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	// Copyright (c) 2019 The Bitcoin Core developers
	// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#include <util/settings.h>

	#include <tinyformat.h>
	#include <univalue.h>

	namespace util {
	namespace {

	enum class Source {
	FORCED,
	COMMAND_LINE,
	RW_SETTINGS,
	CONFIG_FILE_NETWORK_SECTION,
	CONFIG_FILE_DEFAULT_SECTION
	};

	//! Merge settings from multiple sources in precedence order:
	//! Forced config > command line > read-write settings file > config file
	//! network-specific section > config file default section
	//!
	//! This function is provided with a callback function fn that contains
	//! specific logic for how to merge the sources.
	template <typename Fn>
	static void MergeSettings(const Settings &settings,
	const std::string &section,
	const std::string &name, Fn &&fn) {
	// Merge in the forced settings
	if (auto *value = FindKey(settings.forced_settings, name)) {
	fn(SettingsSpan(*value), Source::FORCED);
	}
	// Merge in the command-line options
	if (auto *values = FindKey(settings.command_line_options, name)) {
	fn(SettingsSpan(*values), Source::COMMAND_LINE);
	}
	// Merge in the read-write settings
	if (const SettingsValue *value = FindKey(settings.rw_settings, name)) {
	fn(SettingsSpan(*value), Source::RW_SETTINGS);
	}
	// Merge in the network-specific section of the config file
	if (!section.empty()) {
	if (auto *map = FindKey(settings.ro_config, section)) {
	if (auto values = FindKey(map, name)) {
	fn(SettingsSpan(*values),
	Source::CONFIG_FILE_NETWORK_SECTION);
	}
	}
	}
	// Merge in the default section of the config file
	if (auto *map = FindKey(settings.ro_config, "")) {
	if (auto values = FindKey(map, name)) {
	fn(SettingsSpan(*values), Source::CONFIG_FILE_DEFAULT_SECTION);
	}
	}
	}
	} // namespace

	bool ReadSettings(const fs::path &path,
	std::map<std::string, SettingsValue> &values,
	std::vector<std::string> &errors) {
	values.clear();
	errors.clear();

	// Ok for file to not exist
	if (!fs::exists(path)) {
	return true;
	}

	fsbridge::ifstream file;
	file.open(path);
	if (!file.is_open()) {
	errors.emplace_back(
	strprintf("%s. Please check permissions.", path.string()));
	return false;
	}

	SettingsValue in;
	if (!in.read(std::string{std::istreambuf_iterator<char>(file),
	std::istreambuf_iterator<char>()})) {
	errors.emplace_back(
	strprintf("Unable to parse settings file %s", path.string()));
	return false;
	}

	if (file.fail()) {
	errors.emplace_back(
	strprintf("Failed reading settings file %s", path.string()));
	return false;
	}
	// Done with file descriptor. Release while copying data.
	file.close();

	if (!in.isObject()) {
	errors.emplace_back(
	strprintf("Found non-object value %s in settings file %s",
	in.write(), path.string()));
	return false;
	}

	const std::vector<std::string> &in_keys = in.getKeys();
	const std::vector<SettingsValue> &in_values = in.getValues();
	for (size_t i = 0; i < in_keys.size(); ++i) {
	auto inserted = values.emplace(in_keys[i], in_values[i]);
	if (!inserted.second) {
	errors.emplace_back(
	strprintf("Found duplicate key %s in settings file %s",
	in_keys[i], path.string()));
	}
	}
	return errors.empty();
	}

	bool WriteSettings(const fs::path &path,
	const std::map<std::string, SettingsValue> &values,
	std::vector<std::string> &errors) {
	SettingsValue out(SettingsValue::VOBJ);
	for (const auto &value : values) {
	out.__pushKV(value.first, value.second);
	}
	fsbridge::ofstream file;
	file.open(path);
	if (file.fail()) {
	errors.emplace_back(
	strprintf("Error: Unable to open settings file %s for writing",
	path.string()));
	return false;
	}
	file << out.write(/* prettyIndent= / 1, / indentLevel= */ 4) << std::endl;
	file.close();
	return true;
	}

	SettingsValue GetSetting(const Settings &settings, const std::string &section,
	const std::string &name,
	bool ignore_default_section_config,
	bool get_chain_name) {
	SettingsValue result;
	// Done merging any more settings sources.
	bool done = false;
	MergeSettings(
	settings, section, name, [&](SettingsSpan span, Source source) {
	// Weird behavior preserved for backwards compatibility: Apply
	// negated setting even if non-negated setting would be ignored. A
	// negated value in the default section is applied to network
	// specific options, even though normal non-negated values there
	// would be ignored.
	const bool never_ignore_negated_setting = span.last_negated();

	// Weird behavior preserved for backwards compatibility: Take first
	// assigned value instead of last. In general, later settings take
	// precedence over early settings, but for backwards compatibility
	// in the config file the precedence is reversed for all settings
	// except chain name settings.
	const bool reverse_precedence =
	(source == Source::CONFIG_FILE_NETWORK_SECTION \|\|
	source == Source::CONFIG_FILE_DEFAULT_SECTION) &&
	!get_chain_name;

	// Weird behavior preserved for backwards compatibility: Negated
	// -regtest and -testnet arguments which you would expect to
	// override values set in the configuration file are currently
	// accepted but silently ignored. It would be better to apply these
	// just like other negated values, or at least warn they are
	// ignored.
	const bool skip_negated_command_line = get_chain_name;

	if (done) {
	return;
	}

	// Ignore settings in default config section if requested.
	if (ignore_default_section_config &&
	source == Source::CONFIG_FILE_DEFAULT_SECTION &&
	!never_ignore_negated_setting) {
	return;
	}

	// Skip negated command line settings.
	if (skip_negated_command_line && span.last_negated()) {
	return;
	}

	if (!span.empty()) {
	result = reverse_precedence ? span.begin()[0] : span.end()[-1];
	done = true;
	} else if (span.last_negated()) {
	result = false;
	done = true;
	}
	});
	return result;
	}

	std::vector<SettingsValue> GetSettingsList(const Settings &settings,
	const std::string &section,
	const std::string &name,
	bool ignore_default_section_config) {
	std::vector<SettingsValue> result;
	// Done merging any more settings sources.
	bool done = false;
	bool prev_negated_empty = false;
	MergeSettings(
	settings, section, name, [&](SettingsSpan span, Source source) {
	// Weird behavior preserved for backwards compatibility: Apply
	// config file settings even if negated on command line. Negating a
	// setting on command line will ignore earlier settings on the
	// command line and ignore settings in the config file, unless the
	// negated command line value is followed by non-negated value, in
	// which case config file settings will be brought back from the
	// dead (but earlier command line settings will still be ignored).
	const bool add_zombie_config_values =
	(source == Source::CONFIG_FILE_NETWORK_SECTION \|\|
	source == Source::CONFIG_FILE_DEFAULT_SECTION) &&
	!prev_negated_empty;

	// Ignore settings in default config section if requested.
	if (ignore_default_section_config &&
	source == Source::CONFIG_FILE_DEFAULT_SECTION) {
	return;
	}

	// Add new settings to the result if isn't already complete, or if
	// the values are zombies.
	if (!done \|\| add_zombie_config_values) {
	for (const auto &value : span) {
	if (value.isArray()) {
	result.insert(result.end(), value.getValues().begin(),
	value.getValues().end());
	} else {
	result.push_back(value);
	}
	}
	}

	// If a setting was negated, or if a setting was forced, set done to
	// true to ignore any later lower priority settings.
	done \|= span.negated() > 0 \|\| source == Source::FORCED;

	// Update the negated and empty state used for the zombie values
	// check.
	prev_negated_empty \|= span.last_negated() && result.empty();
	});
	return result;
	}

	bool OnlyHasDefaultSectionSetting(const Settings &settings,
	const std::string &section,
	const std::string &name) {
	bool has_default_section_setting = false;
	bool has_other_setting = false;
	MergeSettings(
	settings, section, name, [&](SettingsSpan span, Source source) {
	if (span.empty()) {
	return;
	} else if (source == Source::CONFIG_FILE_DEFAULT_SECTION) {
	has_default_section_setting = true;
	} else {
	has_other_setting = true;
	}
	});
	// If a value is set in the default section and not explicitly overwritten
	// by the user on the command line or in a different section, then we want
	// to enable warnings about the value being ignored.
	return has_default_section_setting && !has_other_setting;
	}

	SettingsSpan::SettingsSpan(const std::vector<SettingsValue> &vec) noexcept
	: SettingsSpan(vec.data(), vec.size()) {}
	const SettingsValue *SettingsSpan::begin() const {
	return data + negated();
	}
	const SettingsValue *SettingsSpan::end() const {
	return data + size;
	}
	bool SettingsSpan::empty() const {
	return size == 0 \|\| last_negated();
	}
	bool SettingsSpan::last_negated() const {
	return size > 0 && data[size - 1].isFalse();
	}
	size_t SettingsSpan::negated() const {
	for (size_t i = size; i > 0; --i) {
	if (data[i - 1].isFalse()) {
	// Return number of negated values (position of last false value)
	return i;
	}
	}
	return 0;
	}

	} // namespace util

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