// Copyright 2016 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "MacroExpander.h"

#include <algorithm>
#include <sstream>

#include "Diagnostics.h"
#include "Token.h"

namespace pp
{

class TokenLexer : public Lexer
{
 public:
	typedef std::vector<Token> TokenVector;

	TokenLexer(TokenVector* tokens)
	{
		tokens->swap(mTokens);
		mIter = mTokens.begin();
	}

	virtual void lex(Token* token)
	{
		if (mIter == mTokens.end())
		{
			token->reset();
			token->type = Token::LAST;
		}
		else
		{
			*token = *mIter++;
		}
	}

 private:
	PP_DISALLOW_COPY_AND_ASSIGN(TokenLexer);

	TokenVector mTokens;
	TokenVector::const_iterator mIter;
};

MacroExpander::MacroExpander(Lexer* lexer,
                             MacroSet* macroSet,
                             Diagnostics* diagnostics,
                             bool parseDefined) :
	mLexer(lexer), mMacroSet(macroSet), mDiagnostics(diagnostics), mParseDefined(parseDefined)
{
	mReserveToken = nullptr;
}

MacroExpander::~MacroExpander()
{
	for (size_t i = 0; i < mContextStack.size(); ++i)
	{
		delete mContextStack[i];
	}

	delete mReserveToken;
}

void MacroExpander::lex(Token* token)
{
	while (true)
	{
		getToken(token);

		if (token->type != Token::IDENTIFIER)
			break;

		// Defined operator is parsed here since it may be generated by macro expansion.
		// Defined operator produced by macro expansion has undefined behavior according to C++
		// spec, which the GLSL spec references (see C++14 draft spec section 16.1.4), but this
		// behavior is needed for passing dEQP tests, which enforce stricter compatibility between
		// implementations.
		if (mParseDefined && token->text == "defined")
		{
			bool paren = false;
			getToken(token);
			if (token->type == '(')
			{
				paren = true;
				getToken(token);
			}
			if (token->type != Token::IDENTIFIER)
			{
				mDiagnostics->report(Diagnostics::UNEXPECTED_TOKEN, token->location,
				                     token->text);
				break;
			}
			auto iter = mMacroSet->find(token->text);
			std::string expression = iter != mMacroSet->end() ? "1" : "0";

			if (paren)
			{
				getToken(token);
				if (token->type != ')')
				{
					mDiagnostics->report(Diagnostics::UNEXPECTED_TOKEN, token->location,
					                     token->text);
					break;
				}
			}

			// We have a valid defined operator.
			// Convert the current token into a CONST_INT token.
			token->type = Token::CONST_INT;
			token->text = expression;
			break;
		}

		if (token->expansionDisabled())
			break;

		MacroSet::const_iterator iter = mMacroSet->find(token->text);
		if (iter == mMacroSet->end())
			break;

		const Macro& macro = iter->second;
		if (macro.disabled)
		{
			// If a particular token is not expanded, it is never expanded.
			token->setExpansionDisabled(true);
			break;
		}
		if ((macro.type == Macro::kTypeFunc) && !isNextTokenLeftParen())
		{
			// If the token immediately after the macro name is not a '(',
			// this macro should not be expanded.
			break;
		}

		pushMacro(macro, *token);
	}
}

void MacroExpander::getToken(Token* token)
{
	if (mReserveToken)
	{
		*token = *mReserveToken;
		delete mReserveToken;
		mReserveToken = nullptr;
		return;
	}

	// First pop all empty macro contexts.
	while (!mContextStack.empty() && mContextStack.back()->empty())
	{
		popMacro();
	}

	if (!mContextStack.empty())
	{
		*token = mContextStack.back()->get();
	}
	else
	{
		mLexer->lex(token);
	}
}

void MacroExpander::ungetToken(const Token& token)
{
	if (!mContextStack.empty())
	{
		MacroContext* context = mContextStack.back();
		context->unget();
		assert(context->replacements[context->index] == token);
	}
	else
	{
		assert(!mReserveToken);
		mReserveToken = new Token(token);
	}
}

bool MacroExpander::isNextTokenLeftParen()
{
	Token token;
	getToken(&token);

	bool lparen = token.type == '(';
	ungetToken(token);

	return lparen;
}

bool MacroExpander::pushMacro(const Macro& macro, const Token& identifier)
{
	assert(!macro.disabled);
	assert(!identifier.expansionDisabled());
	assert(identifier.type == Token::IDENTIFIER);
	assert(identifier.text == macro.name);

	std::vector<Token> replacements;
	if (!expandMacro(macro, identifier, &replacements))
		return false;

	// Macro is disabled for expansion until it is popped off the stack.
	macro.disabled = true;

	MacroContext* context = new MacroContext;
	context->macro = &macro;
	context->replacements.swap(replacements);
	mContextStack.push_back(context);
	return true;
}

void MacroExpander::popMacro()
{
	assert(!mContextStack.empty());

	MacroContext* context = mContextStack.back();
	mContextStack.pop_back();

	assert(context->empty());
	assert(context->macro->disabled);
	context->macro->disabled = false;
	delete context;
}

bool MacroExpander::expandMacro(const Macro& macro,
                                const Token& identifier,
                                std::vector<Token>* replacements)
{
	replacements->clear();
	if (macro.type == Macro::kTypeObj)
	{
		replacements->assign(macro.replacements.begin(),
		                     macro.replacements.end());

		if (macro.predefined)
		{
			static const std::string kLine = "__LINE__";
			static const std::string kFile = "__FILE__";

			assert(replacements->size() == 1);
			Token& repl = replacements->front();
			if (macro.name == kLine)
			{
				std::ostringstream stream;
				stream << identifier.location.line;
				repl.text = stream.str();
			}
			else if (macro.name == kFile)
			{
				std::ostringstream stream;
				stream << identifier.location.file;
				repl.text = stream.str();
			}
		}
	}
	else
	{
		assert(macro.type == Macro::kTypeFunc);
		std::vector<MacroArg> args;
		args.reserve(macro.parameters.size());
		if (!collectMacroArgs(macro, identifier, &args))
			return false;

		replaceMacroParams(macro, args, replacements);
	}

	for (size_t i = 0; i < replacements->size(); ++i)
	{
		Token& repl = replacements->at(i);
		if (i == 0)
		{
			// The first token in the replacement list inherits the padding
			// properties of the identifier token.
			repl.setAtStartOfLine(identifier.atStartOfLine());
			repl.setHasLeadingSpace(identifier.hasLeadingSpace());
		}
		repl.location = identifier.location;
	}
	return true;
}

bool MacroExpander::collectMacroArgs(const Macro& macro,
                                     const Token& identifier,
                                     std::vector<MacroArg>* args)
{
	Token token;
	getToken(&token);
	assert(token.type == '(');

	args->push_back(MacroArg());
	for (int openParens = 1; openParens != 0; )
	{
		getToken(&token);

		if (token.type == Token::LAST)
		{
			mDiagnostics->report(Diagnostics::MACRO_UNTERMINATED_INVOCATION,
			                     identifier.location, identifier.text);
			// Do not lose EOF token.
			ungetToken(token);
			return false;
		}

		bool isArg = false; // True if token is part of the current argument.
		switch (token.type)
		{
		case '(':
			++openParens;
			isArg = true;
			break;
		case ')':
			--openParens;
			isArg = openParens != 0;
			break;
		case ',':
			// The individual arguments are separated by comma tokens, but
			// the comma tokens between matching inner parentheses do not
			// seperate arguments.
			if (openParens == 1) args->push_back(MacroArg());
			isArg = openParens != 1;
			break;
		default:
			isArg = true;
			break;
		}
		if (isArg)
		{
			MacroArg& arg = args->back();
			// Initial whitespace is not part of the argument.
			if (arg.empty()) token.setHasLeadingSpace(false);
			arg.push_back(token);
		}
	}

	const Macro::Parameters& params = macro.parameters;
	// If there is only one empty argument, it is equivalent to no argument.
	if (params.empty() && (args->size() == 1) && args->front().empty())
	{
		args->clear();
	}
	// Validate the number of arguments.
	if (args->size() != params.size())
	{
		Diagnostics::ID id = args->size() < macro.parameters.size() ?
			Diagnostics::MACRO_TOO_FEW_ARGS :
			Diagnostics::MACRO_TOO_MANY_ARGS;
		mDiagnostics->report(id, identifier.location, identifier.text);
		return false;
	}

	// Pre-expand each argument before substitution.
	// This step expands each argument individually before they are
	// inserted into the macro body.
	for (size_t i = 0; i < args->size(); ++i)
	{
		MacroArg& arg = args->at(i);
		TokenLexer lexer(&arg);
		MacroExpander expander(&lexer, mMacroSet, mDiagnostics, mParseDefined);

		arg.clear();
		expander.lex(&token);
		while (token.type != Token::LAST)
		{
			arg.push_back(token);
			expander.lex(&token);
		}
	}
	return true;
}

void MacroExpander::replaceMacroParams(const Macro& macro,
                                       const std::vector<MacroArg>& args,
                                       std::vector<Token>* replacements)
{
	for (size_t i = 0; i < macro.replacements.size(); ++i)
	{
		const Token& repl = macro.replacements[i];
		if (repl.type != Token::IDENTIFIER)
		{
			replacements->push_back(repl);
			continue;
		}

		// TODO(alokp): Optimize this.
		// There is no need to search for macro params every time.
		// The param index can be cached with the replacement token.
		Macro::Parameters::const_iterator iter = std::find(
			macro.parameters.begin(), macro.parameters.end(), repl.text);
		if (iter == macro.parameters.end())
		{
			replacements->push_back(repl);
			continue;
		}

		size_t iArg = std::distance(macro.parameters.begin(), iter);
		const MacroArg& arg = args[iArg];
		if (arg.empty())
		{
			continue;
		}
		size_t iRepl = replacements->size();
		replacements->insert(replacements->end(), arg.begin(), arg.end());
		// The replacement token inherits padding properties from
		// macro replacement token.
		replacements->at(iRepl).setHasLeadingSpace(repl.hasLeadingSpace());
	}
}

}  // namespace pp