#!/bin/bash

#  This script generates scripts inside each subdirectory of the current directory;
#  so it is expected that each film's files (the film, the subtitles) are put in
#  separate subdirectories.
#
#  The assumption is that the AVI container contains H264-encoded videos, but that's
#  not strictly required, it's just that H264-encoded video seems to be the preferred
#  option these days.
# 
#  The scripts that this script generates *echo* the commands that would need to be
#  run. So the expected workflow is something like:
#
#      mkdir film1
#      cp ... film1/
#      mkdir film2
#      cp ... film2/
#      ./combine-avi-and-srt-into-mkv
#      cd film1
#      ./go          #  does it look ok?
#      ./go | bash
#      cd .. 
#      cd film2
#      ./go          #  does it look ok?
#      ./go | bash
#      cd .. 

for DIR in */; do
    cd "$DIR"
    DIRSTEM=${DIR%/}
    echo "$DIRSTEM ..."
    {
        echo "#!/bin/bash"
        echo "DIRSTEM=\"$DIRSTEM\""
        echo "COUNT=0"
        echo "for SRT in *.srt; do"
        echo "    FILESTEM=\"\${SRT%.srt}\""
        #  AVI cannot be converted "simply" to MKV because AVI lacks timing information that is needed in the MKV. So we
        #  need some special options ('-fflags +genpts') to get the timing information. Note that video is not reencoded
        #  but it should be if it is not already in H264 format.
        echo "    echo \"ffmpeg -nostats -loglevel 0 -y -fflags +genpts -i \\\"\$FILESTEM.avi\\\" -c:v copy -c:a copy \\\"\$FILESTEM-recontainered.mkv\\\"\""
        #  Copy over all streams in the first file ('-map 0') and all streams in the second file ('-map 1')
        echo "    echo \"ffmpeg -nostats -loglevel 0 -y -i \\\"\$FILESTEM-recontainered.mkv\\\" -i \\\"\$FILESTEM.srt\\\" -map 0 -map 1 -c copy -metadata:s:s:0 language=eng \\\"\$FILESTEM-recontainered-with-subs.mkv\\\"\""
        echo "    ((COUNT++))"
        echo "done"
        #  If the film was in multiple *parts* then combine then. Otherwise create a symlink to the combined name
        #  so that the copy-back-to-pub commandline script/loop doesn't need handle the the different cases.
        echo "if ((\$COUNT >= 2)); then"
        echo "    echo \"mkvmerge -q -o \\\"\$DIRSTEM-recontainered-with-subs-and-merged.mkv\\\" \$(FIRST=true; for SRT in *.srt; do FILESTEM=\"\${SRT%.srt}\"; { \$FIRST && echo -n \"\\\"\$FILESTEM-recontainered-with-subs.mkv\\\" \"; } || echo -n \"+\\\"\$FILESTEM-recontainered-with-subs.mkv\\\" \"; FIRST=false; done)\""
        echo "else"
        echo "    echo \"ln -s *-recontainered-with-subs.mkv \\\"\$DIRSTEM-recontainered-with-subs-and-merged.mkv\\\"\""
        echo "fi"
    } > go
    chmod 700 go
    cd ..
done