#!/usr/bin/env bash

#prerequisites:
#  ffmpeg
#  gifski
#  gifsicle

# creates animated images out of all MP4 files
# in the working directory, as well as creating
# a thumbnail out of one frame
# if argument passed to script, the thumbnail
# will be created out of that frame, but none of
# the animated files will be created

# pass an argument to this script to specify
# which frame to use as the thumbnail
# if none passed, use default
if [[ $1 == "" ]]; then
    frame=0.85
else
    frame=$1
fi

# frame passed must be decimal < 1.0 and >= 0.0
if ! ([[ $frame =~ 0\.[0-9]+ ]]); then
    echo frame passed: $frame
else
    # loop through all MP4 files in directory
    for file in *.mp4
    do
        # only proceed if file found
        if [[ $file != *"*"* ]]; then
            # create paths
            input_path=$(pwd)/"$file"
            output_path_animated=${input_path%.*}.webp
            output_path_animated_low=${input_path%.*}-low.webp
            output_path_gif=${input_path%.*}.gif
            output_path_thumb=${input_path%.*}_thumb.webp

            # determine the exact frame to use as thumbnail
            frames_total=$(ffprobe -v error -select_streams v:0 -count_packets -show_entries stream=nb_read_packets -of csv=p=0 "$input_path")
            thumb_frame=$(awk -vnumber="$(awk -v var1=$frames_total 'BEGIN { print (var1 * '$frame') }')" -vdiv="1" 'function ceiling(x){return x%1 ? int(x)+1 : x} BEGIN{ print ceiling(number/div) }')

            # if argument had been passed to script, skip creating
            # animated images and ONLY create thumbnail
            if [[ $1 == "" ]]; then
                #full webp
                ffmpeg -y -hide_banner -loglevel error -i "$input_path" -vcodec libwebp -lossless 0 -loop 0 -preset default -an -fps_mode passthrough -vf "fps=25, scale=-1:500" -quality 80 "$output_path_animated"
                #low webp
                ffmpeg -y -hide_banner -loglevel error -i "$input_path" -vcodec libwebp -lossless 0 -loop 0 -preset default -an -fps_mode passthrough -vf "fps=15, scale=-1:270" -quality 10 "$output_path_animated_low"
                #low gif
                ffmpeg -y -hide_banner -loglevel error -i "$input_path" -f yuv4mpegpipe - | gifski --quiet --height=270 --fps 10 --quality=50 --lossy-quality 50 -o "$output_path_gif" -;gifsicle -O3 --lossy=200 --colors 256 -o "$output_path_gif" "$output_path_gif"
            fi
            #thumb
            ffmpeg -y -hide_banner -loglevel error -i "$input_path" -vf "select=eq(n\,$thumb_frame), scale=-1:270" -c:v libwebp -quality 50 "$output_path_thumb"

            echo $input_path
        else
            echo MP4 not found
        fi
    done
fi