// This file is distributed under the BSD License.
// See LICENSE.TXT for details.

#ifndef LANGKIT_LEXER_HPP_
#define LANGKIT_LEXER_HPP_

#include <boost/regex.hpp>
#include <tr1/memory>
#include <string>

namespace langkit
{
    struct File_Position {
        int line;
        int column;

        File_Position(int file_line, int file_column)
            : line(file_line), column(file_column) { }

        File_Position() : line(0), column(0) { }
    };

    struct Pattern {
        boost::regex regex;
        int identifier;

        Pattern() { }
        Pattern(const std::string &regexp, int id) : regex(regexp), identifier(id) { }
    };

    typedef std::tr1::shared_ptr<struct Token> TokenPtr;

    struct Token {
        std::string text;
        int identifier;
        const char *filename;
        File_Position start, end;

        std::vector<TokenPtr> children;

        Token(const std::string &token_text, int id, const char *fname) : text(token_text), identifier(id), filename(fname) { }
    };

    struct Lexer {
        std::vector<Pattern> lex_patterns;
        Pattern skip_pattern;
        Pattern command_sep_pattern;
        Pattern line_sep_pattern;
        Pattern multiline_comment_start_pattern;
        Pattern multiline_comment_end_pattern;
        Pattern singleline_comment_pattern;

        Lexer operator<<(const Pattern &p) {
            lex_patterns.push_back(p);
            return *this;
        }

        std::vector<TokenPtr> lex(const std::string &input, const char *filename) {
            std::vector<Pattern>::iterator iter, end, iter2, end2;
            std::vector<TokenPtr> retval;
            bool found;
            std::string::const_iterator input_iter = input.begin(), input_end = input.end();

            int current_col = 0;
            int current_line = 0;
            boost::match_results<std::string::const_iterator> what;

            while (input_iter != input_end) {
                found = false;

                if (regex_search(input_iter, input_end, what, singleline_comment_pattern.regex, boost::match_continuous)) {
                    std::string comment_start(what[0]);
                    input_iter += comment_start.size();

                    bool found_eol = false;

                    while ((!found_eol) && (input_iter != input_end)) {
                        boost::match_results<std::string::const_iterator> eol_delim;
                        if (regex_search(input_iter, input_end, eol_delim, line_sep_pattern.regex, boost::match_continuous)) {
                            std::string comment_end(eol_delim[0]);
                            input_iter += comment_end.size();
                            ++current_line;
                            current_col = 0;
                            found_eol = true;
                            break;
                        }
                        if ((!found_eol) && (input_iter != input_end)) {
                            ++input_iter;
                        }
                    }
                }
                else if (regex_search(input_iter, input_end, what, multiline_comment_start_pattern.regex, boost::match_continuous)) {
                    std::string comment_start(what[0]);
                    input_iter += comment_start.size();

                    bool found_eoc = false;

                    while ((!found_eoc) && (input_iter != input_end)) {
                        boost::match_results<std::string::const_iterator> eol_delim;
                        if (regex_search(input_iter, input_end, eol_delim, line_sep_pattern.regex, boost::match_continuous)) {
                            std::string comment_end(eol_delim[0]);
                            input_iter += comment_end.size();
                            ++current_line;
                            current_col = 0;
                        }
                        boost::match_results<std::string::const_iterator> eoc_delim;
                        if (regex_search(input_iter, input_end, eoc_delim, multiline_comment_end_pattern.regex, boost::match_continuous)) {
                            std::string comment_end(eoc_delim[0]);
                            input_iter += comment_end.size();
                            current_col += comment_end.size();
                            found_eoc = true;
                            break;
                        }
                        if ((!found_eoc) && (input_iter != input_end)) {
                            ++input_iter;
                            ++current_col;
                        }
                    }

                    if (!found_eoc) {
                        std::cout << "Incomplete comment block!  Add exceptions!" << std::endl;
                        return retval;
                    }
                }
                else if (regex_search(input_iter, input_end, what, skip_pattern.regex, boost::match_continuous)) {
                    std::string whitespace(what[0]);
                    input_iter += whitespace.size();
                    current_col += whitespace.size();
                    found = true;
                }
                else if (regex_search(input_iter, input_end, what, line_sep_pattern.regex, boost::match_continuous)) {
                    const std::string cr(what[0]);

                    boost::match_results<std::string::const_iterator> if_delim;
                    if (regex_search(cr.begin(), cr.end(), if_delim, command_sep_pattern.regex, boost::match_continuous)) {
                        TokenPtr t(new Token(if_delim[0], command_sep_pattern.identifier, filename));
                        t->start.column = current_col;
                        t->start.line = current_line;
                        current_col += t->text.size();
                        t->end.column = current_col;
                        t->end.line = current_line;
                        retval.push_back(t);
                    }

                    input_iter += cr.size();
                    ++current_line;
                    current_col = 0;
                    found = true;
                }
                else if (regex_search(input_iter, input_end, what, command_sep_pattern.regex, boost::match_continuous)) {
                    TokenPtr t(new Token(what[0], command_sep_pattern.identifier, filename));
                    t->start.column = current_col;
                    t->start.line = current_line;
                    current_col += t->text.size();
                    t->end.column = current_col;
                    t->end.line = current_line;
                    retval.push_back(t);
                    input_iter += t->text.size();
                    found = true;
                }
                else {
                    for (iter = lex_patterns.begin(), end = lex_patterns.end(); iter != end; ++iter) {
                        if (regex_search(input_iter, input_end, what, iter->regex, boost::match_continuous)) {
                            TokenPtr t(new Token(what[0], iter->identifier, filename));
                            t->start.column = current_col;
                            t->start.line = current_line;
                            current_col += t->text.size();
                            t->end.column = current_col;
                            t->end.line = current_line;
                            retval.push_back(t);
                            input_iter += t->text.size();
                            found = true;
                            break;
                        }
                    }

                    if (!found) {
                        const std::string err(input_iter, input_end);
                        std::cout << "Unknown string at: " << err << std::endl;
                        return retval;
                    }
                }
            }
            return retval;
        }

        void set_skip(const Pattern &p) {
            skip_pattern = p;
        }
        void set_line_sep(const Pattern &p) {
            line_sep_pattern = p;
        }
        void set_command_sep(const Pattern &p) {
            command_sep_pattern = p;
        }
        void set_multiline_comment(const Pattern &start, const Pattern &end) {
            multiline_comment_start_pattern = start;
            multiline_comment_end_pattern = end;
        }
        void set_singleline_comment(const Pattern &p) {
            singleline_comment_pattern = p;
        }
    };

}
#endif /* LANGKIT_LEXER_HPP_ */