/*
 * This file is part of solidity.
 *
 * solidity 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 3 of the License, or
 * (at your option) any later version.
 *
 * solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
 *
 * This file is derived from the file "scanner.h", which was part of the
 * V8 project. The original copyright header follows:
 *
 * Copyright 2006-2012, the V8 project authors. All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 * * Neither the name of Google Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Solidity scanner.
 */

#pragma once

#include <liblangutil/Token.h>
#include <liblangutil/CharStream.h>
#include <liblangutil/SourceLocation.h>

#include <optional>
#include <iosfwd>

namespace solidity::langutil
{

class AstRawString;
class AstValueFactory;
class ParserRecorder;

enum class ScannerKind
{
	Solidity,
	Yul
};

enum class ScannerError
{
	NoError,

	IllegalToken,
	IllegalHexString,
	IllegalHexDigit,
	IllegalCommentTerminator,
	IllegalEscapeSequence,
	UnicodeCharacterInNonUnicodeString,
	IllegalCharacterInString,
	IllegalStringEndQuote,
	IllegalNumberSeparator,
	IllegalExponent,
	IllegalNumberEnd,

	DirectionalOverrideUnderflow,
	DirectionalOverrideMismatch,

	OctalNotAllowed,
};

std::string to_string(ScannerError _errorCode);
std::ostream& operator<<(std::ostream& os, ScannerError _errorCode);

class Scanner
{
	friend class LiteralScope;
public:
	explicit Scanner(CharStream& _source):
		m_source(_source),
		m_sourceName{std::make_shared<std::string>(_source.name())}
	{
		reset();
	}

	/// Resets scanner to the start of input.
	void reset();

	/// Changes the scanner mode.
	void setScannerMode(ScannerKind _kind)
	{
		m_kind = _kind;

		// Invalidate lookahead buffer.
		rescan();
	}

	CharStream const& charStream() const noexcept { return m_source; }

	/// @returns the next token and advances input
	Token next();

	/// Set scanner to a specific offset. This is used in error recovery.
	void setPosition(size_t _offset);

	///@{
	///@name Information about the current token

	/// @returns the current token
	Token currentToken() const
	{
		return m_tokens[Current].token;
	}
	ElementaryTypeNameToken currentElementaryTypeNameToken() const
	{
		unsigned firstSize;
		unsigned secondSize;
		std::tie(firstSize, secondSize) = m_tokens[Current].extendedTokenInfo;
		return ElementaryTypeNameToken(m_tokens[Current].token, firstSize, secondSize);
	}

	SourceLocation currentLocation() const { return m_tokens[Current].location; }
	std::string const& currentLiteral() const { return m_tokens[Current].literal; }
	std::tuple<unsigned, unsigned> const& currentTokenInfo() const { return m_tokens[Current].extendedTokenInfo; }

	/// Retrieves the last error that occurred during lexical analysis.
	/// @note If no error occurred, the value is undefined.
	ScannerError currentError() const noexcept { return m_tokens[Current].error; }
	///@}

	///@{
	///@name Information about the current comment token

	SourceLocation currentCommentLocation() const { return m_skippedComments[Current].location; }
	std::string const& currentCommentLiteral() const { return m_skippedComments[Current].literal; }
	/// Called by the parser during FunctionDefinition parsing to clear the current comment
	void clearCurrentCommentLiteral() { m_skippedComments[Current].literal.clear(); }

	ScannerKind scannerKind() const { return m_kind; }

	///@}

	///@{
	///@name Information about the next token

	/// @returns the next token without advancing input.
	Token peekNextToken() const { return m_tokens[Next].token; }
	SourceLocation peekLocation() const { return m_tokens[Next].location; }
	std::string const& peekLiteral() const { return m_tokens[Next].literal; }

	Token peekNextNextToken() const { return m_tokens[NextNext].token; }
	///@}

private:

	inline Token setError(ScannerError _error) noexcept
	{
		m_tokens[NextNext].error = _error;
		return Token::Illegal;
	}

	/// Used for the current and look-ahead token and comments
	struct TokenDesc
	{
		Token token;
		SourceLocation location;
		std::string literal;
		ScannerError error = ScannerError::NoError;
		std::tuple<unsigned, unsigned> extendedTokenInfo;
	};

	///@{
	///@name Literal buffer support
	inline void addLiteralChar(char c) { m_tokens[NextNext].literal.push_back(c); }
	inline void addCommentLiteralChar(char c) { m_skippedComments[NextNext].literal.push_back(c); }
	inline void addLiteralCharAndAdvance() { addLiteralChar(m_char); advance(); }
	void addUnicodeAsUTF8(unsigned codepoint);
	///@}

	bool advance() { m_char = m_source.advanceAndGet(); return !m_source.isPastEndOfInput(); }
	void rollback(size_t _amount) { m_char = m_source.rollback(_amount); }
	/// Rolls back to the start of the current token and re-runs the scanner.
	void rescan();

	inline Token selectErrorToken(ScannerError _err) { advance(); return setError(_err); }
	inline Token selectToken(Token _tok) { advance(); return _tok; }
	/// If the next character is _next, advance and return _then, otherwise return _else.
	inline Token selectToken(char _next, Token _then, Token _else);

	bool scanHexByte(char& o_scannedByte);
	std::optional<unsigned> scanUnicode();

	/// Scans a single Solidity token.
	void scanToken();

	/// Skips all whitespace and @returns true if something was skipped.
	bool skipWhitespace();
	/// Skips all whitespace that are neither '\r' nor '\n'.
	bool skipWhitespaceExceptUnicodeLinebreak();
	Token skipSingleLineComment();
	Token skipMultiLineComment();

	/// Tests if current source position is CR, LF or CRLF.
	bool atEndOfLine() const;

	/// Tries to consume CR, LF or CRLF line terminators and returns success or failure.
	bool tryScanEndOfLine();

	void scanDecimalDigits();
	Token scanNumber(char _charSeen = 0);
	std::tuple<Token, unsigned, unsigned> scanIdentifierOrKeyword();

	Token scanString(bool const _isUnicode);
	Token scanHexString();
	/// Scans a single line comment and returns its corrected end position.
	size_t scanSingleLineDocComment();
	Token scanMultiLineDocComment();
	/// Scans a slash '/' and depending on the characters returns the appropriate token
	Token scanSlash();

	/// Scans an escape-sequence which is part of a string and adds the
	/// decoded character to the current literal. Returns true if a pattern
	/// is scanned.
	bool scanEscape();

	/// @returns true iff we are currently positioned at a unicode line break.
	bool isUnicodeLinebreak();

	/// Return the current source position.
	size_t sourcePos() const { return m_source.position(); }
	bool isSourcePastEndOfInput() const { return m_source.isPastEndOfInput(); }

	enum TokenIndex { Current, Next, NextNext };

	TokenDesc m_skippedComments[3] = {}; // desc for the current, next and nextnext skipped comment
	TokenDesc m_tokens[3] = {}; // desc for the current, next and nextnext token

	CharStream& m_source;
	std::shared_ptr<std::string const> m_sourceName;

	ScannerKind m_kind = ScannerKind::Solidity;

	/// one character look-ahead, equals 0 at end of input
	char m_char;
};

}