only options; if false skip relay-only options.
bool relay;
OptionDefinition_ptr&
lookupDefinitionOrThrow(std::string_view section, std::string_view name);
const OptionDefinition_ptr&
lookupDefinitionOrThrow(std::string_view section, std::string_view name) const;
using SectionVisitor = std::function<void(const std::string&, const DefinitionMap&)>;
void
visitSections(SectionVisitor visitor) const;
using DefVisitor = std::function<void(const std::string&, const OptionDefinition_ptr&)>;
void
visitDefinitions(const std::string& section, DefVisitor visitor) const;
SectionMap m_definitions;
std::unordered_map<std::string, UndeclaredValueHandler> m_undeclaredHandlers;
// track insertion order. the vector<string>s are ordered list of section/option names.
std::vector<std::string> m_sectionOrdering;
std::unordered_map<std::string, std::vector<std::string>> m_definitionOrdering;
// comments for config file generation
using CommentList = std::vector<std::string>;
using CommentsMap = std::unordered_map<std::string, CommentList>;
CommentsMap m_sectionComments;
std::unordered_map<std::string, CommentsMap> m_definitionComments;
};
} // namespace llarp