#!/bin/bash

# remove the # on the following line to turn on debugging
# set -o xtrace

#==================
function initialize ()
{
trap 'summarize ; exit 0' INT     # Handle user interrupts
num_ques=0                        # Number of questions asked so far
num_correct=0                     # Number answered correctly so far
first_time=true                   # true until first question is asked
cd ${QUIZDIR:=~/quiz} || exit 2
}

#==================
function choose_subj ()
{
subjects=($(ls))
PS3="Choose a subject for the quiz from the preceding list: "
select Subject in ${subjects[*]}; do
    if [[ -z "$Subject" ]]; then
        echo "No subject chosen.  Bye." >&2
        exit 1
    fi
    echo $Subject
    return 0
done
}

#==================
function exchange ()
{
temp_value=${questions[$1]}
questions[$1]=${questions[$2]}
questions[$2]=$temp_value
}

#==================
function scramble ()
{
declare -i index quescount
questions=($(ls))
quescount=${#questions[*]}        # Number of elements
((index=quescount-1))
while [[ $index > 0 ]]; do
    ((target=RANDOM % index))
    exchange $target $index
    ((index -= 1))
done
}

#==================
function ask ()
{
exec 3<$1
read -u3 ques || exit 2
read -u3 num_opts || exit 2

index=0
choices=()
while (( index < num_opts )) ; do
    read -u3 next_choice || exit 2
    choices=("${choices[@]}" "$next_choice")
    ((index += 1))
done
read -u3 correct_answer || exit 2
exec 3<&-

if [[ $first_time = true ]]; then
    first_time=false
    echo -e "You may press the interrupt key at any time to quit.\n"
fi

PS3=$ques"  "                     # Make $ques the prompt for select
                                  # and add some spaces for legibility
select answer in "${choices[@]}"; do
    if [[ -z "$answer" ]]; then
            echo  Not a valid choice. Please choose again.
        elif [[ "$answer" = "$correct_answer" ]]; then
            echo "Correct!"
            return 1
        else
            echo "No, the answer is $correct_answer."
            return 0
    fi
done
}

#==================
function summarize ()
{
echo                              # Skip a line
if (( num_ques == 0 )); then
    echo "You did not answer any questions"
    exit 0
fi

(( percent=num_correct*100/num_ques ))
echo "You answered $num_correct questions correctly, out of \
$num_ques total questions."
echo "Your score is $percent percent."
}

#==================
# Main program
initialize                        # Step 1 in top-level design

subject=$(choose_subj)            # Step 2
[[ $? -eq 0 ]] || exit 2          # If no valid choice, exit

cd $subject || exit 2             # Step 3
echo                              # Skip a line
scramble                          # Step 4

for ques in ${questions[*]}; do   # Step 5
    ask $ques
    result=$?
    (( num_ques=num_ques+1 ))
    if [[ $result == 1 ]]; then
        (( num_correct += 1 ))
    fi
    echo                          # Skip a line between questions
    sleep ${QUIZDELAY:=1}
done

summarize                         # Step 6 
exit 0