#!/bin/bash

# README
#
#   ABOUT
#
#       This script generates WEBM or GIF files, depending on your preference, in the folder where it's saved.
#       It will generate 12 WEBM or 30 GIF files per video, as long as the videos are in the same folder as
#       the script. Example: Imagine your folder contains 3 videos - this script will generate 36 WEBMs or 36 GIFs
#       in the same folder.
#
#       The script will evenly create WEBMs or GIFs throughout the length of the video, so you can expect
#       to see WEBMs or GIFs from the beginning, middle, and end of the video.
#
#   PLATFORM
#
#       This script is for Linux, Mac, or Windows.
#       If you're on Windows, install cygwin with bc math package and type bash in command prompt
#       to enter bash mode.
#
#   TOOLS
#
#       You must have ffmpeg installed with --with-libvpx --with-libvorbis
#       If you're on mac, install homebrew and type: reinstall ffmpeg --with-libvpx --with-libvorbis
#             If you're on Windows, I think your ffmpeg already comes with it, but make sure you have ffmpeg with
#       those tools if it doesn't.
#
#   FILES
#
#       This script should work with mp4, avi, wmv, and mpeg files.
#
#   INSTRUCTIONS
#
#       0. Open notepad or a text editor, and save this script as create.sh (or any other name.sh)
#       1. Put this script in a directory which has videos
#       2. In terminal, navigate to your folder containing the script and videos
#               If you want to generate WEBMs type: bash create.sh webm
#               If you want to generate GIFs type: bash create.sh gif
#
#
# TIPS
#
#   1. This script creates 12 WEBMs or 30 GIFs per video by default.
#        You can change numWEBMs or numGIFs value to generate more or less.
#
#   2. The GIFs this script generates are 500px wide by default.
#      Change variable filters' scale value to modify this.
#
#     3. The WEBMs this script generates are 1000px wide by default.
#      Change webmWidth to modify this.
#
#   4. The WEBMs this script generates are 1500K bitrate by default.
#      Change bitrate variable to modify this.
#
#   5. The duration of a WEBM is 10 seconds by default.
#      The duration of a GIF is 1.2 seconds by default.
#
#     6. If you want to shut down the script, hold down control-c in terminal or command prompt. Or simply close
#     the terminal / command prompt.

# Initialize Variables

# GIF variables and settings
gifDuration=1.2; gifWidth=500; numGIFs=30; gifFiles=()
filters="fps=20,scale=${gifWidth}:-1:flags=lanczos"

# WEBM variables and settings
webmDuration=10; webmWidth=1000; numWEBMs=12; webmFiles=(); bitRate="1500K"

# General variables
createCMD=""; videosList=(); mode=$1; numFiles=0; numSegments=0; limit=0; duration=0
cutDeci="| bc | cut -d "." -f1"
numSec="ffprobe -v error -select_streams v:0 -show_entries stream=duration -of \
      default=noprint_wrappers=1:nokey=1"

# Sets various variables and options for script, depending on mode
setModeOptions(){
      if [ "${mode}" == "gif" ]; then
            numSegments=$numGIFs; createCMD="createGif"; duration=${gifDuration}
      elif [ "${mode}" == "webm" ]; then
            numSegments=$numWEBMs; createCMD="createWebm"; duration=${webmDuration}
      else
            echo "Invalid mode"; exit 0
      fi
}

# Gets mp4, wmv, avi, mpeg files in current directory into list
composeVidList(){
      shopt -s nullglob #ffprobe complains otherwise
      for vid in *.{mp4,wmv,avi,mpeg}; do
            if [ `eval "${numSec} '${vid}' ${cutDeci}"` -gt 60 ]; then
                  videosList+=("${vid}")
            fi
      done
}

createGif(){
      fileName="${1}"; start="${2}"; outputName=${fileName%.*}

      echo "Creating ${outputName}_${numFiles}.gif at time: ${start} seconds."

      ffmpeg -ss "${start}" -t "${duration}" -v error -i "${fileName}" \
            -vf "$filters,palettegen" \-y palette.png # Create palette for video
      ffmpeg -ss "${start}" -t "${duration}" -v error -i "${fileName}" \
            -i palette.png -lavfi "$filters [x]; [x][1:v] paletteuse" -y \
            "${outputName}_${numFiles}.gif" # Create GIF

      rm "palette.png" #Remove palette
}

createWebm(){
      fileName="${1}"; start="${2}"; outputName="${fileName%.*}"

      echo "Creating ${outputName}_${numFiles}.webm from time: ${start} seconds."

      ffmpeg -ss "${start}" -t "${duration}" -v error -i "${fileName}" \
            -vf scale=${webmWidth}:-2 -c:v libvpx -b:v ${bitRate} -c:a \
            libvorbis -an "${outputName}_${numFiles}.webm"
}

# Ensures WEBM or GIF of length "t" seconds isn't created at startingTime + t > videoLength
getLenLimit(){
      limit=`echo $totalSeconds - ${duration} | bc | cut -d "." -f1`
      ((limit--))
}

processVideo(){
      video="${1}"
      totalSeconds=`eval "${numSec} '${video}' ${cutDeci}"`
      startingTime=$(( (10#$totalSeconds * 13) / 100 )) # Skip first ~13% of video to pass boring intros
      interval=$(( (10#$totalSeconds - 10#$startingTime) / numSegments ))

      getLenLimit

      for (( k = 0; k < ${numSegments}; k++ )); do
            if [ "${startingTime}" -ge "${limit}" ]; then
                  continue
            fi
            (( numFiles++ ))

            "${createCMD}" "${video}" "${startingTime}"
            startingTime=$(( 10#${startingTime} + 10#${interval} ))
      done

      echo
      numFiles=0
}

main() {
      setModeOptions; composeVidList
      echo
    for (( i= 0; i < ${#videosList[@]}; i++ )); do
        processVideo "${videosList[i]}"
    done
    echo -e "\nComplete.\n"
}

main