#!/bin/bash

# This script is an example captcha script.
# It takes the text to recognize in the captcha image as a parameter.
# It return the image binary as a result. ejabberd support PNG, JPEG and GIF.

# The whole idea of the captcha script is to let server admins adapt it to
# their own needs. The goal is to be able to make the captcha generation as
# unique as possible, to make the captcha challenge difficult to bypass by
# a bot.
# Server admins are thus supposed to write and use their own captcha generators.

# This script relies on ImageMagick.
# It is NOT compliant with ImageMagick forks like GraphicsMagick.

INPUT=$1

TRANSFORMATIONS=(DECOUPE.A DECOUPE.B INTRUS.A INTRUS.B SOMME.A SOMME.B)

if test -n ${BASH_VERSION:-''} ; then
    get_random ()
    {  
	R=$RANDOM
    }
else
    for n in `od -A n -t u2 -N 64 /dev/urandom`; do RL="$RL$n "; done
    get_random ()
    {  
	R=${RL%% *}
	RL=${RL#* }
    }
fi

DECOUPE.A()
{
    LENGTH=${#INPUT}
    MID=$((LENGTH / 2))
    
    echo "Tapez ${INPUT:0:$MID}\n   suivi de ${INPUT:$MID:$MID}"
}

DECOUPE.B()
{
    LENGTH=${#INPUT}
    MID=$((LENGTH / 2))
    
    echo "Saisissez ${INPUT:0:$MID}\n   puis ${INPUT:$MID:$MID}"
}

INTRUS.A()
{
    LENGTH=${#INPUT}
    NUMBERS=$(echo $INPUT | grep -o . | tr '\n' ' ')
    SORTED_UNIQ_NUM=$(echo "${NUMBERS[@]}" | sort -u | tr '\n' ' ')
    INTRUS=-1
    
    for i in 1 2 3 4 5 6 7 8 9
    do
        if [[ ! " ${SORTED_UNIQ_NUM[@]} " =~ " ${i} " ]]; then
            INTRUS=$i
            break
        fi
    done
    
    # Worst case
    if [[ $INTRUS -eq "-1" ]]
    then
        echo Tapez "$INPUT \n   sans changement"
        return
    fi
    
    for num in ${NUMBERS[@]}
    do
        get_random
        R=$(($R % 100))
             
        if [[ $R -lt 60 ]]; then 
            NEWINPUT=${NEWINPUT}${num}${INTRUS}
        else
            NEWINPUT=${NEWINPUT}${num}
        fi
    done
    
    echo "Tapez $NEWINPUT en\n   supprimant les $INTRUS"
}

INTRUS.B()
{
    LENGTH=${#INPUT}
    NUMBERS=$(echo $INPUT | grep -o . | tr '\n' ' ')
    SORTED_UNIQ_NUM=$(echo "${NUMBERS[@]}" | sort -u | tr '\n' ' ')
    INTRUS=-1
    
    for i in 1 2 3 4 5 6 7 8 9
    do
        if [[ ! " ${SORTED_UNIQ_NUM[@]} " =~ " ${i} " ]]; then
            INTRUS=$i
            break
        fi
    done
    
    # Worst case
    if [[ $INTRUS -eq "-1" ]]
    then
        echo Tapez "$INPUT \n   sans changement"
        return
    fi
    
    for num in ${NUMBERS[@]}
    do
        get_random
        R=$(($R % 100))
             
        if [[ $R -lt 60 ]]; then 
            NEWINPUT=${NEWINPUT}${num}${INTRUS}
        else
            NEWINPUT=${NEWINPUT}${num}
        fi
    done
    
    echo "Saisissez $NEWINPUT en\n   enlevant les $INTRUS"
}

SOMME.A()
{
    if [[ $(($INPUT % 2)) -eq 0 ]]; then
        A=$(($INPUT / 2))
        B=$A
    else
        A=$(($INPUT / 2))
        B=$(($A+1))
    fi
    
    get_random
    R=$(($R % 100))
    A=$(($A - $R))
    B=$(($B + $R))
    
    echo "Tapez le résultat\n   de $A + $B"    
}

SOMME.B()
{
    if [[ $(($INPUT % 2)) -eq 0 ]]; then
        A=$(($INPUT / 2))
        B=$A
    else
        A=$(($INPUT / 2))
        B=$(($A+1))
    fi
    
    get_random
    R=$(($R % 100))
    A=$(($A - $R))
    B=$(($B + $R))
    
    echo "Saisissez le résultat\n   de $A + $B"    
}

get_random
RAND_ITALIC=$(($R % 25))
get_random
RAND_ANGLE=$(($R % 3))
get_random
RAND_INDEX=$(($R % ${#TRANSFORMATIONS[@]}))

convert -size 300x60 xc:none -pointsize 20 \
	\( -clone 0 -fill black \
	-stroke black -strokewidth 1 \
	-annotate "${RAND_ANGLE}x${RAND_ITALIC}+0+0" "\n $(${TRANSFORMATIONS[$RAND_INDEX]})" \
	-roll +$ROLL_X+0 \
	-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
	-roll -$ROLL_X+0 \) \
	-flatten -crop 300x60 +repage -quality 500 -depth 11 png:-