## TITLE('Biochemistry: Identify the Law of Thermodynamics')
## DESCRIPTION
## Given the first or second law of thermodynamics, select the statement
## that correctly describes it from a mix of the two core statements
## and two misconception-based distractors.
## ENDDESCRIPTION
## KEYWORDS('thermodynamics','first law','second law','energy','entropy','spontaneous')
## DBsubject('Biochemistry')
## DBchapter('Thermodynamics')
## DBsection('Laws of Thermodynamics')
## Level(2)
## Date('2026-02-25')
## Author('Dr. Neil R. Voss')
## Institution('Roosevelt University')
## Language(en)
# https://github.com/vosslab
# This work is licensed under CC BY 4.0 (Creative Commons Attribution 4.0
# International License).
# https://creativecommons.org/licenses/by/4.0/
# Source code portions are licensed under LGPLv3.

DOCUMENT();

loadMacros(
	'PGstandard.pl',
	'PGML.pl',
	'parserRadioButtons.pl',
	'PGcourse.pl',
);

$showPartialCorrectAnswers = 0;

# ----------------------------
# 1) HTML emphasis spans
# ----------------------------
my $first_emph = "<span style='color:#0077bb;font-weight:700;'>First</span>";
my $second_emph = "<span style='color:#cc6600;font-weight:700;'>Second</span>";

# ----------------------------
# 2) Core correct statements (always both present)
# ----------------------------
my $energy_statement = "the total energy of a system and its surroundings is constant";
my $entropy_statement = "the total entropy of a system and its surroundings increases for a spontaneous process";

# ----------------------------
# 3) Misconception distractor pool (pick 2 per question)
# ----------------------------
my @distractor_pool = (
	"energy is always increasing in a spontaneous process",
	"entropy of the system always increases for a spontaneous process",
	"entropy of the universe is constant",
	"a spontaneous process always releases heat",
	"free energy of the universe always decreases",
	"temperatures will always decrease in a spontaneous process",
);

# ----------------------------
# 4) Stem wording variants
# ----------------------------
my @stem_templates = (
	"The %s Law of Thermodynamics states:",
	"Which statement best describes the %s Law of Thermodynamics?",
	"Select the statement that matches the %s Law of Thermodynamics.",
);

# ----------------------------
# 5) Randomization
# ----------------------------
my $local_random = PGrandom->new();
$local_random->srand($problemSeed);

# pick which law (0 = First, 1 = Second)
my $law_index = $local_random->random(0, 1, 1);

# pick a stem wording variant
my $stem_index = $local_random->random(0, $#stem_templates, 1);

# shuffle distractor pool and pick 2
my @shuffled_indices = (0 .. $#distractor_pool);
# Fisher-Yates shuffle using local_random
for my $i (reverse 1 .. $#shuffled_indices) {
	my $j = $local_random->random(0, $i, 1);
	@shuffled_indices[$i, $j] = @shuffled_indices[$j, $i];
}
my @picked_distractors = (
	$distractor_pool[$shuffled_indices[0]],
	$distractor_pool[$shuffled_indices[1]],
);

# ----------------------------
# 6) Assemble prompt and choices
# ----------------------------
my $law_label;
my $correct_text;
my $hint_text;
my $solution_text;

if ($law_index == 0) {
	$law_label = $first_emph;
	$correct_text = $energy_statement;
	$hint_text = "This law is about conservation. Think about what cannot be created or destroyed.";
	$solution_text = "The First Law of Thermodynamics is the law of conservation of energy. The total energy of a system and its surroundings is always constant; energy can be converted from one form to another but cannot be created or destroyed.";
} else {
	$law_label = $second_emph;
	$correct_text = $entropy_statement;
	$hint_text = "This law is about the directionality of spontaneous change. Think about what tends to increase overall.";
	$solution_text = "The Second Law of Thermodynamics states that the total entropy of a system and its surroundings increases for any spontaneous process. Note: it is the combined entropy of the system AND surroundings that must increase, not the system alone.";
}

# build stem from template
$prompt = sprintf($stem_templates[$stem_index], $law_label);

# build the 4 choices: both core statements + 2 distractors
# then shuffle them so the correct answer moves around
my @raw_choices = ($energy_statement, $entropy_statement, @picked_distractors);

# shuffle the choices using local_random (Fisher-Yates)
for my $i (reverse 1 .. $#raw_choices) {
	my $j = $local_random->random(0, $i, 1);
	@raw_choices[$i, $j] = @raw_choices[$j, $i];
}

# find correct index after shuffle
my $correct_index = 0;
for my $i (0 .. $#raw_choices) {
	if ($raw_choices[$i] eq $correct_text) {
		$correct_index = $i;
		last;
	}
}

# store for PGML
$hint = $hint_text;
$solution = $solution_text;

# ----------------------------
# 7) Build RadioButtons
# ----------------------------
$rb = RadioButtons(
	[@raw_choices],
	$correct_index,
	labels        => 'ABC',
	displayLabels => 1,
	separator     => '<div style="margin-bottom: 0.6em;"></div>',
);

# ----------------------------
# 8) Problem text (PGML)
# ----------------------------
BEGIN_PGML
[@ $prompt @]*

[_]{$rb}
END_PGML

# ----------------------------
# 9) Hint
# ----------------------------
BEGIN_PGML_HINT
[$hint]*
END_PGML_HINT

# ----------------------------
# 10) Solution
# ----------------------------
BEGIN_PGML_SOLUTION
[$solution]*
END_PGML_SOLUTION

ENDDOCUMENT();