#! /bin/zsh
#
# this file:
#   http://user.it.uu.se/~embe8573/conf/.zsh/video-slice
#   https://dataswamp.org/~incal/conf/.zsh/video-slice

     ###################
    ## slice and dice ##
    ## video stuff :) ##
    ###################

# https://video.stackexchange.com/questions/4563/how-can-i-crop-a-video-with-ffmpeg
video-crop () {
    local x=$1
    local y=$2
    local w=$3
    local h=$4
    local vid=$5

    local name=${vid:r}
    local ext=${vid:e}
    local out=${name}-cropped.${ext}

    ffmpeg -y -i $vid -filter:v "crop=$w:$h:$x:$y" -c:a copy ${out}
}

video-remove-border () {
    local border=$1
    local src=$2

    local x_border=$(( 2 * $border ))
    local y_border=$x_border

    local name=${src:r}
    local ext=${src:e}
    local out=${name}-no-border.${ext}

    ffmpeg \
        -y                                           \
        -i $src                                      \
        -vf "crop=in_w-${x_border}:in_h-${y_border}" \
        -c:a copy                                    \
                                                     $out
}

video-add-border () {
    local src=$1
    local w=${2:-1080}
    local h=${3:-1920}

    local name=${src:r}
    local ext=${src:e}
    local dst=${name}-border.${ext}

    local ar="${w}:${h}"

    ffmpeg \
        -y      \
        -i $src \
        -vf "scale=${ar}:force_original_aspect_ratio=decrease,pad=${ar}:(ow-iw)/2:(oh-ih)/2,setsar=1" \
        $dst
}

video-merge () {
    local first=$1
    local second=$2

    local name=${first:r}-${second:r}
    local ext=${first:e}

    local out=${name}.${ext}

    local list_file=both.txt

    echo "file $first" > $list_file
    echo "file $second" >> $list_file

    ffmpeg -f concat -safe 0 -i $list_file -c copy $out
}

slice-video () {
    # usage:
    # slice-video FILE [START_SECONDS=-2] LEN_SECONDS

    local src=$1
    local name=${src:r}
    local ext=${src:e}
    local dst=${name}-sliced.${ext}

    local start
    local len
    case $# in
        (2) start=-2
            len=$2 ;;
        (3) start=$2
            len=$3 ;;
        (*) wrong-number-of-arguments-message ;;
    esac

    # y is overwrite
    ffmpeg -v  quiet   \
           -i  $src    \
           -ss $start  \
           -t  $len    \
           -y          \
           -c:a copy   \
           -c:v copy   $dst
}

video-drop-from () {
    slice-video $1 $2
}

split-video () {
    local parts=$1

    local file=$2
    local name=${file:r}
    local ext=${file:e}

    local video_len=$(video-seconds $file)
    local part_len=$(( int($video_len/$parts) ))

    local part_start
    local part_name
    for p in {1..${parts}}; do
        part_start=$(( ($p - 1)*${part_len} ))
        part_name=${name}-${p}.${ext}
        ffmpeg -ss $part_start \
               -i $file        \
               -t $part_len    \
               -c:a copy       \
               -c:v copy       $part_name
    done
}