/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying

   file LICENSE.rst or https://cmake.org/licensing for details.  */

#include "cmPlaceholderExpander.h"

#include "cmsys/String.h"

std::string& cmPlaceholderExpander::ExpandVariables(std::string& s,

                                                    HandleGenex handleGenex)

{

  std::string::size_type start = s.find('<');

  // no variables to expand

  if (start == std::string::npos) {

    return s;

  }

  std::string::size_type pos = 0;

  std::string expandedInput;

  while (start != std::string::npos && start < s.size() - 2) {

    if (handleGenex == HandleGenex::Yes && start != 0 && s[start - 1] == '$') {

      // this is a generator expression

      // skip it and try to find the next < in the string

      start = s.find('<', start + 1);

      continue;

    }

    std::string::size_type end = s.find('>', start);

    // if we find a < with no > we are done

    if (end == std::string::npos) {

      s = expandedInput;

      return s;

    }

    // if the previous character is a '$',  this is a generator expression

    // or if the next char after the < is not A-Za-z then

    // skip it and try to find the next < in the string

    if ((handleGenex == HandleGenex::Yes && start != 0 &&

         s[start - 1] == '$') ||

        !cmsysString_isalpha(s[start + 1])) {

      start = s.find('<', start + 1);

    } else {

      // extract the var

      std::string var = s.substr(start + 1, end - start - 1);

      std::string replace = this->ExpandVariable(var);

      expandedInput += s.substr(pos, start - pos);

      // Prevent consecutive whitespace in the output if the rule variable

      // expands to an empty string.

      bool consecutive = replace.empty() && start > 0 && s[start - 1] == ' ' &&

        end + 1 < s.size() && s[end + 1] == ' ';

      if (consecutive) {

        expandedInput.pop_back();

      }

      expandedInput += replace;

      // move to next one

      start = s.find('<', start + var.size() + 2);

      pos = end + 1;

    }

  }

  // add the rest of the input

  expandedInput += s.substr(pos, s.size() - pos);

  // remove trailing whitespace

  if (!expandedInput.empty() && expandedInput.back() == ' ') {

    expandedInput.pop_back();

  }

  s = expandedInput;

  return s;

}