#!/bin/bash

# thumbnailer 2016
# needs ffmpeg, ffprobe, bc

# notes:
# http://ffmpeg.org/ffmpeg-all.html#thumbnail
# ffmpeg -ss half-of-video -i input.mp4 -vf thumbnail=50 -frames:v 1 out.png
# ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 input.mp4

# set -x

# checks critical
command -v ffmpeg >/dev/null 2>&1 || { >&2 echo "I need ffmpeg installed." ; exit 1; }
command -v ffprobe >/dev/null 2>&1 || { >&2 echo "I need ffprobe installed." ; exit 1; }
command -v bc >/dev/null 2>&1 || { >&2 echo "I need bc installed." ; exit 1; }

# main 
    while [ $# -gt 0 ]; do
    file="$1"
    base=$(basename "${1}")     # basename, like                file.png
    base="${base%.*}"           # basename without extension    file
    dir=$(dirname "${1}")

    # check if thumb is allready there
    test -f "$dir/$base.jpg" && { >&2 echo "thumb $dir/$base.jpg allready there, skiping" ; shift; continue; }

    # movie duration/2
    dur=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$file")
    halfdur=$(bc -l <<< "$dur / 2.00")

    # if halfdur is unset (input can be image) then let it be 0
    if [ -z "$halfdur" ]; then
    halfdur="0"
    fi

    # width, height
    eval "$(ffprobe -v error -of flat=s=_ -select_streams v:0 -show_entries stream=width,height "$file")"
    height=${streams_stream_0_height}
    width=${streams_stream_0_width}

    echo "$width width"
    echo "$height height"

    # We need to crop to smaller side, so lets compare here
    if ((width > height)); then 
        smaller="$height"
    else    
        smaller="$width"
    fi

    echo "$smaller smaller"
    echo "$dur"
    echo "$halfdur"
    echo "$file"

    # The next line will probably produce weird stuff if PAR != 1 
    ffmpeg -hide_banner -ss "$halfdur" -i "$file" -vf thumbnail=30 -frames:v 1 -vf crop="$smaller":"$smaller",scale=-2:100 "$dir/$base.jpg" -loglevel panic -stats

    # stuff & notes:
    # -vf crop=in_h:in_h,
    # -vf crop="'if(gt(in_h,in_w),in_w,in_w)':'if(gt(in_w,in_h),in_h,in_h)'" < dunno what this is
    # -loglevel panic -stats 
    # crop=in_h:in_h,scale=-2:200"

    shift
done