/*
 * Copyright (c) 2015, 2023, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2.0,
 * as published by the Free Software Foundation.
 *
 * This program is also distributed with certain software (including
 * but not limited to OpenSSL) that is licensed under separate terms,
 * as designated in a particular file or component or in included license
 * documentation.  The authors of MySQL hereby grant you an additional
 * permission to link the program and your derivative works with the
 * separately licensed software that they have included with MySQL.
 *
 * This program 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, version 2.0, for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301  USA
 */
//--------------------------------------------------------------------------------------------------
#include "utils_mysql_parsing.h"

#include "utils_string_parsing.h"

namespace shcore
{
  namespace mysql
  {
    namespace splitter
    {
      //--------------------------------------------------------------------------------------------------

      const unsigned char* skip_leading_whitespace(const unsigned char *head, const unsigned char *tail)
      {
        while (head < tail && *head <= ' ')
          head++;
        return head;
      }

      //--------------------------------------------------------------------------------------------------

      bool is_line_break(const unsigned char *head, const unsigned char *line_break)
      {
        if (*line_break == '\0')
          return false;

        while (*head != '\0' && *line_break != '\0' && *head == *line_break)
        {
          head++;
          line_break++;
        }
        return *line_break == '\0';
      }

      //--------------------------------------------------------------------------------------------------

      /**
       * A statement splitter to take a list of sql statements and split them into individual statements,
       * return their position and length in the original string (instead the copied strings).
       *
       * A tweak was added to the function to return the number of complete statements found, where
       * complete means the ending delimiter was found.
       */
      size_t determineStatementRanges(const char *sql, size_t length, std::string &delimiter,
                                                 std::vector<std::pair<size_t, size_t> > &ranges,
                                                 const std::string &line_break, std::stack<std::string> &input_context_stack)
      {
        int full_statement_count = 0;
        const unsigned char *delimiter_head = (unsigned char*)delimiter.c_str();

        const unsigned char keyword[] = "delimiter";

        const unsigned char *head = (unsigned char *)sql;
        const unsigned char *tail = head;
        const unsigned char *end = head + length;
        const unsigned char *new_line = (unsigned char*)line_break.c_str();
        bool have_content = false; // Set when anything else but comments were found for the current statement.

        ranges.clear();

        while (tail < end)
        {
          switch (*tail)
          {
            case '*': // Comes from a multiline comment and comment is done
              if (*(tail + 1) == '/' && (!input_context_stack.empty() && input_context_stack.top() == "/*"))
              {
                if (!input_context_stack.empty())
                  input_context_stack.pop();

                tail += 2;
                head = tail; // Skip over the comment.
              }
              break;
            case '/': // Possible multi line comment or hidden (conditional) command.
              if (*(tail + 1) == '*')
              {
                tail += 2;
                bool is_hidden_command = (*tail == '!');
                while (true)
                {
                  while (tail < end && *tail != '*')
                    tail++;
                  if (tail == end) // Unfinished comment.
                  {
                    input_context_stack.push("/*");
                    break;
                  }
                  else
                  {
                    if (*++tail == '/')
                    {
                      tail++; // Skip the slash too.
                      break;
                    }
                  }
                }

                if (!is_hidden_command && !have_content)
                  head = tail; // Skip over the comment.

              }
              break;

            case '-': // Possible single line comment.
            {
                        const unsigned char *end_char = tail + 2;
                        if (*(tail + 1) == '-' && (*end_char == ' ' || *end_char == '\t' || is_line_break(end_char, new_line) || length == 2))
                        {
                          // Skip everything until the end of the line.
                          tail += 2;
                          while (tail < end && !is_line_break(tail, new_line))
                            tail++;
                          if (!have_content)
                            head = tail;
                        }
                        break;
            }

            case '#': // MySQL single line comment.
              while (tail < end && !is_line_break(tail, new_line))
                tail++;
              if (!have_content)
                head = tail;
              break;

            case '"':
            case '\'':
            case '`':
            {
                      have_content = true;
                      char quote = *tail++;

                      if (input_context_stack.empty() || input_context_stack.top() == "-")
                      {
                        // Quoted string/id. Skip this in a local loop if is opening quote.
                        while (tail < end && *tail != quote)
                        {
                          // Skip any escaped character too.
                          if (*tail == '\\')
                            tail++;
                          tail++;
                        }
                        if (*tail == quote)
                          tail++; // Skip trailing quote char to if one was there.
                        else
                        {
                          std::string q;
                          q.assign(&quote, 1);
                          input_context_stack.push(q); // Sets multiline opening quote to continue processing
                        }
                      }
                      else // Closing quote, clears the multiline flag
                        input_context_stack.pop();

                      break;
            }

            case 'd':
            case 'D':
            {
                      have_content = true;

                      // Possible start of the keyword DELIMITER. Must be at the start of the text or a character,
                      // which is not part of a regular MySQL identifier (0-9, A-Z, a-z, _, $, \u0080-\uffff).
                      unsigned char previous = tail > (unsigned char *)sql ? *(tail - 1) : 0;
                      bool is_identifier_char = previous >= 0x80
                      || (previous >= '0' && previous <= '9')
                      || ((previous | 0x20) >= 'a' && (previous | 0x20) <= 'z')
                      || previous == '$'
                      || previous == '_';
                      if (tail == (unsigned char *)sql || !is_identifier_char)
                      {
                        const unsigned char *run = tail + 1;
                        const unsigned char *kw = keyword + 1;
                        int count = 9;
                        while (count-- > 1 && (*run++ | 0x20) == *kw++)
                          ;
                        if (count == 0 && *run == ' ')
                        {
                          // Delimiter keyword found. Get the new delimiter (everything until the end of the line).
                          tail = run++;
                          while (run < end && !is_line_break(run, new_line))
                            run++;

                          delimiter = std::string((char *)tail, run - tail);
                          aux::trim(delimiter);

                          delimiter_head = (unsigned char*)delimiter.c_str();

                          // Skip over the delimiter statement and any following line breaks.
                          while (is_line_break(run, new_line))
                            run++;
                          tail = run;
                          head = tail;
                        }
                      }
                      break;
            }
          }

          if (*tail == *delimiter_head)
          {
            // Found possible start of the delimiter. Check if it really is.
            size_t count = delimiter.size();
            if (count == 1)
            {
              // Most common case. Trim the statement and check if it is not empty before adding the range.
              head = skip_leading_whitespace(head, tail);
              if (head < tail || (!input_context_stack.empty() && input_context_stack.top() == "-"))
              {
                full_statement_count++;

                if (!input_context_stack.empty())
                  input_context_stack.pop();

                if (head < tail)
                  ranges.push_back(std::make_pair<size_t, size_t>(head - (unsigned char *)sql, tail - head));
              }
              head = ++tail;
              have_content = false;
            }
            else
            {
              const unsigned char *run = tail + 1;
              const unsigned char *del = delimiter_head + 1;
              while (count-- > 1 && (*run++ == *del++))
                ;

              if (count == 0)
              {
                // Multi char delimiter is complete. Tail still points to the start of the delimiter.
                // Run points to the first character after the delimiter.
                head = skip_leading_whitespace(head, tail);
                if (head < tail || (!input_context_stack.empty() && input_context_stack.top() == "-"))
                {
                  full_statement_count++;

                  if (!input_context_stack.empty())
                    input_context_stack.pop();

                  if (head < tail)
                    ranges.push_back(std::make_pair<size_t, size_t>(head - (unsigned char *)sql, tail - head));
                }

                tail = run;
                head = run;
                have_content = false;
              }
            }
          }

          // Multiline comments are ignored, everything else is not
          if (*tail > ' ' && (input_context_stack.empty() || input_context_stack.top() != "/*"))
            have_content = true;
          tail++;
        }

        // Add remaining text to the range list but ignores it when it is a multiline comment
        head = skip_leading_whitespace(head, tail);
        if (head < tail && (input_context_stack.empty() || input_context_stack.top() != "/*"))
        {
          ranges.push_back(std::make_pair<size_t, size_t>(head - (unsigned char *)sql, tail - head));

          // If not a multiline string then sets the flag to multiline statement (not terminated)
          if (input_context_stack.empty())
            input_context_stack.push("-");
        }

        return full_statement_count;
      }
    }
  }
}
