#!/bin/sh
# TODO: Add hardware acceleration support
# TODO: More consistently find a way to delete ffmpeg log files
usage() {
	printf '%b\n' "${0##*/} -i <input_file> [OPTIONS]"                     \
	              "\noptions:"                                             \
	              "\t-c CODEC     - video codec to use (default: libx264)" \
	              "\t-h           - display this message"                  \
	              "\t-o FILE      - output file (default: out.ext)"        \
	              "\t-p PRESET    - encoding preset to use"                \
	              "\t-t FILE_SIZE - file size to target in MiB (default: 50)"
}

while [ "$*" ]
do
	case $1 in
		-  ) shift; continue ;;
		-- ) shift; break ;;
		-* ) flag=${1#-}; shift ;;
		*  ) shift; continue ;;
	esac

	while [ "$flag" ]
	do
		arg=${flag%"${flag#?}"}

		case $arg in
			c ) VIDCOMP_CODEC=$1; shift ;;
			h ) usage; exit 0 ;;
			i ) VIDCOMP_INPUT_FILE=$1; shift ;;
			o ) VIDCOMP_OUTPUT_FILE=$1; shift ;;
			p ) VIDCOMP_PRESET=$1; shift ;;
			t ) VIDCOMP_TARGET_SIZE=$1; shift ;;
			* ) printf '%s\n' "${0##*/}: -$arg: invalid argument" 1>&2
			    usage 1>&2; exit 1 ;;
		esac

		flag=${flag#?}
	done
done

[ -z "$VIDCOMP_INPUT_FILE" ] && {
	printf '%s\n' "${0##*/}: missing input video" 1>&2
	usage 1>&2; exit 1
}

ext="${VIDCOMP_INPUT_FILE##.*}"
: "${VIDCOMP_OUTPUT_FILE:=out.${ext}}"

: "${VIDCOMP_CODEC:=libx264}"
: "${VIDCOMP_TARGET_SIZE:=50}"

a_bitrate="$(ffprobe -v error -select_streams a:0 -show_entries stream=bit_rate -of default=noprint_wrappers=1:nokey=1 \
  "${VIDCOMP_INPUT_FILE}")"
secs="$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "${VIDCOMP_INPUT_FILE}")"
bitrate="$(fend floor \("${VIDCOMP_TARGET_SIZE} * 8388.608 / ${secs}" - \("${a_bitrate}" / 1000\)\))"


ffmpeg -hide_banner -loglevel warning \
  -i "${VIDCOMP_INPUT_FILE}" -c:v "${VIDCOMP_CODEC}" -b:v "${bitrate}k" \
  ${VIDCOMP_PRESET:+"-preset" "$VIDCOMP_PRESET"} -pass 1 \
  -an -f null -y /dev/null && \
ffmpeg -hide_banner -loglevel warning \
  -i "${VIDCOMP_INPUT_FILE}" -c:v "${VIDCOMP_CODEC}" -b:v "${bitrate}k" \
  ${VIDCOMP_PRESET:+"-preset" "$VIDCOMP_PRESET"} -pass 2 \
  -c:a copy "${VIDCOMP_OUTPUT_FILE}"