use strict;

# This file define functions to read and write different elements of a survey.
# A survey is made up of an array of questions.  
# Questions are defined in a separate file, question_struct.pl
require "question_struct.pl";

# DEBUG: This magic number is stored in the first index of the question array.
# Each function will check that the magic number is valid -- if not, then something
# was gone wrong -- most likely this means you called the function wrong.
use constant SURVEY_MAGIC_NUMBER => 198675432;

# Some constants used internally.  These specify the index in the main array that each
# part of the 'survey' is stored
use constant SURVEY_INDEX_MAGIC             => 0;
use constant SURVEY_INDEX_QUESTIONS         => 1;
use constant SURVEY_INDEX_DUEDATE           => 2;
use constant SURVEY_INDEX_PASSWORD          => 3;
use constant SURVEY_INDEX_ISANON            => 4;

# Internal debug function -- if this complains then you probably called the original function wrong
sub surveyCheckMagic {
  my ($survey, $functionName, $caller_package, $caller_filename, $caller_line) = @_;
  if ($$survey[SURVEY_INDEX_MAGIC] != SURVEY_MAGIC_NUMBER) {
     print "\n\n\n<h1>ERROR! Bad survey magic number in call to $functionName from $caller_filename, line $caller_line.\n " .
           "This probably means you called $functionName wrong.</h1>\n\n\n";
     exit(1);
  }   
}

# Inputs: none
# Returns: a new survey.  
# 
sub surveyCreateNew {
  my @anArray = ();

  my $survey = \@anArray;
  $$survey[SURVEY_INDEX_MAGIC] = SURVEY_MAGIC_NUMBER;      # init magic number
  my @emptyQuestionArray = ();
  $$survey[SURVEY_INDEX_QUESTIONS] = \@emptyQuestionArray; # ref to question array;              

  # By default, survey is not anonymous
  surveySetIsAnon($survey, 0);

  return $survey;
}

# Internal function -- returns whole array of questions
sub helperSurveyGetQuestionArray {
  my ($survey) = @_;
  my $ref_questionArray = $$survey[SURVEY_INDEX_QUESTIONS];
  my @questionArray = @$ref_questionArray;
  return @questionArray;
}

# Inputs: a survey
# Returns: number of questions in that survey
sub surveyGetNumQuestions() {
  my($survey) = @_;              # get the input parameter
  surveyCheckMagic($survey, "surveyGetNumQuestions()", caller());
  my @questionArray = helperSurveyGetQuestionArray($survey);
  my $numQuestions = @questionArray;
  return $numQuestions;;
}

# Inputs: (survey, question) 
#   where survey is the survey to add to, 
#   and question is the question to be added.
# Returns: nothing (but modifies the survey that was provided,
#   adding the questions to the end of the survey)
sub surveyAddQuestion() {
  my($survey, $question) = @_;
  surveyCheckMagic  ($survey,   "surveyAddQuestion()", caller());
  questionCheckMagic($question, "surveyAddQuestion()", caller());
  my $ref_questionArray = $$survey[SURVEY_INDEX_QUESTIONS];
  push @$ref_questionArray, $question;;
}

# Inputs: (survey, questionNum)
#   where survey is the survey to read from,
#   and questionNum is the number of the question to return
#   (indexed from zero)
# Outputs: 
sub surveyGetQuestion {
  my($survey, $questionNum) = @_;
  surveyCheckMagic  ($survey,   "surveyGetQuestion()", caller());
  my @questionArray = helperSurveyGetQuestionArray($survey);
  my $question = $questionArray[$questionNum];
  questionCheckMagic($question, "surveyGetQuestion()", caller());
  return $question;
}

# Inputs: a survey
# Returns: the due date of that survey, or undef
sub surveyGetDueDate {
  my($survey) = @_;              # get the input parameter
  surveyCheckMagic($survey, "surveyGetDueDate()", caller());
  return $$survey[SURVEY_INDEX_DUEDATE];
}

# Inputs: (survey, dueDate)) 
#   where survey is the survey to modify, 
#   and 'dueDate' is the survey due date to be set
# Returns: nothing (but modifies the survey that was provided,
#   setting the due date of that survey))
sub surveySetDueDate() {
  my($survey, $dueDate) = @_;
  surveyCheckMagic($survey, "surveySetDueDate()", caller());
  $$survey[SURVEY_INDEX_DUEDATE] = $dueDate;
}

# Inputs: a survey
# Returns: the due date of that survey, or undef
sub surveyGetPassword {
  my($survey) = @_;              # get the input parameter
  surveyCheckMagic($survey, "surveyGetPassword()", caller());
  return $$survey[SURVEY_INDEX_PASSWORD];
}

# Inputs: (survey, password)) 
#   where survey is the survey to modify, 
#   and 'password' is the survey due date to be set
# Returns: nothing (but modifies the survey that was provided,
#   setting the password of that survey))
sub surveySetPassword() {
  my($survey, $password) = @_;
  surveyCheckMagic($survey, "surveySetPassword()", caller());
  $$survey[SURVEY_INDEX_PASSWORD] = $password;
}

# Inputs: a survey
# Returns: the due date of that survey, or undef
sub surveyGetIsAnon {
  my($survey) = @_;              # get the input parameter
  surveyCheckMagic($survey, "surveyGetIsAnon()", caller());
  return $$survey[SURVEY_INDEX_ISANON];
}

# Inputs: (survey, isAnon)) 
#   where survey is the survey to modify, 
#   and 'isAnon' is the survey due date to be set
# Returns: nothing (but modifies the survey that was provided,
#   setting the isAnon of that survey))
sub surveySetIsAnon() {
  my($survey, $isAnon) = @_;
  surveyCheckMagic($survey, "surveySetIsAnon()", caller());
  $$survey[SURVEY_INDEX_ISANON] = $isAnon;
}


1;