#!/usr/bin/env bash

# 26.03.04 :: klevstul


rotate() {

    test_integer() {
        if ! [[ $1 =~ ^[123]$ ]]; then
            echo "error: variable (times to rotate) must be 1, 2, or 3"
            exit 1
        fi
    }

    filename=$1                                     # ~/syncDir/0_downloads/frodeKlevstul.jpg
    extension="${filename##*.}"                     # jpg
    basename_without_ext="${filename%.*}"           # ~/syncDir/0_downloads/frodeKlevstul
    basename_only="${basename_without_ext##*/}"     # frodeKlevstul

    times_to_rotate=$2                              # how many times to rotate 90 degrees
    times_to_rotate=${times_to_rotate:=1}           # set to 1 if no value is given
    test_integer ${times_to_rotate}                 # make sure the input (if given from the user) is valid

    transpose="transpose=1"                         # add a transpose for each time to rotate
    for ((i = 2; i <= ${times_to_rotate}; i++)); do
        transpose+=",transpose=1"
    done

    # 90 degrees clockwise: transpose=1
    # 90 degrees counterclockwise: transpose=2
    # `-c:a copy` - ensures audio (if present) is copied without re-encoding (not applicable for images, but safe to include).
    ffmpeg -i ${filename} -vf ${transpose} -c:a copy ${basename_without_ext}_rot.${extension}

}


this_file_name=`basename "$0"`
if [ $# -lt 1 ]; then
    echo "error: path to file is missing."
    echo "usage: '$this_file_name [path_to_file] ([times_to_rotate_90_degrees (1)])'"
    exit 1
fi

rotate $1 $2