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// Modifications as part of cpp-ethereum under the following license:
//
// cpp-ethereum 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
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
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// along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.

#pragma once

#include <boost/assert.hpp>

#include <libdevcore/Common.h>
#include <libdevcore/Log.h>
#include <libdevcore/CommonData.h>
#include <libsolidity/BaseTypes.h>
#include <libsolidity/Token.h>

namespace dev {
namespace solidity {


class AstRawString;
class AstValueFactory;
class ParserRecorder;

class CharStream {
public:
    CharStream()
        : m_pos(0)
    {}

    explicit CharStream(const std::string& _source)
        : m_source(_source), m_pos(0)
    {}
    int getPos() const { return m_pos; }
    bool isPastEndOfInput() const { return m_pos >= m_source.size(); }
    char get() const { return m_source[m_pos]; }
    char advanceAndGet() {
        if (isPastEndOfInput()) return 0;
        ++m_pos;
        if (isPastEndOfInput()) return 0;
        return get();
    }
    char rollback(size_t _amount) {
        BOOST_ASSERT(m_pos >= _amount);
        m_pos -= _amount;
        return get();
    }

    /// Functions that help pretty-printing parse errors
    /// Do only use in error cases, they are quite expensive.
    /// @{
    std::string getLineAtPosition(int _position) const;
    std::tuple<int, int> translatePositionToLineColumn(int _position) const;
    /// @}
private:
    std::string m_source;
    size_t m_pos;
};

// ----------------------------------------------------------------------------
// JavaScript Scanner.

class Scanner {
public:
    // Scoped helper for literal recording. Automatically drops the literal
    // if aborting the scanning before it's complete.
    class LiteralScope {
    public:
        explicit LiteralScope(Scanner* self)
            : scanner_(self), complete_(false) {
            scanner_->startNewLiteral();
        }
        ~LiteralScope() {
            if (!complete_) scanner_->dropLiteral();
        }
        void Complete() {
            complete_ = true;
        }

    private:
        Scanner* scanner_;
        bool complete_;
    };

    explicit Scanner(const CharStream& _source);

    // Resets the scanner as if newly constructed with _input as input.
    void reset(const CharStream& _source);

    // Returns the next token and advances input.
    Token::Value next();
    // Returns the current token again.
    Token::Value getCurrentToken() { return m_current_token.token; }
    // Returns the location information for the current token
    // (the token last returned by Next()).
    Location getCurrentLocation() const { return m_current_token.location; }
    const std::string& getCurrentLiteral() const { return m_current_token.literal; }

    // Similar functions for the upcoming token.

    // One token look-ahead (past the token returned by Next()).
    Token::Value peek() const { return m_next_token.token; }

    Location peekLocation() const { return m_next_token.location; }
    const std::string& peekLiteral() const { return m_next_token.literal; }

    /// Functions that help pretty-printing parse errors.
    /// Do only use in error cases, they are quite expensive.
    /// @{
    std::string getLineAtPosition(int _position) const { return m_source.getLineAtPosition(_position); }
    std::tuple<int, int> translatePositionToLineColumn(int _position) const
    {
        return m_source.translatePositionToLineColumn(_position);
    }
    /// @}

    // Returns true if there was a line terminator before the peek'ed token,
    // possibly inside a multi-line comment.
    bool hasAnyLineTerminatorBeforeNext() const {
        return m_hasLineTerminatorBeforeNext ||
                m_hasMultilineCommentBeforeNext;
    }

private:
    // Used for the current and look-ahead token.
    struct TokenDesc {
        Token::Value token;
        Location location;
        std::string literal;
    };

    // Literal buffer support
    inline void startNewLiteral() {
        m_next_token.literal.clear();
    }

    inline void addLiteralChar(char c) {
        m_next_token.literal.push_back(c);
    }

    inline void dropLiteral() {
        m_next_token.literal.clear();
    }

    inline void addLiteralCharAndAdvance() {
        addLiteralChar(m_char);
        advance();
    }

    // Low-level scanning support.
    bool advance() { m_char = m_source.advanceAndGet(); return !m_source.isPastEndOfInput(); }
    void rollback(int amount) {
        m_char = m_source.rollback(amount);
    }

    inline Token::Value selectToken(Token::Value tok) {
        advance();
        return tok;
    }

    inline Token::Value selectToken(char next, Token::Value then, Token::Value else_) {
        advance();
        if (m_char == next) {
            advance();
            return then;
        } else {
            return else_;
        }
    }

    bool scanHexNumber(char& scanned_number, int expected_length);

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

    bool skipWhitespace();
    Token::Value skipSingleLineComment();
    Token::Value skipMultiLineComment();

    void scanDecimalDigits();
    Token::Value scanNumber(bool _periodSeen);
    Token::Value scanIdentifierOrKeyword();

    Token::Value scanString();

    // 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();

    // Return the current source position.
    int getSourcePos() {
        return m_source.getPos();
    }
    bool isSourcePastEndOfInput() {
        return m_source.isPastEndOfInput();
    }

    TokenDesc m_current_token;  // desc for current token (as returned by Next())
    TokenDesc m_next_token;     // desc for next token (one token look-ahead)

    CharStream m_source;

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

    // Whether there is a line terminator whitespace character after
    // the current token, and  before the next. Does not count newlines
    // inside multiline comments.
    bool m_hasLineTerminatorBeforeNext;
    // Whether there is a multi-line comment that contains a
    // line-terminator after the current token, and before the next.
    bool m_hasMultilineCommentBeforeNext;
};

} }