#!/bin/bash 

checkcommand()
{
    local result
    local command="$1"
    which "$command" 1>/dev/null 2>&1
    if [[ $? == 0 ]]; then
        echo "$command requirement OK"
        result=1
    else
        echo "$command requirement MISSING"
        result=0
    fi
    return $result
}

help()
{
    echo "Usage:    tphoto [ -h | -f ] [ *.jpg ]"    
    echo "Rename jpg files using Exif Original Date/Time if exists."
    echo "    -h            Display help."
    echo "    -f            Force rename jpg files with Exif datetime or file datetime."
}

doRename()
{
    local filename=$(basename $1)
    #echo "$filename"
    jhead -nimg%Y%m%d-%H%M%S "$filename"
}

doRenameCarefully()
{
    local filename=$(basename $1)
    #echo "$filename"
    if [[ $filename =~ IMG[12][90][0-9][0-9][01][0-9][0-3][0-9][012][0-9][0-5][0-9][0-5][0-9].* ]]; then
        local target=img${filename:3:8}-${filename:11}
        if [ -e "$target" ]; then
            echo "$filename -r> $target ABORT because file already exists."
        else
            echo "$filename -r> $target"
            mv "$filename" "$target"
        fi
    elif [[ $(exiftool $filename | grep -c "Date/Time Original") > 0 ]]; then
        #echo "yop $filename"
        doRename "$filename"
    else
        echo "$filename IGNORED"
    fi
}

# main
checkcommand "exiftool"
if [[ $? == 0 ]]; then
    exit 1
else
    checkcommand "jhead"
    if [[ $? == 0 ]]; then
        exit 1
    fi
fi

if [[ $# == 0 ]]; then
    find . -maxdepth 1 -type f -iname "*.jpg" | while read path
    do
        doRenameCarefully "$path"
    done
elif [[ "$1" == "-h" ]]; then
    help
elif [[ "$1" == "-f" && $# == 1 ]]; then
    find . -maxdepth 1 -type f -iname "*.jpg" | while read path
    do
        doRename "$path"
    done
elif [[ "$1" == "-f" && $# > 1 ]]; then
    for filename do
        if [[ "$filename" != "-f" ]]; then
            doRename "$filename"
        fi
    done
else
    for filename do
            doRenameCarefully "$filename"
    done
fi