ClickHouse/dbms/include/DB/Parsers/ASTFunction.h

#pragma once

#include <DB/Parsers/ASTWithAlias.h>
#include <DB/Parsers/ASTExpressionList.h>
#include <DB/Functions/IFunction.h>
#include <DB/AggregateFunctions/IAggregateFunction.h>
#include <DB/IO/WriteBufferFromString.h>


namespace DB
{

/** Применение функции или оператора
  */
class ASTFunction : public ASTWithAlias
{
public:
	enum FunctionKind
	{
		UNKNOWN,
		TABLE_FUNCTION,
		FUNCTION,
		AGGREGATE_FUNCTION,
		LAMBDA_EXPRESSION,
		ARRAY_JOIN,
	};

	/// имя функции
	String name;
	/// аргументы
	ASTPtr arguments;
	/// параметры - для параметрических агрегатных функций. Пример: quantile(0.9)(x) - то, что в первых скобках - параметры.
	ASTPtr parameters;

	FunctionKind kind{UNKNOWN};

	ASTFunction() = default;
	ASTFunction(const StringRange range_) : ASTWithAlias(range_) {}

	String getColumnName() const override
	{
		String res;
		WriteBufferFromString wb(res);
		writeString(name, wb);

		if (parameters)
		{
			writeChar('(', wb);
			for (ASTs::const_iterator it = parameters->children.begin(); it != parameters->children.end(); ++it)
			{
				if (it != parameters->children.begin())
					writeCString(", ", wb);
				writeString((*it)->getColumnName(), wb);
			}
			writeChar(')', wb);
		}

		writeChar('(', wb);
		for (ASTs::const_iterator it = arguments->children.begin(); it != arguments->children.end(); ++it)
		{
			if (it != arguments->children.begin())
				writeCString(", ", wb);
			writeString((*it)->getColumnName(), wb);
		}
		writeChar(')', wb);

		return res;
	}

	/** Получить текст, который идентифицирует этот элемент. */
	String getID() const override { return "Function_" + name; }

	ASTPtr clone() const override
	{
		ASTFunction * res = new ASTFunction(*this);
		ASTPtr ptr{res};

		res->children.clear();

		if (arguments) 	{ res->arguments = arguments->clone();		res->children.push_back(res->arguments); }
		if (parameters) { res->parameters = parameters->clone(); 	res->children.push_back(res->parameters); }

		return ptr;
	}

protected:
	void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
};


template <typename... Args>
ASTPtr makeASTFunction(const String & name, Args &&... args)
{
	const auto function = new ASTFunction{};
	ASTPtr result{function};

	function->name = name;
	function->arguments = new ASTExpressionList{};
	function->children.push_back(function->arguments);

	function->arguments->children = { std::forward<Args>(args)... };

	return result;
}


template <typename... Args>
ASTPtr makeASTFunction(const String & name, const StringRange & function_range,
	const StringRange & arguments_range, Args &&... args)
{
	const auto function = new ASTFunction{function_range};
	ASTPtr result{function};

	function->name = name;
	function->arguments = new ASTExpressionList{arguments_range};
	function->children.push_back(function->arguments);

	function->arguments->children = { std::forward<Args>(args)... };

	return result;
}

}