#!/bin/sh
set -euf

###### USAGE #####
#run in new directory(will be polluted with images
#just run ./make-realwallpaper

main() {
  # fetch source images in parallel
  fetch nightmap.jpg \
    http://awka.sourceforge.net/Night_le_huge.jpg &
  fetch daymap.png \
    http://www.nnvl.noaa.gov/images/globaldata/SnowIceCover_Daily.png &
  fetch clouds.jpg \
    http://user.chol.com/~winxplanet/cloud_data/clouds_2048.jpg &
  fetch krebs.sat.tle \
     http://www.celestrak.com/NORAD/elements/stations.txt  
  wait

  check_type nightmap.jpg image
  check_type daymap.png image
  check_type clouds.jpg image

  # downscale daymap to match nightmap
  needs_rebuild daymap-final.png \
    daymap.png \
    && convert daymap.png -scale $(image_size nightmap.jpg) daymap-final.png

  needs_rebuild clouds-final.png \
    clouds.jpg \
    && convert clouds.jpg -scale $(image_size nightmap.jpg) clouds-final.png

  # create nightmap-fullsnow
  needs_rebuild nightmap-fullsnow.png \
    && convert \
        -size $(image_size nightmap.jpg) \
        'xc:#0a3b5c' nightmap-fullsnow.png

  # extract daymap-snowmask from daymap-fonal
  needs_rebuild daymap-snowmask.png \
    daymap-final.png \
    && convert daymap-final.png -threshold 95% daymap-snowmask.png

  # extract nightmap-lightmask from nightmap
  needs_rebuild nightmap-lightmask.png \
    nightmap.jpg \
    && convert nightmap.jpg -threshold 25% nightmap-lightmask.png

  # create layers
  make_layer nightmap-snowlayer.png nightmap-fullsnow.png daymap-snowmask.png
  make_layer nightmap-lightlayer.png nightmap.jpg nightmap-lightmask.png

  # apply layers
  flatten nightmap-lightsnowlayer.png \
    nightmap-lightlayer.png \
    nightmap-snowlayer.png

  flatten nightmap-final.png \
    nightmap-lightsnowlayer.png \
    nightmap.jpg

  # create xplanet output
  needs_rebuild xplanet.config \
    && cat >xplanet.config <<EOF
[earth]
"Earth"
map=daymap-final.png
night_map=nightmap-final.png
cloud_map=clouds-final.png
EOF

  # create xplanet output satellite version
  needs_rebuild xplanet-sat.config \
    && cat >xplanet-sat.config <<EOF
[earth]
"Earth"
map=daymap-final.png
night_map=nightmap-final.png
cloud_map=clouds-final.png
satellite_file=krebs.sat
EOF

  needs_rebuild krebs.sat \
    && cat >krebs.sat <<EOF
25544 "ISS" Image=none trail={orbit,-2,2,1} color=grey thickness=1 fontsize=10
37820 "T1" Image=none trail={orbit,-2,2,1} color=grey thickness=1 fontsize=10
39175 "ATV-4" Image=none trail={orbit,-2,2,1} color=grey thickness=1 fontsize=10
39258 "CYG" Image=none trail={orbit,-2,2,1} color=grey thickness=1 fontsize=10
EOF

  needs_rebuild krebs.mar \
    && cat >krebs.mar <<EOF
EOF

  # rebuild every time to update shadow
  xplanet --num_times 1 --geometry 1466x1200 \
    --output xplanet-output.png --projection merc -config xplanet.config

  # rebuild everytime satellite version
  xplanet --num_times 1 --geometry 1466x1200 \
    --output xplanet-sat-output.png --projection merc -config xplanet-sat.config

  # trim xplanet output
  needs_rebuild realwallpaper.png \
    xplanet-output.png \
    && convert xplanet-output.png -crop 1366x768+100+160 realwallpaper.png

  # trim xplanet-sat output
  needs_rebuild realwallpaper-sat.png \
    xplanet-sat-output.png \
    && convert xplanet-sat-output.png -crop 1366x768+100+160 realwallpaper-sat.png
}

# usage: getimg FILENAME URL
fetch() {
  echo "fetch $1"
  curl -sS -z "$1" -o "$1" "$2"
}

# usage: check_type FILENAME TYPE
check_type() {
  if ! file -ib "$1" | grep -q "^$2/"; then
    echo "$1 is not of type $2" >&2
    rm "$1"
    return 1
  fi
}

# usage: image_size FILENAME
image_size() {
  identify "$1" | awk '{print$3}'
}

# usage: make_mask DST SRC MASK 
make_layer() {
  if needs_rebuild "$@"; then
    echo "make $1 (apply mask)" >&2
    convert "$2" "$3" -alpha off -compose copy_opacity -composite "$1"
  fi
}

# usage: flatten DST HILAYER LOLAYER
flatten() {
  if needs_rebuild "$@"; then
    echo "make $1 (flatten)" >&2
    composite "$2" "$3" "$1"
  fi
}

# usage: needs_rebuild DST SRC...
needs_rebuild() {
  a="$1"
  shift
  if ! test -e "$a"; then
    #echo "  $a does not exist" >&2
    result=0
  else
    result=1
    for b; do
      if test "$b" -nt "$a"; then
        #echo "  $b is newer than $a" >&2
        result=0
      fi
    done
  fi
  #case $result in
  #  0) echo "$a needs rebuild" >&2;;
  #esac
  return $result
}


main "$@"