ncmpcpp/src/format_impl.h

/***************************************************************************
 *   Copyright (C) 2008-2021 by Andrzej Rybczak                            *
 *   andrzej@rybczak.net                                                   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   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 NCMPCPP_HAVE_FORMAT_IMPL_H
#define NCMPCPP_HAVE_FORMAT_IMPL_H

#include <boost/variant.hpp>

#include "curses/menu.h"
#include "curses/strbuffer.h"
#include "format.h"
#include "song.h"
#include "utility/functional.h"
#include "utility/wide_string.h"

namespace Format {

// Commutative binary operation such that:
// - Empty + Empty = Empty
// - Empty + Missing = Missing
// - Empty + Ok = Ok
// - Missing + Missing = Missing
// - Missing + Ok = Missing
// - Ok + Ok = Ok
inline Result &operator+=(Result &base, Result result)
{
	if (base == Result::Missing || result == Result::Missing)
		base = Result::Missing;
	else if (base == Result::Ok || result == Result::Ok)
		base = Result::Ok;
	return base;
}

/*inline std::ostream &operator<<(std::ostream &os, Result r)
{
	switch (r)
	{
		case Result::Empty:
			os << "empty";
			break;
		case Result::Missing:
			os << "missing";
			break;
		case Result::Ok:
			os << "ok";
			break;
	}
	return os;
}*/

template <typename CharT, typename OutputT, typename SecondOutputT = OutputT>
struct Printer: boost::static_visitor<Result>
{
	typedef std::basic_string<CharT> StringT;

	Printer(OutputT &os, const MPD::Song *song, SecondOutputT *second_os, const unsigned flags)
	: m_output(os)
	, m_song(song)
	, m_output_switched(false)
	, m_second_os(second_os)
	, m_no_output(0)
	, m_flags(flags)
	{ }

	Result operator()(const StringT &s)
	{
		if (!s.empty())
		{
			output(s);
			return Result::Ok;
		}
		else
			return Result::Empty;
	}

	Result operator()(const NC::Color &c)
	{
		if (m_flags & Flags::Color)
			output(c);
		return Result::Empty;
	}

	Result operator()(NC::Format fmt)
	{
		if (m_flags & Flags::Format)
			output(fmt);
		return Result::Empty;
	}

	Result operator()(OutputSwitch)
	{
		if (!m_no_output)
			m_output_switched = true;
		return Result::Ok;
	}

	Result operator()(const SongTag &st)
	{
		StringT tags;
		if (m_flags & Flags::Tag && m_song != nullptr)
		{
			tags = convertString<CharT, char>::apply(
				m_song->getTags(st.function())
			);
		}
		if (!tags.empty())
		{
			if (st.delimiter() > 0)
			{
				// shorten date/length by simple truncation
				if (st.function() == &MPD::Song::getDate
				    || st.function() == &MPD::Song::getLength)
					tags.resize(st.delimiter());
				else
					tags = wideShorten(tags, st.delimiter());
			}
			output(tags, &st);
			return Result::Ok;
		}
		else
			return Result::Missing;
	}

	// If all Empty -> Empty, if any Ok -> continue with Ok, if any Missing ->
	// stop with Empty.
	Result operator()(const Group<CharT> &group)
	{
		auto visit = [this, &group] {
			Result result = Result::Empty;
			for (const auto &ex : group.base())
			{
				result += boost::apply_visitor(*this, ex);
				if (result == Result::Missing)
				{
					result = Result::Empty;
					break;
				}
			}
			return result;
		};

		++m_no_output;
		Result result = visit();
		--m_no_output;
		if (!m_no_output && result == Result::Ok)
			visit();
		return result;
	}

	// If all Empty or Missing -> Empty, if any Ok -> stop with Ok.
	Result operator()(const FirstOf<CharT> &first_of)
	{
		for (const auto &ex : first_of.base())
		{
			if (boost::apply_visitor(*this, ex) == Result::Ok)
				return Result::Ok;
		}
		return Result::Empty;
	}

private:
	// generic version for streams (buffers, menus)
	template <typename ValueT, typename OutputStreamT>
	struct output_ {
		static void exec(OutputStreamT &os, const ValueT &value, const SongTag *) {
			os << value;
		}
	};

	// specialization for strings (input/output)
	template <typename SomeCharT, typename OtherCharT>
	struct output_<std::basic_string<SomeCharT>, std::basic_string<OtherCharT>> {
		typedef std::basic_string<SomeCharT> SomeString;
 		typedef std::basic_string<OtherCharT> OtherString;

		// compile only if string types are the same
		static typename std::enable_if<
			std::is_same<SomeString, OtherString>::value,
			void
		>::type exec(SomeString &result, const OtherString &s, const SongTag *) {
			result += s;
		}
	};
	// When writing to a string, we should ignore all other properties. If this
	// code is reached, throw an exception.
	template <typename ValueT, typename SomeCharT>
	struct output_<ValueT, std::basic_string<SomeCharT>> {
		static void exec(std::basic_string<CharT> &, const ValueT &, const SongTag *) {
			throw std::logic_error("non-string property can't be appended to the string");
		}
	};

	// Specialization for TagVector.
	template <typename SomeCharT, typename OtherCharT>
	struct output_<std::basic_string<SomeCharT>, TagVector<OtherCharT> > {
		// Compile only if string types are the same.
		static typename std::enable_if<
			std::is_same<SomeCharT, OtherCharT>::value,
			void
		>::type exec(TagVector<OtherCharT> &acc,
		             const std::basic_string<SomeCharT> &s, const SongTag *st) {
			if (st != nullptr)
				acc.emplace_back(*st, s);
			else
				acc.emplace_back(boost::none, s);
		}
	};
	// When extracting tags from a song all the other properties should be
	// ignored. If that's not the case, throw an exception.
	template <typename ValueT, typename SomeCharT>
	struct output_<ValueT, TagVector<SomeCharT> > {
		static void exec(TagVector<SomeCharT> &, const ValueT &, const SongTag *) {
			throw std::logic_error("Non-string property can't be inserted into the TagVector");
		}
	};

	template <typename ValueT>
	void output(const ValueT &value, const SongTag *st = nullptr) const
	{
		if (!m_no_output)
		{
			if (m_output_switched && m_second_os != nullptr)
				output_<ValueT, SecondOutputT>::exec(*m_second_os, value, st);
			else
				output_<ValueT, OutputT>::exec(m_output, value, st);
		}
	}

	OutputT &m_output;
	const MPD::Song *m_song;

	bool m_output_switched;
	SecondOutputT *m_second_os;

	unsigned m_no_output;
	const unsigned m_flags;
};

template <typename CharT, typename VisitorT>
void visit(VisitorT &visitor, const AST<CharT> &ast)
{
	for (const auto &ex : ast.base())
		boost::apply_visitor(visitor, ex);
}

template <typename CharT, typename ItemT>
void print(const AST<CharT> &ast, NC::Menu<ItemT> &menu, const MPD::Song *song,
           NC::BasicBuffer<CharT> *buffer, const unsigned flags)
{
	Printer<CharT, NC::Menu<ItemT>, NC::Buffer> printer(menu, song, buffer, flags);
	visit(printer, ast);
}

template <typename CharT>
void print(const AST<CharT> &ast, NC::BasicBuffer<CharT> &buffer,
           const MPD::Song *song, const unsigned flags)
{
	Printer<CharT, NC::BasicBuffer<CharT>> printer(buffer, song, &buffer, flags);
	visit(printer, ast);
}

template <typename CharT>
std::basic_string<CharT> stringify(const AST<CharT> &ast, const MPD::Song *song)
{
	std::basic_string<CharT> result;
	Printer<CharT, std::basic_string<CharT>> printer(result, song, &result, Flags::Tag);
	visit(printer, ast);
	return result;
}

template <typename CharT>
TagVector<CharT> flatten(const AST<CharT> &ast, const MPD::Song &song)
{
	TagVector<CharT> result;
	Printer<CharT, TagVector<CharT>> printer(result, &song, &result, Flags::Tag);
	visit(printer, ast);
	return result;
}

}

#endif // NCMPCPP_HAVE_FORMAT__IMPL_H